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Post by silverdragon on May 1, 2014 7:06:20 GMT
I lifted this idea straight from Redneck Rocket scientists, (have altered their idea a little), that has aired over here in the UK.
The basic idea is to get a high altitude balloon up as far as it will go, and launch a rocket from "Up There", or run a pulley system from a dropped weight in that balloon that drops and "Pulls" up the rocket so far / so fast before igniting rocket engines....
From that show, works in principal.
So can this be done.....
SpaceX, a US company, has managed to launch a re-usable rocket stage that landed with almost zero velocity.
Can the two idea's be combined to create a re-useablle rocket technology....
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Post by the light works on May 1, 2014 14:22:47 GMT
I remember balloon assisted rocketry from a youth book published back in the 70s. the older ones destroyed the balloon in the process, but the newer ones sound as though they might not.
my four concerns would be cost/availability, weather tolerance, payload capacity, and launch time. (I.E. how long it takes from leaving the ground to hitting orbit.)
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Post by Cybermortis on May 1, 2014 14:50:59 GMT
The idea is about saving weight, since the higher up the rocket starts its trip into space the less fuel it needs. The less fuel the lower the weight, which in turn means less thrust and fuel needed to get into orbit.
Would this work with balloons? Sure, no reason it shouldn't. In fact for small rockets and payloads it would be considerably cheaper than any alternative since you would only need fuel for the second part of the flight.
NASA has long planned on orbital vehicles that were launched from aircraft - the basic design can be seen in the film Superman Returns. This would be more efficient fuel wise than launching a rocket straight up into the air.
The catch is the size of the balloon you'd need to lift the required payload. As I said, for a small payload it is quite practical. But for larger payloads the size of the balloon needed to provide the lift enters into the impractical.
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Post by the light works on May 1, 2014 15:29:32 GMT
another question which might be relevant is whether the balloon assisted rocket is going for an escape trajectory, or for orbit. it took me a while to learn that the reason rockets need so much acceleration is because it takes a lot of velocity to be in orbit. - which means that a balloon assisted rocket going for orbit would still have to have the same acceleration against its own mass. a rocket going for an escape trajectory would just need to build enough velocity to get where it was going in a timely manner - and could build the majority of its velocity outside the gravity well.
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Post by Cybermortis on May 1, 2014 20:09:38 GMT
Rockets don't even attempt to reach escape velocity until they hit at least 160 km altitude (more or less 100 miles up), since below this friction from the air would either rip the craft apart or burn it up.
Although no high altitude balloon can get close to this altitude (the record is around 31 miles), that is still a significant saving in fuel as the engine would need to fire at the 'lower' setting for only 2/3rds the time as the same rocket taking off from the ground. It might also be the case that the thinner air *might* allow for a somewhat higher speed and faster acceleration than you could get from a ground based launch. Which again might further save on fuel and hence weight (which further increases acceleration and efficiency).
For a large payload this probably wouldn't be remotely practical, since the size of the balloon would be eyewatering. But for smaller payloads it might be practical and cost effective, if you are not too bothered with putting your payload into a specific orbit.
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Post by the light works on May 2, 2014 0:50:18 GMT
the point I was making is that to go into earth orbit, the rocket has to accelerate to between 3300 and 22,000 MPH; depending on the exact orbit needed. whereas for an escape trajectory, they just have to accelerate away from the planet - the velocity is only relevant to how quick you want to get where you are going.
keep in mind, of course, this is musings, and I am not enough of a physics person to say what this means in fuel use.
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Post by watcher56 on May 2, 2014 3:14:12 GMT
Google "Rockoon'. It is done quite often.
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