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Internal combustion, methane and liquid oxygen. So the same fuel as the ERV. Note: natural gas is mostly methane, so this is the same engine as a forklift or taxi that uses natural gas.
In Italy we have a lot of car running with pressurized gas methane or propane: they use the same gasoline engine, just modified with a simple kit.
On Mars we have to add an oxidizer tank and some sort of high temperature heat radiator. I think we need almost two rovers traveling in pair for safety.
Another possibility my an electric engine powered by the 100 KW nuclear reactor towed far from the habitat...
What do you think about the solar powered SEV ( http://en.wikipedia.org/wiki/Space_Exploration_Vehicle ) ?
Mini-magnetosphere is a very thin plasma held in a strong magnetic field. Atmosphere has much greater gas density, even Mars. Wind would blow away the plasma, static discharge would neutralize it's charge, and gas conduction/convection would cool plasma to gas. So no, mini-magnetosphere cannot operate in an atmosphere. You would be restricted to a magnetic field alone.
So we can use it on the Moon, but not on Mars. What's about protecting the base with an interred large coil, made with a superconductive wire?
It is possible to protect the settlement with an artificial mini-magnetosphere, powered by the ERV 100 KW nuclear reactor, when fuel production is finished:
http://earthweb.ess.washington.edu/spac … elding.pdf
If there are iron rich metallic rocks near the base, they will become magnetized enhancing the cosmic ray shielding effect.
MITEE was projected by the same team of Timberwind.
Hi Robert:
Myself, if we do bring back solid core NTR, I wish we would upgrade it to a water working fluid, as in the original 1950-vintage concept. There's an Isp penalty, to be sure, but the working fluid is available as ice in many locations throughout the solar system, including Mars. Melt it, gravitationally settle-out the solids, and run the cleaned water through the engine. Very easy to process with minimal equipment. Your "fuel tank" needs a door through which to load the ice, and a tap from which to draw off the separated solids.
If this can be made to work solid core, then it can likely be made to work in gas core, when that technology is ready to fly.
GW
A water version of the low pressure MITEE can reach an exaust velocity of almost 5-5.5 km/s. Thinking that water is very easy to handle and we can refuel everywhere, a water NTR can be a very good chioce: is it possible to use LH2 for departure trip and water for the return trip with the same rocket?
What's about ammonia propellant?
With a low pressure MITEE, it can reach an exaust velocity of 6.3 km/s: almost half than LH2, but ammonia is very easy to store. We can imagine a Mars mission with a MITEE spaceship that use LH2 for Earth-Mars trip and liquid ammonia for the return trip.
Interesting stuff, this MITEE thing. I doubt that team exists anymore. These small business set-asides rarely (if ever) lead to anything mainstream significant. Unfortunately.
GW
MITEE higher exaust velocity of 10 km/s is due to reduct core-chamber radius, that consent higher temperature (almost 3000°K) with less mechanical stress due to Laplace's Law (wall tension = pressure*radius/2 )
The low pressure variant works at 3400°K so hydrogen is dissociated and exaust velocity can reach 13 km/s. This version is particulary interesting because it can be pressure feeded, resulting a very simple and reliable rocket.
Is it possible to build another variant of this low pressure MITEE that use water instead of hydrogen, reaching more than 5 km/s of exaust velocity?
The Hab brings a pressurized rover in case they miss. If all goes well they use the rover for exploration, but if they miss the rover has enough fuel for up to 1,000km trek to the ERV.
1000 km is a very big range for a rover: wich kind of engine it uses?
With thorium derived U233 it is possible to build a 50% lighter solid core rocket. Another interesting possibility is the solid core matrix rocket MITEE that reach an exaust velocity of 10 km/s in the basic version, 13 km/s in low pressure version and 17 km/s in the hybrid electro-thermal version.
http://web.archive.org/web/200503071638 … mitee.html
http://web.archive.org/web/200503171455 … /PUR-1.PDF
http://web.archive.org/web/200503171455 … /PUR-8.PDF
http://web.archive.org/web/200503171454 … PUR-12.PDF
The same MITEE project team have also studied a liquid core rocket LARS (Liquid Annular Reactor System) with an exaust velocity of 20 km/s, but they have not completely solved the problems of core containement douring rocket acceleration.
It's my understanding from what I have seen and read, that these localized magnetic fields are remnant fields frozen into isolated structures in the crust, left over from a time long ago when Mars had a strong global field. I'm guessing there is no longer any fluid overturn to power the iron core dynamo. May also explain the lack of tectonic plate activity. It all froze solid long ago.
GW
Yes, probably this place are contains iron rich rocks that remain magnetized even if the global field vanished. This local magnetic field may offer protection against cosmic ray. So another possible criteria for landing site choiche may be the presence of a strong local magnetic field.
But this is off-topic. We should discuss this on the other thread.
OK excuse me to go OT.
