Mars 24 Project - To Mars with Existing Commercial Rockets

Shaun Barrett · 2002-10-16 01:33:29

Why the fascination with Earth-Moon L1?
According to what I've read, L1, L2, and L3 are 'meta-stable' points. In other words, they are points of unstable equilibrium, and a station placed at any of them will require 'station-keeping' fuel because of a tendency to drift from the desired position at the slightest provocation.

Why not put a station at L4, which is like a shallow gravity well? A station at L4, even if gently pushed away from its position, will tend to return to the vicinity of L4 all by itself.
It may be marginally more costly to get to L4, but at least we wouldn't need any fuel to stay there.

???

RobS · 2002-10-16 01:40:55

I am not sure why the scientists keep talking about L1 and L2. This is a good question and maybe a Google search will reveal the answer. The only thing I can think of is that L1 and L2 are useful for both the Moon and Mars, whereas L4 and L5 are useful only for Mars. If one has an ion engine--even a small one--it is probably very easy to stay at L1 or L2.

-- RobS

RobS · 2002-10-16 02:24:10

Ah hah! I found it using Google!

"The second class of orbits considered are quasi-periodic orbits near the Earth-Moon triangular libration points. Transfer costs from geostationary transfer orbit amount to 880-1060 m/s plus 50 m/s for mid-course corrections. Annual costs for station-keeping are about 3- 5 m/s. Eclipses will occur only very occasionally. They can be avoided through orbit changes. Data transmission distance is about 350 000 to 400 000 km. Two groundstations will provide about 80-90 per cent time coverage."

This comes from http://216.239.37.100/search?....e=UTF-8

By comparison, geostationary transfer orbit to escape is 700 meters per second. Conclusion: getting to L1 costs
180 to 360 meters per second "extra."

Advantages of L1:
1. Can be used to stage missions to moon as well as Mars
2. Delta-vee requirements to Earth/sun L1 and Earth/sun L2 are only 50 meters per second. Hence Earth/moon L1 can be used as a repair area for telescopes and other equipment destined for Earth/sun L2. The next generation space telescope to replace Hubble may be put at the Earth/sun L2. If it needs repair, a 50 m/sec deltavee can take it to earth/moon L1.
3. From earth/moon L1, one can use gravity assist manuevers with both the Moon and the Earth to go to Mars. This makes up for the extra delta-vee to get to L1 or allows a wider range of launch times (because the moon can be used as an extra stage to perform plane changes).

--RobS

Shaun Barrett · 2002-10-16 06:16:36

Thanks, RobS !

At the same site you linked, it also answers my question from a different angle.
Apparently, L4 and L5 are only theoretically stable equilibrium points. There are sufficient perturbations in the Earth/Sun/Moon system that station-keeping is required at L4 and L5 too!

So we might as well stick with L1 for the advantages you listed, since we'll have to use fuel for station-keeping at any of the Lagrange points anyway!

Much obliged for your prompt response!

RobS · 2002-10-18 10:21:12

A More Efficient Way to Obtain Solar Energy

Last night I was researching Mars balloons and solar-powered aircraft on the Web. There is an incredible amount of information available. In the process, it occurred to me that there is a better way to concentrate solar energy for use as electricity and heat on the Martian surface.

Imagine a cylinder of plastic 100 meters long and 30 meters in diameter. Such a cylinder has a surface area of about 10,000 square meters and an interior volume of 70,000 cubic meters. In spite of the cylinder?s huge size, its mass is actually fairly reasonable. The recent ?Mars balloon? that flew in Colorado this summer had a volume of 0.6 cubic meters and a mass of 60 grams. Its surface area would have been about 3 square meters, so the mass (if all of it were the balloon?s skin) is about 20 grams per square meter. A 10,000 square meter cylinder would therefore mass about 200 kilograms.

The plastic cylinder is inflated with Martian air to keep it rigid. It is silvered on its bottom half and transparent on its top half, except for a stripe of silver along the very top. Covering the very bottom of the cylinder, inside, is a strip of solar panels 100 meters long and 1 meter wide. Their mass is 300 kilograms; this number is derived from the Helios solar-powered aircraft, which has a total mass of 600 kilograms and a wing surface (which is completely covered by solar panels) of 186.6 square meters (3 kilos per square meter, if you assume that propellers, batteries, etc., have some mass. Probably the solar panels? mass a bit less than 3 kg/m2, but let?s be conservative).

The silvering permits all the sunlight falling on the cylinder to be reflected onto the panels if the cylinder is always oriented toward the sun. It is not difficult to orient it, I think. If the cylinder is aligned with its axis north-south, the cylinder need only to be rolled across the ground to point the silvered surface first toward the east at dawn, then overhead, then to the west at dusk. This could be done by attaching cables every few meters along the ?top? running to anchor points with electric powered winches east and west of the cylinder. If the eastern winches pull while the western winches play out the cable, the cylinder will roll toward the east. To make the rolling smooth, the ground around the cylinder has to be smoothed and a plastic membrane put down, so the cylinder?s plastic surface doesn?t snag on anything or get punctured. This would even allow the winches to ?pivot? the cylinder?to pull the southern end of the axis more than the northern end in order to track a sun that rises in the northeast and sets in the northwest in summer.

How much power can the cylinder make? The surface area reflecting sunlight is 30 meters wide and 100 meters long, a total area of 3,000 square meters. Mars receives an average of half a kilowatt of solar energy per square meter, so the cylinder receives 1,500 kilowatts of it. If the panels are 30% efficient, they can make 450 kilowatts of electricity! The panels will be exposed to solar energy about 12 times as intense as on the Earth?s surface, but the new panels now being made can function efficiently at twice that intensity (I read that on the web somewhere). And consider that this entire solar concentrator has a mass of 500 kg! If one makes the cylinder tougher and more durable, includes the mass of the plastic underskirt, beefs up the panels to make them able to handle more intense ultraviolet light, and adds cables and winches, maybe the mass will be 1,000 kilograms, or even 2,000 kilograms. But that?s still only half the mass of the 100-kilowatt nuclear reactor of Mars Direct.

But there?s a bit more. The panels, exposed to such intense light, will get hot. I don?t know how hot, but my guess is that they will quickly heat to at least 100 Centigrade, maybe 200. (Does anyone know how to figure out there equilibrium temperature?). Hence one could run a network of plastic tubes under the panels and blow pressurized Martian air through them to extract the heat. If one extracted half the ?wasted? solar energy as heat, that would be another 450 kilowatts of energy. Thus the ?solar energy cylinder? would give a Mars base a total of 900 kilowatts of useable energy, which is VERY good. The Mars Direct reactor makes 2,000 kilowatts of energy (100 kw of electricity and 1,900 kw of heat), or twice as much as the solar cylinder for twice the mass. But I?m pretty sure the solar power cylinder could not be deployed without people.

