Starship IFT 4 June Update and Hot Gas Thruster Mode for Raptor!
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- Опубликовано: 1 окт 2024
- Can we turn the Starship Raptor into an efficient hot gas thruster for safe staging without a hot stage ring? And would this allow Starship to land on the Moon? Will Starliner ever fly and what is Chang'e 6 doing on the Moon?
All in this rocket science lesson with a Raptor 9 rocket design homework assignment at the end!
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TSA is by far the smartest space tech channel around. Always enjoy your out-of-the-box ideas.
I love Eager Space also, it's another space engineering channel with dry humor that only engineers would appreciate. :)
Thank you so much!
I'll have to check them out... Thanks!
At about 8:00, are you saying to use 20 Raptors as hot gas thrusters to separate Starship?
If i'm not mistaken, Starship has 6 (or 9 maybe) Raptors. It's the booster that has the 20 engines in the outside ring. Using the booster engine in hot gas mode doesn't seem to make sense. Am I missing something?
I was thinking the same thing. Those engines are also cold for not having started yet, so I'm not sure what he meant by hot gas as if we're talking about the booster engines the whole time.
I was too tired from a long trip. Six of the outside vacuum Raptors on Starship. I did the math on the 20 outside booster engines...
@@terranspaceacademy Just keeping us on our toes and paying attention.
This channel provides a timeless presentation into lessons of rocketry. Thank you so much!
You're very welcome!
This will be used for advanced high school and college lessons.
We hope so! :-)
Always hitting myself with a proverbial "clue by four" that the previous and current Starship rockets are just prototypes.
Very true... Can you imagine a big change to SLS between flights 3 and 4?
Best regard and success to Elon and SpaceX team
Indeed!
Beautifully done and narrated program.
Thank you.
Glad you enjoyed it and thanks for watching my friend.
I had to do a similar cold gas efficiency for single species assessment contingency planning with a bipropellent thruster. We had a blow down system.
Very cool!
The ship's manouvering thrusters aren't hot gas. They are cold gas. Hot gas refers to thrusters that actually burn atleast some of the fuel. Ship just wents it.
Actually, no. Hot gas refers to the temperature of the gas expelled only. Resistojets are still hot gas and there is no combustion.
I'm confused how would the 20 outer raptors push the star ship off the booster? I suggested spinning them without igniting them about a year ago. As long as you stay extremely fuel rich it should be fine as you don't want to create a fuel air bomb. IIRC Mush implied that the Raptor 3s don't have igniters, but it was secret sauce.
Because I seem to have had a stroke... It would be the six vacuum Raptors on the second stage.
Raptor 3s still have igniters in the preburners; Raptor 2s already don't have igniters in the main combustion chamber, according to Musk. My guess is that the incoming oxygen-rich and methane-rich hot exhaust streams from the respective pre-burners meet at sufficient temperature and pressure in the main combustion chamber, that, once sufficiently mixed, they ignite spontaneously...
@@terranspaceacademy it happens
ITF-3 flight data indicates that the specific impulse of Raptor 2 is closer to 300s. This is the main reason for the low payload capacity of the present configuration. Maybe Raptor 3 will fix this.
They went high power less efficiency with the 2... I think the added pressure will let them balance it out for 3.
Looks like June 6. Though with Starliner seeing further delays, I would not be surprised to see that June 6 date surreptitiously slip as well.
It must be maddening for the crew.
I think they should make a raptor 7
That would be very cool
Fifth of June, Starship.
Sixth of June I take beer, and a big speaker to party with the Holy Roller at Victoria Park, London Canada. 80th anniversary of D-Day and the Holy Roller, a Sherman tank landed on Juno Beach June 6, 1944 and rampaged all over Western Europe before coming home to the park for a well deserved retirement.
That sounds absolutely awesome!
@@terranspaceacademy
You haven’t heard my singing voice. I’ll probably get noise complaints!
Enjoyed the video. I am excited for IFT-4. Makes me wonder why they have problems with plugging of the plumbing system. One of 2 potential causes seem likely. Maybe they don't purge the tanks and piping with a dry gas and it is humid in South Texas. Seems like a very trivial problem that any engineer or technical person would pick up on immediately. Or maybe their piping introduces particles. Rusty pipe? I certainly don't have the answers, but clogged filters from frozen condensate seems most likely in my book. Maybe they do purge, but it is such a big ship, they aren't able to get all condensate? Normally, a vacuum for an extended period of time is the most efficient method of drying a system, it is used everyday when AC systems are serviced. The only issue with this situation is it would collapse the whole ship.
I was surprised too... Would there be enough ice to block filters?