In the classic Mars Direct, for refueiling a big ERV on Mars surface, the ISPP-unit was powered by a 100 KW nuclear reactor. To get the same amount of energy of a 100 KW 512 Kg Safe-400 operating continously, a PV array has to be very huge and massive: 3000-4000 square meters (plus buffer batteries for the night). Astronauts can easly asseble it in a week of work, but I dont know if such large array can be stowed and deployed automatically by an unmanned vehicle.
It's a crazy way to go about things landing a big ERV. The Apollo method is much better. There should be a small lander/ascent craft.
You land the Mars Hab separately. Then all the crew need to do is transfer from the lander to the hab. I think the Apollo ascent craft had something like 2.6 tonnes of propellant. Scaling up for a 3 man ascent craft, maybe we'd be talking about 10 tonnes fuel being required.
Sure, but Mars Direct was planned in 1989, when automatic orbital rendez-vous and docking procedures were not well developed like now. Zubrin avoided orbital rendez-vous because pilots would be out of training, after spending 500 days on Mars surface. Probably he was right.
Planning Mars Direct now, probably may be a better option sending empity orbital propellant depot and two unmanned lander-tanker with a nuclear recator. So the big ERV will refuel on orbit and two reusable lander can be used to explore multiple sites in the same mission, plus a landing on Phobos.
PV panels have a number of advantages. We do know they work well on Mars. A meteorite strike will not put the whole of the energy generation out of action. It can be split up - so if you want to set up a mining operation a few kms away you don't need to import another nuclear reactor.
There are variants like Mars Oz that use PV panels instead nuke, but they use a little Mars Ascending Vehicle for rendez-vous with an orbital Earth Return Vehicle. To produce almost one hundred tons of LOX-LCH4 to fill the tanks of a landing ERV, PV are not enough.
So from an engineering standpoint of supersonic/hypersonic retro-propulsion, what happens with an engine goes out or does not start; what then when you are already on the way down.
IMHO, the lander has to be projected with multiple rocket and with engine out capability.
Quaoar: "On-Orbit Repair and Assembly Facility" is posted 2-11-14 over at "exrocketman" now.
GW
Fantastic GW!!!
This discussion thread is about updating Mars Direct, not redesigning it. I discussed an alternate mission architecture in another thread. With Mars Direct, the idea is land an ERV with no humans, produce fuel, and ensure the radio signal indicates full propellant tanks before crew even leave Earth. If there's a problem, send a replacement ERV. Furthermore, a second ERV will follow the hab. If something goes wrong, the second ERV will land at the first mission site. If everything is Ok, if astronauts walk over to the pre-landed ERV and inspect it to find everything is working, then the second ERV will land at a new site. That new site will start the second mission. So if the reactor fails, there are backups.
PV on Mars will accumulate dust. As the solar panes are covered, they get less light. That generates less power. Opportunity was lucky, it had several dust devils clean its PV panels. With a human mission, you have crew who can erect multiple panels. You won't have that for the ERV. And if the PV panels get dusty, crew can walk over with a broom. Again, you won't have that with the ERV.
To produce 100 KW on Mars orbit we need 1000 m2 of PV. On Mars surface we need even more. A SAFE-400 nucear reactor will be much lighter and compact than a very large solar array that may be difficoult to deploy automatically. SAFE-400 weight is only 512 Kg: why not to send the ERV with two of them?
The second recator will be a very safe backup and it may produce an excess of propellant that may be use for an hopper.
Why not to rebuild mission architecture sending firstly in LMO an unmanned lander-tanker with a SAFE 400 nuclear reactor and a lot of empty propellent depots?
The lander-tanker will land in place with known ice pack in high latitude like this ( http://www.space.com/1371-ice-lake-mars.html ); melt the ice and use the water for ISPP (LOX-LCH4 or LOX-LH2 if it is possible to produce LH2 with a compact hardware); when the tank is full, the lander will take-off, dock with a propellant depot, fill it and land again to produce more propellant. When all the propellent depots will be full, an orbiter vehicle with the astronaut, two lander and a landing habitat will departure from Earth, aerocapture in LMO, then dock with propellant depots and use the propellant to explore multiple sites.
When the astronaut will find a site in low latitude with a big buried ice reserve, they will land there the landing habitat, that will be the first module of a scientific base.
RobertDyck wrote:Why not use a fold-out heat shield? I keep going back to Mars Direct. This is image is from the original 1989 proposal from Dr. Zubrin and Dr. Baker from Martin Marietta to NASA, the heat shield and landing propulsion module for Mars Direct.
http://www.wired.com/images_blogs/wired … 00x113.jpgInteresting. The web page describes it as...
Eight months after Earth departure, the propellant factory/ERV would aerobrake into Mars orbit behind a 23-meter-diameter, 5.26-metric-ton umbrella-like ”flex-fabric” heat shield. Soon after capture into Mars orbit, the landing propulsion module would ignite its rocket motors to decelerate the propellant factory/ERV for reentry into the martian atmosphere
From the images I had assumed it was a solid heat shield with fold-out panels. After reading about DurAFRSI from Ames Research Center, I thought it was my wonderful idea to use the fabric from DurAFRSI as a parasol or "umbrella-like" heat shield. Once again I have re-invented the wheel. So again I return to Mars Direct. My mission plan is tweaked from Mars Direct. but if you can fit a 23-meter-diameter heat shield in an 8-meter diameter fairing, then what is stopping us?
