5 ms·

Wouldn’t an airship be a more viable option for a long term mission on Mars?

by dogma1138 5y ago

FreeFull 5y ago
I imagine with Mars's thin atmosphere, it'd be hard to get enough buoyancy to lift off.
- modshatereality 5y ago
  It won't work at high altitude until we start polluting there. What is air density in one of those nice big craters though?
jvanderbot 5y ago
The atmo is very thin, making the balloon huge relative to the gondola. Some people are quite enthused about it anyway. Including myself. http://www.gaerospace.com/space-exploration/planetary-aerobots/mars-balloons/ http://www.gaerospace.com/space-exploration/planetary-aerobo... With a thick atmo, plenty of sun, and not too much heat / cold in the upper layers. Venus is a _great_ place for balloons. https://www.nasa.gov/vision/universe/solarsystem/venus-20070827.html https://www.nasa.gov/vision/universe/solarsystem/venus-20070...
- dogma1138 5y ago
  I was thinking about a rigid body vacuum airship, landing would be easy because all you need to do is lose the vacuum which can be done with a valve and cost no power. Taking off again can be done over days so you can power it with solar panels if you can’t fit an RTG. I honestly don’t think winds would be that much of an issue they won’t be strong enough to structurally damage the airship they’ll blow it off sure but not break it apart, and crashing into things isn’t as much of a risk at any reasonable altitudes no buildings no trees, sure there are cliffs and mountains but that can be solved with altitude.
  - jvanderbot 5y ago
    And how would that be packed into a landing shell?
    - dogma1138 5y ago
      Just thinking about some solutions - origami of both load baring hard materials and connecting flexible ones, or even do something whacky like have a composite fabric balloon that you inflate and the impregnate with resin insitu then when the resin hardens you have a large shell that can be emptied to create a vacuum.
      - jvanderbot 5y ago
        Put rough numbers to it to check feasibility and submit: https://www.nasa.gov/directorates/spacetech/niac/index.html https://www.nasa.gov/directorates/spacetech/niac/index.html At least one "garage engineer" was selected this last round.
        dogma1138 5y ago
        Someone else already did https://core.ac.uk/download/pdf/161998356.pdf https://core.ac.uk/download/pdf/161998356.pdf
  - jbay808 5y ago
    I'm not aware of any vacuum container that is strong enough to resist buckling while being light enough to be buoyant.
    - elihu 5y ago
      Well, you have low pressure and low gravity working both for you and against you in this case. It doesn't have to be very strong, because atmospheric pressure is so low. But also, the lifting power is also very low, so it would have to be far less dense than a vacuum container would have to be to work on earth. Low gravity means you need less lift, but low gravity also means the weight of the surrounding air is less so you need more volume. I guess that cancels out. I suspect it's not practical in atmosphere as thin as Mars, but maybe with a light enough or strong enough material it's possible? At any rate, you'd need an enormous volume just to lift relatively small payloads. And, just filling a balloon with hydrogen would probably make more sense in almost any situation. At least one good thing Mars has going for it in terms of airships is that CO2 is more dense than Earth's atmosphere. Even nitrogen would be a weak lifting gas on Mars (though it's not available in abundance there as far as I know). Wikipedia has some useful background information: https://en.wikipedia.org/wiki/Vacuum_airship https://en.wikipedia.org/wiki/Vacuum_airship
skybrian 5y ago
Mars air seems a bit thin for that?
trothamel 5y ago
Airships seem somewhat vulnerable to the weather, in practice, as they're always flying. A nice thing about a helicopter is you can land, and it's a station until you take off again.
- mikepurvis 5y ago
  I don't think we know too much at this point about how Ingenuity will survive dust storms— I see a reddit thread on this but not much else: https://www.reddit.com/r/space/comments/lo6k73/what_will_happen_to_the_ingenuity_helicopter_on/ https://www.reddit.com/r/space/comments/lo6k73/what_will_hap... If there was a dedicated mission for a much larger helicopter, it would obviously be important for it to have a story for weathering these things.
  - XorNot 5y ago
    Dust storms on Mars aren't dust storms on Earth - we're not really talking damaging winds due to the low pressure. Moreover, since Ingenuity does fly, and blow air around, it's going to have a much better chance of cleaning it's own solar panels.
- dogma1138 5y ago
  The weather isn’t that of an issue due to the thin atmosphere. You can land an airship by compressing the lifting gas into a liquid. If you can get enough power reserve at least to do that. The main issue would be the size of the balloon but honestly if we can make some origami rigid airframe a vacuum airship might actually work. At that point controlling buoyancy is also less of an issue from a power perspective since you don’t need a large power reserve to land, and when you are on the ground you can wait until you have enough power to create sufficient vacuum in the airship.
  - rtkwe 5y ago
    In general trying to create a vacuum airship is a loosing game because you have to add so much support to prevent it from collapsing that you can't win the race between volume and weight to achieve buoyancy. The thinner atmosphere is a bonus to decreasing the force for a given volume but you simultaneously have to increase the size of the 'balloon' since it's displacing less air for every unit of volume so it has to get bigger which increases the surface area further. Doing some quick math using the ideal shape of a sphere: Mars surface atmosphere is ~1/60th as dense as the Earth's so you'll wind up with 23x the surface area which at the reduced surface pressures of mars you'd be looking at around 15% of the total forces you'd have to resist. For a sphere that might just push it into the realm of possible options but to get to a 'pure' vacuum you need very fancy and heavy pumps that need cryogenic cooling beyond the difficulty of doing this with an actual blimp shape.
Robotbeat 5y ago
No because you get blown about by the winds. That has led to many destroyed zeppelins on Earth. Can’t afford that on Mars. No ground crew to secure it.
- deleted 5y ago
  [deleted]
- dogma1138 5y ago
  That destroyed zeppelins because there are things they can crash into especially during take off and landing and the winds are strong enough to rip them apart it’s not true for Mars. The winds are to weak because of the thin atmosphere and there aren’t that many things to crash into.
  - Robotbeat 5y ago
    But the zeppelin must be much larger for the same mass (and remember buoyancy is ALSO lower in Mars’ gravity).
    - deleted 5y ago
      [deleted]
    - dogma1138 5y ago
      Same holds true for a helicopter… before ingenuity no one knew if a helicopter could even fly on Mars.
      - Robotbeat 5y ago
        That’s not accurate. You can do math to show a helicopter can fly on Mars. And a helicopter benefits from the lower gravity, which doesn’t help a zeppelin (as buoyancy is also reduced by gravity but lift force is independent of gravity). So even though lift for both a zeppelin and a helicopter include a density term, the zeppelin is about a factor of 3 worse. Since helicopters already outcompete zeppelins on Earth, on Mars where helicopters have a factor of 3 advantage over zeppelins, it’ll have an even harder time. It’s equivalent to a zeppelin at around 100,000 ft at Earth. Possible, but not very practical.
stackedinserter 5y ago
FWIW, based on my napkin math you need ~7m diameter balloon filled with hydrogen to lift 1kg of mass (including its shell).

