New Atmospheric reentry technique

JoshNH4H · 2008-04-01 14:48:19

This is a technique t go from earth, mars, or any planet with an atmosphere's orbit to landing without heavy heat shields.

The spacecraft is in, lets say, LEO. It goes by hohmann transfer orbit to an orbit about 100-110 km above the surface of the earth, or lower if you are in a hurry (but no lower than about 90 km, to avoid the affects of the thicker atmosphere). These orbits only have very short term stability, so within a day, the ship would no longer have orbital velocity. However, if it is at 95% of orbital velocity, it is still 95% weightless. The other 5% is covered by using atmospheric lift. Basically, it slowly transitions from orbit to atmospheric flight, decending as more atmosphere is needed to keep it up.

louis · 2008-04-01 15:25:48

Jumpboy -

Yes I've wondered about that myself - ever decreasing orbits...does anyone know if the science makes this possible. Obviously it can't be that easy to do otherwise it would be done.

Personally I back slow descent with retro rockets.

idiom · 2008-04-02 01:57:42

That is pretty much JP Aerospace all over.

The difficulty is that the 5% of lift is being generated at pretty serious speed. Unless you come in slowly then you will still need shielding.

JP Aerospace's ideas are generally to enter or leave using large ballons.

JoshNH4H · 2008-04-02 13:38:26

very large speed, but very thin atmosphere

JoshNH4H · 2008-04-03 14:16:19

any other opinions?

idiom · 2008-04-03 22:30:17

If its thick enough to provide lift then is probably thick enough to burn you.

However instead of lift you might decrease speed enough to drop into a dynamic soaring mode for a while, skipping on the thick atmosphere. However it will still be pretty warm and I don't know what the next step would be.

What you really need are deflector fields.

Terraformer · 2008-04-04 15:00:21

Wasn't the X-33 going to bounce off the atmosphere for reentry? Or the Hyposoar (same thing?) I know that the X-33 used steel for it's reentry shield.

How long are we talking to reduce speed and what Gs?

If we can ditch the shielding... SSTO?

Terraformer · 2008-04-06 11:12:47

This page is interesting.

Terraformer · 2008-04-09 04:47:09

Inflatable heat shielding?

SpaceNut · 2008-04-09 13:17:16

Inflatable heat shielding?

You can find about this in this topic thread http://www.newmars.com/forums/viewtopic … 9&start=20

JoshNH4H · 2008-04-09 14:07:54

possibly an inflatible wing decelleration. First, the ship would decent to 95 kms altitude. Then it would inflate the wing to 10 bars. At first, the airfoil would create force downwards, to about 90 kms. Then, it would deflate the part of the wing making downward force. it would slowly inflate the up-force wing, as needed, and transform to high-altitude, high- velocity flight.

During this, in the main part of the craft, the heat shield would be shaped so that a small part of the shockwave would be near it. Hydrogen would be sprayed there, to cool the shock wave, and to create some backwards thrust.

SpaceNut · 2008-04-09 18:54:28

There is a thread on inflateable wings that was part of a scout mission that was cancelled.

Airplanes on Mars http://www.newmars.com/forums/viewtopic.php?t=3510

Terraformer · 2008-04-10 03:57:17

I was thinking more along the lines of JP Aerospaces idea.

RobS · 2008-04-12 08:43:59

You'd need an atmospheric physicist to look into this, but I am pretty sure that at 90 kms or so, the air is thick enough to prevent an orbit, but not thick enough to give you any measurable lift. You could roughly figure it out if you can get figures for the density of the earth's atmosphere. One cubic meter of air at sea level masses about 1.3 kilograms. If you have a heat shield that has a surface area of 1 square meter and it is moving forward at 1 meter per second, it will encounter 1 cubic meter of air per second. Orbital velocity is 7,800 meters per second, so that 1 square meter shield will encounter 7,800 cubic meters per second of air. If you know the density of the air, you can figure out the mass encountered, and if you know the mass of the object being slowed, you can figure out the decelleration (assuming the air is not moving at all and assuming the air is accelerated to the same speed as the object, which I suppose it isn't).

-- RobS

dicktice · 2008-04-12 18:23:03

Why not provide an uninsulated reentry vehicle with (1) downward thrust rocket vectoring and (2) sufficient retained fuel aboard, to reduce the rate of descent into the atmosphere until commensurate with the reduction in velocity to avoid burning-up?

JoshNH4H · 2008-04-12 18:32:26

basically the 'brute force' strategy? Use more fuel to slow down?

Terraformer · 2008-04-13 06:47:23

Slow it down with retros to Mach 5 then deploy a Hypercone?

Fuel, fuel, and more fuel. The only a chem rocket could do that is if we had a refueling station in LEO.

JoshNH4H · 2008-04-13 07:14:42

I've been thinking ( :shock: ) What about making a Thermal rocket out of the heat shock. Temperatures nearing 8000 K are generally reached, so CH4/ NH3 would suit this purpose nicely.

Terraformer · 2008-04-13 10:45:09

that's MY idea i proposed A FEW MONTHS ago but APPARANTLY it wouldnt work

It was something to do with retrorockets on a planet with an atmosphere.

dicktice · 2008-04-13 13:05:40

Not retro rockets--but by conserving enough residual fuel to provide downward thrust as needed to reduce the rate of descent enough to prevent burning-up while aerodynamic drag slows down the space vehicle.

Terraformer · 2008-04-13 13:09:05

Please explain.

dicktice · 2008-04-13 14:01:16

Well, I'll try. Once you've deorbited and reconfigured the orbiter to nose-first reentry attitude ... in order to prevent burning-up as the air density increases more rapidly than aerodynamic drag can slow it down, simply tilt the nose up steeply to increase the drag and then use residual fuel to make downward-thrusting burns in order to control the rate of descent into the atmosphere.

Terraformer · 2008-04-13 14:06:14

That's how craft enter now, with the nose up. The other idea is just normal retro rockets.

I still like the idea of inflatable heat shielding to increase drag.

dicktice · 2008-04-13 14:17:16

No, I mean straight up--for the express purpose of using downward thrust.

JoshNH4H · 2008-04-13 18:21:35

I like that Idea. That's like I was proposing, except simpler. Possibly for increaced simplification, we could use the atmospheric thermal rocket previously mentioned. as for this,

that's MY idea i proposed A FEW MONTHS ago but APPARANTLY it wouldnt work
It was something to do with retrorockets on a planet with an atmosphere.

LOL

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