There is one problem to remember: dust storms. They will reduce or eliminate the gain from the silvered surface. The 100 square meters of panels can only make 15 kilowatts of energy if pointed directly at the sun, and probably very little heat. Most of the time during dust storms, one can probably see the disk of the sun at least a little, so the silvering will help somewhat. So solar energy will have to be stored in the form of oxygen and methane for the dust storm season, and efforts requiring a lot of energy?such as making and working metal?would have to be rescheduled.

Dust storms will also require that the cylinder be anchored very carefully; the cables will have to be strong. The cylinder will also get covered with dust, which will have to be blown or brushed off.

There?s another version of this: the solar powered dirigible. A cylinder with a volume of 70,000 cubic meters, I think, can lift about 2,000 kilograms if filled with hydrogen, and as we have already seen its mass, with solar panels, is 500 kg. Trying to point the silvered area toward the sun may be impossible, so there may be no reason to silver part of the cylinder at all; the panels will make 15 kilowatts at high noon if they lie on the bottom of the cylinder (which they will tend to do, since they are the heaviest part of the vehicle). Such a dirigible could have a pod on its bottom with propellers; it would be able to transport over a tonne of cargo (or cargo plus people). It could probably move only slowly under its own power; maybe 30 kilometers per hour. But that speed would be sufficient to circumnavigate the Martian equator in 29 days. If one utilized prevailing winds, one could circle Mars much faster. This would be quite adequate for cargo transport, especially if the vehicle were scaled up somewhat (perhaps doubled, so that it could carry two tonnes of cargo).

Cool, eh?

nebob2 · 2002-10-18 12:13:58

What is the mass of all the batteries you would need for nightime/ emergency use? A dust storm could blot out your pannels for days, requiring considerable storage. Batteries are not light. The advantage of the reactor tis that it will work day and night, clear or covered. And it doesn't have the vulnerability of a thin plastic cylinder.

Shaun Barrett · 2002-10-18 18:16:43

Another fascinating post, RobS.

It never ceases to amaze me that for any given problem related to human exploration of Mars, we always manage to come up with at least one brilliant solution, often more than one.
This 'embarrassment of riches' when it comes to technological solutions, emphasises for me the fact that there really is nothing substantial between us and a permanent outpost (colony) on Mars. All that stands in our way is money! Or at least the lack of it.

People talk about the political will to send humans to Mars, but that too just boils down to the will to spend the money. It's always the money, honey!!

Humanity is WAY MORE than just ready to go to Mars ... we've been ready for years! Hell, it's like being 14 months pregnant, we're so ready to go!!!

Sorry .... I just get a little frustrated every now and then!
???

Keep up the good work, Rob.

nebob2 · 2002-10-18 18:34:30

Mankind is capible of accomplishing nearly anything if we try. We could have gone to Mars with 60's technology. It wouldn't have been easy, but we could have done it. All we need is the will and the means, and that means money for the moment.

RobS · 2002-10-18 21:51:54

You wouldn't use batteries for back up power; you'd use fuel cells. Reversible fuel cells will also do your electrolysis for you. A kilogram of hydrogen-oxygen provides something like five kilowatt hours of electricity. A four-person base needs about ten kilowatts of continuous power to operate life support systems; probably less at night. So fuel cells would need twenty-four kilograms of hydrogen-oxygen (a bit more methane and oxygen; maybe thirty six kilos, there are now methane/oxygen fuel cells) to keep the lights on at night. That amount can be regenerated during the day. Even during a dust storm, the sort of array I described on the first page of the Mars 24 postings would put out ten kilowatts.

If you don't want to use fuel cells, a pressurized rover has an internal combustion engine able to produce far more than ten kilowatts of power. A spare engine would weigh what?; a hundred kilos? How much does a ten kilowatt natural gas electric generator weigh; maybe thirty kilos or fifty kilos? Methane burned in oxygen is, basically, natural gas.

-- RobS

Phobos · 2002-10-19 17:46:01

If you don't want to use fuel cells, a pressurized rover has an internal combustion engine able to produce far more than ten kilowatts of power. A spare engine would weigh what?; a hundred kilos? How much does a ten kilowatt natural gas electric generator weigh; maybe thirty kilos or fifty kilos? Methane burned in oxygen is, basically, natural gas.

You'd have to make sure you didn't burn fuel at a faster rate than you could produce it obviously, but using gas generators could have major advantages in a base that tries to power itself via solar energy. You could offset some of your need for a huge solar cell farm by augmenting your arrays with small gas powered generators. They'd also be nice to have around just for those times when you need an extra dose of electrical energy for some reason.

TJohn · 2002-10-25 11:07:24

So RobS, when is your book coming out concerning your previous posts? Keep up the good work. This is one of first threads that I look for.

RobS · 2002-10-27 00:51:11

I don't have a book. I have started a novel using Mars-24 technology; it's one of the best ways to "test" it. Taking inspiration from Mr. Commarmond, I'm starting with two shuttles and Ihabs flying six astronauts to Mars (two Americans, two Europeans, a Russian, and a Japanese). But I don't have anything to "report" yet.

I have become intrigued by the question of extracting water from the ground. It occurs to me that if one can "easily" drill a "well" that is, say, 200 meters deep, one will probably encounter a reasonable amount of water almost anywhere on the planet. A solar heater that heats Martian air to 100 C, and a pump to compress it and pump it down the well shaft, will be enough to heat the rock walls of the well shaft significantly, to 100C or so. This would cause any ice in the rock to evaporate into the heated air, which, upon exiting the shaft, is run through a heat exchanger to cool it, thereby condensing the water. As the ice in the premafrost melts, the porosity of the bedrock opens up to the penetration of the heated martian air. If the top 20 meters of the wellhead were sealed with concrete around the shaft, then one could pump the heated air down the shaft and build up considerable pressure underneath; say, 1 or 2 terrestrial atmospheres. This would push the heated Martian air into the porosity of the rocks where it would encounter colder, icier rock; then you'd let the air pressure drop, the Martian air would rush out of the shaft, it would flow back through the pores to the shaft and up carrying water with it.

If you heated up the rock with solar-heated air for eight hours every day for a year or two, you could produce quite a reservoir of heated rock underground, and as that heat diffused outward it would melt, the vapor moving inward toward the heat source where it could be extracted. If eventually you heated up all the rock in a sphere underground with a radius of 50 meters, that rock would have a volume of half a million cubic meters and a mass (at two tonnes per cubic meter) of a million tonnes. If the rock contained 5% water, that's 50,000 tonnes of water! And since it comes out of the well as water vapor, it does not require desalination or other purification measures.

So this system over a long period of time could yield a lot of water, I think. But that's not all; it could also yield heat at night and during dust storms, because the heated rock will cool very slowly, deep under ground. You could pump cool air down the well shaft and it would come out heated up. I don't know how long it'd yield heat, but I suspect after a year of pumping 100 kilowatt-hours of heat into the ground every day, you could extract half that much (5 kilowatt-hours) for a month or so. So such a "regolith well" could be very valuable.

