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The MarsDrive roaming mobile plan had cargo lander predispositioned aroung mars as to keep the mass of the RV down if it were to circa navigating of Mars. The same preload plan was also for a localized research radius as well.
The remaining group seems to have gone roage off on there own at this point so marsdrive is sort of stopped in design developement from what I can see.
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The MarsDrive roaming mobile plan had cargo lander predispositioned aroung mars as to keep the mass of the RV down if it were to circa navigating of Mars. The same preload plan was also for a localized research radius as well.
The remaining group seems to have gone roage off on there own at this point so marsdrive is sort of stopped in design developement from what I can see.
Pre-landings always seem the sensible way to go for me.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Quaoar, I can't say I have many details at this time; But presumably it would be something like a habitat on the bed of a large truck.
This does result in a conflict if you're looking to use solar panels because it will be tough to carry around all the panels that you'll need. But then again most of the power would actually be needed for propellant production and not as much for the routine mission/science operations. Propellant production can occur pretty much anywhere on the planet because the crew can just drive there.
I wouldn't expect them to actually circumnavigate the planet, but it certainly would be well within the crew's ability to do so.
Wich kind of engine: electric or LOX-LCH4 internal combustion?
Merry Xmas!
Last edited by Quaoar (2013-12-24 07:22:46)
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Wich kind of engine: electric or LOX-LCH4 internal combustion?
Typically the Rover RV are Electrical as we would not be able to bring that much fuel along to power all of the equipment needed for life support for any long range roving but if a small RTG was to power the RV then we could travel untill food and water supplies were exhausted. LOX-LCH4 if for launch of the MAV and not thought of a transportational fuel thou it could be for local use to fuel creation station.
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Robert Zubrin argued for LOX/LCH4. It's another excuse to use his ISPP. But batteries don't work well in cold; Mars is cold, and unlike the Moon, does have an atmosphere. Spirit/Opportunity have solar panelts, but also nuclear heaters to keep the battery and electronics compartment warm. Curiosity has an RTG.
Elsewhere on this forum, I've argued for trisilane. Not for an exploration mission, but for a permanent base. Trisilane is liquid at Mars temperatures, from room temperature to Mars night. And it burns in CO2, so the rover doesn't have to carry oxidiser. The down side is it produces black smoke with silica scale. A robust turbine engine with Teflon coated blades should withstand it. The M1A1/2 Abrams tank has a gas turbine engine, so transmission for a vehicle is known.
Last edited by RobertDyck (2013-12-24 11:20:24)
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I think you will find there is no turbine design that can handle solids in the stream, either silica particles or massive amounts of soot. And teflon is long gone at useful turbine inlet temperatures. Not even a radial flow design would withstand that kind of beating.
A piston engine might work for a while, but the solids will cause leaky, then burned, valves. It'll handle soot much better than a turbine (diesels do it all the time), but the silica will slowly destroy it.
Some sort of external combustion design might work, if a separator can remove the solids from the stream before it gets to the moving machinery, whatever that is. If the product stream is more solids than gases, then it won't be a very useful engine. Expansion only works with gaseous phases.
I know nothing about any of the silanes. When burning with CO2, how much of the combusted stream is gas?
GW
GW
Last edited by GW Johnson (2013-12-24 12:08:03)
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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This is for mechanical drive, not aircraft thrust. Couldn't you just reduce temperature? The engine for an A-10 Warthog (offically Thunderbolt II) was designed to withstand small arms fire. I'm told engines for an F-18 could not withstand debris such as a bolt ingested from the flight deck.
I don't believe a piston engine could ever withstand it. Tollerance between piston and cylinder is far too close. That's where combustion takes place, so the most likely accululation of silica scale. Even a tiny amount of scale there would cease the engine. And that doesn't address failure of cylinder valves to seal; again due to build-up.
There isn't much work with any of the silanes, because as soon as it touches oxygen it spontaneously combusts. NASA used silane (mono-silane) to ignite the main engines of the Shuttle.
Expect combustion to produce silica (SiO2), soot, carbon monoxide, steam, and unburned carbon dioxide. I don't know the proportions. Dirty stuff. But in the CO2 atmosphere of Mars, it should be no more combustable than gasoline is here on Earth. A turbine engine would have to endure significant out-of-balance operation, and significant clearance between blades and side wall.
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RobertDyck:
Turbine as-we-know-it is restricted to about 2000-2200 F gas temperature at the turbine inlet, limited by weak material properties at high temperatures, while under enormous stresses. There is no way around that dilemma. Reducing temperature kills you in terms of getting any usable energy out of the machine, it just barely works as it is. And that is true of turbo-shaft machines, no different than turbojet, really. Only the compressors differ: turbo-shaft are often centrifugal flow.
