Light weight nuclear reactor, updating Mars Direct

RobertDyck · 2014-02-15 20:51:36

With Mars Direct, crew lands in the Hab. The ERV is sent ahead, launched 26 months before crew depart Earth. It produces fuel, and when they confirm its fuel tanks are full and ready to return to Earth, only then do they send crew. The crew rides the Hab from surface of Earth to surface of Mars. It's one way, the Hab cannot lift off, but it lands within walking distance of the ERV. 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. A second ERV is launched behind the Hab. The second ERV also has no crew. If everything goes well, then the second ERV lands at a different spot, starting the next mission. If the Hab landed more than 1,000km from the first ERV, or if the crew finds something catastrophically wrong with the ERV that they didn't detect remotely, then the second ERV will land beside the Hab.

All this means you can't count on running a cable from the reactor of the first ERV to the Hab. The Hab must have its own power supply.

SpaceNut · 2014-02-15 21:26:37

So how does the Mars Direct plan a tether for gravity if when the hab is sent that an ERV is not sent in the same window? There is only a small 2 month typical window to launch in for mars missions and playing catch up requires lots more fuel... I guess that I am not understanding.

IS it possible that the tether is between the TMI stage and the HAB is that what is meant?

RobertDyck · 2014-02-15 21:46:40

Yes. When going from Earth to Mars, the spent (empty) TMI stage is connected with a tether and spun. That provides artificial gravity. However, the ERV has nothing, so no artificial gravity on the return trip.

Also, the Hab is sent on an express trajectory: 6 months to Mars. The ERV is sent via maximum payload trajectory: 8 months to Mars. It returns via express trajectory, so again 6 months when crew are onboard. But when there's no crew, it's slow. That helps maximize ERV mass, but also ensures the second ERV is far enough behind that crew can make a decision whether to have it land at their site.

Last edited by RobertDyck (2014-02-16 09:38:36)

SpaceNut · 2014-02-16 10:53:19

Earth return vehicle (ERV) has a 100 kWe nuclear reactor mounted in the back of a methane/oxygen driven light truck telerobotically driven a few hundred meters away from the lander, and the reactor is deployed to provide power to the compressors and chemical processing unit.

While I can see off loading the mass from the ERV's return launch with crew on board could be a benifit does the solar stored power have enough capacity to run the ship? Will there be any problems once on the way home of redeploying the panels? Plus can the solar power system handle the greater power levels after not seeing them for a year cycle since earth launch?

I would also like to be able to use the truck if needed without the reactor ISPP system but did not see that in the plans.

It also appears that the HAB is also sending a 100 kWe nuclear reactor to be positioned in the crater and has a pressurized ground rover methane/oxygen internal combustion and generator to support the crew when in use.

surface exploration
With 11 tonnes of methane/oxygen bipropellant allocated for surface operations, about 22,000 ground kilometers can be traversed, ranging up to 500 km out from the base.

Is there any surplus from the ERV as well?

RobertDyck · 2014-02-16 13:29:39

My understanding is the ERV would not deploy solar panels until it launches from Mars. It will have a nuclear reactor until then, so why deploy solar?

The "light truck" will be just wheels, motors, and that lever suspension for 6 wheels. It will also have a navigation camera, but these days that's the size of a phone camera. And it will have a computer that can analyze images to navigate. It won't be much of a truck. In fact won't even have a chassis, just the leavers for wheels bolted to each side of the reactor. The idea is the reactor will drive itself into a crater, then park.

The Hab won't have a separate reactor. It will have a set of solar panels, but those will have to be deployed by astronauts. As long as the Hab does land where it's supposed to, it will be within walking distance of the ERV. That means it will be able to use power from the ERV's reactor, just run a cable. That power will be used to make return propellant, but that will be finished before the Hab leaves Earth. While crew are on Mars, they can use the power. One use is to make fuel for rovers. After all, equipment to make fuel will still be on the ERV. If you send a little extra hydrogen, that can be converted into LOX/LCH4 fuel for rovers. Same ratio as propellant, 1:18. But don't send too much, it has to fit on SLS, and you want to maximize living space in the ERV.

Interesting point. The Hab would need power during transit to Mars for life support. If it's only power is solar, it would have to re-deploy its solar panels for landing.

