Author Topic: Mars EDL technologies  (Read 175822 times)

Offline Lobo

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Re: Mars EDL technologies
« Reply #80 on: 09/09/2009 10:45 pm »
One way to get around shroud volume issues would be to use an expandable aerodynamic decelerator, like the inflatable heatshield NASA just recently tested.

Imagine a circular heatshield launched on a rocket with a 10m fairing expanding to 25m ... such a thing could conceivably bring down cargo in the range from 50t to 60t, just what you need for Semi-Direct missions.

Inflatable heat shield?  Sweet!  It’ll be just like Indiana Jones and the Temple of Doom, when they jumped out of the airplane with the inflatable raft!

But seriously, it’d be something to look at if there was anyway to do it to save mass.  I am assuming the huge inflatable heat shield would slow the craft enough that it wouldn’t see the temperatures during normal entry?  Normally that’d get hot enough to burn up anything inflatable, right?  I’m curious about that.

Perhaps instead of a “heat shield” you have a huge inflatable parachute that you deploy before entry.  More of an inflatable structure that would deploy the canopy when there’s otherwise no atmosphere yet to do it.  Then as you enter the atmosphere, that big inflatable parachute begins to gently create drag and slow the craft before it gets down into the thicker atmosphere.  As you get into the thicker atmosphere, then it acts as more of a conventional parachute.

Offline alexterrell

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Re: Mars EDL technologies
« Reply #81 on: 09/11/2009 08:12 pm »
I think if you want to do some propulsive deceleration it is best to do it as late as possible: let the atmosphere do the work of decelerating you to about 1km/s, and then do the rest propulsively.

Sure, but the problem is that that is very difficult with EELV fairings, unless you come up with something like foldable or inflatable heatshields. By the time you get to just above the surface you would be going too fast and the atmospheric density would be too high to fire your thrusters.


Quote
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Coming in from orbit will reduce the heat load of the heat shield, but it will not significantly reduce the required delta-v. And designing a heat shield for 6km/s hyperbolic entry is not that challenging compared to an earth entry. So if your mission architecture requires hyperbolic entry (e.g. mars direct) you can do it.

From orbit it is something like 3.5 km/s, which is quite a bit less than 6 km/s.

Yes. But the part where the thin atmosphere hurts you the most is not the initial part of the deceleration but the last part of the deceleration. Getting from 6km/s to 2km/s is no problem even with a high ballistic coefficient and the thin martian atmosphere. The part from 2km/s to subsonic is where you need the low ballistic coefficient and/or propulsive braking.

Yes, but the demand on the heat shield is much less. The heating is 1/3 or so and the force is halved. That would allow you to have a much lighter foldable heat-shield - probably all titanium and no carbon-carbon stuff. That would allow foldable heatshields.

See the picture here http://forum.nasaspaceflight.com/index.php?topic=18717.30

Offline A_M_Swallow

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Re: Mars EDL technologies
« Reply #82 on: 09/12/2009 03:22 am »
Are inflatable heat shields reusable?
If not a new heat shield and possible an entire lander needs bringing from Earth for each landing, this will be expensive.


Offline Kaputnik

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Re: Mars EDL technologies
« Reply #83 on: 09/13/2009 09:13 am »
Hey guys.

I was wondering whether anyone has thought about putting some degree of abort-to-surface capability in the mars ascent capsule?

It's quite possible that the ascent vehicle would have a large (ISRU) cryo propulsion unit and a smaller hypergol, or even monoprop, RCS/RoCS/OMS propulsion system built into the crew cabin itself. This would allow the spent cryo stage to be staged, saving overall mass. It would also provide a reliable and simple method of performing attiude/roll control, apogee burn, and rendezvous/proxops burns.
Assuming sufficient thrust from this system, it may be a relatively simply software change to allow this RCS to perform an emergency landing burn after a low-altitude cryo stage separation, i.e. in an ascent abort. This could give protection for a very early ascent abort.
Inclusion of a parachute might allow extension to later ascent aborts, but will now cost mass. To achieve aborts from later on in the ascent, a heatshield would be needed on the cabin, which adds yet more mass.