Most of the turbojet and turboprop aircraft engines, which normally burn kerosene, are certificated to burn aviation gasoline as an emergency fuel for a few hours (usually no more than 100 hours). But only if you do a hot section overhaul afterwards! It seems the minute lead content in avgas (about 2 cc tetra-ethyl lead per US gallon) leads to particulate lead and lead oxide in the combusted stream. This eats the coating off the turbine blades, leading to rapid erosion and blading failure. The older grade 100-130 avgas had 4 cc TEL/gallon, and was infamous for rapidly fouling spark plugs with lead deposits. Same was true of the old leaded automotive gasolines, too. I lived through all of that.
Got a chemical formula for a typical silane? I might be able to work out what the reaction looks like in air and in CO2. Not a chemical engineer, but I did acquire a lot of practical chemistry working solid rockets and ramjets. Especially the ramjets.
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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I'm hoping for trisilane, simply because it remains liquid at any temperature on Mars. Equitorial/tropical latitudes, anyway.
Si3H8
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What if the trisilane is injected into a chamber to heat a sterling or steam engine piston drive? Just clean out the solids with a sweeper lever to the outside as it builds up.
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Regarding mobile habitats:
First, I'd like to suggest that the Hab probably won't be that big. It certainly won't move very fast, and air drag will be immeasureably close to nil. We don't care about high accelerations. If it takes 20 seconds to get up to cruising speed of 15 kph, that's fine! Rather than driving through or over rocks, it should be possible to build a mechanical system where a wheel rises upon hitting an obstacle, in order to save energy. Large wheels will keep the hab from sinking very far into any sand that might be around.
I would expect that with proper lubrication, and the aforementioned techniques, I propose that the hab would be able to drive at a speed of 15 kph with a power of 20 hp. That's about 15 kW. 15 kW for say 15 hours of the day (when there will be no power production occurring) amounting to a total storage requirement of 810 MJ.
This would necessitate more than a tonne of batteries, which is unreasonable. On the other hand, should methlox be used the low efficiency of internal combustion engines means that a large area of solar panels would be necessary.
I propose instead that driving be limited to daytime when enough power is being generated to support it. By upping the driving speed to 25 kph (15 mph) and driving for 10 hours out of the day, it would be possible to circumnavigate the Martian globe in 85 days; However, I'm not suggesting a full circumnavigation. I'd imagine that driving halfway around the globe would be sufficient to cover lots of good potential colony sites, and realistically it would be rather difficult to drive across Tharsis. I'm thinking a drive from the eastern part of Valles Mareneris, straight east to Elysium would be the way to go. It looks to be 10,000 km or so, and covers a whole lot of good-looking territory.
The drive could be one motor for each wheel, for a total of (I figure) 8 4 kW electric engines, so that a higher-than-average power can be used to drive over obstacles or up slopes. This would involve some amount of battery storage, of course, but not nearly as much as driving overnight.
All in all, I would expect it to add a tonne or two to mission mass. But the increase in mission capacity will make it much more than worth it.
-Josh
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Regarding mobile habitats:
First, I'd like to suggest that the Hab probably won't be that big. It certainly won't move very fast, and air drag will be immeasureably close to nil. We don't care about high accelerations. If it takes 20 seconds to get up to cruising speed of 15 kph, that's fine! Rather than driving through or over rocks, it should be possible to build a mechanical system where a wheel rises upon hitting an obstacle, in order to save energy. Large wheels will keep the hab from sinking very far into any sand that might be around.
I would expect that with proper lubrication, and the aforementioned techniques, I propose that the hab would be able to drive at a speed of 15 kph with a power of 20 hp. That's about 15 kW. 15 kW for say 15 hours of the day (when there will be no power production occurring) amounting to a total storage requirement of 810 MJ.
This would necessitate more than a tonne of batteries, which is unreasonable. On the other hand, should methlox be used the low efficiency of internal combustion engines means that a large area of solar panels would be necessary.
I propose instead that driving be limited to daytime when enough power is being generated to support it. By upping the driving speed to 25 kph (15 mph) and driving for 10 hours out of the day, it would be possible to circumnavigate the Martian globe in 85 days; However, I'm not suggesting a full circumnavigation.
So, if I've understood, your mobile habitat will be powered by an orientable solar array, only during daylight, with only little buffer batteries as a reserve of power and to feed the life support system douring the night. It's right to not drive in the night: it may also be dangerous.
