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Culture is the real difference in companies like SpaceX and Rocket Lab...

What will you do when the freighter shows up at its destination? It's highly radioactive even when the engine is off, and unless the cargo has been well shielded, it will also be radioactive.

@@EagerSpace There are three choices that I see. The first is that you stage the nuclear part and finish the journey with a chemical rocket. The second is that we land a fair distance from our imaginary colony, or that they've built some sort of shielded landing pad, and so the burden isn't on the rocket. If this is a space station, I suppose it'd have to be even better shielded that by default. The third is that there are no humans at the destination either, autonomous&remote-controlled systems only. The question of the cargo being radioactive is a good one, I suppose it depends on what the cargo is and what we're willing to tolerate. We could still need some level of shielding, just less than if we were carrying humans, but I'll be honest, I'm not sure how to properly math this.

This one is only NASA so far; they have informed Congress and congress will decide whether to cancel it or fund it.

It's possible. You need a big platform - something like oil derrick side - and those are hard to move around, and they you need tankers to supply them with propellant.

NASA is a government agency and it works on the projects that Congress assigns and gives it money for.

The problem with the teal was that rockets look really cool with transparent backgrounds when the final background is black and really stupid when the final background is not black.

Thanks - I always love to get more deteailed information.

The issues in the videos are mostly about starship - the second stage is very heavy and that means it's very sensitive to small changes in mass and small changes in engine performance. Engine out *mostly* has an effect on the gravity losses. If you lost 3 engines on super heavy, you need to burn your engines 9% longer. That's around 14 seconds longer, and that means we can ballpark the delta v loss at around 140 m/s. Not great, but it's not a huge difference. The losses if you only lose 1 or 2 engines is obviously smaller. Engine out on Starship would be more complicated to analyze. I expect that are you are flying a maximum payload you probably don't have the margin to deal with one engine out on the 6 engine version. When we get to the 9 engine version, it's spicy enough that I think it will be able to deal with one engine failure.

Many startups have a goal of being acquired. Not sure if it's true in this case.

So, you would choose to spend - and I'm just making up numbers here - $50 million to put 250 tons into LEO when you could do it with two $5 million launches instead?

@@EagerSpace No. More like I was wondering if the steep slope on the Starship graph makes it more expensive to put mass into orbit than would a non-reusable upper stage that utilizes the same booster. The flat slope on the Falcon graph looks compelling is what I was thinking about. While Starship will have significant advantages over Falcon, the video brought to my mind the possibility that they never exceed the efficiency of a non-reusable upper stage (using the same booster)

I have all the posleen books, but I don't find a lot of desire to read them again. The tech is fun.

@@EagerSpace Lost fleet by jack campbell is great fun

I've read the whole lost fleet series and I think it's pretty good. I also like the Kris Longknife series.

@@EagerSpace martha wells murderbot enjoyer as well?

I *think* I've seen some proposed designs for that. The problem is building a nozzle that can actually do that, deal with cooling, and keep it light enough so that it's actually worthwhile to do. Oh, and make it work reliably. Given that good designs - and I guess that means the designs *I* like, not ones that use big solids and a small sustainer - are fairly settled on two-stages, it's fairly easy to build good first-stage engines and pack a lot together and then separate vacuum engines for the seconds stage.