It's interesting to explore this idea, but of course the LM had no such capability and instead relied on having the upmost reliablity in the primary system.
"I don't care what anything was DESIGNED to do, I care about what it CAN do"- Gene Kranz

Offline Michael Bloxham

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Re: Mars EDL technologies
« Reply #84 on: 09/13/2009 09:37 am »
I have often heard it said that, if Apollo had been proposed today, it would have been rejected on safety grounds.

This is now the 21st century, and I think we can do better. We should do better.

- Mike

Offline MickQ

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Re: Mars EDL technologies
« Reply #85 on: 09/16/2009 06:54 am »
Hey guys.

I was wondering whether anyone has thought about putting some degree of abort-to-surface capability in the mars ascent capsule?

Because this is Mars, and the atmosphere is thin, I was thinking you could make the ascent capsule reallly wide and fat, but bare-boned and lightweight: Essentially extremely low-density. That way you might be able to get away with just a thin coating of PICA, and less descent propellant but huge parachutes instead. Land the thing on some giant air-bags or something. You could also use the ascent capsule as your earth-reentry capsule. That way you don't have to lug your reentry capsule all the way from earth to mars and then back again with your ERV (or MDS or transhab or whatever you want to call it).

Okay, full abort-to-surface capability might be a bit much. And you have the problem of saving the crews once they land hundreds of kilometers down-range (although this is where orbital caching of emergency supply packs can really help). So how about just a partial abort-to-surface capability: Fly a dog-leg ascent profile, and keeping the low-density capsule idea, allow an abort-to-surface during the vertical part of the ascent only. The capsule should fall nearer where they lifted off, and the sub-orbital reentry environment should be benign enough that you can keep the capsule really lightweight.

So there are two ideas here: 1) Put full EDL systems on your ascent capsule so you can use it as your earth-reentry capsule too. That way you have full abort-to-surface capability, and you don't have to lug your reentry capsule all the way from earth to mars and then back again.

And 2) Using a dog-leg ascent profile, and just putting a minimal abort-to-surface capability in the capsule to allow aborts during the vertical part of the descent only.

Both using extremely low-density capsule designs with big parachutes and minimal-mass landing systems.

Your thoughts guys?

I guess the question for (1) is: Can mars-optimized EDL systems be made to work adequately during earth-reentry (or vice-versa, whichever way you want to look at it). In other words, can you design an EDL system which can accomplish both tasks reasonably well, without resorting to complete duplication of systems?

And for (2): How lightweight can you make the capsule if you only design in abort-to-surface capability during the vertical part of ascent? And would the vertical flight phase last long enough to make a minimal abort-to-surface capability worthwhile?

- Mike

Mike.

Do your orbital supply packs include ISRU units ?? 

Mick.

Offline Michael Bloxham

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Re: Mars EDL technologies
« Reply #86 on: 09/16/2009 08:53 am »
Mick,

I'm surprised you caught that in there ;)

As I imagine them, no. Just a couple of tonnes worth of general supplies, and maybe an inflatable shelter or something (although the capsule would be low-density to be useful for reentry, so the capsule by itself should be quite spacious).

Over at MarsDrive we're looking at an architecture which uses long-range mobile habs. In addition to the 'standard' array of safety advantages that they provide to the architecture (crew are always within stones-throw of their base, bring their radiation protection with them, no need to commute in dinky rovers, etc.) I would imagine that they could also be remotely driven. So as long as the aborted capsule lands within say a few hundred kilometers of the launch area, then it should take only a few days for the mobile habs to reach the crew for rescue. A few tonnes of supplies should last the crew a few weeks, even without recycling. So there should be ample opportunity for rescue. Our current baseline actually uses two mobile habs (as this divides their mass in half, and also allows a fully-paired approach thus further increasing mission safety). Perhaps one of them could be pre-staged downrange before the crew even attempts the ascent? Just musings at this stage of course.

