Author Topic: When you can land anywhere on Mars where’s the best place?  (Read 21731 times)

Online ThereIWas3

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Thicker air is a help to parachute-aided landings, which have been NASA's only experience and probably what they were assuming for this sort of mission.  But SpaceX has demonstrated hypersonic retropropulsion and bullseye landings quite convincingly and that opens up quite a lot more of Mars to consideration.  Looking at those maps, most of the designated spots seem to be in the lowlands.  Elysium Planita is in the equatorial highlands, where the water came from volcanic events.  Estimates back in 2005 when that picture was taken were that the volume of water could be about the same as the North Sea on Earth.  I pick water as the deciding factor for SpaceX's interests, followed by radiation shielding by cliffs, etc.
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Offline philw1776

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Yes, but also more frequent fog and dust storms.  A location with known reserves of water or other resources is more useful.

There are many RSLs seeping water indications in the valley.  Plenty of resources & high atmospheric pressure.
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Offline philw1776

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Thicker air is a help to parachute-aided landings, which have been NASA's only experience and probably what they were assuming for this sort of mission.  But SpaceX has demonstrated hypersonic retropropulsion and bullseye landings quite convincingly and that opens up quite a lot more of Mars to consideration.  Looking at those maps, most of the designated spots seem to be in the lowlands.  Elysium Planita is in the equatorial highlands, where the water came from volcanic events.  Estimates back in 2005 when that picture was taken were that the volume of water could be about the same as the North Sea on Earth.  I pick water as the deciding factor for SpaceX's interests, followed by radiation shielding by cliffs, etc.

The Robotic poster has calculated that the cliffs are not as useful for rad shielding as you and I would have thought at first glance.
Yes drilling right into a steep cliff might be helpful but cliffs up to a ten or tens of degrees from the mid valley floor not as much rad shielding as you'd think.
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Online ThereIWas3

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I am reminded of Hiroko's under-ice settlement in the Red Mars trilogy.
  If those are ice slabs and thick enough, that could be enough shielding
 AND a source of water.
"If you want to build a ship, don’t drum up people to collect wood and don’t assign them tasks and work, but rather teach them to long for the endless immensity of the sea" - Antoine de Saint-Exupéry

Online Robotbeat

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Thicker air is a help to parachute-aided landings, which have been NASA's only experience and probably what they were assuming for this sort of mission.  But SpaceX has demonstrated hypersonic retropropulsion and bullseye landings quite convincingly and that opens up quite a lot more of Mars to consideration. ...
SpaceX is still definitely relying heavily on the atmosphere to slow down. So the idea that low altitude helps a lot is unchanged.
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Online Robotbeat

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Yes, but also more frequent fog and dust storms.  A location with known reserves of water or other resources is more useful.

There are many RSLs seeping water indications in the valley.  Plenty of resources & high atmospheric pressure.
Correct. Multiple different types of water sources in Valles Marineris (some very near each other).

Ultimately, we're going to Mars mainly because it has an atmosphere. So I think it makes sense to maximize that.

Fog is a good thing, by the way, as it means there's good atmospheric water concentration. Also, beautiful. I don't think it lasts long enough in the day to be a real concern about solar power production (and it could be you want to use a lot of fission, anyway).
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Offline the_other_Doug

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Thicker air is a help to parachute-aided landings, which have been NASA's only experience and probably what they were assuming for this sort of mission.  But SpaceX has demonstrated hypersonic retropropulsion and bullseye landings quite convincingly and that opens up quite a lot more of Mars to consideration.

SpaceX has demonstrated getting a stage up to, what, somewhere between one and two km/sec?  And then bringing it back down.

Neither they nor anyone else has demonstrated bleeding off between 5 and 12 km/sec (depending on the speed of approach to Mars) purely aerodynamically, to get down to the quoted 1 km/sec the BFS will be able to handle propulsively, and then being within the needed navigation state to get to their target.

Air density will definitely matter.
-Doug  (With my shield, not yet upon it)

Online Robotbeat

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SpaceX has demonstrated bleeding off 7km/s aerodynamically with Dragon. They intend to add propulsion to Dragon, too.
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Offline the_other_Doug

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SpaceX has demonstrated bleeding off 7km/s aerodynamically with Dragon. They intend to add propulsion to Dragon, too.

Oh, I hear you, and I basically agree.  I'm just pointing out that SpaceX has performed some but not all of these pieces, in far different environments from those contemplated at Mars, and never yet all put all of them together.

I'm not saying they're not going to.  Just that they haven't done it to the extremes they plan to, under the same circumstances, and all together in one mission profile.  I fully expect them to be able to do so, I'm just the kind of guy who hates to count my eggs before they're hatched... ;)
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Offline Tyber1

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If it was up to me, I'd put the colony near the top of the cliffs of Valles Marineris. It's near the equator so there is plentiful potential for solar energy and there is at least 5-6% water in the soil which isn't a ton but it's not nothing. But for me, the biggest draw of this location is that it's perfect for Mars terraforming. It would be located right near the edge of a sea where there would be plentiful water but there would be no chance of the city winding up underwater as sea levels rose. And the view would be fantastic, which can only be a good thing.