Correct me if I'm wrong. But aren't the thrusters on Starship not hot gas thrusters? Aren't they warm gas thrusters? They use the hot gas from the methane and oxygen tanks for Reaction Control. But they don't burn it which is what I always thought was what hot gas thrusters do. They're kind of like mini engines while warm and cold gas thrusters are identical. Just nozzles connected with a valve.
I do think SpaceX should attempt to create hot gas thrusters since they provide considerably more force for less propellant. Yes it would add more weight and complexity, but it's possible the reward outweighs the downsides.
I don't think it would be useful for Super Heavy, but it might be useful for Starship itself since it would eventually be used for long distance traveling
That's probably the best way to describe them...
You and the Everyday Astronaut are my main sources of knowledge about aerospace engineering and the industry.
I just finished high school and my dream is to be an aerospace engineer (specifically propulsion) and your videos has helped me learn a lot.
Thanks for all you do.
Ad Astra Pro Terra🌍.
You are most welcome and have no idea how happy it makes me to hear you say that! If you need some introductions let us know. We have some contacts in the industry.
The issue with your idea for the hot gas is that the booster MUST keep its center engines going to ensure the booster fuel remains settled at the bottom of the tank, and to initiate the separation maneuver. Meanwhile, the ship must pull distance from the booster as fast as possible and that demands exceeding current booster acceleration, which as you recall will be using its inner engines still. So the HGS mode would need to exceed the thrust of the core booster engines of an almost empty booster, and that is just not feasible.
It remains something to be investigaged for moon maneuvering however, but for HLS at least this is already going to be handled by the landing engines
Good point... Still land on the Moon though :-)
You can see how long it takes to edit a video like this in little minor points. For example 20+ hours before this video was posted IFT4 was moved to June 6th, from the 5th. Which clearly would if been missed in the edit phase of production. :) Sometimes it is just lost how much time goes into one of these videos.
I focus a lot on the science and get lost in the details... Story of my life :-)
I'm wondering about pressures in the preburner. With the Oxidizer pump off, the oxygen line would be at the same pressure as in the main tanks, and with the preburner likely running at a higher pressure than them, the oxidizer wouldn't be able to flow correctly, right ?
The oxygen preburner would need to run at a low level.
I need some feedback from you guys. I have an idea about the heat shields.
Look at a heat shield. Let's call the flat top 12 o'clock. Now, rotate it 90° left or right doesn't matter. Looking at the sheild on end. 25% of the way down and 25% of the way up drill or cast in tunnels about 3mm all the way through.
Take a fine braided tungsten wire with fiberglass insolation and thread it through the sheild to the next and so on through all the heat shields. The top of one shield will be lashed to the bottom of the one next to it, and so on. At one end of the wire, there should be a simple spring tensioner that will be covered by a bonded on shield. At the other end, another adjustable spring tensioner. The tension to be calculated. Also ultimately covered by a bonded on shield.
Thank for listening and if you talk to Elon tell him I said
Good luck, Elon, with the launch, and thank you for what you're doing to better mankind.
I wondered about that and did some math on the mass... Quite a bit if you make a "net" able to restrain all the tiles.
CH4 is waaaay worse in terms of greenhouse gas heat-trapping. That's a very dumb idea.
Seriously? I am a firm believer in climate change but one good herd of cows beat that in a day.
I suspect space x will likely scrap all the raptor 2s rather than make anything out of them elon has already mentione that raptor production is relatively cheap compared to most other rocket engines (ive heard as low as a million per unit) sp it most likely isnt cost effective to modify an existing craft to use old stock parts like old raptors. Its probably most cost effective just to scrap them rather than try to make them work.
But it would be so cool! :-)
@@terranspaceacademywhy waste the raptor 2s. Sell it to the rocket power land speed racer gear heads and see what they can do with. 🤣
@@leisureenjoyer1986 it really is a testament to how fast their iterative design approach would be.
@@terranspaceacademy it would be, it could make sense if they sold the old raptor 2 stock off to other rocket companies as well but i highly doubt they'd want to give access to their advanced hardware like that.
Hey Doc, here is my water cooler guess. Once fully operational, Starship will need all the power it can generate to reach orbit w/ payload and over complexity, let alone at stage sep, is not in Elon’s DNA - unless the complexity is reduced to far and requires some addition. Additionally, (with CSI Stsrbase’s Special Report on hotstaging ring jettison out) I am more and more convinced this is why SpaceX is transitioning to the N1 style hotstage configuration. It’s just not as complex. Less than full propulsive landing is an intriguing concept, however, and I could very well see Raptor engineers toy with it once in a more mature phase. Raptor 9 would be an incredible evolution from Falcon and probably much easier to human rate compared to FH, but I feel if anything was really feasible that just human rating FH would be much more cost effective. But damn do I love the sound of a Raptor class of SpaceX rockets!!
