Yes. Actually, I was exagerating very slightly, the trajectory went up at upto a 3 degree angle, at ~25km it leans across to a 5 degree angle. The vehicle mass has been minimised which makes the trajectory pretty steep. A vehicle of this width seems to have great difficulty with atmospherics, the space shuttle is heavy enough it can pretty much ignore the drag of the atmosphere and just needs to make sure the wings don't fall off.On Tue, 07 Jan 2003 19:02:02 +0000, Ian Woollard <[EMAIL PROTECTED]> wrote:The optimised trajectory is interesting though- it goes subsonic, and very nearly vertical up to about 30km and then separates and the second stage burns briefly for a lob up to about 200km and then it restarts its engines and does its orbital insertion burn.That sounds darn weird. Are you getting any advantage at all from Pythagoras?
Once my simulation has separated it does a quick burn at about 25 degrees, and then it's ballistic till it reaches orbital height and then it burns and turns until it actually burns *down* slightly at upto 99 degrees to the vertical (no don't ask me, it's probably circularising the orbit or something ;-) ).
I don't think so.But the first stage really bugs me. I mean it works, mostly, but I'm taking off vertically at about 1/2 the speed of sound and I stay there as my fuel drops from 27 tonnes down to 4 tonnes, and I haven't even gone supersonic ;-(Darned air gets in the way; if I try to go faster I burn all my fuel too soon. If I go slower, then gravity losses do me. Argh.Sounds to me like you've got the drag numbers wrong.
It's not that it has to; it's more that it's better to somehow at this scale. I did wonder if that could affect your strategy with Spike, if you are working in the same drag regime. But Spike is kind of a research/development project so you may like to find out how it works at mach-4.They shouldn't be so bad that you're subsonic all the way to 30 km.
I think that's what's happening. The program needs to get out of the soup. It comes out of the soup with almost enough speed to reach 200km, it just burns just a little more to make it and adds just a little sideways whilst it has the chance. Once it reaches 200km, it scrambles like mad for orbital velocity.Caveat here: for a sounding rocket, going straight up, that is indeed the way to go, according to (either Dan Delong or Doug Jones, whoever worked on Hummingbird - I really need a memory upgrade). For going to orbit, though, you're not looking for altitude; you're looking for horizontal speed. The only reason to go up first is to get out of the soup. So you should be burning for some horizontal component as you're climbing.
Yes, particularly at liftoff when you are in the thick bit of the air. Nice.It would be nice to airbreath, but that sounds rather too complex and lox and tanks are dirt cheap, and you need them above 10km or so anyway. Now John Carmack and Gary Hudson had tried a rocket powered rotor; but both had abandoned them. And I wasn't entirely clear why that would help, what's the theory?As Gary put it a few years ago, "Rocket engineers have been fighting the atmosphere since the days of Goddard. We're going to make it work for us." It was interesting to watch the Roton design develop over the years. Recently Gary confessed that the rotors were an opportunistic design he and Bevin came up with. "We wanted to get the engine out on booms, and spin the booms - instant pump. We had to fair the booms. We thought, 'Why not use the booms to generate lift?'" It increases the effective Isp by an order of magnitude, by using the air as reaction mass.
But the ISP of the rockets PLUS the wings AND the air is lower, not higher. But if you leave the air off, which most sensible people would when calculating ISP then it's much higher. That's the insight I had.Anyway, woke up this morning, and suddenly spotted the theory of why the HMX had the rotating rocket tipped wings at takeoff . It reduces the effective ISP of the engine.No, it increases the Isp, by increasing the chamber pressure.
I guess it doesn't need to. If your rocket is big enough, you can start to worry less about aerodynamics.I think HMX abandoned this idea because of weight growth didn't they?It doesn't scale well.
That's actually good, in a way. I'm looking at how small I can make orbit with some payload. Something that would fit in a pickup would be ideal, but it looks a bit bigger than that right now (11m highish). At the moment everything looks horribly difficult. I'm hoping I'll climb to the top soon and look down and everything will be easy. Yeah right.Given current rotor blade technology, there's a maximum size you can make a Roton. It turns out that's too small to confidently say you can use the technology to make a commercial SSTO.
-R
