How much harder would it have been for Felix to use some powered sled and head for the ISS when he stepped out of his capsule? He was already above most of the atmosphere. BTW, Is that capsule still up there? Why don't more missions use balloons for the first stage?
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3$\begingroup$ In the end this is yet another variant of the "Hey, lets do space launches from high altitude balloons!" theme which we have addressed a few times already. It sounds attractive, until you work the numbers. $\endgroup$– dmckee --- ex-moderator kittenCommented Feb 27, 2013 at 16:44
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$\begingroup$ The capsule is not longer still up there. I saw it two months ago in the Steven F. Udvar-Hazy Center of the Smithsonian National Air and Space Museum. That is where it is at now. $\endgroup$– NeutronStarCommented Sep 19, 2014 at 16:49
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The vertical part is relatively easy, but to be in orbit you need to be going fast enough horizontally, that's around 8km/s in low earth orbit.
The balloon does nothing to help with that. There are launch vehicles that carry a rocket up to altitude underneath a plane and then fire that from 50,000ft. It means you don't need to use the rocket to get through the densest part of the atmosphere, and you always have good weather at the launch height but you are limited to a fairly small rocket.
answered Feb 27, 2013 at 13:42
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$\begingroup$ So how about a power source just powerful enough to get you to altitude and then a controlled elasticity lasso to 'hook a ride'? You hook it on the ISS as it goes by and let it strech out (for miles) while accelerating you only as much as you can stand - then you shorten in up after max extension to continue your max acceleration and get to the ISS? Any idea how flexible and long that lasso would have to be? $\endgroup$– DezCommented Feb 27, 2013 at 13:53
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4$\begingroup$ @Dez Felix Baumgartner's jump was from 39 km, but the ISS orbits at 370 km, so the lasso would have to be at least 330 km, more if the station wasn't directly overhead, and stretch to even longer. Plus you'd need a rocket to get the end of the lasso up that high, and the rope would be very heavy. But even worse is that you'd be pulling on the ISS as well as it pulling on you, so it would have to fire thrusters in order to avoid changing its orbit - and the amount of thrust it would have to use is the same as the thrust you'd have to use to reach its orbit. So you can't save fuel that way. $\endgroup$– N. VirgoCommented Feb 27, 2013 at 14:01
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1$\begingroup$ @Dez Concerning using a rupe: physics.stackexchange.com/questions/40815/… $\endgroup$ Commented Feb 27, 2013 at 16:59