@@21stcenturyguy25 I agree, especially after patreon started booting people based on what they talked about. @spacedock if the reference book was available somewhere else, even for a slightly higher cost, I might consider that.
A guy I used to work with who was in many ways just another junkie you had to be very aware of at work to avoid getting hurt. He always brought up some amazing questions that would really make you think twice. Once he asked if you could hold a gun out the window of the space shuttle on takeoff and shot a bullet up, would it pass the shuttle or would the shuttle pass the bullet when it left the barrel? Another time he asked if you filled an elevator shaft with gas in the bottom and cut the cable with a spark plug set to fire when it fell down would the elevator fly to the top of the shaft like a piston in an engine? Sometimes this guy really freaked us out with his ideas.
The beauty of physics is that you can have any configuration you want and the only things to worry about are materials engineering and placement of maneuvering jets. So you could in fact build a flying saucer or a space plane or a Constitution-class light cruiser and it would work as long as your metallurgy was up to par. (In other words no, you guys and Tyson can go kick rocks with your treatises on design.)
Okay, random thought, but I just realized with physical projectiles as the primary weaponry any mass battles would result in the futuristic version of today’s minefields. With today’s technology our weapons are firing thousands of rounds per minute. A big enough battle and enough guns, we’re going to see clouds of projectiles heading out in every direction for an infinite amount of time--> just armor piercing bullets zooming across space for near eternity.
That's actually a proper thing in the Mass Effect lore, but the cutscenes just stick to the "traditional" way of depicting spacecraft. - hoojiwana from Spacedock
@@hoojiwana yeah but the traditional way is cooler and makes for better looking space battles and travel for a lot of people. Unless you’re a hardcore space nerd it’s a bit difficult to appreciate more scientifically accurate depictions of space combat and travel.
@@awesomehpt8938 a lot of people make this excuse. i disagree intensely. I think audience hunger for new things to watch and digest. thats the reason why tropes and cliches tire us out, and only good writing that subverts expectations really gets praise. If the science nerd method of travel and combat were used more often, people would catch on pretty quick, and think it's cool they learned something new and REAL. Not to mention the storytelling advantages that such uniqueness can present to the narrative.
@@hoojiwana I square that circle by assuming they can “scale down” the drive as you approach the destination, shedding speed as your mass approaches what it should be. So you accelerate most of the way to your destination.
@@ericaugust1501 For me, one of the coolest things about The Expanse was real world physics(RIP Manéo, oyedeng beltalowda), especially the battle scenes. I still like the Star Trek battleship type scenes as well, but the physics completely set The Expanse apart from other sci-fi.
I experienced a big wave of respect for the creators of the BSG reboot when I saw small attitude thrust jets firing on the Vipers to help them maneuver in space when I first watched the series. Although it was done before in scifi, watching Starbuck fly laterally as she pointed her Viper and fired a strafing run on the Resurrection Ship was solid gold.
It's wild that NASA had to actually try and fail first to figure out orbital rendezvous mechanics. KSP and all the accessible information about orbits nowadays make it seem much more intrinsic than it actually was for people at the bleeding edge of the field. Also, I always appreciate the "have fun with it" disclaimer at the end of videos like these. It's encouraging to see real-world principles being broken down and offered as tools for a creator rather than hard rules and must-haves to create the perfect setting or story.
I agree. I actually love that The Expanse went for hyper realism. It's a fun take and nice to see. But you can have non-realistic too. Both are valid for entertainment. Only thing I ask for in an IP is consistency with thier own rules.
@@forestwells5820 Yes! Consistency is the most important, even if there are space wizards once you show the audience how space battles work in a setting changing it around just because you can just makes people lose investment.
I'm a spacecraft propulsion engineer and fluid dynamicist with NASA, and this is an excellent explainer. The propulsion stuff was great, the attitude control stuff was great, the orbits stuff was understandably minimal, but really an all around awesome video. Accessible to lay viewers, gets the details right, and isn't patronizing to expert viewers. Well done! If you're continuing this as a series, I think an important core topic is the tyrrany of the rocket equation, or more generally the idea that it takes propellant to bring propellant, leading to an exponential problem. This tyranny and the resulting all-importance of deltaV budgets absolutely dominates all aspects of rocket and spacecraft design, mission planning, and CONOPS. Not as flashy of a topic as fun flavors of far future fission and fusion propulsion, but definitely introduces and motivates why it is so important to chase the high efficiencies those future propulsion concepts promise (and why it is important to keep pushing for nearer future improvements like Nuclear Thermal Propulsion and Ion Propulsion).
Could there ever be something like the Heisenberg fusion drive in The Expanse? A huge thrust to weight ratio, a slight miscalculation and someone feels ever-increasing g as the spacecraft gets lighter and lighter.
Well put. I am not in the aerospace field now but got my BS in Aerospace Engineering from ERAU back in 1992. I remember being required to calculate the mass of propellent needed to get a bolt into orbit and then having to break it out into stages to get the optimal solution. Gravity is a bitch.
This is a fundamental problem of all logistics usually phrased as, "Everything that can transport food also eats food." Famously, the preindustrial armies that were most effective had excellent logistics.
One of the amazing things about the NASA fact is that later-moon-lander Buzz Aldrin wrote his PhD thesis on "Line-of-Sight Guidance Techniques for Manned Orbital Rendezvous" - and was dedicated to "the crew members of this country's present and future manned space programs. If only I could join them in their exciting endeavors." - Six months after finishing his Doctorate, he was selected as an astronaut. At that point, Gemini 4 was already in the late stages of planning/training, so by the time Aldrin was "fully up to speed", it was too late to assist on Gemini 4. He absolutely was involved in all future rendezvous planning.
For basic 6-degree flight control in zero-G, I've been impressed with how Elite: Dangerous handles the physics. If you choose to fly 100% manually, the game gives you complete freedom in every axis and your spaceship behaves as it should based on its mass and the strength of its various thrusters (for example a given ship may be more responsive in roll than it is in yaw). The game does limit you to a maximum total velocity to limit player exploits, but otherwise it's just as you'd expect from Newtonian physics. If you go to an external view, you can also see the various thrusters firing based on your control inputs. On top of that, there are various assists that you can engage, such as a general flight assist package where a computer juggles all 6 degrees to create a "fly-where-you-point" behavior that's more intuitive and simplifies control inputs, and another assist that auto-syncs your ship to the various rotating space stations you can dock with. If we get to the point where spacecraft are buzzing around like aircraft are today, I think computer assists like that are definitely going to be a thing.
The *BEST* explanation for orbital mechanics I've ever read was from Chuck Yeager's autobiography. In it, he describes going out into a desert in a jeep, turning the steering wheel to the left, and then, using a lot of rope, lashing it down so that it could not move at all. When you start up the jeep, it will go in a big circle; the faster you go, the bigger the circle. He and another pilot each had a jeep and their only control was the throttle, and they practised doing rendezvous.
When I started working on a Space Opera setting for an RPG, I pretty early on decided to base space combat on early 20th century cruisers. They don't do any dodging or fancy maneuvering and simply keep slugging cannon shells at each other from a long distance, more or less just hoping that they will land critical hits first. This makes things so easy for me.
That's similar to a few books I've read handle it. Two forces each charging at each other around, say, .1c each and combined speed of .2c, dump ordinance in the few milliseconds you're in range, next few minutes assess your losses and damage, then next few hours maneuvering around for the next charge Though i guess after writing all that you actually mean they just sit and pound on each other, kinda like.... most space movies actually
How do you balance this with - I would assume - the increased lethality of the weapon systems used? Realistically, you'd expect space warships to be eggshells with sledgehammers. The battle will be over the moment the first hit with a nuclear warhead is scored.
Battletech actually defines the two types of black-water engagement as the Fast Pass, and the Broadside Battle. The former usually happens in transit, and requires computer-assisted targeting, since no human has fast enough reactions to make the required shots when everything is zipping past each other at fractions of the speed of light. Its also utterly terrifying, as you have to just sit there, waiting for the moment of contact, hoping and praying you've got either the better fire plan, or better firepower, or just that the enemy hasn't locked on to you...and then its all over, before you can even take a breath. The second is a more set-piece situation, where the two forces maneuver to be at a halt relative to each other, and then maneuver to gain firing advantage within that frame of reference. Ironically, whilst the two forces may be halted relative to each other, the "battlefield" they're in could be travelling at a fraction of the speed of light relative to the local star, but I'd be more inclined to think that this is more of a situation of attack and defense around a (relatively) stationary objective.
Might be better even to base off early 20th century naval combat, where engagement distances were so long ranged maneuver was almost pointless for cruisers and dreadnaughts, and only smaller frigates were going to be doing much in the way of tactical movement. Plus then you have the fun of destroyers being so small and fast that capital ships couldn't actually depress the guns far enough to shoot at them.
I think the expanse does the best job at predicting future space engagements. They just fire tons of nukes at each other. They fire nukes at the nukes to defend against them. Occasionally they use railguns. I don't think it's realistic ships getting destroyed by PDC's I'd imagine ships in the future would be heavily armored with a large railgun and lots of missiles. Similar to modern day tanks development process of increasing armor thickness and then increasing gun size. Lot's of maneuvering in fights in hopes to throw off the aggressors targeting solution for projectile weapons.
@@Alejandra-cv7rj Another BSG beside the 2003 reimagine version? I hope they focus on the First Cylon War, where Galactica was at her prime, like what we saw in BSG: Razor.
