Aerobraking on the way up

A first step towards building a fully reusable rocket would be to have a reusable first stage. You would want to
minimize maintenance cost on that first stage. Preferably it would be a Buck-Rogers type of first stage, you use it, it
comes back, you fill it up, and you use it again. You want it to be inexpensive to use, so you don't want to need an
army of technicians to work on it between each flight.

I'm trying to figure out what performance such a first stage should perform. If the first stage brings the second stage
to half of orbital speed (4 km/s) it will need a heat shield and a long fly back, that might not be compatible with
inexpensive, rugged and current technological levels. On the other hand, if it only accelerates straight up to 5 km, you
won't need a heat shield and fly back will be easy, but it doesn't provide much of a boost.

So, what should be the task of the first stage? I'm trying to figure out the maximum performance it could have, without
a significant heat shield and with line of sight fly back (never goes over the horizon). An idea I had while thinking
about that is to aerobrake on the way up. Let's say you have first stage separation at an altitude of 80 km. Because of
momentum, the first stage will continue to go up and further away. You might want to turn the first stage side ways, so
it starts decelerating. Then as it goes up lower atmospheric pressure stops the aerobraking, lets the first stage cool
down for a minute or two before reentery at a lower velocity than if it had not aerobraked on the way up.

Does it make any sense to aerobrake on the way up? Probably not. The problem is that your highest speed is at the
densest part of the atmosphere so this is probably not a good way to minimize the need for thermal protection. But
still, I can't think of a strong argument showing that there isn't some altitude where it would make sense to start
aerobraking on the way up.

Does anyone know if this kind of thing has ever been studied before? Or does anyone know of an argument that would show
that aerobraking on the way up does/doesn't make sense?


Alain Fournier

Alain Fournier wrote:

A first step towards building a fully reusable rocket would be
to have a reusable first stage. You would want to minimize
maintenance cost on that first stage. Preferably it would be a
Buck-Rogers type of first stage, you use it, it comes back, you
fill it up, and you use it again. You want it to be inexpensive
to use, so you don't want to need an army of technicians to work
on it between each flight.

Reliable, cheap, third generation.

Pick two.

D.
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http://derekl1963.livejournal.com/

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

Until, unless, the global energy problem is solved, your proposal, while
it makes good engineering sense to delve into, wont get the political
support to get off the ground. Never mind orbit.

Eco freaks will be screaming about the air pollution should chemical
rockets ever be used in enough numbers to do anything substantial in space.

The only way to do it now, would be to build a nuke at the base of some
equatorial mountain, and use it to power a mag lev up the side of that
slope to get so high above the atmosphere that there wont be any video
of the smoke trail when the 2nd stage boosters come on.

While the upfront costs would be horrendous, the damn thing would be
able to send up a first stage booster every 20 minutes like a bus. If it
didnt have the 2nd and 3rd stage, it could fly suborbital to deliver
passengers and freight at hypersonic speed, with zero gravity for
several minutes, which'd pay off in tourist tickets.

Course, in the meantime, if they develop nuclear fusion, then anybody
could launch from anywhere to go anywhere.

In sci.space.tech message
dakotatelephone, Sun, 31 May 2009 02:28:16, Pat Flannery
posted:
Alain Fournier wrote:

Does it make any sense to aerobrake on the way up?

I would think that would make a _lot_ of sense; as soon as stage one
separates, anything you can do to start slowing it down immediately
rather than having it coast higher and the start falling ballisticlly
back into the atmosphere makes a lot of sense in regards to both
thermal and aerodynamic stress on its way back down.


If you look into the height at stage separation, I suspect that you will
find that there is so little atmosphere up there that the effect will be
very small. A small effect is of some use; but not if it carries a mass
penalty.

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Day Brown wrote:

Eco freaks will be screaming about the air pollution should chemical
rockets ever be used in enough numbers to do anything substantial in space.

Only the ignorant ones - which is admittedly probably a large proportion
of them.

At least, as long as we're talking about hydrogen/oxygen rockets.

Sylvia.

Originally Posted by Sylvia Else

Day Brown wrote:

Eco freaks will be screaming about the air pollution should chemical
rockets ever be used in enough numbers to do anything substantial in space.

Only the ignorant ones - which is admittedly probably a large proportion
of them.

At least, as long as we're talking about hydrogen/oxygen rockets.

Sylvia.

Single stage to low Earth orbit has been done, but it remains more costly than two stages to low Eath orbit. Perhaps three stages to higher orbit will eventually prove more practical (skiping LEO), then areo braking after separation at perhaps 50 kilometers altitude may be practical, for the first stage.
Adding water vapor to the upper atmosphere may have some detrimental effects, but none are proved at the recent low rate of launches. Neil