You've actually brought up quite an interesting question. Perhaps the case can be made for a small ISRU plant and recyling onboard the orbitally cached 'rescue pack'? But keeping in mind that this thing would be in orbit for at least a few years before being used and therefore cant really store hydrogen onboard, then what sort of ISRU could you use?

Other options which might fit within the ~2 tonne payload envelope might include a small open rover with supplies, or perhaps even something like the Apollo LRF/LESS?

Interesting topic. Is there a spereate thread for 'mars rescue options' and such? I'll have a look...

- Mike
« Last Edit: 09/16/2009 09:16 am by Michael Bloxham »

Offline A_M_Swallow

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Re: Mars EDL technologies
« Reply #87 on: 09/16/2009 11:15 pm »

You've actually brought up quite an interesting question. Perhaps the case can be made for a small ISRU plant and recyling onboard the orbitally cached 'rescue pack'? But keeping in mind that this thing would be in orbit for at least a few years before being used and therefore cant really store hydrogen onboard, then what sort of ISRU could you use?

ISRU hydrogen can be made from the electrolysis of water.  Ice is suspected to be on the surface of Mars.  Ice can be melted with a lens and sunlight.

Offline MickQ

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Re: Mars EDL technologies
« Reply #88 on: 09/17/2009 01:31 am »
Mick,

I'm surprised you caught that in there ;)

As I imagine them, no. Just a couple of tonnes worth of general supplies, and maybe an inflatable shelter or something (although the capsule would be low-density to be useful for reentry, so the capsule by itself should be quite spacious).

Over at MarsDrive we're looking at an architecture which uses long-range mobile habs. In addition to the 'standard' array of safety advantages that they provide to the architecture (crew are always within stones-throw of their base, bring their radiation protection with them, no need to commute in dinky rovers, etc.) I would imagine that they could also be remotely driven. So as long as the aborted capsule lands within say a few hundred kilometers of the launch area, then it should take only a few days for the mobile habs to reach the crew for rescue. A few tonnes of supplies should last the crew a few weeks, even without recycling. So there should be ample opportunity for rescue. Our current baseline actually uses two mobile habs (as this divides their mass in half, and also allows a fully-paired approach thus further increasing mission safety). Perhaps one of them could be pre-staged downrange before the crew even attempts the ascent? Just musings at this stage of course.

You've actually brought up quite an interesting question. Perhaps the case can be made for a small ISRU plant and recyling onboard the orbitally cached 'rescue pack'? But keeping in mind that this thing would be in orbit for at least a few years before being used and therefore cant really store hydrogen onboard, then what sort of ISRU could you use?

Other options which might fit within the ~2 tonne payload envelope might include a small open rover with supplies, or perhaps even something like the Apollo LRF/LESS?

Interesting topic. Is there a spereate thread for 'mars rescue options' and such? I'll have a look...

- Mike

Hey Mike.

I was thinking along the lines of if the capsule came down somewhere not easily accessable for a rescue, say down in Marineris or on  Olympus as  extreme examples, then it could be quite a while before they hook up with a Hab/rover.  Water and oxygen may run short especially if one or more of the crew are injured or are actively trying to find a way out.

Mick

Offline MickQ

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Re: Mars EDL technologies
« Reply #89 on: 09/17/2009 01:42 am »
Mick,

I'm surprised you caught that in there ;)

As I imagine them, no. Just a couple of tonnes worth of general supplies, and maybe an inflatable shelter or something (although the capsule would be low-density to be useful for reentry, so the capsule by itself should be quite spacious).

Over at MarsDrive we're looking at an architecture which uses long-range mobile habs. In addition to the 'standard' array of safety advantages that they provide to the architecture (crew are always within stones-throw of their base, bring their radiation protection with them, no need to commute in dinky rovers, etc.) I would imagine that they could also be remotely driven. So as long as the aborted capsule lands within say a few hundred kilometers of the launch area, then it should take only a few days for the mobile habs to reach the crew for rescue. A few tonnes of supplies should last the crew a few weeks, even without recycling. So there should be ample opportunity for rescue. Our current baseline actually uses two mobile habs (as this divides their mass in half, and also allows a fully-paired approach thus further increasing mission safety). Perhaps one of them could be pre-staged downrange before the crew even attempts the ascent? Just musings at this stage of course.