@@AlexSDUmost probably it will focus more on Adama’s gender identity as a strong lesbian black woman and Caprica 6 struggle with racist humans that don’t accept her as an equal
This is one of the many reason why I love this channel. I've been working on a sci-fi book the last few years and mapped out a way to introduce these concepts into a story that the audience can understand. I've always decided not to use artificial gravity and have some of the ships use gimbaled decks for when transitioning from orbital to flight and landing to space flight. It really adds flavor to a story instead of just handwaving away gravity with artificial gravity.
The thing I always find interesting about orbital mechanics is how counter intuitive it is. If you try and deorbit something by pushing it down towards earth. It will speed up, pass in front of you, slow down and then hit you on the head. To actually deorbit you have to slow down by thrusting forwards. In Gemini, by thrusting right at the target he ended way above it, without ever inputting any vertical thrust.
I love this kinda take that blends-in some realism, but doesn't require 100% accurate physics nonsense. Its good to see it gaining popularity and acceptance in the writing and reviewing spaces.
About that part with using a gun as propulsion... never forget: "A reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive." - The Kzinti Lesson, Larry Niven.
Even back in the 90s shows like Babylon 5 and Space: Above and Beyond used RCS thrusters to maneuver their fighters in space and conserved momentum with the ship able to point in a different direction than it was moving. I really appreciated that attention to detail
@@TheEvilmooseofdoom It's true that they ran their engines constantly on S:AAB, but I did appreciate that they showed RCS thrusters firing when they maneuvered and they did occasionally do moves like cutting thrust, doing a 180 maintaining their vector, and then firing at an enemy that was tailing them.
B5's 'Starfurys' were shown in some amazing fight sequences... it doesn't hurt that the very ship-design, with it's prominently mounted RCS engine nozzles and their blast-flaps, really hint at what they had in mind for it's operational realism.
Its amazing how even NASA experienced the "first kerbal orbiter docking" issue, you think you can just point at the other vessel and go but it simply doesnt work that way
@@Voltaic_Fire The Expanse has 100% realistic maneuvers including actual orbital mechanics and realistic flight times. B5 doesn't. Not even remotely. Not sure why you would even think so. B5 is very space opera even if the spaceship designs of the humans are pretty realistic.
I love when 3d space sandbox games (like avorion or space engineers) do exactly this, where it's realistic space movement and you need to account for basically everything. Getting a hands on experience placing your own directional thrusters really makes you appreciate the art.
Too bad that game fails to deliver realistic space combat and instead it settles for WW2 naval warfare with a black background. I hoped for more when it first came out.
I kind of bounced hard off the gameplay in it and the heavy micro it seems to require so probably not. We do try to put it in now and then though such as with the OSP plasma weapons! - hoojiwana from Spacedock
@@hoojiwana Ah well, it's not for everyone. I feel like the micro is a little less intense if you use a ballistics-centric fleet instead of a missile one, but it's good to know you guys try to talk about it occasionally!
@dragoscostache4 it's intentionally like that because honestly Realistic space combat would suck. Moving in the triple digits of speed, never seeing your opponent, and if your engines get taken out congratulations you are now heading hundreds of thousands of km away from the battle.
In older Star Wars canon, there is something called an aether rudder, which is based on the old science that there is a medium in space that lets electromagnetic energy move. The rudder would use this medium to turn. For more modern lore, vehicles like the X-wing got RCS, gyroscopes, thrust vectoring, etc.
Aetheric rudders male more sense for Star Wars. Yes, you COULD explain their maneuvering with RCS and stuff, but it becomes way more effort than it's worth. Just accept that they can produce drag and exert force on the fabric of spacetime (not entirely farfetched since they have antigravity and such) and suspend your disbelief about the fighters not following Newtonian paths.
As someone 7+ years into KSP, this is an _excellent_ entry level explanation of an extremely complex topic. +1 for the footage from Copenhagen Suborbitals and Nick Stevens too
Certain science fiction writers do manage to provide an excellent grounding in it. Larry Niven in particular, in his Smoke Ring novels and The Descent of Anansi.
I think it genuinely is, theres nothing like hands on experience for helping you really *understand* something, compared to just knowing about it. - hoojiwana from Spacedock
@@DrakeAurum you could write whole libraries full of stuff about orbital mechanics I'd never understand it like I do when I play KSP (and I still barely understand anything XD)
In a sci-fi setting where artificial gravity and other gravitational manipulations are available, you can also maneuver by keeping the thruster and shifting the center of mass instead. E.g. If your main thruster is in the central axis of the ship, and you can achieve that one side or wing becones considerably heavier (higher inertia) than the other, the thrust vector will not align with the center of mass and your ship will turn.
could also create a gravity-well in the direction you want to move and have said grav-well move with the craft with similar gravitational manipulations.. SnG's Chamber did effectively this if i recall.. could even do it planet-side..
@@niteriderevo9179 fun fact, the check for merge block magnatism only goes one sub grid down, so a merge block on a piston on a rotor can push itself against the main grid super energy efficient and incredible acceleration, even in a gravity well
@@chaingun1701 above and below, relative to the deck orientation, and deeper (more open) at the front. The goal seems to be a local change in space/time to allow greater acceleration. Some inertia gets dumped to the wedge, too.
There's an old Jeff Minter game (actually a mini-game) called Hallucin-O-Bomblets, where your ship can only rotate on the spot and shoot, and shooting causes you to move in the opposite direction to the direction of fire. Probably not a method of propulsion people would appreciate IRL, but not much madder than Project Orion.
KSP is fantastic for teaching orbital mechanics and Space Engineers / Elite Dangerous (with flight assists disabled) are fantastic for teaching newtonian flight physics. With Space Engineers allowing for complete control when designing spacecraft I learned a lot about how small scale battles would actually occur. If your vessel is big, armoured and full of guns the simple "sail past the enemy with gimballed guns" is super effective If you constrain the design though by limiting power outputs, and number of guns to be quite low you end up with something that sort of blends a BSG Viper with The Expanse's Roci: Big engine to push forwards, only small ones for lateral adjustment - and most weaponry also pointing forward, maybe a gimballed gun for defence. Fast gimballing, to change directions quickly Small frontal cross section, and relatively light weight. Where speed and lateral movement are your best defence, you can turn off flight assists, burn in at an angle slightly off from your target then when within gun range you turn to point at the enemy and keep burning the primary engine. This makes you a small target to the enemy with high lateral speed, your guns are pointed at them nearly the whole time and your main engine causes you to arc around them in an orbit. Like if you put a weight on a string and spin it in a circle, only instead of using string the same force is provided by the engine pointing perpendicular (radial out) to the orbit
I really love realistic space combat and I’ve had a lot of fun playing Nebulous Fleet Command becuase it has that same feel, I really love if spacedock check that game out
I absolutely love it when you use gundam footage as an example. Though the AMBC system of mobile suits would be a good example of the flywheel systems.
A big thing with Star Wars in particular having different mechanics for moving in space, is that space in Star Wars is not an empty void. There's something called the Aether, (originally mentioned in the now-canon X-Wing books, iirc), which allows some types of starfighters and other ships to use control surfaces to move like a plane. Actually, I'd love to see a video about intentionally altering physics itself in Sci-Fi. Franchises that do it, what they change and why, etc.
Lost Fleet definitely makes the most interesting use of realistic combat maneuvering of anything I've read or watched so far, including the Expanse. Come to think of it I don't believe it has been mentioned before on this this channel, which is a little disappointing, but on the other hand there's a lot of sci-fi out there.
@@EGRJ That's a good point, I don't recall books being mentioned specifically, apart from Sojourn of course. Then again a lot of technologies that haven't appeared on screen have been mentioned. What I'd really like to see is some Lost Fleet battle breakdown videos that youtubers make for Star Wars and other sci-fi. Those are neat.
I've got a BS in Aerospace Engineering. When it comes to orbital maneuvers, one of the easiest ways I've learned to understand it (outside of playing Kerbal Space Program) is to think of the orbit kind of like a rubber band between two fingers. Every time a spacecraft makes a burn, it's like pulling or rotating the *_entire rubber band_* , not just a single point on it. If you try to stretch it in one direction (like you're adjusting the apoapsis or periapsis), the band narrows in the other direction. If you try to rotate it (like an inclination change), the whole band rotates so one side moves up and the other moves down. You have to plan to make a burn on one side of an orbit in the name of affecting what happens on the other. It's what makes orbits so challenging to understand: you're not "moving where you are" in a maneuver, you're just trying to speed up or slow down to "move where you're going".
THE EXPANSE showed spaceship movements and orbital trajectories much better than most sci-fi. Only 2001: A Space Odissey comes to mind as being better.
I think Babylon 5 (Starfuries) and Wing Commander are probably some of the best examples of this kind of neutonian physics in Sci-Fi. While if you cut throttle in Wing Commander you do slow down, they have full maneuverability ratings for Yaw/Pitch/Roll for pretty much every craft in the games (although WC1 and 2 I think were on a 1-10 scale while 3, 4, and Prophecy actually had actual Degrees Per Second). And I believe you guys already covered the Starfury from Babylon 5 so won't touch on why that fighter is so awesome.
Interestingly, the Omegas were supposed to have a gimballed engines so they could maneuver realistically with the rotating hab module. Unfortunately, it would have taken too much time to explain how thrust works with rotating bodies and why they would burn "down" to turn left.
I think the idea behind those other vehicles (Minbari, Vorlon, etc.) was to show how much more advanced their technology was, as compared to Earth Alliance tech.
