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https://www.universetoday.com/17040/nasa-to-install-shock-absorbers-to-mitigate-thrust-oscillation/
It's complicated.
(rework. How do you maximize delta-v for a given stage?
Let's use Falcon 9 as an example.
The first decision is the engine, and SpaceX already had the Merlin and thought they could build a vacuum version. They knew what their NASA ISS resupply contract required, and they had initial ideas on how much Dragon would mass.
So, you start there. You have a second stage and it's going to have a big engine for a second stage because it's going to be based on Merlin. Choose an arbitrary size for your propellant tanks, and that controls how much delta-v you can get. You now have a wet weight for the payload of the second stage and a rough idea of how much delta v you need for the first stage. Pick a size for your propellant tanks, choose the appropriate number of engines so you have enough thrust to get off the ground. Does that give you enough
Rockets that aren't clean sheet designs have more constraints. ULA's Vulcan, for example, was going to fly centaur as the second stage, and that meant
Start with Falcon 9 approach...
You need to stage slow enough so that the first stage can reenter and land without too much reentry heating. It's also helpful to do it early so you aren't very far from your launch site. And you need a first stage that doesn't use solid rockets as they will a) push your staging later and b) be expendable (yes shuttle reused solids, but it didn't really save any money). And obviously you need enough extra propellant to come back and land successfully or wings if you want to do with wings (don't, it's probably a bad decision).
Then you need a big beefy second stage that can do most of the work to get into orbit.
That's falcon 9.
If you want to make your second stage reusable, it's a lot harder. You need to design a second stage that is also a reentry vehicle, which means some way of protecting it against the heat, some way to control it during reentry and while in the atmosphere, and some way to land it. All of these capabilities add mass, and every kilogram of mass you add is one less kilogram of payload that you get from the system. SpaceX looked at making the second stage of falcon 9 reusable, but it turns out that the added mass removes enough payload mass to make it uneconomical. For example, Falcon 9 can *barely* launch most geosync satellites on the geosynchronous transfer orbit that they need, and full reuse would mean losing those customers.
That's why starship is so big; it masses more than 8 times what Falcon 9 does at liftoff.
Yes.
Solar is great because it's low tech and has no moving parts; you just put the panels out on the surface, hook them up, and you're making power. If you want more power, deploy more panels. And there are numerous companies throughout the world continuously working to make solar panels cheaper and lighter.
But solar obviously doesn't work through the night. You can deal with that by batteries, but they are heavy, and anybody on earth with an off-grid solar system knows that they are also very expensive.
Nuclear would be a great solution for the initial power and longer-term baseline power. There a research project with one of my favorite names - The Kilowatt Reactor Using Stirling TechnologyY - or Krusty - that built and testing a prototype for a 1000 watt reactor that only weighs 400 kg. Just the thing to take on an initial mission. Put it up a sufficient distance from your base, run a cable to carry power, turn it on, and it will pretty much run itself for 10 years. You can use the same technology up to 10 kw, and NASA says that 4 of those would be enough power for 4-6 astronauts.
https://ntrs.nasa.gov/api/citations/20205009350/downloads/03-KRUSTY%20Reactor%20Design.pdf
There are lots of launch assist methods out there; balloons (rockoons), rockets dropped from planes, all the various gun designs (see link), spinlaunch (link),
Wikipedia non-rocket spacelaunch
Then there are more esoteric approaches, like launch loops, lightcraft, microwave propulsion, space elevators, Orbital rings, sky hooks, etc.
I'm going to do a video on at least some of these in the future, but the short answer is that I'm not very excited about them, as they require one or more of the following:
Development of advanced materials that will, at best, be very expensive to create.
Deployment of large and expensive structures on the ground
Deployment of large and expensive structures in orbit
Very large power supplies (the energy needs to come from somewhere)
Require complex operations, such as connecting an ascending vehicle with a rotating tether travelling at many times the speed of sound.
The problem is that these are pretty much all multi-billion $ projects, and those sort of projects tend to take longer and cost more than you would think, and the cost/kg of the resulting solution isn't easy to predict. And these are all big structures that provide no utility until they are totally done and if your engineering isn't good enough, you could blow up the whole investment in a single day.