You've actually brought up quite an interesting question. Perhaps the case can be made for a small ISRU plant and recyling onboard the orbitally cached 'rescue pack'? But keeping in mind that this thing would be in orbit for at least a few years before being used and therefore cant really store hydrogen onboard, then what sort of ISRU could you use?

Other options which might fit within the ~2 tonne payload envelope might include a small open rover with supplies, or perhaps even something like the Apollo LRF/LESS?

Interesting topic. Is there a spereate thread for 'mars rescue options' and such? I'll have a look...

- Mike

Hey Mike.

I was thinking along the lines of if the capsule came down somewhere not easily accessable for a rescue, say down in Marineris or on  Olympus as  extreme examples, then it could be quite a while before they hook up with a Hab/rover.  Water and oxygen may run short especially if one or more of the crew are injured or are actively trying to find a way out.

Mick

Another thought.  Maybe for your rescue pack or just as a general piece of exploration equipment,  remember the old "Lost in Space" rocket pack.  How would something like that work in Mars G with methane fuel?

Mick.

Offline jongoff

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Re: Mars EDL technologies
« Reply #90 on: 10/17/2009 12:48 am »
Fun article in the latest AIAA Journal of Spacecraft and Rockets (Vol. 46, No. 5, September–October 2009):

"Survey of Supersonic Retropropulsion Technology for Mars Entry, Descent, and Landing" by Ashley M. Korzun, Robert D. Braun of Georgia Institute of Technology, and Juan R Cruz of NASA Langley.

It was a pretty interesting review of all the work done over the past 50 years on the topic.  Apparently it looks like having a few peripheral rocket engines ends up being much more effective than a central rocket engine.  Still more work to be done, but I figured I'd share the reference.

~Jon

Offline MickQ

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Re: Mars EDL technologies
« Reply #91 on: 11/06/2009 01:02 am »
Has anyone done any work on parachute/parafoil landing systems recently for Mars ???   Is there a formula for area vs landing mass ???

Mick.

Offline Jim

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Re: Mars EDL technologies
« Reply #92 on: 11/06/2009 01:11 am »
Has anyone done any work on parachute/parafoil landing systems recently for Mars ???   Is there a formula for area vs landing mass ???


Parachutes can't be use for landing, only deceleration.  Rockets or airbags are needed for final descent

Offline MickQ

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Re: Mars EDL technologies
« Reply #93 on: 11/06/2009 01:24 am »
Has anyone done any work on parachute/parafoil landing systems recently for Mars ???   Is there a formula for area vs landing mass ???


Parachutes can't be use for landing, only deceleration.  Rockets or airbags are needed for final descent

Sorry Jim.  I should have said Descent Mass.  I was just trying to relate chute size to what you might try to put on the surface.

Mick.

Offline MickQ

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Re: Mars EDL technologies
« Reply #94 on: 11/12/2009 02:02 am »
Some time ago I read something about the shape of a "Shuttlecock" being investigated for use in aero-braking.

Anyone heard this ???

Mick.

Offline jml

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Re: Mars EDL technologies
« Reply #95 on: 11/12/2009 03:01 am »
Some time ago I read something about the shape of a "Shuttlecock" being investigated for use in aero-braking.

Anyone heard this ???

Mick.
You mean like Burt Rutan's SS1?

Offline Danny Dot

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Re: Mars EDL technologies
« Reply #96 on: 11/12/2009 03:07 am »
I would be glad to help out on these thread if we can stick to english.  I literally can't read most of the posts here. 

Danny Deger
Danny Deger

Offline MickQ

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Re: Mars EDL technologies
« Reply #97 on: 11/12/2009 04:56 am »
Some time ago I read something about the shape of a "Shuttlecock" being investigated for use in aero-braking.