-- RobS

Shaun Barrett · 2002-10-27 18:30:52

Sounds like you've put a great deal of thought into this, Rob.

It all sounds very promising to me. The only question I have, is whether or not you anticipate any problems with subsidence as the water is removed from the well?

RobS · 2002-10-29 11:18:35

Subsistence is always a possible problem when one pumps water out of the ground. That's one reason Venice is getting flooded right now. But usually the ground sinks uniformly. If your well was not next to your base, you could let a sinkhole develop and ignore it.

A bigger problem is abration from flying dust scratching the envelope and diffusing the sunlight, which would not allow it to focus on the panels. Rolling the cylinder to keep the focus pointed toward the sun would abrade the plastic membrane as well. So it would have to be replaced every few years. And, of course, solar energy simply is not as reliable as nuclear because the former are affected by dust storms. Nukes are better, but their political incorrectness may prevent their use.

The best nuclear scenario, actually, is to build a breeder reactor using natural plutonium on the Martian surface, mine the uranium on Mars, and export the U-235 and plutonium to space operations elsewhere. That way the space program could be nuclear and the greens wouldn't have to worry about nuclear materials being launched into space on top of tonnes of explosive propellants.

-- RobS

TJohn · 2002-10-29 12:47:10

Ya know RobS, I'm beginning to like your plans for Mars 24 every time I come back here. Can't wait for the book! Have you presented these ideas to anyone else other than postings here?

RobS · 2002-10-29 20:55:28

No, I haven't presented them elsewhere, because it is always dangerous for amateurs to tread in areas where there are experts. But possibly I can refine the plans a bit more, at which point they could be good enough to bounce off some experts. Maybe the Mars Society annual meeting would be the next stop.

The big problems with all Mars plans are not engineering; they are political. The politics occur within the agency launching the plan, which has to accommodate the plan among existing constituencies struggling for money; and then there are the inter-space agency politics, Congress, and foreign relations to take into consideration.

As is clear from the New Mars Forums, there are no shortages of ideas. But even simple matters like how to get the Mars vehicle to low earth orbit is complicated. A heavy lift vehicle is cheaper, but politically difficult because of the up-front costs and because it might look like an admission the space shuttle was a bad idea. From low earth orbit to trans Mars injection: a big rocket would allow chemical boosters like the Saturn V and Apollo; the Star Wars types in the Pentagon would love to see a nuclear booster and reactor developed because they could then use it; the anti-nuke people will oppose even peaceful uses of nuclear power in space because of their possible military applications; solar-electric engines are expensive to develop and would allow smaller boosters to put high-orbiting satellites into low earth orbit, thereby undercutting the existing rocket market. Then there are these issues: a Mars program undercuts the moon lobby; a moon project undercuts the Mars lobby; many prominent scientists repeatedly emphasize that it is unsafe to send people and machines will do the work just fine, though slowly; anyone wanting to send anything up has to be careful not to "dejustify" the space station or compete with it for funds; etc., etc. These are the REAL problems!

-- RobS

RobS · 2003-04-20 01:16:43

Mars 24: A Progress Report

In October 2002 I put together a proposal to go to Mars that I called ?Mars 24? based on the idea that one could launch it to Mars using existing commercial expendable launch vehicles (the larger ones of which can put 24-27 tonnes into low Earth orbit (LEO), hence ?Mars-24,? because I have assumed a launch capacity of 24 tonnes to LEO). The proposal borrowed heavily from Michael Duke?s ?A Lunar Reference Strategy,? a summary of which can be found at http://members.aol.com/dsportree/MM22.htm (note, this is a new web address). Duke?s strategy continues to strike me as the simplest, cleverest, and most feasible plan for getting astronauts to the moon and, by extension, to Mars. Duke?s use of the term ?reference strategy? (echoing NASA?s ?Mars Reference Mission?) indicates the importance of the proposal.

In the six months that have elapsed since proposing Mars 24, I have refined some of the details. I have done some further research, and in a few cases information I needed has come to me fortuitously. Also, I have created a novel titled ?Mars Frontier? and run it through several years on Mars, which allowed me to ?test? the equipment. (The novel will be serialized on the Mars Society?s website soon.) Here are some of the results.

1. LEO to Lagrange 1. Duke?s ?Lunar Reference Strategy? assumes that the space shuttle (25 tonnes to LEO) launches a ?solar-electric vehicle? (SEV) and sixteen tonnes of payload. The SEV appears to be a scaling up of the Deep Space 1 ion engine; it would have a dry mass of about four tonnes, would have about four tonnes of xenon propellant, and would push the payload to the lagrange point between the Earth and the moon in about six months. I am assuming use of expendable rockets instead of the shuttle and that the SEV is already in orbit; thus each 24-tonne launch would include 5 tonnes of xenon propellant and 19 tonnes of payload. Alternately, if a 24-tonne launch lifted four 6-tonne tanks of xenon, each one could push an entire 24 tonne launch to lagrange.

Xenon is 3.5 times denser than water and is a liquid at ?110C, so it is very storable; however, it is very expensive ($20/liter of gas at STP, a liter having 5.9 grams of gas; that?s $3.4 million per tonne, but the figure comes from my 1971 CRC manual and thus is 30+ years old). If argon can be used instead it would be much cheaper (10 cents per cubic foot in 1971) and the ion engines could easily be refueled at Mars, if there were a reason to do so (I do not assume it is necessary below).

One question that was raised by Robert Dyck on this Forum was the problem that a spacecraft delivered to a lagrange point must have its orbit circularized. This is actually not a problem for a SEV because it accelerates the vehicle very slowly and constantly circularizes the orbit it is in, as it goes. But it is an issue for chemically fueled vehicles bearing humans. The L1 point requires a circularization maneuver of 0.43 km/sec (one can calculate this because L1 is 325,000 kilometers from the Earth and circles the Earth once every 27.3 days, the sidereal revolution period of the moon), which is not very much, and it has since occurred to me that if the spacecraft were looped around the moon first, the moon would do most of the work. The moon has been used to help circularize the orbits of satellites destined for geosynchronous orbit.

2. Lagrange 1. Lagrange 1 has been proposed by the NASA NExT team as the location of a space station they call ?Gateway.? Gateway would be used, they propose, to service spacecraft bound for the moon and Mars and to service radio telescopes and other scientific equipment destined for the Earth/Sun L2 point (where the Earth shields the radio telescope from some of the sun?s radio noise). The station at L1 could easily be of the same design as the interplanetary habitation that would house astronauts in their flight to Mars. Thus its development would be a step forward for Mars exploration. NExT calls for Gateway to be developed about 2015.