Good point. I really think there are already several technical solutions to the problem of aerobraking the large mass needed for a crew module arriving at Mars.
Bob Clark
NASA is studing this kind of umbrella like heat shield:
http://www.youtube.com/watch?v=f_eWC7OZx2E
http://www.lpi.usra.edu/vexag/Nov2012/p … cinski.pdf
I ask to the engineers of this forum if supersonic retropropulsion can be avoided with an umbrella shield large enough.
Quaoar:
Yep, you're right. I need to post this idea as a fleshed-out design concept.
GW
Great GW!!!
Quaoar:
It's fairly easy to fix the lighting and temperatures thing with a very lightweight space frame around the work zone, covered with aluminized-plastic sheet tarps. Hang the work lights on the frame inside, and use the reverberatory radiation oven effect to bring all workpieces to near room temperatures, while at the same time providing nice, bright lighting from all directions to eliminate shadows.
GW
Why not posting on your blog a concept study for an orbital assembly facility?
It may be possible to build some sort of orbital pressurized hangar where technicians may assembly spaceship without suit?
Launcher shroud diameter is only an issue if you ignore the now-proven option of assembly by docking in LEO from smaller components that do fit the various launchers in your available fleet.
If you add a direct fabrication-assembly capability in LEO (which only requires a supple space suit, appropriate sun shades, and appropriate lighting), you can pretty much build anything imaginable from components, parts, and supplies sent up by your existing launcher fleet.
Things have changed drastically since Apollo. This LEO assembly option is so attractive, I have to wonder why anybody today would even consider trying to launch stuff direct to Mars or anywhere else, without stopping in LEO for assembly. It's just too restrictive on vehicle and hardware designs to do otherwise, and that's fundamentally expensive.
GW
Without orbital fabrication capability, it is possible to assembly by docking in LEO a conic lander, with a 12 meter diameter aeroshell (like that you projected in your blog)?
Tom, Dragon is being designed by a private corporation, not Congress. It will be a lot safer than Shuttle - or Orion. As for backup, you have Boeing making a capsule, plus the DreamChaser. Use one of those. There is no need for NASA to waste money on another launch system to compete with those three, especially if doing so will make it less likely they get developed.
The only problem of Falcon Heavy is its diameter. For LEO mission it's perfect, but for a future manned mission to Mars it's impossible to launch a lander with moore than 5.4 meters of diameter. So a future mission based on Falcon H will be forced to use a narrow biconic slender body lander (like Mars Oz Lander), or a narrow vetical body lander with a deployable aeroshell like ADEPT ( http://www.youtube.com/watch?v=f_eWC7OZx2E ).
Here is an interesting study by GW Johnson for a Mars subglacial habitat with aquaculture
http://exrocketman.blogspot.it/2012/03/ … -mars.html
It has also a very very good radiation shield.
When will be ready SpaceX Dragon Rider?
I have an Interplanetary Transit Vehicle (ITV) instead of an ERV; astronauts live there during transit from Earth to Mars, and again during transit from Mars back to Earth. The surface habitat goes with astronauts from Earth, so if free-return is required, all the food for the surface habitat is with them. If all goes well, then descend from Mars orbit to Mars surface. The MAV is sent ahead, with just a seat per astronaut and space for sample containers, but a oversized propellant tank. It docks, astronauts transfer to the ITV, then they fire up the MAV engines again to push them toward Earth. As an additional backup, a surface lab is landed beside the MAV. Again, sent ahead before astronauts leave Earth. The lab has a pressurized rover with life support. The lab could act as a backup surface hab, although you would have to dump all the lab equipment outside to make room for living space. And the pressurized rover would have to stay parked, connected to the lab so it's life support equipment supplies the lab. If everything works, then the surface hab will provide life support to the lab. So this has even more backups than Zubrin's plan. However, it does require both surface rendezvous and orbitial rendezvous.
It seems a very robust mission architecture.
Zubrin doesn't like the idea of requiring more than one rendezvous. Yea, he considers orbital rendezvous risky. Everything you said is correct. However, also remember he and his partner Dr. Baker came up with Mars Direct in 1989. We have better computers and better guidance systems now. In fact one company is working on a 3D laser scanner than can map the ground as the lander is coming down, with an autopilot to ensure it picks a safe landing spot. Spirit, Opportunity, and Curiosity landed with such extreme precision that I argue JPL has landing down extremely well. If they add the laser thing, then they could land on a dime. And not only did Apollo do orbital rendezvous well, but regular visits to ISS by Dragon show how well even automated systems work today. I think it's safe now.
Probably he was right: in 1989 a manual controlled orbital rendez-vous would be dangerous with pilots who are spent 500 days on surface and are out of training.
Any more excuses, or can we just go already?
Thanks and go!
