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#100
by
William Barton
on 29 Apr, 2009 12:14
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The first mission to mars should be a preparatory unmanned mission that carries the initial module of the mars orbiting habitat and a surface shuttle loaded with a Sabatier reactor. After the habitat is orbited, the shuttle would descend, land, deploy the reactor, refuel, ascend, and re-dock with the habitat.
This would be the proof of concept mission to qualify the shuttle and reactor for a manned mission. Because there's no crew to support and nothing to return to earth, smaller or fewer launch vehicles would be required and/or a larger habitat can be delivered.
I think that demonstrating the production of propellant from the martian atmosphere would go a long way to impress the kinds of people we need to engage in order to protect and expand funding for space exploration, and this is a short path to that milestone.
For a long term plan, perhaps your model makes sense. But I think that we accomplish exploration of Mars using more proven systems first. I want to see a Mars landing in my lifetime.
I do think, though, that your reasoning may be off. Mars orbit is not really a safer place than the surface. You aren't really any closer to getting home since you still have to wait for a launch window.
Let's look at worst case scenarios- some major malfuction to a propulsion system strands you at Mars.
If you're on the surface, you can continue to grow food, generate oxygen, mine water ice, even manufacture new propellant in case you suffered a leak and lost the first batch. You might have to sit tight till the next launch window but you'll basically be alright.
If you're in orbit, and a failure loses you the launch window, then you need either a 100% closed ECLSS or a huge margin of reserve consumables to tide you over while you wait on a rescue mission at the next window.
I know where I'd rather be.
That scenario assumes an ISRU-based architecture in the first place, and I will be surprised if it gets done that way. If it was, some parts of ISRU (like fuel manufacture, since it may be a chondritic body) may not be out of the question at a Phobos base, which would do just fine for an orbital site at Mars. It may not have much gravity, but it has enough components left lying on the ground aren't going to simply drift away. One other benefit of an LMO or Phobos based expeditionary architeture is, it makes resupply from Earth easier. Assuming you had HLLV available (doesn't matter which one, could be Ares V, JS-246, or evolved EELV), you can ship fresh supplies via something like ATV, HTV, or even Dragon or Orion (the last two might allow you to consider aerobraking at Mars). People tend to forget the opposition class trajectory is to maximize payload and minimize flight time simultaneously. With a smaller payload, you can shorten flight times for non-opposition (non-Hohmann) trajectories. If I were planning an orbital/Phobos-based expeditionary architecture to explore Mars, I'd want that unmanned almost-anytime resupply capability as part of the architecture from day one. Planning for survival by ISRU on the ground means your architecture is essentially a Mars-base architecture.
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#101
by
butters
on 29 Apr, 2009 12:44
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For a long term plan, perhaps your model makes sense. But I think that we accomplish exploration of Mars using more proven systems first. I want to see a Mars landing in my lifetime.
The unfortunate aspect of the surface-oriented mission profile is that launching two separate long-term life support vessels for transit and surface, although incurring a substantial mass penalty, is still a better option than launching and landing a rocket stage big enough to lift the habitat for the return voyage.
I say, put off the long-term surface base for now and do a 2-day flag-planting photo-op using a small lander departing from an orbiting long-term habitat and ERV. Landing men on mars is easier than supporting men on mars for any extended stay, so shouldn't we accomplish that first?
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#102
by
Kaputnik
on 29 Apr, 2009 13:23
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That scenario assumes an ISRU-based architecture in the first place, and I will be surprised if it gets done that way.
I've actually come to the conclusion that an ISRU ascent stage is virtually a necessity.
Run the numbers on a ISRU MAV- for a crew of four to six you're talking anywhere from about 20-45t entry mass depending on how you calculate it. Big, but within the potential capabilities of systems similar to those used already and scaled up to fit on an SDLV.
The mass for a pre-fuelled MAV is just scary, by comparison. The extra mass of the ascent propellant drives up the mass of the rest of the design, so you're talking 60-100t at entry. You're trying to land a fully fuelled rocket on the surface, and it will not be easy, cheap, or safe. It will absolutely require a fundamental change in entry/descent technology- it will make STS look easy by comparison.
If it was, some parts of ISRU (like fuel manufacture, since it may be a chondritic body) may not be out of the question at a Phobos base, which would do just fine for an orbital site at Mars. It may not have much gravity, but it has enough components left lying on the ground aren't going to simply drift away.