Michael Duke proposes that the sixteen tonnes of payload his SEV would deliver to lagrange in turn would be split in half; eight tonnes would be cargo destined for the lunar surface and eight tonnes would be a fueled ?lunar-based vehicle? (LBV) able to land the cargo. The LBV appears to have a dry mass of about 1.5 tonnes and can hold up to sixteen tonnes of liquid hydrogen and oxygen (thus when it arrives at lagrange from Earth it is only partially fueled). The first LBV lands an eight-tonne fuel manufacturing plant at the lunar south pole. The plant would be unloaded and set up remotely from Earth. The plant includes a one tonne power source, either solar or nuclear, capable of making 25 kilowatts (this mass agrees with the Mars Direct?s 3.5-tonne, 100 kw reactor quite closely). The fuel plant ingests icy regolith, extracts the water, breaks it into hydrogen and oxygen, and slowly refuels the LBV; the LBV can be filled with sixteen tonnes of LOX/LH2 in six months (maybe less). Fully fueled with sixteen tonnes of LOX/LH2, the LBV can return to lagrange and still have eight tonnes of fuel left to bring another eight tonnes of cargo to the lunar surface. This is the elegance of Duke?s plan; once a fuel making plant is on the surface, it enables additional cargo to be landed on a regular basis.

I?d favor a slightly larger LBV, able to hold twenty tonnes of fuel and therefore to lift ten tonnes of fuel to lagrange, and using the ten, land ten tonnes of cargo on the lunar surface. Thus a 24-tonne launch from Earth to LEO (19 tonnes of cargo and 5 tonnes of SEV propellant) could be split into two packages and landed on the lunar surface, half at a time, in less than a year.

Duke proposes two shuttles launches, each putting an SEV and LBV into LEO; the first would land an eight-tonne fuel making plant on the moon and the second would land an eight-tonne inflatable habitat on the moon. The third launch would lift an eight-tonne crew vehicle and a seventeen-tonne fueled stage that would push the crew vehicle to lagrange quickly. The stage could essentially be another partially fueled LBV. At Gateway the crew vehicle (which might end up being a modified version of the proposed aerospace plane, if that plane is an eight-tonne vehicle) would detach from the stage and dock to an LBV that had flown up from the moon with eight tonnes of fuel. The LBV would land the crew vehicle on the moon, where it would be refueled by the fuel making plant; when the visit were over, the LBV would launch the crew vehicle straight back to Earth, then would return to the moon for refueling.

3. Lagrange to Mars. An LBV launched from the moon with twenty tonnes of LOX/LH2 (and arriving at Gateway with ten of the twenty tonnes of fuel) could in turn be used to push cargo and vehicles to Mars. Two 24-tonne launches from Earth could deliver two 19-tonne payloads to Gateway; they could be docked together and docked to an LBV, which would first slow the vehicles slightly so that they fall to the moon, where the moon would redirect them toward Earth, and as they skimmed a few hundred kilometers above the atmosphere (perhaps 7-10 days after leaving Gateway) the LBV would fire its engines and accelerate everything by 0.6 km/sec, enough to send it on a Hohmann transfer orbit to Mars. That would consume only six or seven tonnes of the ten tonnes of fuel on the LBV; the LBV would have plenty to fly back to the moon. An LBV with ten tonnes of fuel could push 30 tonnes to Mars Direct?s six-month trajectory to Mars; if an LBV could be refueled at lagrange by another LBV, it could push 60 tonnes to Mars, plenty for the entire Mars Direct project.

Alternately, the delta-vee from Gateway to a Hohmann transfer orbit for a solar-electric vehicle is about 3.2 km/sec (this figure comes from an old book by Arthur C. Clarke called The Promise of Space). This is about half the delta-vee to get to Gateway from LEO. Thus a 24-tonne launch with 17 tonnes of payload and 7 tonnes of SEV propellant, docking in orbit to an existing SEV, could send the seventeen tonnes of cargo to Mars in about nine month?s time. A gravity-assist maneuver using the moon might be able to reduce the time somewhat.

4. Cargo Vehicles. Assuming we deliver 19 tonnes of payload to lagrange and dock it to an awaiting LBV, the payload would have to include a 3-tonne heatshield for aerobraking on arrival at Mars (the rule of thumb, apparently, is 15% of total mass); thus 16 tonnes of payload can be put into Mars orbit. Landing the cargo on Mars (assuming the aeroshield is used again for atmospheric entry before landing, and a parachute is used as well) requires a delta-vee of 0.7 km/sec. This is also roughly the velocity needed to circularize an orbit to land cargo on Phobos or Deimos. Fuel and engines for such a delta-vee would mass about 3 tonnes, so this system, which starts with a 24-tonne launch into LEO, can put 13 tonnes on Phobos. The Martian surface would require a bit more structure and a parachute, so the landable cargo would be maybe 12 tonnes. If the cargo vehicle can obtain its landing fuel at lagrange from an LBV, the cargo increases by about two or three tonnes. The work below assumes 14 tonnes of usable cargo landed on Mars out of 24 tonnes rocketed off the Earth.

5. Interplanetary Hab. To transport astronauts from Gateway to Mars orbit, one would use an interplanetary habitat. If one used a design similar to Mars Direct?s ?hab? in size (though a different shape) it could easily have a mass of 19 tonnes, including all the consumables for the round trip; thus it could be launched by one expendable rocket, pushed to Gateway by an SEV, a crew could fly up quickly in a crew vehicle or aerospace plane, then an LBV could push it to Mars. (The Mars Direct Hab, minus cargo and spares and margin, has a mass of 20 tonnes.) The interplanetary hab would include a 3 tonne heatshield and would aerobrake into an elliptical orbit that would carry it beyond Deimos, then down to a periapsis of a few hundred kilometers above the surface. Such an orbit requires a delta-vee of 5.4 km/sec from the surface of Mars; a delta-vee of 0.2 km/sec to escape from Mars entirely; a delta-vee of 1.5 km/sec to reach a fast transfer orbit (6 months) back to Earth.

6. Mars Shuttle. The Mars shuttle would be a single stage reusable vehicle with a mass about 70% larger than Mars Direct?s ERV. My calculations indicate that it would have a dry mass of about 17 tonnes, including 7.5 tonnes of tanks and engines, 5.5 tonnes of heat shield, and 4.0 tonnes of crew module. It would be able to aerobrake itself plus 15 tonnes of cargo (which would include 9 tonnes of liquid hydrogen on the first flights) and 8 tonnes of landing fuel to soft land itself on Mars. If the landing fuel were transferred on board at Gateway, most of the hydrogen could be launched from Earth with the vehicle (combined mass, 26 tonnes).

