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Parachute For Reentry

Spacescifi

By Spacescifi
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Spacescifi

Spacescifi

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Physically I think this idea borders the line of cutting edge to not possible.

Before reentry with a large vessel, deploy an even larger parachute. Magnetize the parachute somehow.

Massive parachute and super long tethers.

Do reentry, massive magnetic parachute catches the plasma and air and slows ship more than it would without it.

Saving rocket propellant for landing.

Ideally in the future we can make lightweight magnetic fabrics and liquids common and heat resistant. Since that is required for this to work.

What do you think?

Edited by Spacescifi
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RCgothic

RCgothic

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I think - firstly, very little propellant is used to de-orbit.  The shuttle OMS had a capability for just 300m/s DV, and that was used for orbital insertion as well as de-orbit. The vast majority is scrubbed off through atmospheric drag. Increasing the drag just increases the g-loading.

Secondly, I don't think any such flimsy structure has even a slight hope of withstanding re-entry conditions.

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sevenperforce

sevenperforce

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1 hour ago, RCgothic said:

I think - firstly, very little propellant is used to de-orbit.  The shuttle OMS had a capability for just 300m/s DV, and that was used for orbital insertion as well as de-orbit. The vast majority is scrubbed off through atmospheric drag. Increasing the drag just increases the g-loading.

Secondly, I don't think any such flimsy structure has even a slight hope of withstanding re-entry conditions.

It's not actually a bad idea. If you make surface area enough, you can get meaningful drag at very high altitudes, before you hit typical "re-entry conditions" at all. The "fire zone" for re-entry is the boundary between the stratosphere and the mesosphere -- 49 to 80 km. Any drag higher than that simply decreases your speed in the fire zone and thus decreases both g-loading and peak heating. 

If you can scrub a significant portion of your speed high in the mesosphere, you drop peaking heating and g-loading considerably. Elon has actually mused about this -- giving the Starship "dragon wings" of deployable stainless steel ribbons. It's just very hard to get right, and almost impossible to get right without sacrificing the drag surfaces...which in turn means a separation event during the worst part of the flight envelope.

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Spacescifi

Spacescifi

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1 hour ago, sevenperforce said:

It's not actually a bad idea. If you make surface area enough, you can get meaningful drag at very high altitudes, before you hit typical "re-entry conditions" at all. The "fire zone" for re-entry is the boundary between the stratosphere and the mesosphere -- 49 to 80 km. Any drag higher than that simply decreases your speed in the fire zone and thus decreases both g-loading and peak heating. 

If you can scrub a significant portion of your speed high in the mesosphere, you drop peaking heating and g-loading considerably. Elon has actually mused about this -- giving the Starship "dragon wings" of deployable stainless steel ribbons. It's just very hard to get right, and almost impossible to get right without sacrificing the drag surfaces...which in turn means a separation event during the worst part of the flight envelope.

 

You filled in the details quite nicely. Thank you.

The big irony of space travel is the bigger your vessel the safer you are in space.

The main problem with big vessels is less launch and more landing .

That's why I thought of the parachute.... hey! 

Can ya test this in KSP?

I know KSP is not IRL, but it IS the next best thing.

Edited by Spacescifi
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Bill Phil

Bill Phil

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Well there are proposals for "ballutes", balloon parachutes that should perform well at supersonic speeds. Maybe not hypersonic, but I'm not sure.

That's the issue with parachutes, at least the normal kind. 

But a ballute could increase the drag of the vehicle in the upper atmosphere enough to reduce peak gee loads and make the temperature more survivable. Of course keeping the ballute could be a challenge in its own right, but it may be possible...

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sevenperforce

sevenperforce

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21 minutes ago, Spacescifi said:

The big irony of space travel is the bigger your vessel the safer you are in space.

In some ways. However the bigger your vessel, the more cross-section you have to get hit by a meteor large enough to penetrate your prop tanks, and if you need those, you're hosed. That's another reason why the Starship's use of header tanks for landing is a good idea.