The "Eagle Transporter" craft from Space:1999 were the first realistic concept spacecraft I ever saw on Tv. Main forward thrust engines in the back, lift engines underneath, 4 separate drive pods with directional thrusters pointed in all possible directions. I've always used those concepts in designing my own spacecraft. Two bad they didn't have the CGI to show how really maneuverable they were - they were in combat plenty of times, and I always thought when a target is heading straight for one of them, was that the Eagle should wait just before the enemy fired and used it's lift thrusters to move vertically out of range. Since they do a VTOL in gravity fields above the Earth's, they would be powerful enough for some serious vertical lift maneuvering. Just too much two- dimensional thinking, I guess.
-All I could think of with this topic were the space 1999 eagles, also. Maybe it’s just an age thing? It was long before re-imagined battlestar galactica, though that was cool, too.
@@sci-fyguy7767 I still have a few model kits of Eagles, as well as the kit of the entire Alpha Moon base. Still in the box - I have no place right now to set them up.
Full thrust to the halfway point then full reverse the other half. ETA: I remember one story where the vessel powered towards the enemy. Upon reaching the enemy they flipped, and did a maximum burn which melted portions of the hull and super structure.
I'm curious what your opinion/analysis of the concept of Active Mass Balance Auto-Control or AMBAC introduced in Mobile Suit Gundam would be. Basically, AMBAC is the primary means for mobile suits, the giant robots used in both space and ground warfare in the setting, to reorient themselves in space and involves utilizing the angular momentum from swinging their mechanical limbs around to adjust their orientation while moving along on any given trajectory. It essentially works similar in principle to a momentum wheel, but unlike a momentum wheel, due to their variable geometry a spacecraft utilizing AMBAC is capable of shifting its center of mass outside of itself so it can perform more complex maneuvers while conserving delta-v.
One issue that Scott Manley highlighted about space fighters is that the thrust of turning (pitch, yaw) is usually depicted as way more than the main engine So if you wanted Star Wars style dogfights with real space craft, you'd need your thrusters to be several times bigger than your main engine
i have allready done that in a sci fi space game called avorion allready with them very big rcs thuster clusters untill the main enegine are needed. shure it might be a flying brick but its a very fast and menruvable flying brick when realstic pisces are involed! it is also like very very very big!
Yeah this is what bothers me about a lot of spacecraft. So often they keep the main engine burning, struggle to pull up, and turn in a big arc . . . using what force exactly? This isn't an aircraft!
@@skylark6167 well in battletech space units for the most part the main engine on space battltech units is bacly both a reactor that prrvides power and alot of plamsa for the engines. these are for battletech dropships, warships and aerospace figthers. these battletech aerospace enngies also do porvide power for rcs that are both chemcal but also plamsa arcjet and plamsa thrusters for mnuivering thrusters as well. but the battletech K-F ftl drive doesnt use any fuel but is just only actaly pasvly recarged by both solar radation from the nearest star or if there no actral star in the sisitem it is in then it recharges from backgronud coismic radation instead. but howver the later is at a some what of slower rate but its still far faster then any startrek ship thats not a borgcube using transwarp that is.
@@skylark6167 well while you can use very large rcs thrusters but there also a real life easer way of alowing space ships to turn and rotate with just using big control moment gryoscopes+ Reaction wheels that can also work for just makein starships turn and rotate wihout needing so much fuel consuming rcs thrusters. you comibe those with realy big main thuster engines and that will save alot of fuel.
Fun fact: Buzz Aldrin literally wrote the book on maneuvering in orbit: _Line-of-Sight Guidance Techniques for Manned Orbital Rendezvous,_ Edwin Eugene Aldrin, Jr. Major, USAF. 1963.
Another way I've put it was that you throw mass around violently. You can throw more mass or more violently (or both!) to achieve more thrust, but you start running into walls of either running out of mass or the reaction getting so violent it explodes. This is one of the trades made by things like plasma or other electric drives: they throw a tiny amount of mass very very hard in order to make the mass last longer since it's difficult to refuel. Engines also have issues with sustained reactions, as they can begin to overheat. One thing I liked was the idea of a center mass engine with relatively low thrust but could be fired continuously, with outboard 'combat thrusters' with high performance, but need frequent cooling down breaks or they'd overheat.
Gundam does neat twist on the reaction wheels. the "AMBAC Auto Mass Balance Computer" which uses the Mobile suits limbs to change which way its pointing with out using propellant
you could always hand wave naval/plane spaceflight as simulated with just computers and RCS blasting all the time constantly and at ridiculous strength which is already done by hyper compact and efficient remass (though, maybe that's why explosions are so violent...). I do like when space opera settings do occasionally acknowledge newtonian physics in edge cases though. Like Poe in TLJ, or when Gundams are maneuvering slowly. SBY's inclusion of RCS systems in designs and in some shots is also very cute, especially in the context of their very naval based designs.
Brief explanation/expansion on the last bit of orbital mechanics; What you do Now changes your orbit on the opposite side, 180 degrees from Now. If you burn forwards along your orbit (we call this prograde) the height of orbit goes up. On the other side of the body you're orbiting. But once you've done a complete lap, the height were you did your burn is the same. If you burn the opposite way, backwards, i.e. slowing down (retrograde) your orbit lowers. Again, on the opposite side from where you are. So if you are in a circular orbit and want to go to a larger or smaller circle, you need two burns. The first one makes your orbit oval, then when you're at the other side, you make it a circle again by changing the orbit where you did your first burn. That's why if you just point at something you want to meet up with ends up putting you further away. You're changing your orbit to be different to your target, and as you and your target continue along their respective orbits you drift apart. What you need to do is kill your relative velocity. If your target appears to be coming right at you, what you do is burn *away* from it. And yes, it's counter-intuitive, which is why even NASA had problems with it to start with.
It's just amazing that Ken Burnside was able to come up with a playable table-top.3D vector movement game (with a big assist from Tony Valle). I just player against a guy who had been away from the game for *eleven* years and he only had on question about movement (which way the numbers on the pitch tracks ran).
as a big enjoyer of Kerbal Space Program and realistic sci-fi there was little new for me in this video, but I can confirm that to the best of my knowladge this is all very accurate
I read, some time ago, that in B5 the Omega-class destroyers were going to use realistic flight patterns. However, people found it confusing because of the rotating gravity bays: the engines would gimbal up or down in order to turn the ship left, or whatever. (It's been a _long_ time since I took physics, and don't remember how to figure all that.)
On the topic of long-distance journeys, one of my issues with The Expanse is the whole "flip and burn" maneuver. If you're burning for days, taking 5 minutes to flip the ship *while under thrust* will be hardly noticeable, and the correction needed is going to be within the margin for error of navigation anyway at that point in the journey. There's absolutely no need to subject the entire ship to zero g. And actually worse than zero g, because objects will float around differently depending on where they are in the ship.
I'm pretty sure for a flip and burn stuff can be secured so its doesn't just fall. And you'd be strapped in a chair most likely. But you do realise that not cutting out the engine and rotating causes the ship to fly around the place, which will need another burn to correct?
@@floseatyard8063 For a 2 AU journey, with the flip after 1 AU, at 1/3 g: The deceleration will take about 90 hours. If you flip such that you add the equivalent of 5 minutes of lateral acceleration, you have added about 900 m/s of lateral speed. To cancel out that lateral speed (and arrive at the same spot you would have without it), you would need an acceleration of 0.0005 g over the remaining travel time. Your thrust vectoring will have to compensate more than that for someone walking around the ship.
In the expanse the ships are actually "on the float" for a time in the middle of their journey to save reaction mass, especially for belters who have older drives/ can afford less fuel
A note about the efficiency of rockets. High velocity remass is more MASS efficient, it is less ENERGY efficient. Conservative of momentum means doubling the remass velocity means half the mass is needed for the same acceleration but the kinetic energy equation shows that halving mass and doubling velocity takes twice as much energy.
9:03 an interesting way ive seen this done is in elite dangerous, where realistic physics DO apply, but your ship has a built in flight assist that automatically manages the thrust to allow you to fly it like an aircraft, since essentially, instead of you controlling the thrust, you decide what movement you want to make, and the assist controls the thrust to make it happen. this also has the benefit of being able to switch that assist off, and fly purely according to newtonian physics, allowing for manuvers that are otherwise impossible, regularly being used in combat for the extra manuverability, and the ability to travel in any direction relative to a target while keeping forward facing weapons aimed at the target, such as how AX pilots sometimes use a technique known as cold orbiting, where they reduce heat signature to make themselves harder to detect, while flying sideways relative to the target and circling it, mimicing an orbit (the ships thrusters replace gravity in maintaining this orbit)
It’s always interesting the physical controls (sticks, keyboards, pedals) that get used. Cars basically only care about two of the six degrees of freedom (yaw + forward/back) with you hands handling steering and your feet handling acceleration/breaking. Air planes generally only care about four (yaw, pitch, roll and forward/back) with one hand handling pitch and roll, the other hand handling thrust/speed and your feet handling yaw. Helicopters are interesting because they work like airplanes except rather than your thrust handling forward/back, it handles up/down. So, if we wanted to control a space ship, we would need some way to handle two more inputs. I’m sure there are designs for controls that do this, but I’m not familiar with any of them. I’d be really curious to know how any of them would work along with the ergonomics of them.
