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https://www.youtube.com/watch?v=lyWtNbtW_-0
A nicely clear overview of Musk's ITS from Ryan MacDonald (does he ever post here?).
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Notice this guy says MCT will connect to propellant plant that provides LOX and liquid methane fuel, mined from subsurface ice and atmosphere. So that propellant plant has to be in place first, before the first MCT arrives. The graphic says ice mining, although we have already discussed using steam to liquefy a glacier and hose to suck up melt water. I keep talking about how to prepare all that.
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Also a nice link in that You Tube video blurb to this:
http://waitbutwhy.com/2015/08/how-and-w … ars.html/5
Some excellent background stuff in that as well.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Will he be sending in a scouting team is going to go in on the Red Dragon to prepare that...?
Notice this guy says MCT will connect to propellant plant that provides LOX and liquid methane fuel, mined from subsurface ice and atmosphere. So that propellant plant has to be in place first, before the first MCT arrives. The graphic says ice mining, although we have already discussed using steam to liquefy a glacier and hose to suck up melt water. I keep talking about how to prepare all that.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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I don't see humans riding Red Dragons to the surface of Mars, because it's a one-way trip with very little in the way of supplies or equipment. Red Dragon has about 1 km/s delta-vee in those Super Draco thrusters. It's said to be able to carry maybe 2 metric tons to the surface of Mars.
That's just enough to land retropropulsively after coming out of the hypersonics-of-entry. But it's a very far cry from the 3.6+ km/s required to reach Mars orbit (probably nearer 4 km/s for reliability), and there's just no room in its structure for that much propellant. Dragon and Dragon v2 both have 1200 kg of MMH-NTO in tanks inside the mold line but outside the pressure vessel of the cabin. I don't think Red Dragon is any different. It's supposed to be a rework of the manned v2, but with the seats and life support ripped out.
So, talking of "adapting" or "modifying" Red Dragon for successful ascent is not very realistic. It just needs a booster rocket to do that. Besides, the MMH-NTO propellants the Super Dracos burn, are not something made on Mars in any way that we understand, and those thrusters just don't burn LOX-LCH4. I could see a Dragon as the crew cabin and emergency abort feature on something much larger that would make such ascents, but not by itself. Not at all.
There's a date disparity in Musk's timeline that he showed in Guadalajara, which might be an indirect hint into what he has planned for the very earliest missions. He's showing first MCT on Mars in late 2022, and first men to Mars in late 2024. This is after Falcon-Heavy/Red Dragon unmanned pathfinder shots in 2018, 2020, and presumably into 2022.
No one has revealed just what equipment and instruments he intends to land with those Red Dragon pathfinders. But if he is to make thousands of tons of propellant in only several months, with LOX:LCH4 at about 3:1 by mass, he must find a site with considerable buried ice. Don't forget that the LCH4 is useless without all that LOX.
That first MCT may be landed without a crew, but with the propellant factory on board. Who knows? Musk ain't saying. If that is what they do, I don't see how they will do the ice mining for the water, without a crew. But maybe they're working on that. Again, who knows? They're not saying.
As for landing stability, to me it appears the thing has about 2.5-3 times the height as it does landing leg span. It will necessarily be restricted to very flat, level ground, very clean of obstructions like lots of boulders. I don't know, but I think that's part of what the pathfinder shots are about. That and buried ice. Putting tons on pads on top of sand should be rather like it was on the moon. They'll sink in a few inches, but should hold after that. If there's rocks in the regolith, the depressions will be shallower because the load-bearing ability of the regolith will be higher.
Somewhere I've got some numbers for load-bearing ability of sand and other soils like that.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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OK, here's the safe bearing loads versus soil types that I used to use thrust-blocking fire mains in the fire protection engineering business. None of my fire mains ever, ever moved. And fire mains are big pipe at pressures factor 6 above typical city water pressures. These criteria are fire code requirements, and about factor 2 to 4 conservative versus what Mark's ME's Handbook lists for foundation bearing loads.
loose, uncompacted, or disturbed backfill (similar to loose sand) 500 lb/sq.ft = 23.9 KN/sq.m
compacted backfill materials at 90% compaction 1500 lb/sq.ft
undisturbed blackland clay (with or without cobbles) 4000 lb/sq.ft
solid white rock or very tight-packed white rock cobbles 10,000 lb/sq.ft
A fully fueled and fully loaded MCT (without booster) lists as 2550 metric tons, per Musk's presentation. That's 5.62 million pounds on Earth, 2.14 million pounds on Mars. It seems to have 3 landing legs, nominally carrying 712,000 lb each on Mars. Each pad at 500 psf should be 1420 sq.ft = 131 sq.m; that corresponds to round feet about 12.9 m diameter. That's for deep loose sand or backfill, and for which 500 psf is a very conservatively-weak value.