Many of the SSTO spaceplane concepts from the 80s and 90s used wet wings that would be filled with props (usually liquid hydrogen) on launch, then vented to vacuum once orbit was reached. They used hypergols for deorbit. Their increased drag cut down on g-loading and re-entry heat, and then they could be used for aerodynamic lift to get a nice clean rolling landing for "free". 

21 minutes ago, Spacescifi said:

The main problem with big vessels is less launch and more landing .

That's why I thought of the parachute.... hey! 

The sort of parachute which works for re-entry is not the sort of parachute which will let you land safely,

21 minutes ago, Spacescifi said:

Can ya test this in KSP?

I know KSP is not IRL, but it IS the next best thing.

Unlike in real life, KSP has a sharp cutoff of atmosphere (and hence drag) at 70 km, so you can't get truly slow and gradual deorbits.

 

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Spacescifi

Spacescifi

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51 minutes ago, sevenperforce said:

In some ways. However the bigger your vessel, the more cross-section you have to get hit by a meteor large enough to penetrate your prop tanks, and if you need those, you're hosed. That's another reason why the Starship's use of header tanks for landing is a good idea.

Many of the SSTO spaceplane concepts from the 80s and 90s used wet wings that would be filled with props (usually liquid hydrogen) on launch, then vented to vacuum once orbit was reached. They used hypergols for deorbit. Their increased drag cut down on g-loading and re-entry heat, and then they could be used for aerodynamic lift to get a nice clean rolling landing for "free". 

The sort of parachute which works for re-entry is not the sort of parachute which will let you land safely,

Unlike in real life, KSP has a sharp cutoff of atmosphere (and hence drag) at 70 km, so you can't get truly slow and gradual deorbits.

 

 

I was aware that the reenrty parachute won't slow the ship enough. To do that would require truly massive parachutes.

But I a magnetic ballute siunds feasible, more than with a normal parachute since it it is more enclosed.

No reason why we cannot have this in the future some day.

We can minaturize magnets into the fabric or even make the fabric a kind of electromagnet.

Future I say, because minaturizing all the tech to do that would be hard.

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sevenperforce

sevenperforce

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13 minutes ago, Spacescifi said:

I was aware that the reenrty parachute won't slow the ship enough. To do that would require truly massive parachutes.

But I a magnetic ballute siunds feasible, more than with a normal parachute since it it is more enclosed.

No reason why we cannot have this in the future some day.

We can minaturize magnets into the fabric or even make the fabric a kind of electromagnet.

Future I say, because minaturizing all the tech to do that would be hard.

What is it about magnets that you suppose will help?

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Spacescifi

Spacescifi

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1 minute ago, sevenperforce said:

So will electromagnetism...like a heat shield.

 

I guess... you get what you pay for in space travel.

The more control you have over dangerous situatiojs the better I say.

Why let reentry have whatever way it wants with you?

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sevenperforce

sevenperforce

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Just now, Spacescifi said:

I guess... you get what you pay for in space travel.

The more control you have over dangerous situatiojs the better I say.

Why let reentry have whatever way it wants with you?

My point is that magnetism doesn't do anything to plasma under those conditions.

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wumpus

wumpus

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2 minutes ago, Spacescifi said:

 

I guess... you get what you pay for in space travel.

The more control you have over dangerous situatiojs the better I say.

Why let reentry have whatever way it wants with you?

 

Just now, sevenperforce said:

My point is that magnetism doesn't do anything to plasma under those conditions.

The other issue is that any [magnetic] force you can exert to reduce orbital velocity can be trivially reversed and used to go from orbital to escape velocity.  You can move a satellite by moving against Earth's magnetic field, but it is only good for stationkeeping, not significantly changing velocity.

It also only works on a few planets, Earth being one of them (Jupiter might be another).

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sevenperforce

sevenperforce

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4 minutes ago, Spacescifi said:

Depends on field configuration and strength no?

Futuristic tech could do it... modern see's it as impossible.

It doesn't really depend on field configuration or field strength, no. The plasma inducement is the result of compression heating. If you had a way to use magnetism to interact with the plasma and slow down, you wouldn't have the compression heating and so you wouldn't have the plasma to work with.

You can, however, use magnetism in the thermosphere to slow down more slowly and reduce re-entry speed that way.

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