Anyone heard this ???

Mick.
You mean like Burt Rutan's SS1?

Not as such, though I think the basic principle applies to Space Ship One.

What I was refering to is something like a stiff skirt fixed to the rear of an  entry vehicle that acts in the same way as a shuttlecock to slow and stabilize the craft for a substantial part of it's descent before parachutes and/or propulsive systems take over. 

Mick.

Offline Michael Bloxham

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Re: Mars EDL technologies
« Reply #98 on: 01/20/2010 09:24 am »
Question:

Could a viking-style entry vehicle, designed for the martian entry environment, theoretically also work sufficiently well at earth-entry?

I'm thinking it might; as presumably you can just open the chutes at an earth altitude analogous to that which they are designed for deploying at mars, right?

In other words, whatever the entry environment they are designed for at mars (the determining factors being entry speed and atmospheric pressure) can presumably be found at some entry altitude at earth: Just pop the chutes at that altitude, and the lander should glide safely down to earth, right?

Or not? The major spanner in the works that I can see is the possibility that the entry vehicle will enter the thicker part of the earths atmosphere too fast, as the deceleration is far less at the higher mars-analog altitude. Therefore, the parachutes may be under far more stress at this point. In other words, the maximum dynamic pressure may be much higher during earth entry than at mars entry.

However, current parachute technology seems to handle such pressures reasonably well (e.g. Apollo, StarDust, etc.). So I can only assume that, if the "max q" at earth entry is much greater than at mars entry, that this would not be a major problem to deal with (if one was inclined to design a parachute system that worked equally well for both entry environments, for whatever reason that may be ;-).

The reason I ask, of course, is that I want to look into the possibility, for a manned-mars-mission, of re-using the mars ascent capsule as the crews earth-reentry capsule. Doing that may be a good trade for a few reasons (as surmised during previous posts in this thread):

1. It means the ERV staged in mars' orbit doesn't have to carry a dedicated earth-reentry capsule all the way from earth to mars' orbit and then back again. You could add a little more mass to the ERV vehicle instead.

2. The ascent capsule and earth reentry capsule both have similar requirements, functions, and restraints: They both need to be as lightweight as possible, yet have just enough volume to accomodate the full mission crew for a few days at most. They also both need comms equipment, an OMS, life support, a few days worth of supplies, etc.

3. Putting mars-qualified re-entry systems on the capsule would allow an abort-to-surface anywhere within the ascent profile. That is perhaps only beneficial if your particular architecture is able to support the crews wherever they happen to land during an abort. As per previous posts, a maximally dog-leg ascent profile is envisioned, but it is also conceivable that we could land the next missions assets beside the crew wherever they happen to land their capsule, or else send a dedicated 'emergency supply' vehicle that had been previously staged in mars' orbit for just a contingency.

4. Why not? I don't see any huge disadvantages. Except perhaps that the ascent capsule will be heavier (given that it now has a heatshield and parachutes to be able to abort-to-surface; I envision that the small retro-rocket stage required for mars-landing would be used to provide the final boost to orbit or else be integrated with the OMS system anyway). But in our particular case, this may not be so much of an issue, as we have plenty of spare margin available in our ascent fuel-producing ISRU lander.

Any takers please?

Thanks in advance.

- Mike

Offline Hop_David

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Re: Mars EDL technologies
« Reply #99 on: 01/20/2010 02:40 pm »
Is there a formula for area vs landing mass ???

Mick.

I think you're thinking of the ballistic coefficient.

If you examine the formula in the Wikipedia article I linked to, you'll see mass and cross sectional area are in the formula.

Also in the equation is density. A thin atmosphere makes it harder to slow stuff down.

In my opinion, one of the more interesting efforts to increase cross sectional area are inflatable heat shields.

As stuff gets bigger, it gets harder to slow down. All these objects have the same ratio of mass to cross sectional area:


Which is why it's easier to land a rover than a hab:
« Last Edit: 01/20/2010 02:41 pm by Hop_David »

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