Note the original plan for Mars Direct included 1 pressurized rover, and 2 light open rovers. "Open rovers" would probably be single-person 4-wheel ATVs, but as flimsy as a lunar rover. But the original plan also called for the Hab to have a single floor. The lower deck was exclusively for the landing rocket engine, fuel tanks for landing, rovers just strapped to the underside of the Hab, and storage for field science equipment. Recent versions have an enclosed lower floor. While paintings show a garage door to get the rover out, analogue research stations (FMARS & MDRS) fully utilize both floors. That's not realistic. Where does the landing rocket go? The movie "Mission to Mars" showed the first mission based on Mars Direct. That Hab may be more realistic. It showed a smaller lower floor, with the airlock moved to the lower floor. Instead of one big landing engine in the centre, where it would get in the way, use 3 or 4 smaller engines around the periphery. Like the landing rockets of Viking or Phoenix. Or 4 pairs of landing engines, like the "sky crane" of Curiosity; but mounted on the outside of the lower floor.

Last edited by RobertDyck (2014-02-16 13:57:16)

SpaceNut · 2014-02-16 20:02:51

The solar panels for the hab would need to track the suns location while creating gravity does not sound like its all that possible.

http://www.nasa.gov/pdf/491544main_orion_book_web.pdf

Providing power for our nation’s next-generation spacecraft, Orion’s UltraFlex solar arrays will support all
of the electrical power needs for life support, propulsion and communications systems, and other electrical
systems for both Earth-orbiting and deep space missions. Rechargeable lithium-ion batteries will
store that power for use when the vehicle is away from sunlight. Each of the two circular solar arrays for Orion unfold to approximately 19 feet in diameter and provide over 6,000 watts of power – enough to power about six
three-bedroom homes. The individual solar cells on UltraFlex are very efficient – they are able to convert
nearly 30 percent of the sun’s energy into electricity.

I am thinking that the new panels and lithium-ion batteries have less mass than the original numbers, plus the lighting can now be LED which gets rid of the ballasts for flourencent lights saving some more mass.

Here is the company for the batteries used on Mars currently http://www.yardney.com/Lithion/lithion.html

I sort of wish there was a seperate topic from the same starting point for just the hab.

It is ashame that the reactor from the ERV is not just driven to the next Hab landing site as that would give the next mission power for growth.

Last edited by SpaceNut (2014-02-16 20:22:39)

SpaceNut · 2014-02-16 20:57:35

I started over looking at the first post and was thinking that the dragonrider does not have the room needed for the return trip and wonder if docking the dragon plus a connecting node solves the problem of the dragon rider by itself. The solar panels for the dragon and the dragonrider would give you plenty of power. Leaving the dragon plus node in orbit for redock with all the consumables for once the ERV is launched for the return trip. No need to send the food to the hab site as its go plenty.

Last edited by SpaceNut (2014-02-16 21:07:52)

RobertDyck · 2014-02-16 21:09:01

Of course, in 1989 Robert Zubrin advocated human exploration over a vast area. Eventually selecting a site for a permanent base. He argued that made more sense than robotic exploration. That made sense in 1989, but today I argue that robotic exploration is complete. Done, finished, over. So select a location for a permanent base, start construction with the very first human mission. That way we don't need to move the reactor, just keep using the same one.

The alternate mission plan that I described includes the ability to replace expendable propulsion stages with reusable ones. That would require a propellant depot in Earth orbit and either Mars surface or one of its moons, as well as tankers to deliver propellant to the vehicle. I had originally argued for a Mars shuttle based on DC-XA, but now that SpaceX is building a reusable Falcon 9, why not base the Mars shuttle on that? Design the shuttle to carry crew from Mars surface to the ITV in Mars orbit, and return to base on the surface. If the shuttle can do that on a single tank of propellant, it should be able to fly two suborbital hops on a single tank. That means fly from base to an exploration site, and back to base in time for dinner. But the same plan starts modest.

RobertDyck · 2014-02-16 21:19:02

I didn't say DragonRider, I said Dragon. DragonRider has launch escape rockets embedded within the capsule itself. Necessary to launch crew from Earth. However on Mars, if you abort launch and return to the surface, you're dead. Lauch from Mars is one shot, just like the Apollo LM. The version of Dragon used to resupply ISS has more interior volume. It also has pressure, a window, temperature control, and communications. My later posts about life support conclude we need an extension module for life support. To keep it modest, I propose a module just barely large enough for life support equipment, with enough room for one crew member to enter the module for repairs. On ISS we've seen repairs are required. The extension module would have a rigid hull so that equipment can be bolted to the hull itself; made of the same aluminum alloy isogrid as an ISS module. The Dragon capsule itself will have non-recycling life support for the last few minutes of Earth atmosphere entry.

SpaceNut · 2014-02-16 21:32:46

I am still trying to get my head around all the different parts but what I see is a changing ERV and Hab based on always going back to the same site on Mars. Also when you start to make the ERV a reuseable then you need a water mining capability in just a few trips to mars. That also ends the need to send another ERV to Mars as well, if all we are doing is developing just one site.