The stuff on Mars is very likely more like Earthly desert hardpan sand, which should resemble compacted backfill in strength, at a very conservative 1500 psf. Reduce pad areas to 473 sq.ft = 43.7 sq.m. That's 7.5 m dia. And that's not all that far from what we saw in Musk's presentation.
I rather doubt the weights are quite that high, too. I've got a full cargo load in that weight. 150 metric tons ship, 450 tons cargo, and 1950 tons propellants. Probably not flying with much cargo, and probably not dead-level full of propellants, either.
I really don't think there's much risk of sinking into the Martian regolith. The danger is coming down on rough or uneven ground, or hitting a big boulder with one landing pad. You take care of that with pad span = vehicle height and using 4 legs. Musk didn't do that, so he intends to land on really flat, really clean sites.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Nice run down on Red Dragon... So building a first stage for the capsule to set on from parts from the other cargo landers would need to be part of any manned mission using this capsule along with the ability to make the fuel to refill the units for a return flight back to orbit.
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GW,
ITS, as specified in Mr. Musk's presentation, with max cargo mass and 5% remaining propellant would weigh 264t (gravity calculated as .38% of Earth's) at touchdown on Mars.
I've been looking at maps of the Hellas Basin, but the resolution isn't nearly high enough to pick a good landing spot. It needs to be within walking distance of the glaciers.
The next rover sent to Mars needs ground penetrating radar, a helicopter with a high resolution camera to develop a 3D map of the terrain to pick potential landing spots, and a drill to determine what kind of water we can expect to obtain from the glacier.
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I was thinking the ship would be heavier at takeoff than landing, because of refuelling. Even without significant cargo, that should still be true. It was supporting that takeoff weight that I was looking at. If that's OK, landing support is a cinch.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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GW,
That's true. It'll be substantially heavier when it returns to Earth. What I was concerned about was vertical velocity at touchdown since I don't know what the vertical velocity will be. If vertical velocity exceeds 3m/s with a 10% remaining propellant load, it'll impact with more force than it exerts when fully fueled, ready to return to Earth. IIRC, the Falcon 9 booster's vertical velocity at landing is around 30m/s or thereabouts. I could be wrong, but I think touchdown will be a pretty delicate maneuver.
Edit:
I knew that had to be too high for the F9 booster to land. The F9 booster's touchdown velocity is a little higher than 5m/s. Even at that vertical velocity, it hits pretty hard.
Last edited by kbd512 (2016-10-28 15:11:01)
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What is we modify the Red Dragon with a new first stage as part of the lander in the truck version with a methane engine and tanks empty for refueling on the surface of mars.
What fuel did the red dragon thrusters use and can we make it on mars to refuel there engines to make a 2 stage to orbit out of the capsule?
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I think I already posted this above, but Red Dragon uses the Super Draco thrusters, which are fueled with very-storable MMH-NTO propellants, hypergolic ignition, but not producible easily on Mars. Red Dragon, Dragon v2, and Dragon V1 all have about 1200 kg of these propellants on board, no more.
It would not seem to be very feasible to replace these with locally-produced LOX and LCH4, because those are absolutely NOT hypergolic. All of the thruster engine hardware would have to be replaced in its entirety. Plus, the basic Dragon design does not include even moderate cryogens as part of its on-board propellant storage capability, not in any of the 3 forms.
I can see some Dragon version as the abort capsule/crew module on a larger lander, but I cannot foresee its routine use for anything on Mars but one-way landings of very modest payloads.
Sorry.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Pace GW.
A modified Dragon might use HTP and methanol, both of which are storable at Mars temperatures and both could be made on Mars starting with water and CO2. No cryogenic tankage required. The old UK Black Knight rocket used 85% peroxide with kerosene, which is still hypergolic. Others have used higher concentrations but these are more difficult to deal with. New engines would need to be designed and the capsule might need to be derated because of the reduced Isp. A first stage would be needed to get the capsule to orbit if you want to use it as part of the earth return system.
