Quote from: Jim on 01/20/2011 11:31 amQuote from: rklaehn on 01/20/2011 08:45 amThis is kind of funny. Like the kremlinology of old, except for spacex. I would not be surprised to see major changes from this promotional video to the final configuration.One thing I would really like them to do is to change the fuel combination to something more easy to handle. Hydrogen peroxide/Kerosene, like the x37 uses? Peroxide is not easy to handle and anyways X-37 doesn't use it.OK. Thanks for the correction. Compared to nitrogen tetroxide/hydrazine, wouldn't peroxide/kero be easier to handle? At least it is not toxic and carcinogenic. (I did not say easy to handle. No rocket propellant is easy to handle. I said more easy to handle, compared to what dragon uses now)
Quote from: rklaehn on 01/20/2011 08:45 amThis is kind of funny. Like the kremlinology of old, except for spacex. I would not be surprised to see major changes from this promotional video to the final configuration.One thing I would really like them to do is to change the fuel combination to something more easy to handle. Hydrogen peroxide/Kerosene, like the x37 uses? Peroxide is not easy to handle and anyways X-37 doesn't use it.
This is kind of funny. Like the kremlinology of old, except for spacex. I would not be surprised to see major changes from this promotional video to the final configuration.One thing I would really like them to do is to change the fuel combination to something more easy to handle. Hydrogen peroxide/Kerosene, like the x37 uses?
Also, because of a fatal accident in 1934 Werner von Braun nixed it in his designs.
I am sure N2H4 will be trouble as well. But probably, due to its toxicity, nobody ever tried to use it on board a submarine.
Guess no one saw what these photographers eyes see: 3 landing struts, not 4 or 6. If Dragon has 6 of those structures, perhaps 3 carry the bulk of the the launch load and the other can 3 extend for landing.
If Dragon lands on legs, it will be 3 or 4 legs. Using 3 legs usually means the least mass for the necessary loads. 6 legs don't make sense.
Peroxide at high concentration is very dangerous and it is not easy to handle. Even at the low concentrations you need a stablizer to keep it from breaking into water and oxygen before you can use it.
Quote from: Robotbeat on 01/21/2011 12:57 amIf Dragon lands on legs, it will be 3 or 4 legs. Using 3 legs usually means the least mass for the necessary loads. 6 legs don't make sense.I don't see any value in 4 legs. If one fails, you're likely to topple over. Make it 3 to save weight, or 5 or more for redundancy.Thrusters, same thing. 4 is useless. you can have 8 in 4 pairs, but that's just inefficient - no better than 3 pairs, but worse than 6 spread all around, since then any single or any non-adjacent pair can fail)And remember - more engines, without allowing for more failures, is a decrease in overall system reliability/availability.
maybe the answer to the question: "how much thrust / what ISP does a hypergolic kestrel have" would explain whey they feel the need to have eight of them.
( . . . )A lot of this discussion is speculative, but it will be fun to keep track of posts when design details are eventually revealed by SpaceX.Numerical speculation is encouraged. E.g. "I estimate the total LAS impulse to be XXXX N-Sec", or "There will be 6 motors, XXX lbf each". It is ok to base speculation on calculations and other reverse-engineering techniques, not just direct interpretation of pictures and graphics.Being "wrong" is 100% alright - that's why it is called "speculation".
I don't see any value in 4 legs. If one fails, you're likely to topple over. Make it 3 to save weight, or 5 or more for redundancy.Thrusters, same thing. 4 is useless. (...)