The 9 tonnes of hydrogen would be used to make 9 tonnes of water and 150 tonnes of LOX and methane; 130 tonnes to launch the shuttle plus a tonne or two of Mars samples to the interplanetary habitat, and twenty tonnes to push the shuttle and interplanetary habitat to a six-month trajectory back to Earth. Subsequently, once the shuttle can be refueled using Martian water (about sixty tonnes needed to make 150 tonnes of methane and oxygen), it would have the following capabilities:

Flight to Phobos (delta-vee from Martian surface, 5.4 km/sec is about the same as to the interplanetary hab; returning to the top of the Martian atmosphere requires 1.4 km/sec more), and since the shuttle would arrive at Phobos with twenty tonnes of fuel, it would have plenty to return to the surface as well (I assume the landing delta-vee with a parachute is 0.7 km/sec and without a parachute is 1.5 km/sec, and that the parachute can be used the first time only. Thus Phobos to the Martian surface requires a delta-vee of 2.9 km/sec). A flight to either moon once a year would make gradual exploration of them possible and would allow maintenance of automated fuel-making facilities on them (Phobos and Deimos are both made out of chondrite and contain a substantial fraction of water chemically bound to their bedrock). The fuel-making plants, like those on the moon, would mass about eight tonnes.

Cargo flights to low Mars orbit. Once the Mars shuttle can be refueled, it is more efficient to use automated cargo vehicles to carry cargo from Earth to Mars orbit, and use the shuttles to deorbit the cargo. A Mars shuttle fueled with 150 tonnes of methane and oxygen could fly to low Mars orbit (delta-vee, 4.2 km/sec); transfer sixteen tonnes of cargo from the cargo vehicle to its cargo bay; transfer sixteen tonnes of cargo (brought up from Mars) from its cargo bay to the cargo vehicle; transfer sixteen tonnes of LOX/methane fuel to the cargo vehicle, enough for it to fly back to Earth orbit with the cargo from Mars; and the shuttle would still have fourteen tonnes of fuel, enough to soft land it and the sixteen tonnes of terrestrial cargo on Mars. (This assumes an unmanned shuttle flight without the crew module; if crew went along, the cargo carried up would have to be several tonnes less.) Thus a combination of Mars shuttle and automated cargo vehicle can haul sixteen tonnes of cargo in either direction between the planets. Mars could export gold (worth $10 million per tonne on Earth), fossiliferous rocks, etc., and it could match imports tonne for tonne if it desired to.

The Mars shuttle would have to be reusable at least three times, preferably five times, before it had to be returned to Earth for refurbishing. I?m not sure how easy that would be. The shuttle would probably be capsule shaped, with doors in its heat shield that would open for its engines to fire. I had wondered how feasible such a design is, but as we all now know, the shuttle had similar doors for its landing gear.

7. Solar-powered airplane. I call this a ?sunwing.? The Helios aircraft already flown on Earth is able to fly at 100,000 feet (where the air is as thin as Mars?s) and in twenty years such vehicles should be able to stay aloft literally for months, flying on rechargeable fuel cells at night. The Helios has a mass of only 700 kilos and can carry 300 kilos of cargo. Its 80-meter wingspan would require assembly by a crew on Mars, but it would be well worth its mass; it would allow low level reconnaissance, resupply of expeditions, possibly even crew rotation of expeditions, and rescue of astronauts stranded when a shuttle landed in the wrong place. I am assuming a 1-tonne version could be assembled on Mars and could carry 400-500 kg of cargo.

8. Optimal Flight Schedule. I am assuming that humans return to the moon first and establish a Gateway Station, SEVs, LBVs, etc., as a lunar transportation system. Once that system is established, this rhythm would allow a robust Mars exploration effort:

Mission 0: Launch a Mars shuttle, nuclear reactor, 9 tonnes of hydrogen fuel, consumables (two launches from Earth, total), push to Mars using an LBV. Launch two automated cargo vehicles with Mars landing capability and fourteen tonnes of cargo each (two more launches from Earth, total). The cargo vehicles land near the shuttle, which refuels itself and provides emergency backup capability. The twenty-eight tonnes of cargo would include an inflatable fourteen-tonne hab (bigger and more durable than the one used on the moon), a pressurized rover (like the one used on the moon), drills capable of drilling 100 meters down or more (essential for hitting water, since it?s probably down there if you drill far enough), scientific equipment, greenhouses, etc. The shuttle and two cargo vehicles would land 47 tonnes of cargo, more than Mars Direct.

Mission 1: The first human mission. Launch two Mars shuttles, 2 interplanetary habitats, and three automated cargo landers (total of nine launches over twenty-six months). The tenth launch takes up the six-person crew (the shuttles and interplanetary habs have a capacity to house or transport four each or eight for the total mission, but the first time you fly, you fly six people to maximize redundancy). By flying two interplanetary habs and two shuttles, you have plenty of redundancy against an Apollo-13 type of accident en route. The three automated cargo landers would carry a complete duplicate set of everything brought by the landers of Mission 0 and then some; that way if the two shuttles accidentally landed at different places, each crew could obtain everything they need to survive. After arrival, Mars would have three shuttles, guaranteeing that six people and one shuttle (and one interplanetary hab) can get home. If all went well, two shuttles could remain on Mars and only one flown back to Earth.

On the flight out (or back) each shuttle could be docked to an interplanetary hab and the pair rotated to produce artificial gravity; if each vehicle were capsule shaped and about 15 meters long, 4 revolutions per minute would create Martian gravity in the lowest level of the hab. If four vehicles were flow out, they could be rotated as two pairs about a kilometer apart, or as a four-spoked complex with a ?docking cube? in the middle holding them together.

Mission 2: Duplicate of Mission 1, except the crew would number 8, and one automated cargo vehicle would fly two fuel-making plants to Phobos. If the first fuel making plant worked well, the second one could be flown to Deimos.

Mission 3: Mission 1?s two interplanetary habitats and two shuttles from Mission 1 and Mission 0 would return to Earth during mission 2 and would be available for Mission 3, thanks to reusability. An additional interplanetary habitat?a third?could be flown with two Mars shuttles, allowing a crew of 12 to be sent to Mars. Probably three automated cargo vehicles would be sufficient because by then a lot of cargo would already be on Mars, landing accuracy would be well demonstrated, there would be considerable experience using the solar-power airplanes so rescue capacity would be well developed, there would be at least three pressurized rovers on the surface, etc.

Mission 4: Duplicate of mission 3, crew of 12. Some Mission 3 or Mission 4 crew might agree to remain on Mars an additional two years, making the habitation continuous.

Mission 5: One could add a fourth interplanetary habitat and fly 16 to Mars. That many habitats may allow more crewmembers as well; maybe 18 could be flown safely to Mars. A third shuttle may be wise to increase the number on Mars. Automated cargo flights would probably remain at three. By mission five, automated cargo vehicles would be reused.

Subsequently, one could add an interplanetary hab every two years and a shuttle every four or six. Gradually the number of people flown to Mars would increase. An early priority would be to design and fly inflatable domes to Mars. Well designed, a dome 40 meters across could include the housing and agriculture to support 12-24 people.