I'd imagine that driving halfway around the globe would be sufficient to cover lots of good potential colony sites, and realistically it would be rather difficult to drive across Tharsis. I'm thinking a drive from the eastern part of Valles Mareneris, straight east to Elysium would be the way to go. It looks to be 10,000 km or so, and covers a whole lot of good-looking territory.
Valles Marineris may be very interesting: starting from Elysium Planetia, do you suggest to reach it cruising only in the northen depression, avoiding highlands (go eastward, circumnavigate Tharsis and reach Vallis Marineris) ?
In this case we can explore Cerberus Fossae that is very interesting. It may also be interest to circumnavigate the Elysium Volcano wit a stop in the ice lake in the Vastitas Borealis.
The drive could be one motor for each wheel, for a total of (I figure) 8 4 kW electric engines, so that a higher-than-average power can be used to drive over obstacles or up slopes. This would involve some amount of battery storage, of course, but not nearly as much as driving overnight.
All in all, I would expect it to add a tonne or two to mission mass. But the increase in mission capacity will make it much more than worth it.
Eight electric motors will also provide a good redundancy in case of failure.
Last edited by Quaoar (2013-12-26 05:07:08)
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Renewed Congressional Push for a NASA Return to the Moon.
Sparked by Chinese Chang'e 3/Jade Rabbit.
Mark Whittington, Yahoo Contributor Network
Dec 21, 2013COMMENTARY | One salutary thing about the Chinese landing the Chang'e 3/Jade Rabbit probe on the lunar surface is that it has caused a new congressional push for an American return to the moon. But will President Obama heed it?
Rep. Frank Wolf, R-VA, the chairman of the appropriations subcommittee that funds NASA, has sent the president a letter in which he urges him to hold a White House conference gathering the best minds, not only in the United States, but from among America's international allies, to devise a lunar exploration program to start within ten years. The coalition that would return to the moon would include such entrepreneurial companies such as Golden Spike and Moon Express.
Wolf is retiring at the end of the current Congress. The man who is likely to replace him as chief House NASA appropriation, John Culberson, echoed Wolf's sentiments in a recent interview. Culberson specifically singled out the presence of rare earth elements, which have become crucial for making high tech products, on the moon as a rationale for going and for not allowing the Chinese to be the sole lunar explorer.
http://voices.yahoo.com/renewed-congres … 63138.html
Scientists Petition U.S. Congress for Return to the Moon.
www.space.com
China’s Chang’e 3 robotic landing on the moon has helped spur a political crusade in the United States to more aggressively explore and utilize the moon.
http://www.space.com/24068-destination- … gress.html
Bob Clark
Old Space rule of acquisition (with a nod to Star Trek - the Next Generation):
“Anything worth doing is worth doing for a billion dollars.”
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The Light weight nuclear reactor, updating Mars Direct by RobertDyck initial posts of information for upgrades to existing methods and systems is what is being moderated for that topic.
It is not the first time that Mars Direct has been discussed and those that think the mass was way to low, the size of return habitat space, the tethered artificial gravity ect.. have been discussed all to well.
So if we can lets try an focus on just the ERV for a bit...
Taking a hard look at what lands versus why we have what we do for the ERV in mission 1 and why certain elements of the design were included to have been part of what lands is what we have talked about before.
We have some thoughts on large mass landing but why push for that technology as part of a mission when we should be looking at small chunks if possible to make up what we are calling the ERV mission 1. I do like the idea of using a lighter mass nuke as well as making the crews earth return out of the space x DragonRider as the first post would like to do to the ERV.
The DragonRider on page 3 is from http://www.redorbit.com/media/uploads/2 … 12-003.jpg which needs to be retrofitted with life support and toilet plus I am sure with more. I also make note that the solar power may not be enough to power those additional services.
I also question why the lite Truck that carriers the nuclear reactor is not more capable as its a shame to waste it when we are trying to build up a toe hold by landing at the same site.
There is also the question of why send the food to the surface when its going to be a launch wind plus 6 months before anyone would even be there to eat it if we had to. Then we are going to wait until re launch for return on this Ship for the long 6 month return really is starting to push the freshness of it at best. If we really need an emergency cache of food then send it with the Habitat in a seperate small efficient ship to keep it as fresh as possible.
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I did suggest moving discussion of alternate mission architectures to this discussion thread. The reason is my architecture is different. Mine uses a reusable Interplanetary Transit Vehicle (ITV). It goes from ISS in Low Earth orbit to high Mars orbit, and back. Using a fabric heat shield for aerocapture. That's similar to the one described in Mars Direct for the ERV. But some in NASA criticise Mars Direct for using artificial gravity. Although it solves a lot of human problems, the issue is how to manoeuvre while rotating in tethered flight. My ITV is simply zero-G, with the same exercise equipment as ISS. It's about the size of a single module of ISS, say the US Hab module.
