Airship on Earth but a reentry glider on Mars

[MUZE]

Could a hybrid airship like spacecraft ever so slowly shed speed using Mars' atmosphere while remaining low orbit while buoyant enough to serve as a glider?

 

[russ_watters]

Could a hybrid airship like spacecraft ever so slowly shed speed using Mars' atmosphere while remaining low orbit while buoyant enough to serve as a glider?

I'm sorry, but this post doesn't make much sense to me. The terms you are using don't seem to apply to how you are using them:
1. A spaceship in orbit has no need for or ability to have buoyancy.
2. Gliders aren't buoyant, they glide on wings.

I'm not sure how this airship idea is forming, but mars's atmosphere is really thin...

 

[MUZE]

I'm sorry, but this post doesn't make much sense to me. The terms you are using don't seem to apply to how you are using them:
1. A spaceship in orbit has no need for or ability to have buoyancy.
2. Gliders aren't buoyant, they glide on wings.

I'm not sure how this airship idea is forming, but Mars's atmosphere is really thin...

The extra surface area of an airship/glider will slow differently compared to a rocket at a much higher altitude, but how? The airship would need some rigidity, provided from the internal air pressure. Because the atmosphere does not have a solid line like water and the airship on contact with the atmosphere at interplanetary speeds would not "splat." Ideally once inside the atmosphere and landed, the inflatable portion of the ship can be used to create a biodome. Would a feather burn up on reentry?

 

[russ_watters]

The extra surface area of an airship/glider will slow differently compared to a rocket at a much higher altitude, but how?

Aerobraking is possible without going to such lengths; it's already a normal component of all spacecraft that go to planets with atmospheres (including Earth).
https://en.wikipedia.org/wiki/Aerobraking

I don't see what value an airship/glider configuration would add, and you're not really saying what value you think it will add. Even if you are just trying to ask "would it work?" I still need to know what you want it to work at in order to be able to answer.

The airship would need some rigidity, provided from the internal air pressure. Because the atmosphere does not have a solid line like water and the airship on contact with the atmosphere at interplanetary speeds would not "splat." Ideally once inside the atmosphere and landed, the inflatable portion of the ship can be used to create a biodome. Would a feather burn up on reentry?

Other than being capable of being used as a biodome, what benefit would the airship provide? I'm not seeing that you're saying anything about what it would do once inside the atmosphere.

 

[DaveC426913]

You're talking about aerobraking.

1. Build your spaceship for maximum spaceflight functionality (i.e. no hybridization).
2. Attach a balloon with an air tank to the nose.
3. The balloon needs little, if any, rigid structure - meaning it is trivial in weight and volume.
4. Deployment is also trivial.
5. Before re-entry, deploy the balloon at the bow. It takes the brunt of re-entry, sheds heat and slows the craft.
6. Eject it when your speed drops below supersonic (or simply reconfigure it as a parachute.)
7. Either way, eject it before landing, so as not to foul the landing.
8. Once your habitat is set up, go and recover the material and use as-needed.

The question to ask is: what is to be gained by all the risks, weight and machinery of a hybrid craft - over two distinct, simple and foolproof flight modes?BTW, the atmo on Mars is about 2% of Earth's. It is a virtual vacuum. You can fly, but it'll be very limited and specialized - a craft as light as possible, carrying absolute minimum equipment to do its specialized reconnaissance job. You sure don't want to be hauling your house, power plant, food, water, interplanetary fuel/tanks and all sorts of other dead-weight paraphernalia around with you everywhere.

 

[mfb]

If you have strong interaction with the atmosphere you are not in an orbit any more, or at least not for long. In principle it's possible to use a low periapsis to do plane changes, as X-37 can do on Earth, but that's a pretty obscure application.

An airplane on Mars needs to be very fast and with a large wing area but low drag to generate enough lift in its thin atmosphere. A lighter than "air" ship would need a large volume with a low structural mass - something balloon-like. That comes with a high drag and doesn't allow high speeds.

The usual approach is deceleration with a heat shield, then parachutes, and finally either rockets or big airbags.

 

[MUZE]

Aerobraking is possible without going to such lengths; it's already a normal component of all spacecraft that go to planets with atmospheres (including Earth).
https://en.wikipedia.org/wiki/Aerobraking

I don't see what value an airship/glider configuration would add, and you're not really saying what value you think it will add. Even if you are just trying to ask "would it work?" I still need to know what you want it to work at in order to be able to answer.

Other than being capable of being used as a biodome, what benefit would the airship provide? I'm not seeing that you're saying anything about what it would do once inside the atmosphere.

The ship could land without or use far less fuel. On departure the blimp materal could be left behind.

 

[russ_watters]

The ship could land without or use far less fuel.

All recent Mars landers I'm aware of have landed without fuel, using parachutes and/or airbags (landers on Earth never use fuel). I suppose a balloon would work as a way to provide a soft landing, but it would probably need to act as or be in addition to a parachute first. And it would add the weight of the envelope and extra hydrogen tanks. It doesn't offer any advantages I can think of.

It might be enlightening to try and estimate the size of a balloon that would be necessary to support a lander such as the Curiosity rover. Do you know how to calculate that from the mass of the rover and density of the atmosphere?

 

[Dullard]

"BTW, the atmo on Mars is about 2% of Earth's. It is a virtual vacuum."

This was my 1 major complaint about "The Martian" (which I otherwise loved). Somehow, that thin atmosphere managed to shred his habitat.

 

[DaveC426913]

"BTW, the atmo on Mars is about 2% of Earth's. It is a virtual vacuum."

This was my 1 major complaint about "The Martian" (which I otherwise loved). Somehow, that thin atmosphere managed to shred his habitat.

You mean the storm.

And it also caused the repaired mylar hatch to flap loosely and spiritedly in the wind - despite an internal air pressure high enough for Watney to live in.

 

[DaveC426913]

@muse : I hope we're not naysaying or discouraging you. I hope we're nudging you towards a thoughtful analysis of the factors involved in what the problem is that needs to be solved, a what viable solutions will have to be accounted for in terms of trade-offs to meet the specific goal.

There's a lot to it, and this is a great start. Carry on.