If the MAV is ISRU, then it should be a mission rule that it is ready to launch by the time the crew get there. This means robotic deployment and operations. All near-term proposals have used atmospheric ISRU only, because it is a globally available, homogenous resource, that can be sucked in by a far no matter where you are on the planet. It can be processed easily by cryogenic distillation. Regolith processing, whether on Mars or Phobos, requires a whole different set of tools- a dose of good luck to land in the right place, machinery to grind up the material, and massive amounts of heat to drive off the substances that you want. It just doesn't sound like something you could achieve without a human presence, and certianly is out of the question for the first missions.
One other benefit of an LMO or Phobos based expeditionary architeture is, it makes resupply from Earth easier. Assuming you had HLLV available (doesn't matter which one, could be Ares V, JS-246, or evolved EELV), you can ship fresh supplies via something like ATV, HTV, or even Dragon or Orion (the last two might allow you to consider aerobraking at Mars). People tend to forget the opposition class trajectory is to maximize payload and minimize flight time simultaneously. With a smaller payload, you can shorten flight times for non-opposition (non-Hohmann) trajectories. If I were planning an orbital/Phobos-based expeditionary architecture to explore Mars, I'd want that unmanned almost-anytime resupply capability as part of the architecture from day one. Planning for survival by ISRU on the ground means your architecture is essentially a Mars-base architecture.
Your fast flight time requires a lot of braking at the other end. For unmanned cargo flights, why not just employ direct entry and landing on Mars? This will be a lot lower mass than propulsive capture and rendezvous with Phobos. It will also make more sense than aerocapture followed by Phobos rendezvous.
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#103
by
Kaputnik
on 29 Apr, 2009 13:26
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For a long term plan, perhaps your model makes sense. But I think that we accomplish exploration of Mars using more proven systems first. I want to see a Mars landing in my lifetime.
The unfortunate aspect of the surface-oriented mission profile is that launching two separate long-term life support vessels for transit and surface, although incurring a substantial mass penalty, is still a better option than launching and landing a rocket stage big enough to lift the habitat for the return voyage.
I say, put off the long-term surface base for now and do a 2-day flag-planting photo-op using a small lander departing from an orbiting long-term habitat and ERV. Landing men on mars is easier than supporting men on mars for any extended stay, so shouldn't we accomplish that first?
A Mars mission MUST last two to three years. From the moment you complete TMI, you are commited to that length of mission.
So your suggestion is that crew spend two days on Mars and then return to orbit to wait for the remaining eighteen months for their launch window? And the benefit is what, exactly?
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#104
by
DfwRevolution
on 29 Apr, 2009 23:00
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Some people do advocate 'colonising' by building up surface resources at a single location from the first mission onwards. But most people, myself included, would opt for a series of initial missions visiting different locations.
IMO, it is a very reasonable compromise to begin clustering hardware together from the first missions. This is especially true with the distances and durations involved with a Mars mission. The cost and safety advantages are too great to ignore. Scavenging a part from a previous mission could save a science objective if an instrument failed or perhaps save a crew if something critical failed.
Regarding exploration activities, it's hard to imagine that a single expedition would exhaust all the research opportunities within the range of a given landing site. A pressurized rover with a few hundred kilometers of range would keep the first few expeditions plenty busy. By the later missions, perhaps a suborbital "hopper" could open even greater distances.
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#105
by
A_M_Swallow
on 30 Apr, 2009 02:00
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If it was, some parts of ISRU (like fuel manufacture, since it may be a chondritic body) may not be out of the question at a Phobos base, which would do just fine for an orbital site at Mars. It may not have much gravity, but it has enough components left lying on the ground aren't going to simply drift away.
If the MAV is ISRU, then it should be a mission rule that it is ready to launch by the time the crew get there. This means robotic deployment and operations. All near-term proposals have used atmospheric ISRU only, because it is a globally available, homogenous resource, that can be sucked in by a far no matter where you are on the planet. It can be processed easily by cryogenic distillation. Regolith processing, whether on Mars or Phobos, requires a whole different set of tools- a dose of good luck to land in the right place, machinery to grind up the material, and massive amounts of heat to drive off the substances that you want. It just doesn't sound like something you could achieve without a human presence, and certianly is out of the question for the first missions.
The gas ISRU lander and the solid ISRU lander can be different machine at different locations, providing there is a way of moving the refined resources to the Mars outpost. This will reduce the mass of each lander at the cost of an extra launch vehicle.