A primer in Orbital Mechanics courtesy of a Larry Niven book about Trees: Forward is Out, Out is Back, Back is In and In is Forward. Relative to something that has matched your orbit: If you accelerate forward, the size of your orbit expands, pushing you out. If you accelerate outwards, you move higher. The distance you now need to travel within your orbit expands but your speed does not so you move back. Think record player inner vs outer velocity. If you accelerate backward, against your orbit, it shrinks. Maybe to the point where you don't miss the ground this time around. If you accelerate inwards, your orbit shrinks. Keeping your old orbital velocity, but having less 'ground' to travel, makes you speed up.
I'm a reader of Freefall and quite a while back, we had a discussion about controlling the Savage Chicken, the hero ship of the comic. I proposed that the the strongest engines pointed aft. Less-strong ones pointed for and still very strong ones pointed down and I argued that that might make banking make sense as you roll and then pitch rather than yawl as the M.F. does but in reverse (as they tend to pitch THEN roll). I was ignored as well as my I thought innovative and almost realistic design for the motor itself which I called a Thorn Thruster. Eh, I probably deserved it. ;)
It's worth noting that orbital mechanics was the PhD thesis topic of one Dr Edwin "Buzz" Aldrin. You might have heard of him. One fairly straightforward way to get a basic grasp of orbital mechanics is to consider what your thrust is doing to the entire orbit. Imagine your orbit is like Larry Niven's Ringworld. If you burn your engine with the capsule facing "forwards" (prograde) in its orbit, you add energy to the orbit, which makes the orbit higher. Higher orbits are slower than lower ones, so you use this if you have overshot your rendezvous target. If you do the opposite (thrust while the capsule is facing "backwards", or retrograde thrust), you remove energy from the orbit, making it lower and thus faster. (In the Ringworld analogy, this would be like stretching or shrinking the ring.) If you thrust towards or away from the centre* of the orbit, you move the entire orbit in the direction your capsule was facing (assuming you use your capsule's main engine). If you are in a low earth orbit, this is usually not a good idea, as you may find yourself entering the thicker parts of the atmosphere half an orbit after you applied the thrust. If you thrust to the left or right of your capsule's direction of travel, you will change the angle of the orbit relative to Earth's equator. (Or, indeed, relative to any other planet's equator, depending on where exactly your spacecraft is in the universe.) This is an oversimplification, with a lot of the subtleties elided over, but it's a good, intuitive (-ish) starting point before you go getting into all of the calculus. * Since all orbits are ellipses, there are actually two centres, known as the foci of the ellipse. ("Foci" is the plural of "focus".) In many of the orbits used in historical crewed spaceflight, the two foci were so close together that it made little difference.
I never really got the higher orbits are slower part though. like slower how? I play KSP so I understand that if you're in a higher orbit a space craft in a lower orbit "behind you" will catch up to you but whenever you start burning prograde your orbital speed increases. so how is that going slower? (like a higher orbit has a longer orbital period compared to lower orbits but you are going faster around the planet right?!)
@@zwenkwiel816 - it's not only the orbital period of a higher orbit that is longer. The actual speed of the vehicle / moon / whatever relative to the planet is slower. My understanding is far from complete, but this explains how the first attempt at orbital rendezvous in the Gemini programme had completely counter-intuitive results. Although, from on board, it looks like the two vehicles are static, they're still travelling at about 11 km/s (give or take a bit) relative to the Earth's surface.
@@nigeldepledge3790 but then what exactly is this orbital velocity I see on my Navball in KSP? cuz that definitely increases as I burn prograde and to get in a higher orbit you just "add" delta-V to your trajectory which basically means adding speed right?! and then when you enter an atmosphere you're going a lot faster if you enter from a high orbit.... (like If I re-enter Kerbin's atmosphere straight from the mun I'm going way faster than if I'm coming from a low Kerbin orbit.) this shit is confusing, no matter how I think about it I still see it as going faster XD (like most of the time in KSP I don't even know why I'm doing what I'm doing. sort of got an intuitive feeling of orbits and rendezvous' and everything by just playing a lot and experimenting)
@Zwenk Wiel - the higher re-entry speed from a higher orbit is because you started at a higher point in the planet's gravity well. There was more gravitational potential to be converted into speed on the way down. I have an idea why the KSP speed indicator reads a faster speed when you burn prograde. It's one of the details I omitted to keep things simple. Strap in: this may take a while. If you're starting from a circular (or near-circular) orbit and you burn prograde, you lift the apogee of the orbit. The perigee, however, remains at the same altitude. The point at which you made your burn becomes the perigee of a more elliptical orbit. You have raised the apogee altitude and increased the orbital period; and you have decreased the orbital velocity at apogee, but the speed at perigee does indeed increase. An orbit that is highly elliptical is characterised by a large difference between the speed at perigee and the speed at apogee. This is analogous to the path of a stone if you throw it upwards at a steep angle : its velocity decreases as its height increases, until it's moving only slightly at the top of its arc (and that is just the horizontal component of its velocity, as its vertical velocity is momentarily zero). It then speeds up again as it descends back to the ground. Any object in an elliptical orbit will travel faster near perigee than it does near apogee (or, to generalise, I should say periapsis and apoapsis, because apogee and perigee refer only to orbits around the Earth). This is in accordance with Kepler's third (I think) law of planetary motion : that equal areas are swept in equal times. When you burn prograde or retrograde in an orbit, you change the velocity at your current position of the orbit, and change the altitude at the opposite point of the orbit. This is how you might make a Hohmann transfer orbit to get from Earth to Mars: you burn prograde (thinking heliocentrically here) for so long that your orbit's aphelion matches the position of Mars's orbit. When you arrive at Mars, you would burn retrograde to enter an areocentric orbit, but if all you wanted to do was match your heliocentric orbit to that of Mars, you would burn prograde to lift your perihelion to match Mars's orbit. Sometimes, it actually *is* rocket science.
I realise you were probably simplifying for the general public, but (most) watercraft and aircraft don't generate thrust by sucking in the surrounding fluid and pushing it out the back. Propellor driven craft use lift to generate thrust (the propellor is just a bunch of wings which are spinning through the fluid). Water jet propulsion is the main exception to this, as it literally does suck in water, then shoot it out the back at higher pressure. This system is a relative rarity though, as it's expensive and doesn't work as primary propulsion for large ships. Aircraft jet engines don't work this way though, as they inject fuel into the air supply and ignite it to generate thrust. Simply firing the air out the back would not generate enough thrust for passenger planes or military jets.
Get "Designing the Perfect Space Fighter - A Spacedock Reference Book" here!
www.patreon.com/posts/77243474/
I'm interested in your book - but I'm not going to join patreon just for that.
@@21stcenturyguy25 I agree, especially after patreon started booting people based on what they talked about. @spacedock if the reference book was available somewhere else, even for a slightly higher cost, I might consider that.
A guy I used to work with who was in many ways just another junkie you had to be very aware of at work to avoid getting hurt. He always brought up some amazing questions that would really make you think twice. Once he asked if you could hold a gun out the window of the space shuttle on takeoff and shot a bullet up, would it pass the shuttle or would the shuttle pass the bullet when it left the barrel? Another time he asked if you filled an elevator shaft with gas in the bottom and cut the cable with a spark plug set to fire when it fell down would the elevator fly to the top of the shaft like a piston in an engine? Sometimes this guy really freaked us out with his ideas.
The beauty of physics is that you can have any configuration you want and the only things to worry about are materials engineering and placement of maneuvering jets. So you could in fact build a flying saucer or a space plane or a Constitution-class light cruiser and it would work as long as your metallurgy was up to par.
(In other words no, you guys and Tyson can go kick rocks with your treatises on design.)
Okay, random thought, but I just realized with physical projectiles as the primary weaponry any mass battles would result in the futuristic version of today’s minefields.
With today’s technology our weapons are firing thousands of rounds per minute. A big enough battle and enough guns, we’re going to see clouds of projectiles heading out in every direction for an infinite amount of time--> just armor piercing bullets zooming across space for near eternity.
“Why is the ship turning around we’re only halfway there?”
-Commander Shepard
That's actually a proper thing in the Mass Effect lore, but the cutscenes just stick to the "traditional" way of depicting spacecraft.
- hoojiwana from Spacedock
@@hoojiwana yeah but the traditional way is cooler and makes for better looking space battles and travel for a lot of people. Unless you’re a hardcore space nerd it’s a bit difficult to appreciate more scientifically accurate depictions of space combat and travel.
@@awesomehpt8938 a lot of people make this excuse. i disagree intensely. I think audience hunger for new things to watch and digest. thats the reason why tropes and cliches tire us out, and only good writing that subverts expectations really gets praise. If the science nerd method of travel and combat were used more often, people would catch on pretty quick, and think it's cool they learned something new and REAL. Not to mention the storytelling advantages that such uniqueness can present to the narrative.
@@hoojiwana I square that circle by assuming they can “scale down” the drive as you approach the destination, shedding speed as your mass approaches what it should be. So you accelerate most of the way to your destination.
@@ericaugust1501 For me, one of the coolest things about The Expanse was real world physics(RIP Manéo, oyedeng beltalowda), especially the battle scenes. I still like the Star Trek battleship type scenes as well, but the physics completely set The Expanse apart from other sci-fi.
I experienced a big wave of respect for the creators of the BSG reboot when I saw small attitude thrust jets firing on the Vipers to help them maneuver in space when I first watched the series. Although it was done before in scifi, watching Starbuck fly laterally as she pointed her Viper and fired a strafing run on the Resurrection Ship was solid gold.
What do you hear?
@@MonkeyJedi99 Nothin' but the rain.
@@swordmonkey6635 Then grab your gun and bring in the cat!
@@swordmonkey6635 Then grab your gun and bring in the cat.
@@graveyardshift6691 So say we all.
