Quick, quick question: Which motor in a two stager should have longer burn-time, impulse, ect? Is there a general rule of thumb? Like high impulse, short burn first stage with long weak upper stage or something?
Thanks!
Thanks!
It really depends on what your desired flight characteristics are. Obviously you need a sufficient thrust-to-weight ratio at liftoff, reliable sustainer ignition, and workable recovery. Beyond that, anything goes.Quick, quick question: Which motor in a two stager should have longer burn-time, impulse, ect? Is there a general rule of thumb? Like high impulse, short burn first stage with long weak upper stage or something?
Thanks!
Thanks! Good thing I recently became a member.Fred Taverni has written some absolutely excellent articles on designing multiple stage flights (the design being the things you’re asking.) They’re in the last and next HPR Magazine, which are online magazines available to all Tripoli members for free.
I agree, it is interesting that so much more altitude can be achieved through longer delays. Is this just because the decrease in speed causes less drag? It doesn't seem like a worthwhile tradeoff.My simulations nearly always tell me that a long burn in the sustainer gives me the most altitude. Another interesting question is how long should I make the delay between 1st stage cutoff and sustainer ignition? On his 293,000 foot flight, Kip had 17 seconds between the two. I’ve never gone more than a couple of seconds.
That’s precisely why. Drag increases with the square of airspeed, although there are some unusual phenomena once you get into the transonic range.I agree, it is interesting that so much more altitude can be achieved through longer delays. Is this just because the decrease in speed causes less drag? It doesn't seem like a worthwhile tradeoff.
That and air density decreases at higher altitudes. If you can delay the ignition of the sustainer as long as possible you get into thinner air and get a futher drag reduction.I agree, it is interesting that so much more altitude can be achieved through longer delays. Is this just because the decrease in speed causes less drag? It doesn't seem like a worthwhile tradeoff.
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