On Mars the hydrogen appears to be in the form of the solid called ice. Before the big ISRU equipment arrives mini rovers may be needed to prospect for surface ice. If they move at 2 miles per hour during day light they should be able to cover about
2 * 24.6 / 2 = 24.6 miles.
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#106
by
Jim
on 30 Apr, 2009 02:10
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If they move at 2 miles per hour during day light they should be able to cover about
2 * 24.6 / 2 = 24.6 miles.
meaningless numbers. What determines the 2 mph? Also not all the daylight hours are usable.
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#107
by
Jim
on 30 Apr, 2009 02:15
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The gas ISRU lander and the solid ISRU lander can be different machine at different locations, providing there is a way of moving the refined resources to the Mars outpost. This will reduce the mass of each lander at the cost of an extra launch vehicle.
read the post, this is not for the early missions. Again, you bring up things not appropriate for the early missions. None of these missions, both lunar and martian are settlements, they are outposts. There won't be mining or excavators for many years, they are way outside the timeframe of discussions on these threads. When are you going realize this and stop inserting them needlessly into the discussions.
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#108
by
A_M_Swallow
on 01 May, 2009 07:01
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If they move at 2 miles per hour during day light they should be able to cover about
2 * 24.6 / 2 = 24.6 miles.
meaningless numbers. What determines the 2 mph? Also not all the daylight hours are usable.
E = 0.5 * m v
2The current Mars rovers show that energy is restricted by the size of the solar panels and mass restrictions mean we can only have small panels.
2 mph is walking speed. Slower than that and only small areas can be surveyed. Even with restricted day light hours the rover should be able to travel 80 to 90 miles in 4 days. Hopefully the probe can be landed that close to its target location.
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#109
by
A_M_Swallow
on 01 May, 2009 07:23
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The gas ISRU lander and the solid ISRU lander can be different machine at different locations, providing there is a way of moving the refined resources to the Mars outpost. This will reduce the mass of each lander at the cost of an extra launch vehicle.
read the post, this is not for the early missions. Again, you bring up things not appropriate for the early missions. None of these missions, both lunar and martian are settlements, they are outposts. There won't be mining or excavators for many years, they are way outside the timeframe of discussions on these threads. When are you going realize this and stop inserting them needlessly into the discussions.
I am aiming this at the
initial boots and flag mission.
The other posters are planning to use ISRU propellant for the return fuel. See quotes below.
The ascent propellant could be pure hydrogen or its compound methane. Since there are only trace quantities of hydrogen in Mars's atmosphere usable quantities of hydrogen will have to be extracted from ice in the soil.
See
Posted on: 29 April 2009, 13:23:42
Posted by: Kaputnik
Quote from: William Barton on 29 April 2009, 12:14:06
That scenario assumes an ISRU-based architecture in the first place, and I will be surprised if it gets done that way.
I've actually come to the conclusion that an ISRU ascent stage is virtually a necessity.
Run the numbers on a ISRU MAV- for a crew of four to six you're talking anywhere from about 20-45t entry mass depending on how you calculate it. Big, but within the potential capabilities of systems similar to those used already and scaled up to fit on an SDLV.
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#110
by
kkattula
on 01 May, 2009 07:24
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If they move at 2 miles per hour during day light they should be able to cover about
2 * 24.6 / 2 = 24.6 miles.
meaningless numbers. What determines the 2 mph? Also not all the daylight hours are usable.
E = 0.5 * m v2
The current Mars rovers show that energy is restricted by the size of the solar panels and mass restrictions mean we can only have small panels.
...
Oh please.
That's the formula for the kinetic energy of a moving mass. Not for how much power you need to compensate for friction at a particular speed, in a particular environment.
It's completely irrelevant in this context.
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#111
by
Jim
on 01 May, 2009 10:06
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E = 0.5 * m v2
The current Mars rovers show that energy is restricted by the size of the solar panels and mass restrictions mean we can only have small panels.
2 mph is walking speed. Slower than that and only small areas can be surveyed. Even with restricted day light hours the rover should be able to travel 80 to 90 miles in 4 days. Hopefully the probe can be landed that close to its target location.
Another meaningless and clueless post
The current mars rovers did nothing of the sort. The fact is common sense which is something absent in the post
What mass restrictions?
A rover wouldn't be able to travel that far in four days with current collision avoidance systems
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#112
by
Kaputnik
on 01 May, 2009 13:34
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Given how long it's taking NASA to design a 'simple' lunar lander ...
For a manned program there is no such thing as a simple lander.
Agreee, hence my use of inverted commas.