It's wild that NASA had to actually try and fail first to figure out orbital rendezvous mechanics. KSP and all the accessible information about orbits nowadays make it seem much more intrinsic than it actually was for people at the bleeding edge of the field.
Also, I always appreciate the "have fun with it" disclaimer at the end of videos like these. It's encouraging to see real-world principles being broken down and offered as tools for a creator rather than hard rules and must-haves to create the perfect setting or story.
I agree. I actually love that The Expanse went for hyper realism. It's a fun take and nice to see. But you can have non-realistic too. Both are valid for entertainment. Only thing I ask for in an IP is consistency with thier own rules.
@@forestwells5820 Yes! Consistency is the most important, even if there are space wizards once you show the audience how space battles work in a setting changing it around just because you can just makes people lose investment.
@@forestwells5820 did you reply to a wrong comment?
@@NoNameAtAll2 nope. I'm agreeing with the second half of this one.
@@forestwells5820 but the comment said nothing about Expanse?
I'm a spacecraft propulsion engineer and fluid dynamicist with NASA, and this is an excellent explainer. The propulsion stuff was great, the attitude control stuff was great, the orbits stuff was understandably minimal, but really an all around awesome video. Accessible to lay viewers, gets the details right, and isn't patronizing to expert viewers. Well done!
If you're continuing this as a series, I think an important core topic is the tyrrany of the rocket equation, or more generally the idea that it takes propellant to bring propellant, leading to an exponential problem. This tyranny and the resulting all-importance of deltaV budgets absolutely dominates all aspects of rocket and spacecraft design, mission planning, and CONOPS. Not as flashy of a topic as fun flavors of far future fission and fusion propulsion, but definitely introduces and motivates why it is so important to chase the high efficiencies those future propulsion concepts promise (and why it is important to keep pushing for nearer future improvements like Nuclear Thermal Propulsion and Ion Propulsion).
whats your take on issac arthurs channel specifically his mini series of vids on becoming a space faring civ?
The rocket equation problem was well demonstrated in the movie Hidden Figures.
Could there ever be something like the Heisenberg fusion drive in The Expanse? A huge thrust to weight ratio, a slight miscalculation and someone feels ever-increasing g as the spacecraft gets lighter and lighter.
Well put. I am not in the aerospace field now but got my BS in Aerospace Engineering from ERAU back in 1992. I remember being required to calculate the mass of propellent needed to get a bolt into orbit and then having to break it out into stages to get the optimal solution. Gravity is a bitch.
This is a fundamental problem of all logistics usually phrased as, "Everything that can transport food also eats food."
Famously, the preindustrial armies that were most effective had excellent logistics.
I love any time gundam gets mentioned for its attempt to be realistic even with giant robots
One of the amazing things about the NASA fact is that later-moon-lander Buzz Aldrin wrote his PhD thesis on "Line-of-Sight Guidance Techniques for Manned Orbital Rendezvous" - and was dedicated to "the crew members of this country's present and future manned space programs. If only I could join them in their exciting endeavors." - Six months after finishing his Doctorate, he was selected as an astronaut. At that point, Gemini 4 was already in the late stages of planning/training, so by the time Aldrin was "fully up to speed", it was too late to assist on Gemini 4. He absolutely was involved in all future rendezvous planning.
The first time you turn off flight assist in Elite Dangerous really catches you by surprise just how different an atmosphere makes.
For basic 6-degree flight control in zero-G, I've been impressed with how Elite: Dangerous handles the physics. If you choose to fly 100% manually, the game gives you complete freedom in every axis and your spaceship behaves as it should based on its mass and the strength of its various thrusters (for example a given ship may be more responsive in roll than it is in yaw). The game does limit you to a maximum total velocity to limit player exploits, but otherwise it's just as you'd expect from Newtonian physics. If you go to an external view, you can also see the various thrusters firing based on your control inputs.
On top of that, there are various assists that you can engage, such as a general flight assist package where a computer juggles all 6 degrees to create a "fly-where-you-point" behavior that's more intuitive and simplifies control inputs, and another assist that auto-syncs your ship to the various rotating space stations you can dock with. If we get to the point where spacecraft are buzzing around like aircraft are today, I think computer assists like that are definitely going to be a thing.
The *BEST* explanation for orbital mechanics I've ever read was from Chuck Yeager's autobiography. In it, he describes going out into a desert in a jeep, turning the steering wheel to the left, and then, using a lot of rope, lashing it down so that it could not move at all. When you start up the jeep, it will go in a big circle; the faster you go, the bigger the circle. He and another pilot each had a jeep and their only control was the throttle, and they practised doing rendezvous.
When I started working on a Space Opera setting for an RPG, I pretty early on decided to base space combat on early 20th century cruisers.
They don't do any dodging or fancy maneuvering and simply keep slugging cannon shells at each other from a long distance, more or less just hoping that they will land critical hits first. This makes things so easy for me.
That's similar to a few books I've read handle it. Two forces each charging at each other around, say, .1c each and combined speed of .2c, dump ordinance in the few milliseconds you're in range, next few minutes assess your losses and damage, then next few hours maneuvering around for the next charge
Though i guess after writing all that you actually mean they just sit and pound on each other, kinda like.... most space movies actually
How do you balance this with - I would assume - the increased lethality of the weapon systems used?
Realistically, you'd expect space warships to be eggshells with sledgehammers. The battle will be over the moment the first hit with a nuclear warhead is scored.
Battletech actually defines the two types of black-water engagement as the Fast Pass, and the Broadside Battle. The former usually happens in transit, and requires computer-assisted targeting, since no human has fast enough reactions to make the required shots when everything is zipping past each other at fractions of the speed of light. Its also utterly terrifying, as you have to just sit there, waiting for the moment of contact, hoping and praying you've got either the better fire plan, or better firepower, or just that the enemy hasn't locked on to you...and then its all over, before you can even take a breath.
The second is a more set-piece situation, where the two forces maneuver to be at a halt relative to each other, and then maneuver to gain firing advantage within that frame of reference. Ironically, whilst the two forces may be halted relative to each other, the "battlefield" they're in could be travelling at a fraction of the speed of light relative to the local star, but I'd be more inclined to think that this is more of a situation of attack and defense around a (relatively) stationary objective.
Might be better even to base off early 20th century naval combat, where engagement distances were so long ranged maneuver was almost pointless for cruisers and dreadnaughts, and only smaller frigates were going to be doing much in the way of tactical movement. Plus then you have the fun of destroyers being so small and fast that capital ships couldn't actually depress the guns far enough to shoot at them.
I think the expanse does the best job at predicting future space engagements. They just fire tons of nukes at each other. They fire nukes at the nukes to defend against them. Occasionally they use railguns. I don't think it's realistic ships getting destroyed by PDC's I'd imagine ships in the future would be heavily armored with a large railgun and lots of missiles. Similar to modern day tanks development process of increasing armor thickness and then increasing gun size. Lot's of maneuvering in fights in hopes to throw off the aggressors targeting solution for projectile weapons.
BSG does this excellently- I wish there were more series like this
The Expanse.
Babylon 5
Well a new BSG has already been announced but nobody really knows if it's a reboot, prequel or sequel.
@@Alejandra-cv7rj Another BSG beside the 2003 reimagine version?
I hope they focus on the First Cylon War, where Galactica was at her prime, like what we saw in BSG: Razor.
@@AlexSDUmost probably it will focus more on Adama’s gender identity as a strong lesbian black woman and Caprica 6 struggle with racist humans that don’t accept her as an equal
This is one of the many reason why I love this channel. I've been working on a sci-fi book the last few years and mapped out a way to introduce these concepts into a story that the audience can understand. I've always decided not to use artificial gravity and have some of the ships use gimbaled decks for when transitioning from orbital to flight and landing to space flight. It really adds flavor to a story instead of just handwaving away gravity with artificial gravity.
The thing I always find interesting about orbital mechanics is how counter intuitive it is. If you try and deorbit something by pushing it down towards earth. It will speed up, pass in front of you, slow down and then hit you on the head. To actually deorbit you have to slow down by thrusting forwards. In Gemini, by thrusting right at the target he ended way above it, without ever inputting any vertical thrust.
You can deorbit that way with enough thrust, but it would be inefficient and you'd be belly flopping into the atmosphere.
I love this kinda take that blends-in some realism, but doesn't require 100% accurate physics nonsense. Its good to see it gaining popularity and acceptance in the writing and reviewing spaces.
About that part with using a gun as propulsion... never forget:
"A reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive." - The Kzinti Lesson, Larry Niven.
Even back in the 90s shows like Babylon 5 and Space: Above and Beyond used RCS thrusters to maneuver their fighters in space and conserved momentum with the ship able to point in a different direction than it was moving. I really appreciated that attention to detail
B5 did a reasonable attempt. Space still did the engines constantly one airplane like thing for the most part.
@@TheEvilmooseofdoom It's true that they ran their engines constantly on S:AAB, but I did appreciate that they showed RCS thrusters firing when they maneuvered and they did occasionally do moves like cutting thrust, doing a 180 maintaining their vector, and then firing at an enemy that was tailing them.
B5's 'Starfurys' were shown in some amazing fight sequences... it doesn't hurt that the very ship-design, with it's prominently mounted RCS engine nozzles and their blast-flaps, really hint at what they had in mind for it's operational realism.
Its amazing how even NASA experienced the "first kerbal orbiter docking" issue, you think you can just point at the other vessel and go but it simply doesnt work that way
Most realistic space craft maneuvering I have seen is from the Expanse
Argreed!!
we think
What about the Starfury from Babylon 5? Not that The Expanse is at all bad, I just think B5 did it better.