RobertDyck · 2014-02-16 22:47:37

I linked the thread where I talked about my alternate architecture. Should we re-focus this discussion to Mars Direct, and start another thread for reusable equipment? That's two different mission architectures. Mars Direct is not reusable. That means the ERV is not reusable.

You guys keep raising issues with Mars Direct itself. I started this discussion to update Mars Direct with modern equipment, not redesign it. But you want one single solution. Ok. The first question is whether artificial gravity is required. The mission I proposed in the other thread does not use artificial gravity at all. That eliminates the problems of maneouvring while rotating in tethered flight, as well as balancing all the add-on modules. My architecture has a reusable ITV, with a Dragon attached as an emergency escape pod, and the Earth-to-Mars transit also has the surface hab.

SpaceNut · 2014-02-17 00:08:54

Analysis of Launch and Earth Departure Architectures for Near-Term Human Mars Missions

DEPARTURE ENERGIES, TRIP TIMES AND ENTRY SPEEDS FOR HUMAN MARS MISSIONS

Interplanetary Mission Design Handbook Earth-to-Mars Mission Opportunities and Mars-to-Earth Return Opportunities 2009–2024

RobertDyck · 2014-02-17 00:49:58

Mars Direct: Humans to the Red Planet within a Decade - NASA

This link is a Power Point presentation that Dr. Zubrin gave to NASA, dated July 30, 2009. It's only slides, but includes his original Mars Direct designs. For more details, get the book The Case for Mars.

Quaoar · 2014-02-18 04:30:17

RobertDyck wrote:

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?

RobertDyck · 2014-02-18 10:43:01

Quaoar wrote:

1000 km is a very big range for a rover: wich kind of engine it uses?

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.

Quaoar · 2014-02-20 01:42:37

RobertDyck wrote:

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 ) ?

RobertDyck · 2014-02-20 10:09:24

A Mars Direct Hab would only have room for one pressurized rover. In fact, even Robert Zubrin's slides only include one rover, the open rovers are deleted. The table on the first post of this thread is from his book "The Case for Mars".

A rover with a trailer holding a nuclear reactor? It would have enough power, but the spacecraft would only have enough capacity for the mass of one reactor. And to keep mass down, that reactor has very little radiation shielding. That's why it's driven away and parked in a crater. You would be better off leaving the reactor with the ERV, and using it's fuel factory to make traditional fuel.

The Space Exploration Vehicle is an interesting design. The wheels and suspension are too heavy for the Moon, what you see is designed for Earth gravity. Also note the artists concept shows a round hatch, while photographs of the prototype show a smaller rectangular hatch. And the version for an asteroid looks clumsy. Just replacing wheels and suspension with propellant tanks? Balance is off. You would need a dedicated design for zero-G.

Last edited by RobertDyck (2014-02-20 13:04:41)

RobertDyck · 2014-02-20 10:47:10

This is an image of DragonRider. The version configured as ERV would be similar, but with just the 4 upper seats. One of the lower seats would be replaced with a space toilet, one with Mars sample containers, and the centre seat would be empty space that astronauts could use for excercise. But you can see, that's not a lot of room.

Here are images of the Shuttle and ISS space toilets.

The extension module would have just enough room for life support equipment, plus one crew member to enter for repairs. That centre space would be packed full with food. Remember you need 6 months for 4 crew members. For repairs, all that food would have to be unpacked, and tucked in the excercise space. When repairs are finished, it would have to be tucked back up there again. And you don't want crew members excercising around dellicate life support equipment; that would just ask to get something broken.

Last edited by RobertDyck (2014-02-20 10:49:41)

RobertDyck · 2014-02-20 12:43:03

Water Processor Assembly, and Urine Processor. Installed on US side of ISS, sized for 3 astronauts.

Oxygen Generation System, with space reserved for Sabatier

Carbon Dioxide Removal Assembly

Quaoar · 2014-02-20 15:04:34

RobertDyck wrote:

A Mars Direct Hab would only have room for one pressurized rover. In fact, even Robert Zubrin's slides only include one rover, the open rovers are deleted. The table on the first post of this thread is from his book "The Case for Mars".

But if there will be an engine failure when the rover is 100-150 km far from the habitat the crew will be doomed. With only one rover astronatus cannot go out of a walking return range.

RobertDyck · 2014-02-20 16:04:03

It won't fit. And using the rover to drive to the ERV is a backup anyway, not normal operation.