Someone had the briliiant idea of making the Starship landing legs the actual hot stage hardware...
@@terranspaceacademy That would be a good idea, however, they would still need to be retractable for reentry. What about liner actuating posts that could retract after stage sep then extend upon landing? They could also be use for leveling as well. Tesla is making their own actuators for Optimus, I’m sure they could whip up some Starship sized ones in no time.
Would still need to keep enough pressure in the oxygen pump to feed the CH4 preburner.
That's true... Running the oxygen preburner at pressurization levels?
All of that math sounds great. But this is a Full Flow Staged Combustion Engine. So what Oxygen is being used to power the Methane turbine if the Oxygen is turned off? A small amount of Oxygen is needed to power the turbine. All that Oxygen flows through one Oxygen pump so a separate valve would have to be used past the Oxygen pump to shut of the main Oxygen flow to the combustion chamber, but the turbine, therefore the pump, would still have to be operating to send Oxygen to the Methane turbine that powers the Methane pump as well as a small amount of Methane to still power the turbine that powers the Oxygen pump, even at a reduced flow. Now, those small amount hot burned combustion products are still going to be sent to the combustion chamber. Lastly, even if you somehow got a small amount of Oxygen to power the Methane turbine, the Methane flowing through the engine would still be at cryogenic temperatures as it flows through the combustion chamber and out the exhaust nozzle, not "hot" gas. The only "hot" gas is from the turbines powering all this flow. Now if you were to plumb a by-pass system to allow the Methane to go around all this, expand into gas then back out the exhaust nozzle, then we're talking a much more complicated system. Not the way Elon designs things. "The best part, is no part". Just my observation, Did I missed something?
The oxygen preburner can operate to pressurize the tank without the engine running... The same should provide enough oxygen to the methane side.
@@terranspaceacademy Don't you need both pumps running to provide Methane and Oxygen to the entire system?
Not so much a net but a 2.5 mm wire half encircling the ship twice per heatshield hight.
Let say one 2.5 mm wire with fiberglass insolation, every 6 inches.
Let's say 45 feet per wire.
It just seems like a big roll of tungsten wire to me.
I live that, what would the total mass be?
Not sure. Let's say about 2000 meters of 1mm tungsten wire. A 3 strand brade would probably work best.
So let's say 6000 meters of 1mm tungsten wire.
I'll find the weight of the tungsten and calculate it and comment you back.
Hot gas thruster mode sounds amazing! Surely somebody at SpaceX is thinking of this, but if not, I sure hope they see this lesson! That could REALLY simplify Lunar Starship!
Back in the Apollo days, there was a development program to upgrade and simplify the J-2 engine. The J-2X developed for Ares I built on that work. But as I understand it, one of the variants had a low-thrust, pressure-fed mode where combustion started before turbopumps, allowing a tap-off of the exhaust gases to spin the turbopumps, thus eliminating the need for high-pressure helium or solid-propellant gas generator cartridges to spin-up the pumps. Also, this pressure-fed mode could run on gas or liquid, meaning that it wasn't necessary to settle the propellant before starting the engines. This was ideal for on-orbit restarts, as it eliminated the need for ullage motors as well. I don't have any knowledge of exactly how the J-2S was going to be able to pull all this off, but it would definitely have been utilitarian!
That's right! They even had an aerospike version way back then... Amazing engineers.
@@terranspaceacademy Yes, indeed! I've had the honor of meeting a few of the Engineers from Apollo and even back as far as Gemini. Brilliant folks!
Hmm.... I'm confused. I understand the concept and the match but how would turning the 20 Raptor Boost engines on the Booster into hot gas thrusters push the Ship away from the Booster? Wouldn't that only reduce the thrust on the Booster (like shutting down all but the inner 3 core engines)? Would it instead be turning only on the three RVac engines methane turbo pumps on and then ramping them up?
Excellent job walking through the math though. I think this is the first time I understood all the numbers. Don't know if I could do it on my own (!) but now Ii think I get more of the concepts.
That was my one error for everyone to look for :-) Seriously it should have been the six outer vacuum Raptors.
@@terranspaceacademy Still an interesting concept. It would basically be igniting the pre-burners, wouldn't it?
Yes... to turn them into "weak" hot gas thrusters with low exhaust velocity so a Moon landing could be performed without additional engines high on the rocket.
