Inverted Aerobraking

Hi Lucio,

at least you're half right with your interpretation :*).
Maybe you will find some time to read it again?

Lucio de Souza Coelho wrote:

>I am not sure if I understood the concept. (I read the article quite
>quickly and maybe I am missing details, so forgive with I show obvious
>misinterpretations below.) Are you talking about creating a kind of
>"chemical Orion flying in a flammable stream of fuel droplets"? That is:
>
Hm, Orion was the concept of driving a space ship/shuttle using atomic
bombs?
No, no. Please don't mix that.
First of all I'm mostly talking about kinetical energy. Chemical energy
might help
to safely transfer kinetical energy, but basically it's irrelevant. See
the numbers in the text.
Secondly a (semi-)continuous stream of gas (which carries the kinetical
energy)
is necessary. Otherwise it will be too destructive.

I was told that kinetical energy of anything at a delta vee of 8 to 12
km/s has many times
the chemical bonding energy of any material. Per molecule. When
colliding directly it will destroy
a lot of the shield or plate or parachute or whatever you try to use, no
matter how strong
the material is that you use.
If aerobraking wouldn't be a demonstrated technology, I would consider
my idea impossible.
Apparently with aerobraking the gas/air compressed in front of the space
ship
is effectively a protective cushion.

>a) Something in space drops fuel in the atmosphere.
>
Not into the atmoshpere.
The space ship goes out of the atmosphere in a traditional way.
The big problem is _not_ to go to space. The big problem is to go to
orbital speed!
It is very important to understand the difference.
(I was very surprised when I realized it myself.)

>b) Your ship enters the fuel stream and somehow ignites fuel behind it.
>
Ignition is misleading. The problem is to place the gas into space. It
will expand fast.
(But much slower than 8 or 12 km/s.) One possibility I suggest to
investigate is to deposit
it as a boiling fluid a few seconds or milliseconds before it hits the
ship. If there are any drops
of liquid that are not evaporated yet, I hope the "exhaust" of the space
ship will take
care of that and turn them into gas before any drop of liquid can hit
the space ship like
a little grenade.

I am deliberatly vague on the kind of the fuel.
If you need something specific for a first discussion, try to imagine
oxygen or water.

>c) The "continuous explosion" of fuel propels the ship to outer space.
>
The ship is pushed to orbital speed (say low earth orbit) by a
continuous stream of gas,
ideally. Just how continuous it has to be is an open question.

>Supposing that (a) and (b) can somehow be solved (and supposing that I
>understood the concept :-), then there is still the eternal
>chicken-and-egg problem: your "inverted aerobraking" needs
>extraterrestrial fuel sources to provide CATS, but extraterrestrial fuel
>sources probably need CATS to be explored in a viable way.
>
It's not a concept for the next space shuttle. It needs more than a
dozen space flights per
year to become economical. No question about that.
But if NASA seriously considers to ship fuel from outer space to low
earth orbit (and
I think they still do, in the long run) then inverted aerobraking
wouldn't need very much
more economic effort.