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I'm interested in space technologies and have basic understanding of rocket flights. When looking at large commercial rocket launches, i noticed that the lift of process from ground takes very long (slow speed of flight) and then rocket gains in speed.

When calculating needed propulsion for small rockets (e.g. size of person), usually a problem arises that the mass/weight of the propellant outnumbers the force of propulsion, which will result in unsuccessful launch to space.

Given the fact, that the lift-of does consume a lot of propellant already, I've started to think about the following questions:

  • What amount of propellant could be saved if the lift of process is done by a device attached on the rocket, eg. a slider on a pole accelerated by pressured gas?
  • What would it be possible/suitable to build a second, recyclable device that transports and accelerates the rocket to a certain speed and altitude, like a miniature jet airplane
  • What would be the gain of launching the rocket from a high-speed jet, e.g. a combat jet, that's flying at maximum speed towards maximum altitude and then launch the rocket from its wings (like a guided missile)

Sure all those ideas are not suitable for commercial large rockets, but I'm thinking about smaller rockets to launch small spacecraft and satellites (e.g. Cube-Sat etc).

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  • $\begingroup$ Pretty straight-forward: calculate the speed imparted from the launch mech (e.g. aircraft carrier sling) or the jet carrying the rocket, and remove the amount of propellant needed to go from zero to that speed. In the case of the jet aircraft, you also start from a much less dense atmosphere. BTW ASAT missiles launched from aircraft are a thing $\endgroup$
    – Carl Witthoft
    Commented Apr 6, 2020 at 11:36
  • $\begingroup$ Your first bullet-point is likely answered by this question about catapult launches. TL;DR version: you need a really huge catapult, or any meaningful speed gain will cause far too strong acceleration forces. Launching orbital rockets from planes actually is a thing. but you need to get really high and really fast for it to have any benefit. $\endgroup$
    – Philipp
    Commented Apr 6, 2020 at 13:05
  • $\begingroup$ @Philipp I think a major reason for plane launch is that you can get exactly to the optimum point on Earth to launch from. $\endgroup$
    – Steve Linton
    Commented Apr 6, 2020 at 14:39
  • $\begingroup$ One more thing to add: The velocity of satellites in orbit is a bit over 7km/s. Even the fastest planes go only a couple hundred m/s, so the benefit isn't that big, espacially considering the additionally required plane. Usually, complexity is just lower with a bigger rocket $\endgroup$
    – DaGroove
    Commented Apr 6, 2020 at 14:50
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    $\begingroup$ This is three separate suggestions that are each, individually, duplicated on the site. $\endgroup$
    – Russell Borogove
    Commented Apr 6, 2020 at 16:34

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