@@Voltaic_Fire The Expanse has 100% realistic maneuvers including actual orbital mechanics and realistic flight times. B5 doesn't. Not even remotely. Not sure why you would even think so. B5 is very space opera even if the spaceship designs of the humans are pretty realistic.
@@XMysticHerox I was thinking of the Starfury specifically, not the B5 universe as a whole.
I love when 3d space sandbox games (like avorion or space engineers) do exactly this, where it's realistic space movement and you need to account for basically everything. Getting a hands on experience placing your own directional thrusters really makes you appreciate the art.
That Nebulous Fleet command music in the background, nice.
Speaking of, I wonder if they're ever going to make any videos about it?
Too bad that game fails to deliver realistic space combat and instead it settles for WW2 naval warfare with a black background. I hoped for more when it first came out.
Yes please!
I kind of bounced hard off the gameplay in it and the heavy micro it seems to require so probably not. We do try to put it in now and then though such as with the OSP plasma weapons!
- hoojiwana from Spacedock
@@hoojiwana Ah well, it's not for everyone. I feel like the micro is a little less intense if you use a ballistics-centric fleet instead of a missile one, but it's good to know you guys try to talk about it occasionally!
@dragoscostache4 it's intentionally like that because honestly
Realistic space combat would suck. Moving in the triple digits of speed, never seeing your opponent, and if your engines get taken out congratulations you are now heading hundreds of thousands of km away from the battle.
In older Star Wars canon, there is something called an aether rudder, which is based on the old science that there is a medium in space that lets electromagnetic energy move. The rudder would use this medium to turn.
For more modern lore, vehicles like the X-wing got RCS, gyroscopes, thrust vectoring, etc.
Aetheric rudders male more sense for Star Wars. Yes, you COULD explain their maneuvering with RCS and stuff, but it becomes way more effort than it's worth. Just accept that they can produce drag and exert force on the fabric of spacetime (not entirely farfetched since they have antigravity and such) and suspend your disbelief about the fighters not following Newtonian paths.
@@sethb3090 Wasn't hating on Star Wars for this. Just adding to the knowledge.
As someone 7+ years into KSP, this is an _excellent_ entry level explanation of an extremely complex topic.
+1 for the footage from Copenhagen Suborbitals and Nick Stevens too
I'm loving the inclusion of the For all mankind clips and such recently
I'm loving these videos! They're helping me and a lot of other people write some great stories!
“I’ll try spinning that’s a good trick”
-Darth Vader
"falling sideways so fast, you miss the ground.." I love it.. LOVE it!!!!
I always loved the Starfury from B5. So much so I still have a model of it!
It was such a good design NASA investigated the design!
KSP is the best way to learn orbital mechanics.
Certain science fiction writers do manage to provide an excellent grounding in it. Larry Niven in particular, in his Smoke Ring novels and The Descent of Anansi.
I think it genuinely is, theres nothing like hands on experience for helping you really *understand* something, compared to just knowing about it.
- hoojiwana from Spacedock
@@DrakeAurum you could write whole libraries full of stuff about orbital mechanics I'd never understand it like I do when I play KSP (and I still barely understand anything XD)
@Nikita Nazarov principia
Also, already being good at rendezvous and docking in KSP made adapting to Flight Assist off flying in Elite Dangerous.
In a sci-fi setting where artificial gravity and other gravitational manipulations are available, you can also maneuver by keeping the thruster and shifting the center of mass instead. E.g. If your main thruster is in the central axis of the ship, and you can achieve that one side or wing becones considerably heavier (higher inertia) than the other, the thrust vector will not align with the center of mass and your ship will turn.
could also create a gravity-well in the direction you want to move and have said grav-well move with the craft with similar gravitational manipulations.. SnG's Chamber did effectively this if i recall.. could even do it planet-side..
@@niteriderevo9179That's actualy an (unintended) means of propelling your ship in Space Engineers.
@@VoxAstra-qk4jz i know, artificial mass blocks and grav-gens, is pretty efficient, too..
@@niteriderevo9179 fun fact, the check for merge block magnatism only goes one sub grid down, so a merge block on a piston on a rotor can push itself against the main grid super energy efficient and incredible acceleration, even in a gravity well
For exotic propulsion methods you could look at Honor Harrington. The Impeller Wedges in that series are very interesting.
Think Alcubierre drives.
@@wbrennan2253 for Honor Harrington? Not really, because both of the stress bands are behind and above the ship.
@@chaingun1701 above and below, relative to the deck orientation, and deeper (more open) at the front. The goal seems to be a local change in space/time to allow greater acceleration. Some inertia gets dumped to the wedge, too.
@@wbrennan2253 yes
I LOVE playing KSP because it forces you to understand these concepts to play the game.
Can not wait for more the advanced propulsion videos!
I just want to say how much I appreciate you including the source for every one of your clips. Thanks!
There's an old Jeff Minter game (actually a mini-game) called Hallucin-O-Bomblets, where your ship can only rotate on the spot and shoot, and shooting causes you to move in the opposite direction to the direction of fire. Probably not a method of propulsion people would appreciate IRL, but not much madder than Project Orion.
First time i watched the re-imagined BST and saw the Vipers pull those crazy cool realistic manoeuvrers ....
"Falling sideways and missing the ground. "
The spirit of Douglas Adams smiles down.
it's always good to see some Vipers flyin'
What do you hear?
Nothing but the rain!
Both real and fictional
Using the Wall-E fire extinguisher space flight as your example for reaction control systems? A man of culture I see! 😄
KSP is fantastic for teaching orbital mechanics and Space Engineers / Elite Dangerous (with flight assists disabled) are fantastic for teaching newtonian flight physics.
With Space Engineers allowing for complete control when designing spacecraft I learned a lot about how small scale battles would actually occur.
If your vessel is big, armoured and full of guns the simple "sail past the enemy with gimballed guns" is super effective
If you constrain the design though by limiting power outputs, and number of guns to be quite low you end up with something that sort of blends a BSG Viper with The Expanse's Roci:
Big engine to push forwards, only small ones for lateral adjustment - and most weaponry also pointing forward, maybe a gimballed gun for defence.
Fast gimballing, to change directions quickly
Small frontal cross section, and relatively light weight.
Where speed and lateral movement are your best defence, you can turn off flight assists, burn in at an angle slightly off from your target then when within gun range you turn to point at the enemy and keep burning the primary engine. This makes you a small target to the enemy with high lateral speed, your guns are pointed at them nearly the whole time and your main engine causes you to arc around them in an orbit.
Like if you put a weight on a string and spin it in a circle, only instead of using string the same force is provided by the engine pointing perpendicular (radial out) to the orbit
Oh man, having the Nebulous soundtrack kick in right off the start made me Very happy
I was not expecting to see Zephyr One from agents of shield in this video!
I really love realistic space combat and I’ve had a lot of fun playing Nebulous Fleet Command becuase it has that same feel, I really love if spacedock check that game out
This is the quality content they made RUclips for, thanks
Love the Kerbal Space Program usage. My favorite game ever on one of my favorite channels!
Video suggestions:
Gravitational weapons explained
Types of sci fi power sources
I absolutely love it when you use gundam footage as an example. Though the AMBC system of mobile suits would be a good example of the flywheel systems.
A big thing with Star Wars in particular having different mechanics for moving in space, is that space in Star Wars is not an empty void. There's something called the Aether, (originally mentioned in the now-canon X-Wing books, iirc), which allows some types of starfighters and other ships to use control surfaces to move like a plane.
Actually, I'd love to see a video about intentionally altering physics itself in Sci-Fi. Franchises that do it, what they change and why, etc.
Lost Fleet definitely makes the most interesting use of realistic combat maneuvering of anything I've read or watched so far, including the Expanse. Come to think of it I don't believe it has been mentioned before on this this channel, which is a little disappointing, but on the other hand there's a lot of sci-fi out there.
Oh yeah! That series was pretty good
It's also a book series.
@@EGRJ That's a good point, I don't recall books being mentioned specifically, apart from Sojourn of course. Then again a lot of technologies that haven't appeared on screen have been mentioned. What I'd really like to see is some Lost Fleet battle breakdown videos that youtubers make for Star Wars and other sci-fi. Those are neat.
@@Arashmickey it would make a great tactical breakdown
but boy the premise makes no sense
@@NoNameAtAll2 Somehow... everybody forgot space combat tactics. Which space combat tactics? Yes.
Great to see Gundam getting some love and screen time, on top of an already great video!
I've got a BS in Aerospace Engineering. When it comes to orbital maneuvers, one of the easiest ways I've learned to understand it (outside of playing Kerbal Space Program) is to think of the orbit kind of like a rubber band between two fingers. Every time a spacecraft makes a burn, it's like pulling or rotating the *_entire rubber band_* , not just a single point on it. If you try to stretch it in one direction (like you're adjusting the apoapsis or periapsis), the band narrows in the other direction. If you try to rotate it (like an inclination change), the whole band rotates so one side moves up and the other moves down. You have to plan to make a burn on one side of an orbit in the name of affecting what happens on the other. It's what makes orbits so challenging to understand: you're not "moving where you are" in a maneuver, you're just trying to speed up or slow down to "move where you're going".
THE EXPANSE showed spaceship movements and orbital trajectories much better than most sci-fi. Only 2001: A Space Odissey comes to mind as being better.