Wouldn’t an airship be a more viable option for a long term mission on Mars?

FreeFull 5y ago

I imagine with Mars's thin atmosphere, it'd be hard to get enough buoyancy to lift off.

modshatereality 5y ago
It won't work at high altitude until we start polluting there. What is air density in one of those nice big craters though?

jvanderbot 5y ago

The atmo is very thin, making the balloon huge relative to the gondola. Some people are quite enthused about it anyway. Including myself. http://www.gaerospace.com/space-exploration/planetary-aerobots/mars-balloons/ http://www.gaerospace.com/space-exploration/planetary-aerobo... With a thick atmo, plenty of sun, and not too much heat / cold in the upper layers. Venus is a _great_ place for balloons. https://www.nasa.gov/vision/universe/solarsystem/venus-20070827.html https://www.nasa.gov/vision/universe/solarsystem/venus-20070...

dogma1138 5y ago
I was thinking about a rigid body vacuum airship, landing would be easy because all you need to do is lose the vacuum which can be done with a valve and cost no power. Taking off again can be done over days so you can power it with solar panels if you can’t fit an RTG. I honestly don’t think winds would be that much of an issue they won’t be strong enough to structurally damage the airship they’ll blow it off sure but not break it apart, and crashing into things isn’t as much of a risk at any reasonable altitudes no buildings no trees, sure there are cliffs and mountains but that can be solved with altitude.
- jvanderbot 5y ago
  And how would that be packed into a landing shell?
  - dogma1138 5y ago
    Just thinking about some solutions - origami of both load baring hard materials and connecting flexible ones, or even do something whacky like have a composite fabric balloon that you inflate and the impregnate with resin insitu then when the resin hardens you have a large shell that can be emptied to create a vacuum.
    - jvanderbot 5y ago
      Put rough numbers to it to check feasibility and submit: https://www.nasa.gov/directorates/spacetech/niac/index.html https://www.nasa.gov/directorates/spacetech/niac/index.html At least one "garage engineer" was selected this last round.
      - dogma1138 5y ago
        Someone else already did https://core.ac.uk/download/pdf/161998356.pdf https://core.ac.uk/download/pdf/161998356.pdf
- jbay808 5y ago
  I'm not aware of any vacuum container that is strong enough to resist buckling while being light enough to be buoyant.
  - elihu 5y ago
    Well, you have low pressure and low gravity working both for you and against you in this case. It doesn't have to be very strong, because atmospheric pressure is so low. But also, the lifting power is also very low, so it would have to be far less dense than a vacuum container would have to be to work on earth. Low gravity means you need less lift, but low gravity also means the weight of the surrounding air is less so you need more volume. I guess that cancels out. I suspect it's not practical in atmosphere as thin as Mars, but maybe with a light enough or strong enough material it's possible? At any rate, you'd need an enormous volume just to lift relatively small payloads. And, just filling a balloon with hydrogen would probably make more sense in almost any situation. At least one good thing Mars has going for it in terms of airships is that CO2 is more dense than Earth's atmosphere. Even nitrogen would be a weak lifting gas on Mars (though it's not available in abundance there as far as I know). Wikipedia has some useful background information: https://en.wikipedia.org/wiki/Vacuum_airship https://en.wikipedia.org/wiki/Vacuum_airship