I was comparing the Altair design effort with the work required to build the capability to manufacture lunar-derived propellants for a Mars mission. i.e. if it takes many years and billions of dollars to do Altair, what will it take to make machines that work in harsh lunar conditions grinding up regolith and processing it into useful propellant? Not to mention spacecraft to deliver that propellant to where it's needed.
Perhaps it will be a reality one day. But why do people want to put it on the criticla path to Mars?
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#113
by
A_M_Swallow
on 07 May, 2009 18:55
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What mass restrictions?
The manned Mars transfer vehicle may be constructed in space but the ISRU lander may have to go up on a single launch. Any associated rover will have to be restricted to only some of that mass.
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#114
by
Jim
on 07 May, 2009 19:20
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What mass restrictions?
The manned Mars transfer vehicle may be constructed in space but the ISRU lander may have to go up on a single launch. Any associated rover will have to be restricted to only some of that mass.
Where does it say there are rovers with the ISRU lander?
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#115
by
A_M_Swallow
on 07 May, 2009 21:29
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What mass restrictions?
The manned Mars transfer vehicle may be constructed in space but the ISRU lander may have to go up on a single launch. Any associated rover will have to be restricted to only some of that mass.
Where does it say there are rovers with the ISRU lander?
That is my suggestion.
The rover(s) would collect the water for the ISRU chemical processor.
I will not preclude a trade study finding separate landers for the processor and rovers to be cheaper but I am not assuming it.
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#116
by
Spacenick
on 07 May, 2009 21:49
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Who says a future rover needs to avoid small rocks? there is a project ongoing on earth that uses a inflatable ball as the basis for a roving system, and there are many other options.
If you look at current robotics technology on earthyou we see the fastet progress in history currently ongoing, this is because there are now competitive events focusing on autnomous robotics.
Look at these soccer playing robots
it's worth noting that both teams play without any human interaction (except for starting/stopping the game), they have all sensors mounted on board (notice the mirror on the top that is used for 360 degree vision with a single camera) and they also carry all their computing power on board.
That will put the possibilities of automated collision avoidance into perspective.
I think the biggest obstacle for really autonomous rovers is risk aversity. one needs to trust the AI to do it's thing. We are seeing this on the current rovers as well as they have completed their primary mission more and more of the navigation needs is done directly on the rovers and even though they are really old now they travel faster then ever before.
I think the best thing for Rover technologies would be to do a price, e.g. the team that sends a rover through desert X within the timeframe Y wins a million dollars. I think this concept could work very well for rovers because the entry barrier is low enough (those soccer playing robots have a building cost below 10 000 $)
The hardware we'd need for efficient rovers is available what we need to do is make it radiation hardened (e.g. the Robots from above run on standard laptops (they are no high end models though a Netbook would be enough)) and we need to write the software of which many problems will be solved by projects like those soccer playing robots.
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#117
by
Kaputnik
on 16 May, 2009 17:10
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Zubrin suggested packaging a rover with the ISRU lander, so as to carry the reactor to a safe distance.
However it all depends on what you cna actualy land in one go. There's no sense in needlessly splitting things up, but many payloads could be divided without a lot of difficulty.
The ascent vehicle could be separate from the ISRU plant. The reactor could be separate from both of these, and the rover separate again. But it doesn make life difficult and probably increases total landed mass because you have to factor in the connections between these units. It also introduces new failure modes, e.g. if the connections are damaged.
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#118
by
butters
on 16 May, 2009 18:32
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I presume that everything needed to land on mars, refuel, and return to earth must be tested prior to sending a crew.
So at the risk of potentially delaying a manned mars mission, why don't we pursue a flagship robotic mars mission that combines heavy exploration rovers with heavy sample return based on ISRU?
This would exercise most of the capabilities we will need for a manned mission, on a sufficiently large but somewhat smaller scale.
The general public perceives the MER program far more positively than anything else that NASA has done recently. So now we send robots to find martian water and bring it back to earth using propellants manufactured from martian atmosphere.
That's how we write the missing chapter in the future history of space exploration that connects what we've already done with where we want to go. We've proven that we can send robots to mars. Now we send robots to prove that we can send humans to mars.
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#119
by
Kaputnik
on 16 May, 2009 19:20
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Some people, me included, suggest a 'mission zero' be flown prior to a manned mission. This would use only slightly modified hardware and go through all crucial mission phases, returning a cargo of rock samples. Depending on the mission design, you might need such a mission to pre-place some elements anyway.