Thanks

I agree with the assesment that the development costs will be astronomically high (pun intended) and that NTRs are the purview of governments, but maybe not for exactly the same reasons. Maybe the biggest restriction is the reactor fuel. Sure, you CAN build an NTR with 'low' enriched uranium thats like 20-35% U-235, but the weight penalties are painful. I mean the weight of the REACTOR alone, but its worse because the physical size goes up too and that necesitates either a larger (and heavier) shadow shield to get the same half-angle or sticking the crew module even further away. (Also the thrust is just plain worse) This is for an engine type that already is heavy as sin and where designs with acceptable mass shadow shields are, from fore to aft, the crew module, equipment bay, propellant tankage, then a looooooooooong truss-girder, shadow shield and finally the reactor/engine. And thats with using like 90% enriched uranium. I'm about as pro-nuclear as they come and i've read everything i could get my hands on regarding every orphan sourse event, ARS casualty, power excursion, criticality event and isotope release. I'd love to see an NTR fly, and if the math says you gotta use bomb grade fissile material then thats what you gotta do. Nothing wrong with a civilian agency possesing the stuff, or even a private corporation. But i think that stuff needs controls for the same reason i think firearms should live in a locked gun safe. Even setting aside security concerns the only industrial expertiese in fabricating high enrichment uranium is military, same with the facilities that can do that work. A government, military or international orginisation pretty much HAS to be involved. As for regulatory athority, its kinda a mess? Since the law of rockety is super tyranical the aditional on-paper laws are mostly national intrest stuff or common sense kinda 'standard practice' measures. You know, play nice with the other kids in geostationary orbit, try to keep the garbage to a minimum and for the love of god don't test ASATS willy nilly lest you invite the Kessler syndrom kraken on us all. But nuclear stuff? Don't orbit any bombs and other than that it can't be worse than what the soviets were doing. Theres a whole bunch of decomissioned reactors orbiting us right now, all but two of them were the powerplants for soviet radar sats. Each one was roughly 100 pounds of uranium and enriched to a whopping 95% Fast neutron spectrum, so no modderator needed, liquid metal cooled and power produced by the thermoelectic effect. (A braytoncycle gets much better conversion efficiency, i thibk these things managed 5%) Roughly 100 watts of electrical output. Its as light as you can make a nuclear reactor, doubly so since the materals used can tollerate the hellish bombardment of hard neutrons. Or at least degrade gracefully. The whole point of using nuclear-electric instead of photovolaics was so they could be in very very low orbit, to get better radar resolution. Orbital lifetime was limited by propellant, and after that drag from the atmosphere would shortly cause rentry. The whole dang satalite was radioactive to some degree from neutron activation, but not super concerning. The reactor though, and especially all the fission products, that really would not be good to be incinerated in the earths atmosphere. So the reactor would be ejected and boosted into a high orbit, and being soviet tech this worked almost all the time! When fully successful they only leaked a little bit of their liquid metal coolant and are in a high enough orbit that we don't have to worry about them reentrering any time soon. Thats good, because they won't stop being horrifically radioactive any time either! They're probably the worst nuclear waste humanity has ever created, greater activity than any fuel element no matter how high the burnup. We normally entomb that stuf in molten glass, sleeve it in various metal shells, dig a deep hole to stick the cask in and cover it in concrete. Oh, and somewhere geolocially stable far from human habitation. But the soviet space reactors? Theres nothing between you and it except for a lot of distance. Thats one thing space has in spades, is distance. Totally fine, nothing to worry about. Also, even though each reactor has enough fissile material for several warheads and is literally floating there for anyone to grab A) space is hard and rockets are expensive and B) You would be super duper cooked before you got close enough to retrieve it. (Also, you'd have to get it back groundside in one piece, which is a chore, then put it through chemical reprocessing to get rid of all the unwanted fission producs) So i think peaceful space aplications should get a free pass to use nuclear energy. Whatever the worse scenerio someone can think of for launching rockets with nuclear reactors aboard, its already happened. Theres one at the bottom of the ocean off Japan right now, along with the twisted wreckage of the launch vehicle. Another burned up during rentry over the south atlantic and if you took a random gallon of seawater from any ocean thered be a few molecules of what used to be the reactor of Kosmos 1402. Freakin Kosmos 954 contaminated a swath of Cannada and required an obscene amount of man hours to clean up. They sued the soviets for the clean up costs, rightfully so, but they didn't actually recieve any money for way way too many years.

The Valor series is nice because (spoiler) the energy is not the enemy and the different aliens aren't just humans with different shapes.

Glad you enjoy it!

Not right now, but thanks for the offer.

Both the CLPS and spacesuit projects are just going great...

Just farther down the line. I - obviously - like the documentary style books if they are good, and Simberg's book is fairly influential in how I see things. I don't spend a lot of time with what I would call "deep advocates". I have some reason why but it might be unfair so I'm sharing it.

Honestly, the real reason I have a minor in math is because I had to talk multidimensional calculus and linear algebra instead of matrix math, and for 6 credits it was a pretty small investment. Way cheaper than my business minor which was 5 classes IIRC. I have a good friend who got a math major, and in multidimensional calc we would check our homework and he was always disappointed that my favorite method of integration was "integration by tables" where you open the front or back cover of the calc book and find the integration listed there. He always did it the hard way, which served him well when he got to math analysis.

Show me a real one that works and has published specs, and then we can talk...

Yes. The picture I showed for the NASA nuclear video is one of the NASA designs, where the stage just has this framework and the liquid hydrogen is - AFAICT - stored in what looks like a mylar balloon. Then they use the hydrogen in one tank and drop it off.

Definitely, though I think it's a little less accessible than the other books I mentioned.