Timeline for Why do spacecrafts take off with rockets instead of just ascending like an aircraft until they reach space?
Current License: CC BY-SA 2.5
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| Mar 20, 2015 at 15:52 | comment | added | Jim | This is silly. The plane doesn't have to reach 20000mph and there is a fundamental physical reason why airplanes can't fly into space. They require an input of air into the engine and there simply isn't enough to sustain engine operations even close to the edge of space. Furthermore, you can't flood the engine with too much or too little air, which means there's a maximum and a minimum velocity of the craft that will provide the right amount. Sadly, at high altitudes, there is not enough airflow over the wings to maintain the required lift within these speeds and the plane will stall. | |
| Dec 30, 2012 at 6:27 | comment | added | Christopher James Huff | It also might be informative to read up on the "Air Breather's Burden": islandone.org/Propulsion/SCRAM-Spencer1.html | |
| Feb 28, 2011 at 15:52 | history | edited | Daniel Chisholm | CC BY-SA 2.5 |
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| Feb 28, 2011 at 15:35 | comment | added | Daniel Chisholm | @timur for a rocket the atmosphere is nothing but an obstacle so trajectories are chosen to get the rocket out of the atmosphere ASAP (i.e. go straight up til you clear most of it, then tip over). For an airbreathing craft it is a tradeoff, staying low in the atmosphere is good for your engine (more oxidizer, so more power can be produced) but bad for your airframe (more air means more drag). There's an even bigger problem though - the thrust-to-weight ratio of airbreathing engines turns out to usually be a bigger penalty than their improved fuel consumption | |
| Feb 27, 2011 at 18:18 | comment | added | dmckee --- ex-moderator kitten | @timur: It is not a stupid idea. Every time someone writes a report on inexpensive access to orbit there is a chapter on hybrid launch systems. But so far, the engineers keep coming back to rocket from the ground up. Looking forward, I think one of the private firms is really looking at a airplane for the first stage. | |
| Feb 27, 2011 at 18:08 | comment | added | timur | @dmckee: Thanks a lot for your reply. Maybe then it would help if spaceplanes go straight up from the point they start the second, more powerful engine. Or would it contradict the whole point of using air as much as possible during their ascent? | |
| Feb 27, 2011 at 17:59 | comment | added | dmckee --- ex-moderator kitten | @timur: They do have a heating problem, but by going up instead of across they don't stay in the atmosphere for long. The switch to across happens gradually, and mostly further up than that. | |
| Feb 27, 2011 at 17:23 | comment | added | timur | About your second to last point: Wouldn't the ordinary rockets face the same problem of heating? Why don't they look burning red when they are going up? | |
| Feb 27, 2011 at 15:57 | history | answered | Daniel Chisholm | CC BY-SA 2.5 |