The ITV would dock with ISS upon returning to Earth. Various vehicles could then ferry crew from ISS down to Earth. One option is DreamChaser. But the ITV would include one Dragon spacecraft as an emergency escape pod aka lifeboat. That's in case aerocapture fails. If the ITV finds itself on a suicide descent into Earth's atmosphere, the astronauts could bail out in their Dragon. Of course that means one option to return to Earth from ISS is just that same Dragon. I would like to use a reusable spacecraft, but technically Dragon is.
Note this configuration could use DragonRider as-is, no modification.
I also recommend starting construction of the permanent base with the very first human mission. That means the first mission will have one pressurized rover and one unpressurized rover. The second mission will add another of each. The third just adds another unpressurized rover.
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True just about any crew capable capsule or plane which can go to the ISS will serve as a taxi its the remainder of the concept that needs to be cost controlled as well kept to a minimal of launches.
The Interplanetary Vehicle is also one that depending on the building blocks or a big dumb booster meets the needs for orbit to orbit as well. The complexity comes from covering the artificial gravity plus what is used for the descent and ascent vehicle on the mars side of the mission.
The Habitat is straight forward until what is still needed for mission concepts equipment which then puts the landing mass budgets out of the capability and we either compromise to doing less or coming up with another launch to get it all to mars surface.
Can man do more with less sometimes but when it comes to safety of a crew thats the problem as we can not afford a loss.
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I'm very suspicious of a mission design that does not include artificial gravity. It's 6 to 8.5 months one-way to Mars, something OK with exercise on the ISS, if you accept loss of muscle tone. And maybe the other effects. We know it's recoverable in one case (only) of exposure to about 400 days.
It's roughly a year at Mars waiting for the orbits to be right for your return. And there is not one shred of direct (note that I said "direct") evidence to suggest that 0.38 gee is enough to be therapeutic. The assumed therapeutic effects of 0.38 gee seem to be the unspoken assumption in most of these mission plans. And, it is an assumption, nothing more.
Then it's another 6 to 8.5 months in zero gee home.
Roughly 2.5 years total at reduced-to-zero gravity. And what awaits you at journey's end? High-speed/high gee reentry.
It's several gees (3-6) from LEO if you recover them in orbit (1-4 gee burn by the way). If it's a free return, you hit the atmosphere at 50,000 feet/sec (about 17 km/s). Coming back from the moon at 2/3 that speed was an 11 gee proposition.
So, here's a crew with almost no strength and muscle tone left, significantly (or even seriously) weakened and embrittled bones, and possibly with vision and immune systems compromised, suffering high (or even really high) gees to come home. (Not to mention radiation sickness.) Trouble is, it won't kill them outright. They will most likely be crippled for the rest of their lives by this.
Why not just do the spin gravity? (And do the radiation shielding with the water and wastewater you already know will be going with them.) Does not ethical behavior demand it?
GW
Last edited by GW Johnson (2014-02-25 12:58:01)
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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Why not just do the spin gravity?
It would not be too hard to alter my mission plan to do that. Balance would be a bit tricky considering the ITV would have a DragonRider attached during both transits, Earth->Mars and Mars->Earth, and would have a Mars lander attached for just one transit: Earth->Mars. Besides balance, the most difficult thing is manoeuvring while rotating. How do you do that? NASA's experiments with long tethers haven't been successful. They didn't spin, so strain from artificial gravity would help resolve their issues with oscillations. But NASA doesn't believe manoeuvring while rotating would work. And course corrections are necessary. How do you do that?
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NASA has launched dozens of unmanned spacecraft and they all spin, but they also manage to communicate to Earth and perform midcourse corrections. I gather they use short, timed engune bursts.
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The spin is not end over end but a spiral like a barber pole sign.
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Mid course with spin gravity:
You de-spin for every maneuver, then re-spin. Could be thrusters, could be inertia wheels. But you can NOT do this easily (or even with difficulty) with a cable-connected rig. It needs to be a "rigid" structure.
Which way do you spin?
If you spin around the long axis of a typical shape, the radius of your ship would have to be 56 m to provide 1 gee at the outer fiber, at 4 rpm, which is just about the max credible for long-term exposure. That way lies "Battlestar Galactica" problems. But, if you build it as a long, slender baton, the end-over-end mode is not only the most practical way to achieve a 56+ m "radius", it is also the most stable spin mode (the one with maximum mass moment of inertia).