All this fuel clogging makes me wonder if it’s some kind of ice’s or pieces of the internal structure of the starship coming loose and clogging fuel lines, I think I heard about some reinforcement around the grid fins mount areas as well as other places?
I think it must be ice though there is probably a little other debris. What else could be coming loose that wouldn't destroy everything?
@@terranspaceacademy
Yep that one of many reason to hope for a controlled soft landing on next flight.
Your content: 10/10! 🔥
Thank you so much!
The temperature in raptor preburners is limited at 800°C to not damage the gas turbines blades, actuall hot gase thrusters of the future orbital maneuvering system engines would need to have a exhaust of 2200 °C for reaching 300 second specific impulse, so a raptor used in that mode would have a much lower performance.
That did seem quite high... 160 and above should work fine for this purpose.
@@terranspaceacademy you don't understand my objection, most of the performance of a rocket engine is given by only two parameters, the molecular mass of the exhaust (the smaller the better) and temperature of the exhaust (the higher the better), if you try to use only the preburners as a propulsion system you get a really shitty rocket engines, those preburners were designed to work at a relatively low temperature to spare the gas turbines blades so wouldn't adequate at all, also your math seems to be sketchy, low specific impulse means also low thrust, with sixth engines running at 50% the upper stage cannot do hot-staging from a almost empty booster that uses even a single engine (you see fuled upper stage is 1400 tons and the booster only 300 probably) . As a side note, If you want to get a accurate estimate of the specific impulse related to temperature and molecular mass you can check on the nuclear thermal rocket numbers, Scott Manley made a video recently and used a chart that do not contain methane, but ammonia since those two have almost the same molecular mass that would be useful.
That's the entire point... To dramatically reduce the power of the engines so they can be used to land on the Moon without kicking regolith back to Earth. We WANT low thrust...
@@terranspaceacademy you are speaking about hotstagging, maybe you don't understand in order for two stages to separate you need that upper stage to have a thrust to weigh ratio bigger than the booster, otherwise the booster would keep pushing into the upper stage, it's a reason why the upper stage have that thrust it need it for correct separation and it's probably minimum required when is fully loaded.
How about get rid of the fire ring and just add another skin on top the booster and run the methane burner by itself until there's enough distances then start the o²
That's what we were thinking... Someone said make the landing legs the "hot ring" I like that too.
I think there going to build a legged ship. They'll have to, to land in different places around the world.
I think it's simpler to design it this way first. Refine the ship first for its primary job, then add legs. There going to need legs for mars, the moon, and earth , but they build the most useful product first
That ship has three external engines, not 20.
You are quite correct
I love the "This IS rocket science" intro line.
Thank you!!!
That should be how the current system works using the autogenous pressurization vents for thrusters, the methane tank gets pressurised using hot methane rich exhaust from the methane preburner , when more reaction thrust is needed the preburner can produce extra pressure which gets vented out the appropriate vents
I wondered about that... Makes perfect sense.
@@terranspaceacademy After watching a few more videos about the auto pressure system its possible Im completely off about how it works, Ive heard that all thats needed is to take some of the gas out, heat it into a gas and return it to the tank. That should work, though the gas returned to the tank would just chill and turn back to liquid, however the tank would increase its pressure by heating up. So it seems to me that a better way to achieve this is using preburner exhaust anyway because that would be the best way to increase the temperature to the tank. Now though i wonder what actually happens to preburner gas returned to the tank, methane would produce water vapour and co2, the c2 is fine but water vapour turning to ice would potentially cause a clog and lead to propellant issues. Im looking forward to more details about how this system works from the experts.
@@terranspaceacademy So it has been clarified, the iced up ullage thrusters and the engine blockage issue were both on the oxygen side. I look forward to the results from tonights test flight anyway.
@@Marc83Aus That is some fine thinking. If I understand correctly, it has been theorized that the co2 will also become ice as it's freezing temperature is only -70 degrees and that this is a major contributor to filter blockage. Although this information doesn't come from SpaceX so it's only theoretical. Still I'm impressed with your coming up with this idea before IFT 4.
@@jimcrawford2833 Yeah its been confirmed this is how starship repressurizes , Zacc golden goes into details on the last CSI starbase video, theres several tons of co2 'snow' inside the oxygen tank by the point of landing.
On the interview Jeff bezos did with timm dodd he mentions that new glenn only uses heated propellants as autogenous regas, not preburned propellants. I would love to hear what performance impact that makes but at least they dont have to deal with ice forming inside the tanks
its the 6th now
Maybe where you are :-) for us it's still the 5th.
@@terranspaceacademy no. its on the 6th. the launch.