We already have a very good launch assist method, known as a "first stage". There is literally tons of prior art so you can easily predict how much it will cost and what it will do, it's cheap to build the first one, and if it blows up on the pad, you just rebuild the pad, figure out what went wrong, fix it, and go back to launching.
And we now know how to reuse this launch assist method.
Tanks on earth - just put a pump between them or use gravity to move the fluid.
Tanks in orbit; everything is floating around so you can't easily separate the fluid from the liquid. If you are using hypergolic propellants, you can use containers with pressurize membranes - like residential water tanks used by people who have wells - but those membranes do not play well with cryogenic liquids.
So, to do with cryogenic propellants, you need a way to separate the liquids. You can do this with a little bit of thrust - known as ullage thrust - to settle the tanks. Or you could hook the rockets together with a tether and spin them to settle the propellant.
My guess is that the most practical method is to use some very light thrusters, build some good liquid/gas separators, and then small pumps to do the pumping. You can probably power the pumps with "ullage gas" from the tanks and then exhaust that both to provide thrust and to get the power to move the liquids.
Disclosure: I have an amusement-sized investment in rocket lab.
There are numerous small companies trying to break into the launch market. I get it - rockets are cool - but it makes very little sense as a business strategy.
Add in link to markets and moats talk.
The basic problem is the cost of rockets is:
Fixed cost (factory, engineers, launch pad, etc) / launch rate + hardware/propellant cost per launch
SpaceX is going to launch 50 times in 2022, so their fixed costs are going to be spread over 50 launches. How are you possibly going to compete with that when you are trying to launch a new rocket and get up to 5 launches a year?
To put it in market terms, launch is largely a *commodity*, and commodity markets are dominated by the cheapest provider. As evidenced by SpaceX walking over the bulk of its competition.
What you want is something that makes you different, what we call a "differentiator". ULA has one in that it is one of two companies certified to launch NSSL payloads. Good luck trying to take that away, as the bar is very high.
Rocket Lab is able to undercut spacex for launches that want a specific orbit and since they're the only real smallsat launcher right now, that is working for them. But there are other launchers out there that are more capable waiting in the wings.
Photon is their attempt to differentiate - to provide end-to-end services that make it much easier for companies who want to get into space to get what they want. There is a market there, though it's not clear how big it is yet, but the satellite bus market has largely been dominated by boeing and (others), who make big busses. Rocketlab has the chance to move into the lower mass market and, through vertical integration, do the same thing to that market that SpaceX did to launch.
I think it's a great move strategically.
Maybe a 5?
I think it can be built and will probably work and I don't think it's likely to blow up your ship.
But thrust seems problematic. Only some of the fission produces free fragments and only some of those can be aimed in the right direction. The designs claim that there is some magnetic approach to steer the fragments in the right direction, but the exhaust velocity is something like 2% the speed of light, so good luck with that.
The more complex designs are probably a 7.
I think the jury is still out on nuclear propulsion making sense *at all*. With any luck the current NASA program (link) will produce a real reactor and then maybe we can end up with some real numbers to compare with chemical engines.
The NASA design, however, is pretty conservative when it comes to mass, and that doesn't bode well for overall performance. If they only do as well as NASA hopes, they will end up with a thrust/mass ratio of about 1/16th of what you get from an RL-10.
But I could be wrong; advocates have for years been saying "advanced lightweight materials", and we'll see what they come up with.
I decline the contract.
$100 million isn't much for design, and now I need a nuclear design - see last question - plus everything else.
It's a $1 billion task IMO.
In 1979, the Russians carried out a space experiment on rat reproduction but were unable to complete it because of weightlessness.
Japanese researchers have fertilized mouse eggs in an artificial micro-g device called a clinostat.
But that's not what you are really asking.
In 1992, astronauts Mark Lee and Jan Davis met during training for STS-47 and secretly got married without telling NASA until it was too late to change the crew, and they flew together in shuttle. If the rest of the crew was cooperative, experimentation would have been possible.
But there have been a lot of humans on both shuttle and ISS, and there's been a lot of speculation.
To my knowledge, nobody is talking.
If you enjoyed this video, please check out the atomic rockets site.