I think Babylon 5 (Starfuries) and Wing Commander are probably some of the best examples of this kind of neutonian physics in Sci-Fi. While if you cut throttle in Wing Commander you do slow down, they have full maneuverability ratings for Yaw/Pitch/Roll for pretty much every craft in the games (although WC1 and 2 I think were on a 1-10 scale while 3, 4, and Prophecy actually had actual Degrees Per Second). And I believe you guys already covered the Starfury from Babylon 5 so won't touch on why that fighter is so awesome.
Looking forward to the Orion Drive video and I hope you cover the Medusa sail too
Medusa will be in the same video along with its older sibling.
- hoojiwana from Spacedock
B5 StarFury nailed it. The rest of the B5 vehicles, not so much.
Interestingly, the Omegas were supposed to have a gimballed engines so they could maneuver realistically with the rotating hab module. Unfortunately, it would have taken too much time to explain how thrust works with rotating bodies and why they would burn "down" to turn left.
I think the idea behind those other vehicles (Minbari, Vorlon, etc.) was to show how much more advanced their technology was, as compared to Earth Alliance tech.
"orbit themself involved falling sideways so quickly around an object, that you miss the ground". Amazing explanation 😂
That credit goes to Douglas Adams.
One of the reasons I loved the Fury fighter in Babylon 5 so much. Practical flight - just endless fuel!
The "Eagle Transporter" craft from Space:1999 were the first realistic concept spacecraft I ever saw on Tv. Main forward thrust engines in the back, lift engines underneath, 4 separate drive pods with directional thrusters pointed in all possible directions. I've always used those concepts in designing my own spacecraft. Two bad they didn't have the CGI to show how really maneuverable they were - they were in combat plenty of times, and I always thought when a target is heading straight for one of them, was that the Eagle should wait just before the enemy fired and used it's lift thrusters to move vertically out of range. Since they do a VTOL in gravity fields above the Earth's, they would be powerful enough for some serious vertical lift maneuvering. Just too much two- dimensional thinking, I guess.
-All I could think of with this topic were the space 1999 eagles, also. Maybe it’s just an age thing? It was long before re-imagined battlestar galactica, though that was cool, too.
@@sci-fyguy7767 I still have a few model kits of Eagles, as well as the kit of the entire Alpha Moon base. Still in the box - I have no place right now to set them up.
Nebulous: fleet command OST spotted, very respectful of you to include that
Loving the Nebulous Fleet Command music! 🎉
Full thrust to the halfway point then full reverse the other half.
ETA: I remember one story where the vessel powered towards the enemy. Upon reaching the enemy they flipped, and did a maximum burn which melted portions of the hull and super structure.
I'm curious what your opinion/analysis of the concept of Active Mass Balance Auto-Control or AMBAC introduced in Mobile Suit Gundam would be.
Basically, AMBAC is the primary means for mobile suits, the giant robots used in both space and ground warfare in the setting, to reorient themselves in space and involves utilizing the angular momentum from swinging their mechanical limbs around to adjust their orientation while moving along on any given trajectory.
It essentially works similar in principle to a momentum wheel, but unlike a momentum wheel, due to their variable geometry a spacecraft utilizing AMBAC is capable of shifting its center of mass outside of itself so it can perform more complex maneuvers while conserving delta-v.
It’s nice to see that your using nebulous fleet command music. It’s a really underrated rts game
The Lost Fleet as a book series leans heavily into realistic maneuvering, pretty much as realistic as you can get.
One issue that Scott Manley highlighted about space fighters is that the thrust of turning (pitch, yaw) is usually depicted as way more than the main engine
So if you wanted Star Wars style dogfights with real space craft, you'd need your thrusters to be several times bigger than your main engine
i have allready done that in a sci fi space game called avorion allready with them very big rcs thuster clusters untill the main enegine are needed. shure it might be a flying brick but its a very fast and menruvable flying brick when realstic pisces are involed! it is also like very very very big!
Yeah this is what bothers me about a lot of spacecraft. So often they keep the main engine burning, struggle to pull up, and turn in a big arc . . . using what force exactly? This isn't an aircraft!
@@skylark6167 well in battletech space units for the most part the main engine on space battltech units is bacly both a reactor that prrvides power and alot of plamsa for the engines. these are for battletech dropships, warships and aerospace figthers. these battletech aerospace enngies also do porvide power for rcs that are both chemcal but also plamsa arcjet and plamsa thrusters for mnuivering thrusters as well. but the battletech K-F ftl drive doesnt use any fuel but is just only actaly pasvly recarged by both solar radation from the nearest star or if there no actral star in the sisitem it is in then it recharges from backgronud coismic radation instead. but howver the later is at a some what of slower rate but its still far faster then any startrek ship thats not a borgcube using transwarp that is.
@@skylark6167 well while you can use very large rcs thrusters but there also a real life easer way of alowing space ships to turn and rotate with just using big control moment gryoscopes+ Reaction wheels that can also work for just makein starships turn and rotate wihout needing so much fuel consuming rcs thrusters. you comibe those with realy big main thuster engines and that will save alot of fuel.
Ok! That thrust vectoring in that Starwars show scene was freaking awesome!
Fun fact: Buzz Aldrin literally wrote the book on maneuvering in orbit: _Line-of-Sight Guidance Techniques for Manned Orbital Rendezvous,_ Edwin Eugene Aldrin, Jr.
Major, USAF. 1963.
I believe that was his doctorate thesis. The other astronauts sort of dirisevely nicknamed him "Dr. Rendezvous".
I really want more video games that use these types of mechanics.
Another way I've put it was that you throw mass around violently. You can throw more mass or more violently (or both!) to achieve more thrust, but you start running into walls of either running out of mass or the reaction getting so violent it explodes. This is one of the trades made by things like plasma or other electric drives: they throw a tiny amount of mass very very hard in order to make the mass last longer since it's difficult to refuel.
Engines also have issues with sustained reactions, as they can begin to overheat. One thing I liked was the idea of a center mass engine with relatively low thrust but could be fired continuously, with outboard 'combat thrusters' with high performance, but need frequent cooling down breaks or they'd overheat.
Gundam does neat twist on the reaction wheels. the "AMBAC Auto Mass Balance Computer" which uses the Mobile suits limbs to change which way its pointing with out using propellant
Woo, new spacedock! Set your G-Diffusers.
Wow, that Battlezone 2 intro music was a blast to the past haha!
Elite Dangerous taught me how terrifying slowing down before reaching your destination can be. Even with the seven second rule!
Once again, good job spacedock!
you could always hand wave naval/plane spaceflight as simulated with just computers and RCS blasting all the time constantly and at ridiculous strength which is already done by hyper compact and efficient remass (though, maybe that's why explosions are so violent...). I do like when space opera settings do occasionally acknowledge newtonian physics in edge cases though. Like Poe in TLJ, or when Gundams are maneuvering slowly. SBY's inclusion of RCS systems in designs and in some shots is also very cute, especially in the context of their very naval based designs.
Brief explanation/expansion on the last bit of orbital mechanics;
What you do Now changes your orbit on the opposite side, 180 degrees from Now.
If you burn forwards along your orbit (we call this prograde) the height of orbit goes up. On the other side of the body you're orbiting.
But once you've done a complete lap, the height were you did your burn is the same.
If you burn the opposite way, backwards, i.e. slowing down (retrograde) your orbit lowers. Again, on the opposite side from where you are.
So if you are in a circular orbit and want to go to a larger or smaller circle, you need two burns. The first one makes your orbit oval, then when you're at the other side, you make it a circle again by changing the orbit where you did your first burn.
That's why if you just point at something you want to meet up with ends up putting you further away. You're changing your orbit to be different to your target, and as you and your target continue along their respective orbits you drift apart.
What you need to do is kill your relative velocity. If your target appears to be coming right at you, what you do is burn *away* from it. And yes, it's counter-intuitive, which is why even NASA had problems with it to start with.
My D&D in space setting combines nuclear fissionr reactors and decanters of endless water for fun effect!
as a D&D DM in a spelljammer campaign, this video is very useful.
I recognize that soundtrack you used instantly. Nebulous Fleet Command should totally be something you make a video on next!
Ironically, 2-D asteroids does a better job of this than most other games.
Came here to say this
The game Star Citizen has a really realistic way of starship propultion/maneuvering
It's just amazing that Ken Burnside was able to come up with a playable table-top.3D vector movement game (with a big assist from Tony Valle). I just player against a guy who had been away from the game for *eleven* years and he only had on question about movement (which way the numbers on the pitch tracks ran).
as a big enjoyer of Kerbal Space Program and realistic sci-fi there was little new for me in this video, but I can confirm that to the best of my knowladge this is all very accurate
Thanks for the detailed explanation of Newton's 3rd, from all of us who thought that "remass" was a real-estate agency! 😉
I will always be thankful to Kerbal Space Program for giving me a basic understanding of how orbital travel works.
I read, some time ago, that in B5 the Omega-class destroyers were going to use realistic flight patterns. However, people found it confusing because of the rotating gravity bays: the engines would gimbal up or down in order to turn the ship left, or whatever. (It's been a _long_ time since I took physics, and don't remember how to figure all that.)
Can you put out a video on how mobile suits use AMBACS to rotate around instead of using thrust vectoring?
On the topic of long-distance journeys, one of my issues with The Expanse is the whole "flip and burn" maneuver. If you're burning for days, taking 5 minutes to flip the ship *while under thrust* will be hardly noticeable, and the correction needed is going to be within the margin for error of navigation anyway at that point in the journey. There's absolutely no need to subject the entire ship to zero g. And actually worse than zero g, because objects will float around differently depending on where they are in the ship.