RobS · 2004-01-09 00:31:45

I've been extensively rewriting my "Mars-24" Plan over the last two weeks. I've checked delta-vees, revised mass figures, added details, changed a few names, and written appendices detailing other uses of the system. I'll post the plan in installments because it is now pretty long. I welcome suggestions for continued revision. It sounds like the new space initiatives by President Bush will bear a rough resemblance to this plan.

-- RobS

TJohn · 2004-01-09 21:06:58

RobS,

Is it possible for you to put this in a .pdf? I'm getting back from vacation and am currently skimming through the boards.

RobS · 2004-01-10 23:09:54

I don't have a way to create a pdf, but I have it in Word and can email it to you if you'd like.

-- RobS

RobS · 2004-01-10 23:18:23

[color=#000000:post_uid0]Mars 24, Version 5, Part 3
Phase 2B and Later Phases

OVERVIEW OF PHASE 2B (YEARS 7 AND 9, MISSIONS 3 AND 4; OR LATER)

By the end of the second mission, the surface facility should be able to obtain all the water needed for making fuel; raise enough food for three or four crewmembers; generate 225 kilowatts of power; and the habs can accommodate up to 12 personnel (8 with adequate redundancy). Further expansion is now possible.

Fuel making capacity on Phobos and Deimos exceeds the ability of Mars shuttles to transport it to Earth (because of their flimsy heat shields). Electrical capacity on the surface is sufficient to fuel two or three flights of the Mars Shuttle per 26-month cycle. Landing systems should be sufficiently reliable to guarantee that Mars Shuttles land at the outpost, which means flights need not be accompanied by two ACVs carrying basic equipment. Furthermore, since there are three sunwings on the surface, and at least two Mars shuttles that can be refueled, adequate emergency provisioning capacity exists.

Since two Ihabs and three Mars shuttles have been launched and are reusable, it is now possible to launch one new one each opposition and send two Ihabs and two shuttles to Mars every 26 months.

Consequently, phase two includes a second shuttle and IHab flying between planets; establishes a permanent human presence on Mars; expands the surface base population to at least eight; flies a wider diversity of equipment to Mars; and embarks on a global exploration of the red planet.

The global Mars exploration strategy in phase 2B involves the clearing of a network of "highways" (dirt tracks) that are sufficiently smooth and wide to allow rapid movement (up to 40-50 kilometers/hr or 25-30 miles/hr) of human- or computer-driven vehicles. This involves some bulldozing. Typically, an expedition involves two vans with two crew each, with a robotic truck bearing a nuclear reactor following behind. The two vans set out from base with their bulldozer blades down and clear a track free of rocks, reasonably smooth and straight, and five meters wide. Typically they cannot progress faster than walking pace, or about five kilometers per hour. Each day the expedition can progress 50-60 kilometers. Every day or two each van approaches the nuclear reactor, empties its waste water into the processing facility, and fills its tanks with methane, oxygen, and pure water. If the expedition needs additional water, it deploys a water extraction tent, a 100-kg, 30-meter in diameter polyethylene bubble that traps solar heat. The crew anchors its edge with regolith and installs a cold plate, onto which water released from the regolith freezes. They can extract up to thirty kilograms of water a day from the regolith, though ten kilograms per day is more common. If near-surface ice is available, the crew may use a drill.

The expedition stays self-sufficient in energy and water. The highway is extended about 1,000 kilometers per month (there being a lot of side trips to sites of geological interest). After about two months, the crew clears a sunwing landing strip, allowing a sunwing to transport in new personnel and fly the old crew back to the Outpost. In this manner the expedition can push forward almost continually. A highway from equator to pole (5,000 km) can be cleared in five months; one all the way around the equator (21,000 kilometers) in 21 months. At 30 km/hr, a robotic truck with accompanying nuclear power source could drive 740 km per 24.6 hour day; it could go half way around Mars (11,000 km) in 15 days. At 100 km/hr, a sunwing could fly the same distance in 4.5 days (at 300 km/hr, the trip would take 1.5 days).

EQUIPMENT, PHASE 2B

16. AUTOMATED CARGO VEHICLE B (ACV-B) (4.5 tonnes)
Aeroshell 4.0 tonnes (15% of total)
Avionics, Reaction Control System 0.5 tonnes
Cargo 19-24 tonnes

The ACV-B is reusable and is designed to shuttle cargo from earth orbit to Mars orbit and back. ACV-Bs are orbited separately from cargo; cargo is mated with them at Gateway. A Lifter pushes the ACV-B and cargo to a Hohmann transfer orbit to Mars, usually accompanying the ACV to provide propulsion. The ACV-B and Lifter aerobrake into an elliptical Phobos transfer orbit (apoapsis at the same height as Phobos's orbit, periapsis just above the Martian atmosphere). A shuttle flies up and transfers its cargo into the shuttle's hold. Any cargo bound for Earth is transferred to the ACV-B. A Phobos-based Lifter pushes the ACV-B back to Earth. After an 18-month flight the ACV-B and Lifter reach Gateway and in two months they are refurbished to fly back to Mars at the next opposition.

Delta vee from high Earth orbit to fast trajectory to Mars: 1.2 km/sec (mass ratio 0.33:1 for LOX/LH2, 0.4:1 for LOX/ methane)

Delta vee from Phobos transfer orbit to fast trajectory back to Earth: 2.0 km/sec (mass ratio 0.7:1 for LOX/methane) (Hohmann trajectory, 1.5 km/sec [including 0.1 km/sec course correction] [mass ratio 0.45:1 methane, 0.36:1 hydrogen])

The Mars Shuttle requires minor modification to be able to aerobrake and land 24 tonnes on the Martian surface (the original design calls for 16 tonnes instead); the parachute system needs to be heavier (2.6 tonnes), the aerobrake bigger (7.2 tonnes) and more landing fuel is needed (12 tonnes). Because refueling in Mars orbit is possible, the shuttle need not transport methane and oxygen from Earth, beyond the amount needed for course corrections.

YEAR 7, Mission 3: Seven launches. In year 5, Ihab1 and Mars Shuttle 1 (MS1) returned to Earth orbit; they are now at L1-Gateway and available for reuse.

Launch 1: SEV propellant (5 tonnes), Ihab3 (12.6 tonnes), plus 6.4 tonnes extra consumables and spares. The Ihab is checked out in low earth orbit and sent to Gateway a year or more before the Mars mission, so that its use as part of Gateway can serve as a "shakedown."

Launch 2: Two ACV-Bs (9 tonnes total), SEV propellant (15 tonnes).

Launch 3: Cargo 1, 24 tonnes, including 12-tonne habitat (10 meters in diameter), 2-tonne Sunwing-B, 6 tonnes industrial and scientific equipment, 4 tonnes construction and earth-moving equipment.

Launch 3: Cargo 2, 24 tonnes, including three 4-tonne greenhouses, 4-tonne pressurized rover and supplies, 4 tonnes of connecting tunnels and airlocks, 2-tonne crane, 1 reactor (1 tonne) 1 tonne of TROVs.