How do we build such a thing without having to build a "Battlestar Galactica"?
Build it from modules docked together, with quick-disconnect plumbing and wiring connections. More or less like we built the ISS, but with a lot of the exact same modules (the propellant tanks). Both end-to-end and lateral connections, so you can reconfigure as a slenderer baton of the same length after each empty tank stage-off.
So why is cable-connected "bad"?
It is very difficult to spin up / spin down a "loosey-goosey" cable rig. Plus, one meteor hit on the cable cuts the cable, leaving you "dead" when your spinning vehicle comes apart while spinning, separating crew hab from propulsion. It is easy to spin-up / spin-down rigid structures, and meteor hit is just a leak to plug, not a complete vehicle loss.
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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Now given the fact a rigid structure doesn't work, how do you do it?
I know, you'll ask why not. The fact is, to achieve Earth level gravity with a rotation of 4 rpm, the distance from centre of rotation to habitat floor must be 55.74 metres. Using the spent (empty) TMI stage as your counter weight, it will mass substantially less than the hab. That means length from centre of gravity (centre of mass) of the TMI stage to centre of rotation will be greater than centre of gravity of the hab to centre of rotation. You could reduce that by using Mars gravity, or increase the spin rate. But "The Case for Mars" cites a NASA study that 6 rpm is the maximum humans can tollerate. Above that they get dizzy. You don't want to push it to the max, that's just asking for nausia. At 6 rpm rotation is quite noticable, so I agree 4 rpm is the max credible for long-term. And do you want that level of gravity at an astronaut's feet, or his/her chest/heart?
Mars Direct did not try to spin down the cable rig. Instead just cut the cable on approach to Mars. This would leave the hab spinning at the same rpm, but it's a lot easier to spin down the hab than the whole rig. My design is not Mars Direct, but it makes sense to do the same thing.
Meteoroid? A hit by a substantial size meteoroid would be catastrophic to the hull. It's easy to design extra strength into cable so it can withstand micrometeoroid hits. And remember, the counterweight is just dead weight. Before rotation starts, the stage is completely empty. All remaining propellant is in the hab, so loss of the spent stage just means zero-G for the remainder of the journey.
If manoeuvring a spinning satellite can be done, then manoeuvring a tethered rotating rig should be about the same. Ensure rotation is the in the plane of the vehicle's tranfer orbit. Time it so when the hab is "pointed" in the direction of desired thrust, then always apply thrust "down". By "down" I mean away from the centre of rotation. That will pull on the counterweight. And be gentle, no dramatic tugs that could induce oscillation in the tether.
The tether will require some elasticity, so it can handle a certain amount of bounce. It would be based on mountain climber's rope. After all, spectra has greater tensile strength than kevlar, and greater impact strength along the length of the fibre. Not as stiff, but for rope that's a good thing. Modern mountain climbing rope uses spectra. Mountain climbing rope is designed to allow a climber to drop from a substaintial height without breaking the rope. Elasticity can spread that jolt across more time, so less instantaneous acceleration. The rope has to withstand the climber's weight multiplied by that acceleration. And ensure acceleration doesn't break the climber's body. A tether requires all the same things.
But the point is the weight would be far too much for a truss or pipe for rigid structure of that length with enough tortional and bending strength to spin up and down.
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If both, hab and TMI, use opposit firing outed canted rockets to keep the cable in tension while manuvering, and all the manuvers are assisted by a specific software that controls allineament and tension, I think they can do spinning, despinning and course corrections easly.
At the times of Gemini 11 and Agena computer and software were at the stone age. Now we can do it better.
Why not to start manuvering tests with two little satellites?
Last edited by Quaoar (2014-02-26 10:06:47)
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Spinning rigid structures work very well, actually. One sees them at Friday night football games all over the US, in season. The baton twirlers throw their batons spinning end-over-end high into the air. They are extremely stable, and easily controlled. Basic spinning dynamics says so, too.
Most of the missions that actually address maximized crew health maintenance and survivability are not like Mars Direct (a really minimalist approach). For survivability, health, and "a way out" at every mission phase, you must have at least a habitat, a bunch of propellant, and some engines, both ways. And on the way there, maybe landers plus their propellants, too, unless they go separately. It's just not two simple modules you can cable connect.
Having a bunch of modules is really easy to rig as a spinning baton, just like at the football games.
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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That avoids the question. The problem is mass. Such a large structure is very heavy. We're trying to reduce launch weight, not increase it.
Heavy = expensive
Expensive = no mission
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