More New Details on NASA's CEV Launcher Studies 361
TheEqualizer writes "Continuing on the NYT story on NASA's current CEV launcher plans, spaceref has an even
more extensive look with detailed assessments of the available options. By all accounts, it looks like NASA is picking up where it left off with Apollo but also combining it with established Shuttle technology -- the capsule concept of the 1960s atop the shuttle boosters of the 1970s being the winning combination under the current budgetary limitations. However, is this coupling of
old technology and designs really the best we can do?"
Re:If it ain't broke... (Score:3, Informative)
The shuttle program is equivalent to saying "These paddleboats just have no future. Let's go back to sails."
I'd rather say that the space shuttle is like a paddleboat before the steam engine was invented. Perhaps it's a good idea, perhaps not, but without a steam engine to turn those paddles there's not much point in it. Sailing usually beats muscle power (rowing or turning the paddles by hand).
The hard things in space flight at our current technology level is getting to orbit and reentry. Putting wings on a space craft is optimizing for the wrong problem. As can be seen by the fact that with a "traditional" capsule on top design the astronauts would have survived a Challenger style accident, and the Columbia accident would never have happened.
Re:If it ain't broke... (Score:2, Informative)
Barring the fire on the pad, I can't actually think of anybody that died in those two programs. It's just safer to put the payload and crew on top of the boosters. The idea of a reusable plane was cool, but it's just not feasable yet.
Re:If it ain't broke... (Score:4, Informative)
There are a number of factors to consider when launching a rocket and Florida provides the best launch location for the US. Here are the factors to consider...
- You have to launch east so you get the added help of the rotational velocity of the Earth.
- You want to launch over unpopulated areas (the ocean is pretty unpopulated for a long way). The Russians use the giant desert in their southern regions for this but don't care as much about the people living under the launch path (have you seen the pictures of rocket debris in Russian villages?). The Europeans also use the ocean (from French Guiana)
- You want to launch from the lowest possible latitute because you can only reach higher latitude orbits in one go (you can reach any orbit from the equator but you can't reach an equatorial orbit from the tropic of cancer without changing orbit in space)
- The ideal US launch facility from a physics standpoint would be Hawaii but the cost of getting the vehicle to Hawaii would be insane so we opt for a higher latitude, continental launch facility).
Re:If it ain't broke... (Score:3, Informative)
I remember in high school a younger neighbor of mine got a GI Joe space shuttle. It was a lifting body with a rocket powered and MANNED booster stage. It was not a jet, but it was a liquid fueled space craft on it's own (well, it looked like it was). Anyway, I always thought why did they not build something like that instead of the current design?
I think I have seen some drawings of some booster stage with flyback capability. With todays electronics, there's no need to have it manned though. But anyway, the problem it that the wings add weight. It's just cheaper to put parachutes on the boosters and pick them up where they land.
Anyway, I think the plane format has merit as soon as we figure out how to make more compact and efficient rocket engines.
Rocket engines are plenty compact and efficient already. The problem is that there is only so much thrust you get from chemical fuels. We're already pretty near the limit. Nuclear might be an option, but suffers from political problems.
If they figured out how to make engines with equivalent thrust to the SSME's without the massive fuel requirements, it could work.
Um well, if they could get that to work pretty much any sci-fi scheme would work too. With chemical fuels it won't happen.
Re:What about... (Score:3, Informative)
Who says?
Len Cormier is working on a very realistic concept where the first stage will climb to around 30 km but will do so at subsonic speeds. It will have a very large wing area compared to its weight to be able to generate lift at such low speed and thin air. The wings will be a fabric-covered frame and the whole thing will look more-or-less like a giant ultralight. Unlike conventional aircraft which are optimized for cruising at maximum fuel efficiency this thing is designed to be simple and climb rapidly. It turns out that the best engine for it is a rocket because of its high thrust to weight ratio and ability to work efficiently at high altitude. Yes, a subsonic rocket-powered giant hang glider. It sounds weird but it makes perfect sense from an engineering point of view and is pretty low tech in comparison to spacecraft and conventional aircraft.
The second stage can use efficient high expansion ratio engines that can't work at sea level. The second stage does not need to suffer a rough and fast ride through the dense atmosphere (max Q). A short and chubby body can be used, which is much better for containing large amounts of fuel in a lightweight envelope than a skinny cylinder. A large empty tub also has a much easier time on reentry - temperatures are much lower when the mass divided by cross section is lower, reducing TPS weight and allowing use of materials less fragile and with far lower maintenance than shuttle tiles.
These things make a big difference. Although the second stage needs almost as much performance as a full SSTO it can be much easier to build when it starts at 30km altitude.