I'm pretty sure for a flip and burn stuff can be secured so its doesn't just fall. And you'd be strapped in a chair most likely. But you do realise that not cutting out the engine and rotating causes the ship to fly around the place, which will need another burn to correct?
@@floseatyard8063 For a 2 AU journey, with the flip after 1 AU, at 1/3 g:
The deceleration will take about 90 hours. If you flip such that you add the equivalent of 5 minutes of lateral acceleration, you have added about 900 m/s of lateral speed. To cancel out that lateral speed (and arrive at the same spot you would have without it), you would need an acceleration of 0.0005 g over the remaining travel time.
Your thrust vectoring will have to compensate more than that for someone walking around the ship.
@Edward Barton fair enough then. So basically that trip would be straight line, small curve and straight line again?
In the expanse the ships are actually "on the float" for a time in the middle of their journey to save reaction mass, especially for belters who have older drives/ can afford less fuel
A note about the efficiency of rockets. High velocity remass is more MASS efficient, it is less ENERGY efficient. Conservative of momentum means doubling the remass velocity means half the mass is needed for the same acceleration but the kinetic energy equation shows that halving mass and doubling velocity takes twice as much energy.
Good explanation! Not quite what I expected, but still very good.
9:03 an interesting way ive seen this done is in elite dangerous, where realistic physics DO apply, but your ship has a built in flight assist that automatically manages the thrust to allow you to fly it like an aircraft, since essentially, instead of you controlling the thrust, you decide what movement you want to make, and the assist controls the thrust to make it happen. this also has the benefit of being able to switch that assist off, and fly purely according to newtonian physics, allowing for manuvers that are otherwise impossible, regularly being used in combat for the extra manuverability, and the ability to travel in any direction relative to a target while keeping forward facing weapons aimed at the target, such as how AX pilots sometimes use a technique known as cold orbiting, where they reduce heat signature to make themselves harder to detect, while flying sideways relative to the target and circling it, mimicing an orbit (the ships thrusters replace gravity in maintaining this orbit)
5:18 spacedock plays ksp lessgoo
It’s always interesting the physical controls (sticks, keyboards, pedals) that get used. Cars basically only care about two of the six degrees of freedom (yaw + forward/back) with you hands handling steering and your feet handling acceleration/breaking. Air planes generally only care about four (yaw, pitch, roll and forward/back) with one hand handling pitch and roll, the other hand handling thrust/speed and your feet handling yaw. Helicopters are interesting because they work like airplanes except rather than your thrust handling forward/back, it handles up/down. So, if we wanted to control a space ship, we would need some way to handle two more inputs. I’m sure there are designs for controls that do this, but I’m not familiar with any of them. I’d be really curious to know how any of them would work along with the ergonomics of them.
You must like that particular Slo Mo Guys video! (No worries, it's one of my favorites too!)
A primer in Orbital Mechanics courtesy of a Larry Niven book about Trees: Forward is Out, Out is Back, Back is In and In is Forward.
Relative to something that has matched your orbit:
If you accelerate forward, the size of your orbit expands, pushing you out.
If you accelerate outwards, you move higher. The distance you now need to travel within your orbit expands but your speed does not so you move back. Think record player inner vs outer velocity.
If you accelerate backward, against your orbit, it shrinks. Maybe to the point where you don't miss the ground this time around.
If you accelerate inwards, your orbit shrinks. Keeping your old orbital velocity, but having less 'ground' to travel, makes you speed up.
Oh yeah, love the battlezone 2 music 😊
I'm a reader of Freefall and quite a while back, we had a discussion about controlling the Savage Chicken, the hero ship of the comic. I proposed that the the strongest engines pointed aft. Less-strong ones pointed for and still very strong ones pointed down and I argued that that might make banking make sense as you roll and then pitch rather than yawl as the M.F. does but in reverse (as they tend to pitch THEN roll).
I was ignored as well as my I thought innovative and almost realistic design for the motor itself which I called a Thorn Thruster. Eh, I probably deserved it. ;)
It's worth noting that orbital mechanics was the PhD thesis topic of one Dr Edwin "Buzz" Aldrin. You might have heard of him.
One fairly straightforward way to get a basic grasp of orbital mechanics is to consider what your thrust is doing to the entire orbit. Imagine your orbit is like Larry Niven's Ringworld.
If you burn your engine with the capsule facing "forwards" (prograde) in its orbit, you add energy to the orbit, which makes the orbit higher. Higher orbits are slower than lower ones, so you use this if you have overshot your rendezvous target. If you do the opposite (thrust while the capsule is facing "backwards", or retrograde thrust), you remove energy from the orbit, making it lower and thus faster. (In the Ringworld analogy, this would be like stretching or shrinking the ring.)
If you thrust towards or away from the centre* of the orbit, you move the entire orbit in the direction your capsule was facing (assuming you use your capsule's main engine). If you are in a low earth orbit, this is usually not a good idea, as you may find yourself entering the thicker parts of the atmosphere half an orbit after you applied the thrust.
If you thrust to the left or right of your capsule's direction of travel, you will change the angle of the orbit relative to Earth's equator. (Or, indeed, relative to any other planet's equator, depending on where exactly your spacecraft is in the universe.)
This is an oversimplification, with a lot of the subtleties elided over, but it's a good, intuitive (-ish) starting point before you go getting into all of the calculus.
* Since all orbits are ellipses, there are actually two centres, known as the foci of the ellipse. ("Foci" is the plural of "focus".) In many of the orbits used in historical crewed spaceflight, the two foci were so close together that it made little difference.
I never really got the higher orbits are slower part though. like slower how? I play KSP so I understand that if you're in a higher orbit a space craft in a lower orbit "behind you" will catch up to you but whenever you start burning prograde your orbital speed increases. so how is that going slower? (like a higher orbit has a longer orbital period compared to lower orbits but you are going faster around the planet right?!)
@@zwenkwiel816 - it's not only the orbital period of a higher orbit that is longer. The actual speed of the vehicle / moon / whatever relative to the planet is slower. My understanding is far from complete, but this explains how the first attempt at orbital rendezvous in the Gemini programme had completely counter-intuitive results. Although, from on board, it looks like the two vehicles are static, they're still travelling at about 11 km/s (give or take a bit) relative to the Earth's surface.
@@nigeldepledge3790 but then what exactly is this orbital velocity I see on my Navball in KSP? cuz that definitely increases as I burn prograde
and to get in a higher orbit you just "add" delta-V to your trajectory which basically means adding speed right?!
and then when you enter an atmosphere you're going a lot faster if you enter from a high orbit.... (like If I re-enter Kerbin's atmosphere straight from the mun I'm going way faster than if I'm coming from a low Kerbin orbit.)
this shit is confusing, no matter how I think about it I still see it as going faster XD
(like most of the time in KSP I don't even know why I'm doing what I'm doing. sort of got an intuitive feeling of orbits and rendezvous' and everything by just playing a lot and experimenting)
@Zwenk Wiel - the higher re-entry speed from a higher orbit is because you started at a higher point in the planet's gravity well. There was more gravitational potential to be converted into speed on the way down.
I have an idea why the KSP speed indicator reads a faster speed when you burn prograde. It's one of the details I omitted to keep things simple.
Strap in: this may take a while.
If you're starting from a circular (or near-circular) orbit and you burn prograde, you lift the apogee of the orbit. The perigee, however, remains at the same altitude. The point at which you made your burn becomes the perigee of a more elliptical orbit. You have raised the apogee altitude and increased the orbital period; and you have decreased the orbital velocity at apogee, but the speed at perigee does indeed increase.
An orbit that is highly elliptical is characterised by a large difference between the speed at perigee and the speed at apogee. This is analogous to the path of a stone if you throw it upwards at a steep angle : its velocity decreases as its height increases, until it's moving only slightly at the top of its arc (and that is just the horizontal component of its velocity, as its vertical velocity is momentarily zero). It then speeds up again as it descends back to the ground.
Any object in an elliptical orbit will travel faster near perigee than it does near apogee (or, to generalise, I should say periapsis and apoapsis, because apogee and perigee refer only to orbits around the Earth). This is in accordance with Kepler's third (I think) law of planetary motion : that equal areas are swept in equal times.
When you burn prograde or retrograde in an orbit, you change the velocity at your current position of the orbit, and change the altitude at the opposite point of the orbit. This is how you might make a Hohmann transfer orbit to get from Earth to Mars: you burn prograde (thinking heliocentrically here) for so long that your orbit's aphelion matches the position of Mars's orbit. When you arrive at Mars, you would burn retrograde to enter an areocentric orbit, but if all you wanted to do was match your heliocentric orbit to that of Mars, you would burn prograde to lift your perihelion to match Mars's orbit.
Sometimes, it actually *is* rocket science.
I realise you were probably simplifying for the general public, but (most) watercraft and aircraft don't generate thrust by sucking in the surrounding fluid and pushing it out the back.
Propellor driven craft use lift to generate thrust (the propellor is just a bunch of wings which are spinning through the fluid).
Water jet propulsion is the main exception to this, as it literally does suck in water, then shoot it out the back at higher pressure. This system is a relative rarity though, as it's expensive and doesn't work as primary propulsion for large ships.
Aircraft jet engines don't work this way though, as they inject fuel into the air supply and ignite it to generate thrust. Simply firing the air out the back would not generate enough thrust for passenger planes or military jets.
Newtonian physics…. Personally I like the blend FA off in Elite Dangerous. It is not true hard science, but a good compromise.