To add another perspective here - this as yet unproven technology - but in principle you might possibly, with the right spaceship, be able to come in with no g loading at all, and no aerobraking. Just gradually decelerate with ion thrusters over a period of many days.
For that to work your spacecraft needs to be able to float in the upper atmosphere. So needs to be extremely light. The idea is to make it a kilometer scale vessel filled with hydrogen or helium at low pressure, similar pressure to the atmosphere at a height of 60 km and upwards. So it is filled with an "almost vacuum" but even so it would float on the denser upper atmosphere.
There's a difficult transition there when your vessel is traveling at several times the speed of sound in the upper atmosphere, supported partly by buoyancy and partly just because it is still moving so fast, so almost in orbit.
However at that point the air also is very thin. The proponents of this idea cite an example of an early Echo balloon which did a sub orbital hop through the upper atmosphere and survived most of it intact. When it did explode, this was mainly because they made a mistake and left too much gas in it.
There were no follow up experiments to find out the effects of the upper atmosphere on suborbital balloons - the remaining Echo balloon flights were in orbit which of course is no problem for a balloon.
Once you get down to 60 km, at that point just floating in the atmosphere like a normal helium or hydrogen balloon, you would then transfer to a normal airship rated for Earth surface conditions. The kilometer scale balloon would return to orbit and just shuttles back and forth like that.
You can hear John Powell, the man himself talk about it in a recent Spaceshow talk, and decide for yourself. They have a very interesting philosophy also, it's a company that does its development in the slow lane. They've been working towards this for decades and finance their development by the discoveries they make along the way.
Find out more here: Guest: John Powell. Topics: Updates on JP Aerospace and the Airship To Orbit program.
See also
Projects To Get To Space As Easily As We Cross Oceans - A Million Flights A Year Perhaps - Will We Be Ready?
For that to work your spacecraft needs to be able to float in the upper atmosphere. So needs to be extremely light. The idea is to make it a kilometer scale vessel filled with hydrogen or helium at low pressure, similar pressure to the atmosphere at a height of 60 km and upwards. So it is filled with an "almost vacuum" but even so it would float on the denser upper atmosphere.
There's a difficult transition there when your vessel is traveling at several times the speed of sound in the upper atmosphere, supported partly by buoyancy and partly just because it is still moving so fast, so almost in orbit.
However at that point the air also is very thin. The proponents of this idea cite an example of an early Echo balloon which did a sub orbital hop through the upper atmosphere and survived most of it intact. When it did explode, this was mainly because they made a mistake and left too much gas in it.
There were no follow up experiments to find out the effects of the upper atmosphere on suborbital balloons - the remaining Echo balloon flights were in orbit which of course is no problem for a balloon.
Once you get down to 60 km, at that point just floating in the atmosphere like a normal helium or hydrogen balloon, you would then transfer to a normal airship rated for Earth surface conditions. The kilometer scale balloon would return to orbit and just shuttles back and forth like that.
You can hear John Powell, the man himself talk about it in a recent Spaceshow talk, and decide for yourself. They have a very interesting philosophy also, it's a company that does its development in the slow lane. They've been working towards this for decades and finance their development by the discoveries they make along the way.
Find out more here: Guest: John Powell. Topics: Updates on JP Aerospace and the Airship To Orbit program.
See also
Projects To Get To Space As Easily As We Cross Oceans - A Million Flights A Year Perhaps - Will We Be Ready?
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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