skybrian 5y ago

Mars air seems a bit thin for that?

trothamel 5y ago

Airships seem somewhat vulnerable to the weather, in practice, as they're always flying. A nice thing about a helicopter is you can land, and it's a station until you take off again.

mikepurvis 5y ago
I don't think we know too much at this point about how Ingenuity will survive dust storms— I see a reddit thread on this but not much else: https://www.reddit.com/r/space/comments/lo6k73/what_will_happen_to_the_ingenuity_helicopter_on/ https://www.reddit.com/r/space/comments/lo6k73/what_will_hap... If there was a dedicated mission for a much larger helicopter, it would obviously be important for it to have a story for weathering these things.
- XorNot 5y ago
  Dust storms on Mars aren't dust storms on Earth - we're not really talking damaging winds due to the low pressure. Moreover, since Ingenuity does fly, and blow air around, it's going to have a much better chance of cleaning it's own solar panels.
dogma1138 5y ago
The weather isn’t that of an issue due to the thin atmosphere. You can land an airship by compressing the lifting gas into a liquid. If you can get enough power reserve at least to do that. The main issue would be the size of the balloon but honestly if we can make some origami rigid airframe a vacuum airship might actually work. At that point controlling buoyancy is also less of an issue from a power perspective since you don’t need a large power reserve to land, and when you are on the ground you can wait until you have enough power to create sufficient vacuum in the airship.
- rtkwe 5y ago
  In general trying to create a vacuum airship is a loosing game because you have to add so much support to prevent it from collapsing that you can't win the race between volume and weight to achieve buoyancy. The thinner atmosphere is a bonus to decreasing the force for a given volume but you simultaneously have to increase the size of the 'balloon' since it's displacing less air for every unit of volume so it has to get bigger which increases the surface area further. Doing some quick math using the ideal shape of a sphere: Mars surface atmosphere is ~1/60th as dense as the Earth's so you'll wind up with 23x the surface area which at the reduced surface pressures of mars you'd be looking at around 15% of the total forces you'd have to resist. For a sphere that might just push it into the realm of possible options but to get to a 'pure' vacuum you need very fancy and heavy pumps that need cryogenic cooling beyond the difficulty of doing this with an actual blimp shape.

Robotbeat 5y ago

No because you get blown about by the winds. That has led to many destroyed zeppelins on Earth. Can’t afford that on Mars. No ground crew to secure it.

deleted 5y ago
[deleted]
dogma1138 5y ago
That destroyed zeppelins because there are things they can crash into especially during take off and landing and the winds are strong enough to rip them apart it’s not true for Mars. The winds are to weak because of the thin atmosphere and there aren’t that many things to crash into.
- Robotbeat 5y ago
  But the zeppelin must be much larger for the same mass (and remember buoyancy is ALSO lower in Mars’ gravity).
  - deleted 5y ago
    [deleted]
  - dogma1138 5y ago
    Same holds true for a helicopter… before ingenuity no one knew if a helicopter could even fly on Mars.
    - Robotbeat 5y ago
      That’s not accurate. You can do math to show a helicopter can fly on Mars. And a helicopter benefits from the lower gravity, which doesn’t help a zeppelin (as buoyancy is also reduced by gravity but lift force is independent of gravity). So even though lift for both a zeppelin and a helicopter include a density term, the zeppelin is about a factor of 3 worse. Since helicopters already outcompete zeppelins on Earth, on Mars where helicopters have a factor of 3 advantage over zeppelins, it’ll have an even harder time. It’s equivalent to a zeppelin at around 100,000 ft at Earth. Possible, but not very practical.

stackedinserter 5y ago

FWIW, based on my napkin math you need ~7m diameter balloon filled with hydrogen to lift 1kg of mass (including its shell).