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What are you saying? You want to cobble together a return vehicle from parts for other purposes? You realize Red Dragon just has enough propellant to land. Even if propellant tanks were full, it doesn't have enough to achieve Mars orbit. And you aren't going to build a rocket stage from rover parts.
I did post the idea of using Dragon as the capsule for a Mars Direct ERV. That would use Dragon 1 because launch abort rockets are useless. Even if you did abort to the surface of Mars, once there you're dead. And Dragon requires a Cygnus PCM to house recycling life support for the 6 month journey back to Earth. Dragon can't abort with a heavy PCM on top. So don't even try. Launch would require a substantial rocket stage, possibly 2 stages. The stage(s) would be fuelled via ISPP using LCH4/LOX. However, also note Falcon Heavy can only launch Red Dragon to Mars. It cannot launch an entire ERV. Your only options are SLS block 2, SLS block 2B, or Earth orbit assembly with multiple launches of Falcon Heavy. Unless you're willing to consider foreign launchers.
However, I still prefer my plan. My plan would park in Mars orbit an Interplanetary Transit Vehicle (ITV) aka Deep Space Habitat (DSH). The Mars Ascent Vehicle (MAV) would be a very light-weight capsule, not designed for atmospheric entry. The entire MAV would have Mars landing systems, the capsule would not have it's own. Astronauts would ride in their spacesuits, the MAV capsule would not have its own life support. It would have an oversized upper stage because it would be the TEI stage for the ITV/DSH. This provides a substantial ITV/DSH for return to Earth, not just a capsule. I have suggested the ITV/DSH would have a single deck and not be as large as a Mars Direct hab. Mars Direct was designed to have the same outside diameter as the Ares launch vehicle, SLS is based on Ares so it has the same diameter. I have suggested ITV/DSH could be the same diameter as Skylab, so 6.6m instead of 8.4m outside diameter. And life support equipment would be inside that one deck, taking up space. This allows for artificial gravity on the return to Earth, using the same tether spin system as the Mars Direct hab. The ITV/DSH would aerocapture into Earth orbit, and aerobrake down to LEO where it would rendezvous and dock with ISS. As an emergency escape pod aka lifeboat, the ITV/DSH would have a Dragon capsule.
What if the MAV used Dragon instead of a light-weight capsule? Then the ITV/DSH would not require a separate Dragon. But launch mass of Dragon is 8.8 metric tonnes, that would substantially increase launch mass from the surface of Mars. And there's no way capsule life support would last 6 months. For the MAV to have sufficient propellant to be the TEI stage, it can't consume that propellant to achieve Mars orbit. And if you expect Dragon to return to Earth without the ITV/DSH, it requires a Cygnus PCM packed with heavy life support equipment. So better to leave the heavy stuff for return to Earth parked in Mars orbit. Keep launch from Mars surface minimal.
The terms ITV and MAV come from NASA design reference mission aka Mars Semi-Direct. The term DSH is current, NASA wants someone to design a DSH.
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RobertDyck. I agree that the earth return hardware and stores should be parked in Mars orbit. Surface hardware and stores should be predelivered directly to the selected base site by separate transfers and people should not be sent until their needs are confirmed as being met. People then will have to be transferred from Mars orbit in some kind of capsule with thrusters for landing. This probably would be a Dragon or something similar.
To give the crews maximum mobility I was looking at air transport. Helicopters appear marginal at best and I discounted fixed wings due to the lack of runways. That leaves some kind of rocket powered hopper and we have a rocket powered capsule available. It would, however have to be fuelled by locally produced propellant as there is little chance that Methyl Hydrazine and Nitrogen Tetroxide would be easily produced by an automated system on Mars, so it would have to have a new engine. If it were fuelled with methane /Oxygen or CO/Oxygen it would require massive changes to accommodate the cryogenic tankage and equipment and in addition these aren't hypergolic, so I discounted them. Storable propellants could be made on Mars- Peroxide and Methanol spring to mind and this gives a lesser change to the capsule design. This mix would be hypergolic.
So if we have a couple of Dragon type capsules which can be used as hoppers as well as landers, could we use them as ascent vehicles? Probably, with another stage to get them there. Maximum use of mass delivered will minimise the mass that you have to send
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