If you're going to question the basics of Mars Direct, I again direct you to Yet another Mars architecture.

SpaceNut · 2014-02-20 18:06:43

What is the landing legs total mass on the ERV, as I see that as wasted fuel to carry them back to orbit.

Someething else that bothers about the use of nuclear reactor on the lite truck is that once the ERV launches is that it becomes totally useless for the future and is just junk left on mars.

Plus what is the mass of the sabetier reactor, compressor that will be launched back to orbit, seems like something that is not needed for the trip home in the ERV in light that we will only have solar for the trip.

Looking at the HAb I am wondering just how much of the cabinetry and other furnishing could be consolidaed and what internal non load supporting walls could be changed to foam with a cloth covering.

Last edited by SpaceNut (2014-02-20 18:20:24)

RobertDyck · 2014-02-20 20:04:54

You can read the tables as well as I can. Further detail would require a structural engineer. I don't know how much mass for landing legs. However, I can say the "ERV cabin" is the Dragon spacecraft plus shell for the extension module. Aeroshell is budgetted at 1.8 tonnes, and propulsion stages at 4.5 tonnes. I assume "aeroshell" includes fabric heat shield, umbrella-like ribs to hold it, the section of solid heat shield, as well as parachute. Are landing legs included? The Apollo LM used a landing stage that acted as a launch platform for its upper stage. The upper stage did not have legs. The Mars Direct ERV could eject legs with explosive bolts the second it lifts off the surface. I'm assuming landing with the first stage for ascent.

Propellant production plant is budgetted at 0.5 tonnes. That includes Sabatier reactor, water electrolysis tank, Mars Atmosphere Carbon Dioxide Freezer, etc. That also could be dropped on lift-off.

Yea, years ago I proposed using soft walls for the hab. I proposed using fabric similar to cubicle walls: rigid enough and sound deadening. Exterior walls for the cylinder would be rigid. Mars Direct called for "weldalite" which is aluminum lithium alloy. Same stuff as the ultra-light-weight external tank for the Shuttle. Since it's pressurized, the dome roof would have to hold pressure in, not hold anything up. Is there any need for interior walls to be load bearing? Not sure, would have to ask a structural engineer. One interesting technology developed by Mercedes-Benz is aluminum foam. They built a concept vehicle with a body made of two pieces of aluminum sheet metal filled with aluminum foam. The result was light yet strong. That was 1997; I see a 2012 article on the Popular Mechanics website that says this is coming to production cars. Cabinets could have aluminim foam shelves, with doors made of fabric stretched over aluminum alloy frames. Or rigid polymer film with edges reinforced with carbon fibre.

RobertDyck · 2014-02-21 20:42:30

Found more detail about Dragon.
index.php?action=dlattach;topic=29182.0;attach=419279;image

According to these drawings, Dragon CRS and DragonRider are essentially the same. The only difference are addition of SuperDrago escape thrusters, replacing the CBM hatch with APAS, and removing the graple post for CanadArm2. After all, if DragonRider docks itself to an APAS port on ISS (where Shuttle used to dock), then it doesn't need help from the arm. Shuttle APAS is a bit more involved (detailed) that this drawing. It has shock absorbers for a 100 tonne shuttle. The images for DragonRider don't have shock absorbers. Are they planning a rubber tunnel? Or a metal tunnel and just a rubber O-ring between Dragon and ISS? Or are they planning the full APAS, this is just a simplification? I do see the allignment petals are hollow; again suitable for a 12 tonne (fully loaded/wet weight) spacecraft instead of a 115.3 tonne (fully loaded/wet weight) Shuttle.

Last edited by RobertDyck (2014-02-23 19:53:43)

SpaceNut · 2014-02-23 19:10:45

I have been reviewing the power systems for ISS and have begun to wonder why so little power is needed for the HAB on Mars. What am I missing that makes the level on the ISS so High or is the level for mars to low.

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#51 2014-02-15 20:51:36

Re: Light weight nuclear reactor, updating Mars Direct

#52 2014-02-15 21:26:37

Re: Light weight nuclear reactor, updating Mars Direct

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Re: Light weight nuclear reactor, updating Mars Direct

#54 2014-02-16 10:53:19

Re: Light weight nuclear reactor, updating Mars Direct

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Re: Light weight nuclear reactor, updating Mars Direct

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Re: Light weight nuclear reactor, updating Mars Direct

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Re: Light weight nuclear reactor, updating Mars Direct

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Re: Light weight nuclear reactor, updating Mars Direct

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Re: Light weight nuclear reactor, updating Mars Direct

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Re: Light weight nuclear reactor, updating Mars Direct

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