Offline Torbjorn Larsson, OM

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Thicker air is a help to parachute-aided landings, which have been NASA's only experience and probably what they were assuming for this sort of mission.  But SpaceX has demonstrated hypersonic retropropulsion and bullseye landings quite convincingly and that opens up quite a lot more of Mars to consideration.

SpaceX has demonstrated getting a stage up to, what, somewhere between one and two km/sec?  And then bringing it back down.

Neither they nor anyone else has demonstrated bleeding off between 5 and 12 km/sec (depending on the speed of approach to Mars) purely aerodynamically, to get down to the quoted 1 km/sec the BFS will be able to handle propulsively, and then being within the needed navigation state to get to their target.

Air density will definitely matter.

Yes, and if so, head room. The original Red Dragon had a projected trajectory of ~ 1000 km hugging the ground before slowing down to Mach 2-3 (~ 1 km/s on Mars) and engaging retrorockets. The best (only?) spot would be the martian lowland on the north, which has ~ 3500 km diameter. Incidentally that could place it near water ice.

But it seems the current Red Dragon may have a relaxed brake trajectory. The (my) bets are off, except that the first RD may attempt the easy out as per above anyway. But I suspect the OP was too optimistic. "Land anywhere on Mars" isn't on the martian horizon.

ADDED: I forgot, the original RD brake trajectory is emulating Apollo atmospheric conditions, including a final skip start before inverting the lift vector. [I'm not sure that is the technical name. I'm no rocket scientist.]

So I'm not sure the idea of not bleeding off the interplanetary approach speed in the atmosphere targeting some landing zone being demonstrated before is viable? Is it the "bulls eye" factor that would get us astray?
« Last Edit: 08/18/2016 08:46 AM by Torbjorn Larsson, OM »

Offline Jcc

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I don't know what the solution space is for RD either, but I would think that you can also bleed off velocity in thinner atmosphere, it just takes longer (time and distance) and would be more difficult than in thicker atmosphere, with a risk of being ejected back into space. Agree that the first RD landing will go for an easier location until proved.

Online AncientU

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Thicker air is a help to parachute-aided landings, which have been NASA's only experience and probably what they were assuming for this sort of mission.  But SpaceX has demonstrated hypersonic retropropulsion and bullseye landings quite convincingly and that opens up quite a lot more of Mars to consideration.

SpaceX has demonstrated getting a stage up to, what, somewhere between one and two km/sec?  And then bringing it back down.

Neither they nor anyone else has demonstrated bleeding off between 5 and 12 km/sec (depending on the speed of approach to Mars) purely aerodynamically, to get down to the quoted 1 km/sec the BFS will be able to handle propulsively, and then being within the needed navigation state to get to their target.

Air density will definitely matter.

JCSAT-16 was 2.25km/sec. at MECO;  EM has stated up to 2.75 (10,000km/h) is possible. 
With adequate propellant on board, the first stage could land from LMO or LLO if adequate navigation was available.  LMO is 3.6km/s; LLO is1.6km/s. 

That's the beauty of propulsive landings -- from orbit, you can land anywhere you choose.
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Online Robotbeat

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Dragon is kind of more analogous to what BFS will be doing. Orbital entry. And yeah, Dragon HAS demonstrated that. Hopefully it'll soon demonstrate propulsive landing after hypersonic reentry, too.
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Online guckyfan

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Dragon is kind of more analogous to what BFS will be doing. Orbital entry. And yeah, Dragon HAS demonstrated that. Hopefully it'll soon demonstrate propulsive landing after hypersonic reentry, too.

I don't see an absolute need to do both in one mission. Propulsive landing after an air drop would be good enough. We do know they can do earth reentry. If anything they would want to demonstrate supersonic retropropulsion in the high atmosphere even if not needed for landing on earth.

Offline ZachF

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I also vote for the Mariner Valley. Thicker atmosphere, near equator, also being geographically striking should be helpful for colony morale. Watching the fog roll over massive canyon walls on a martian sunset would be more interesting than desert as far as the eye can see in every direction.

Offline sanman

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Valles Marineris runs pretty deep - but so does Hellas Basin - both are interesting places to look for water.

Offline mclumber1

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I'm guessing you're talking about a PWR. That also needs a 200atm pressure vessel to hold it.

Most space nuclear reactor designs run considerably hotter and use a liquid metal heat pipe system for heat transfer.

Such designs are much more compact and lighter (but then they don't generate the 100s of MW that PWRs generate.

Realistically anything whose outlet temperature after power generation had been done is over 0c can be used to melt ice.

A gaseous CO2 reactor might work well on Mars.  It would produce relatively low temperature gas to run a turbine, and if you ever needed to add more working fluid, that is easily achieved by the atmosphere surrounding the plant.

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