Cargos are transferred to the two ACV-Bs in low earth orbit. Each is pushed to Gateway separately by an SEV. A Lifter pushes each to a Hohmann transfer trajectory to Mars, aerobrakes separately, refuels in orbit, and flies to Phobos for full refueling.

Launch 4: SEV propellant (3 tonnes), and Mars shuttle cargo package (21 tonnes), including 13 tonnes consumables, 1 tonne TROVs and 1 moonlet fuel making plant (7 tonnes).

Launch 5: Mars Shuttle (MS4) (17 tonnes total; 10 tonnes stucture and 6 tonnes aerobrake), parachute (2.6 tonnes), 4.4 tonnes SEV propellant. The contents of launch 4 are transferred to the Mars shuttle cargo bay at Gateway.

Launch 6: SEV propellant (5 tonnes) and Mars shuttle cargo package (19 tonnes), including 9 tonnes metal refining and working equipment, a 2-tonne docking cube with remote manipulator arm, and 8 tonnes of consumables and spares for Ihab1. The contents of launch 6 are transferred to MS1's cargo bay or to Ihab1 at Gateway.

Launch 7: Uses only part of one launch from Earth to lift eight crew members to orbit, One CRV using lunar fuel transports all eight to Gateway.

At Gateway is located MS-1, MS-4, Ihab-1, and Ihab-3. LifterBs fly up from the lunar surface to fill each Mars shuttle with twenty-two tonnes of hydrogen and oxygen fuel; twenty-one tonnes to push each shuttle and docked Ihab to a six-month orbit to Mars and one tonne to maneuver in Mars orbit (where the shuttle will pick up eleven tonnes od fuel to land it Mars). The crew rearranges the supplies, fuels the shuttles, then heads for Mars. The docking unit is a cube that can dock up to six items together; it accommodates two shuttles, two Ihabs, and the remote manipulator arm easily. Once on the way, the four vehicles dock and rotate to produce artificial gravity.

On arrival at Mars, the Ihabs go into a Deimos transfer orbit. A Lifter docks and the moonlet fueling plant is transferred to it, which it flies to Deimos. The crew visit Deimos as well in one shuttle, refueling using fuel from the Lifter, and make sure the fueling plant is set up properly. The shuttles refuel, then land with the eight crew and cargo.

Six weeks are dedicated to expanding the outpost and setting up all new equipment. Then ACV-B1 and ACV-B2 arrive in Mars orbit. Two Mars shuttles fly up, pick up their cargo, and fly them back to the surface. The two ACVs head back to Earth with twenty tonnes of water each, pushed on their way by Lifters using Phobosian fuel.

Fifteen months of exploration of the surface begins, creating bulldozed dirt "highways" from the outpost in four or five different directions. Total exploration (50 km day, average, 350 days) is 17,500 kilometers, about half building the highways, about half side trips. A highway to the north polar terrain is a priority.

Mission 3 leaves Mars in two Mars shuttles, but one returns to the surface, increasing the total number of shuttles on Mars to two. Subsequent missions fly to Mars with two Ihabs but only one shuttle. Two crew remain on Mars, establishing a permanent presence on the planet.

YEAR 9, Mission 4: A repeat of year 7. Surface routes now cover 30,000 km, circling the planet at the equator and reaching both poles. Four of eight arrivals agree to remain two cycles, pushing the resident population to twelve.

OVERVIEW OF PHASE 2C (YEARS 11 AND 13, MISSIONS 5 AND 6; OR LATER)

The base now has 5 habs and 7 greenhouses, able to accommodate up to 24 people (18 with redundancy) and feed about 10. Electrical capacity on Mars is now about 375 kilowatts; a shuttle can be refueled in three months. Four lifters are located on Phobos and Deimos. Transportation capacity between the planets is now 8 people in either direction. Phobos and Deimos provide almost enough fuel to supply all the needs of Mars missions, including pushing the automated cargo vehicles to Mars.

There are now three Mars Shuttles at Mars most of the time. No more are needed for several years. Two pairs of Ihabs now ply space between the worlds. The surface base now has considerable life support self sufficiency, extensive exploration capacity, and modest construction capacity.

Phase 3's goals are to expand the life support and construction capacity so that the base can carry a greater share of the effort to expand Martian facilities. This requires launching a third Ihab each time, expanding the transport capacity to 12 and the surface population to 16 or more.

EQUIPMENT, PHASE 3: None New

YEAR 11 (MISSION 5) Seven launches necessary

Launch 1: Ihab5, 6.4 tonnes extra consumables, 5-tonne SEV tank with propellant

Launch 2: Consumables (19 tonnes) and a 5-tonne SEV tank with propellant

Launch 3: Hab (8 tonnes), greenhouse (4 tonnes), spares (3.2 tonnes), LifterB2 (3.8 tonnes) and a 5-tonne SEV tank with propellant

Launch 4: Solar panels (9.7 tonnes) and 5.5 tonnes of regolith moving and processing equipment, with 5-tonne SEV tank and propellant and LifterB3 (3.8 tonnes)

Launch 5: Chemical and plastic synthesis equipment (8.7 tonnes) and 6.5 tonnes of equipment for Phobos (solar panels, more drilling equipment, another docking pad), with 5-tonne SEV tank and propellant and LifterB4 (3.8 tonnes)

Launch 6: 7 tonnes of refurbishment supplies for Ihab1 and Ihab3, 5.2 tonnes parachutes for the two shuttles, 6.8 tonnes margin, and a 5-tonne SEV tank with propellant

Launch 7: 12 astronauts. They fly to Gateway in a preexisting taxi vehicle using 30 tonnes of Phobosian propellant and carrying 4 tonnes of ecological supplies (fish in fishtanks, rabbits, chickens, seeds, seedlings, etc.).

Total mass going to Mars with astronauts: 19 (launch 1) + 19 (launch 2) + 4 (launch 6) + 16 (Ihab 1) + 16 (Ihab 3) + 19.6 (Mars Shuttle1) + 19.6 (Mars Shuttle 2) = 113.2 tonnes, requiring 38 tonnes of Phobosian LOX/methane (note that the refurbishment supplies in launch 6 replace some of the mass in the Ihabs and thus does not increase their mass). The three landers require 15 tonnes more, and the 12 astronauts and taxi 30 tonnes more; total 83 tonnes (the previous mission flew 70)

Launches 1-3 propel themselves to L1. The astronauts fly up as well.

The central docking "cube" is arranged as follows: Ihab1 and Ihab3 opposite each other; Ihab5 and Mars Shuttle1 opposite each other; Mars Shuttle2 with nothing opposite it (it will occupy the spin axis). The three habs and two shuttles aerobrake separately and rendezvous in a high Mars elliptical orbit. Four fly to Phobos in MS2 and remain in the hab there for two weeks doing routine maintenance and exploring the moon. MS1 and eight crew fly to the surface. A week later, MS2 lands on Mars with the other 4 crew.

Once the ACV-Bs arrive, the shuttles fly up and bring the cargo down to the surface. The cargo of launch 5 includes items for Phobos; a crew flies up, flies it to Phobos, sets it up, refuels, and returns to the surface.

With 15 astronauts on Mars, exploration continues apace but considerable more human resources are devoted to chemical and plastic synthesis and metal refining. Methane and carbon monoxide are starting materials for many plastics and metal carbonyls (which are liquid at reasonable temperatures and easy to pour and cast). After four years the base can make metal buildings, plastic greenhouses, furniture, and many other items. Total power output: 260 kw.

YEAR 13 (MISSION 6) Six launches necessary. A repeat of Mission 5, except Launch 4's regolith moving equipment is replaced by more automated supply carts, and Launch 5 carries an 8-tonne hab and a Moonlet Fueling Plant to Deimos. The Mars Shuttle visits Deimos for a month when the cargo from launch 5 arrives, deploys the fueling plant, sets up the hab, and explores the moonlet. Total power output on Martian surface hits 290 kw.

Dirt track "Highways" now circle Mars near the equator and extend to the north and south polar regions. A track now runs the length of Valles Marineris and to the top of at least one of the Tharsis volcanoes.

OVERVIEW OF PHASE 4 (YEARS 15 AND 17, MISSIONS 7 AND 8; OR LATER)

With surface manufacturing ability, it is no longer necessary to import habs and greenhouses. Additional space vehicles are also not needed. Three Ihabs now cross between the planets every two years and they have proven reliability; rather than flying four people each time, six are accommodated in them (there is sufficient space for six if reliability is assured, and three habs provide each other with considerable redundancy). The population of Mars expands to about 20. Two shuttles continue to fly with the Ihabs; since their reliability is better known and there is more experience flying them, more can be demanded of them in terms of shuttling cargo to the surface. With four shuttles and two Ihabs at Mars at all times and ample fuel making on the moons, and with considerable experience with the transportation system, quick missions to Mars-crossing asteroids can be contemplated.

Tommorrow: Applications of Mars-24 to the Moon, Asteroids, Venus, and Mercury[/color:post_uid0]

RobS · 2004-01-14 18:22:09

This is the last installment of Mars-24, version 5. The entire text is available from me as a Word file; write me at rstockman at usbnc dot org.

-- RobS

Other Uses of the Mars Transportation System

The Mars transportation system has many uses other than flying people and cargo to Mars.

1. NEAR-EARTH ASTEROIDS

Ihab (13 tonnes) and 12 tonnes consumables (enough for 4 people for 21 months)

Mars Shuttle (10 tonnes) plus aerobrake (2.8 tonnes) plus crew module (4 tonnes) plus 5 tonnes of scientific equipment and spares.

Total mass: 46.8 tonnes.

The Ihab provides 78 square meters of living space, the shuttle 28 square meters of work space. The consumables provide considerable radiation shielding.

With 68 tonnes of LOX and liquid hydrogen (full load): delta-vee, 4.1 km/sec
With 155 tonnes of LOX and liquid methane (full load): delta-vee, 5.5 km/sec

Many near-earth asteroids can be reached within these delta-vee limitations and flight times. Mars-crossing asteroids could be reached similarly from Mars. Objects in the asteroid belt can be reached using a LANTR tug (see Mercury section) with fuel manufacturing using the moonlet fueling plants (see Mars section).

2. VENUS ORBIT STATION

2 Ihabs (12.6 tonnes each) and 14 tonnes consumables (enough for 4 people for 24 months)
Lifter-B (4.3 tonnes) plus aerobrake (3 tonnes) plus 10 tonnes of scientific equipment and spares plus 13 tonnes return methane/oxygen fuel

Total mass: 69.5 tonnes (requires 3 EELV launches from Earth, 2 Lifter-B launches from moon).

The two Ihabs provides 78 square meters of living space each and complete life support redundancy in Venus orbit. The consumables provide considerable radiation shielding.

Delta-vee, Gateway to Venus: 0.2 km/sec (Earth flyby via the moon) + 0.7 km/sec (trans-Venus injection) + 0.1 km/sec (course correction) = 1.0 km/sec; mass ratio 0.25:1 (hydrogen), 0.3:1 (methane)(Note: Hohmann orbit to Venus from Gateway is only 0.5 km/sec, but a slight increase in velocity cuts transit time from 140 days to 100).

Hydrogen/oxygen fuel for departure to Venus: 18 tonnes

The Lifter-B propels the two Ihabs to Venus, where all three vehicles separately aerobrake into an elliptical orbit around Venus that takes 24 hours per revolution, with periapsis over the sun side of Venus and the apoapsis over the night side. If the orbit stays close to Venus's shadow, but out of it most of the time, the vehicles' solar arrays will have sunlight but Venus will still cover part of the solar corona, thereby decreasing dangerous solar radiation. For the Earth, a geosynchronous transfer orbit has a period of about twelve hours; to escape terrestrial gravity from there requires a delta-vee of 0.7 km/sec. Venus has a gravity well very similar to Earth's, so escape from Venus from a twenty-four hour elliptical orbit will be less that 0.7 km/sec. A transfer orbit to the Earth will be about another 0.7 km/sec.

Delta-vee, highly elliptical Venus orbit to Earth: 1.5 km/sec (including course corrections); mass ratio 0.4:1 (hydrogen), 0.5:1 (methane; preferable because of storability)

Mass returning to Earth: 1 Ihab (14 tonnes) plus consumables (2 tonnes) plus Lifter-B (4.3 tonnes) plus aerobrake (3 tonnes) plus miscellaneous (1 tonne); total 24.3 tonnes; methane/oxygen fuel for return flight, 13 tonnes

Note: Every flight to Venus can leave an Ihab there, allowing the orbital facility to grow in size. The first flight should include an extra 14 tonnes of supplies (in case a crew gets stranded at Venus an entire 19-month synodic cycle) and three communications satellites to maintain continuous communication with the Earth and with the entire Venus surface. Subsequent flights could include water payload, to provide additional radiation protection and a potential fuel reserve.

A Venus orbital station would make an excellent test mission for a Mars flight because the total delta-vee to Venus is much less and the trip duration (22 months) is similar to a Mars trip (28 months). The purpose of such a station would be to study Venus intensively, especially via live control of TROVs on the surface and sunwings, aircraft, and balloons in the atmosphere. Sample return from the Venus surface is possible, as is extraction of deuterium from the Venus atmosphere.

3. MERCURY OUTPOST

ORBITAL DATA

Mercury escape velocity: 4.2 km/sec
Mercury orbit velocity (minimum): 3 km/sec

Gateway to Mercury Direct (from low Earth orbit, add 3.2 km/sec)
Delta-vee Gateway to Mercury: 1.5/2.5/3.5 km/sec (trans-Mercury injection; least when Mercury is at aphelion, most when it is at perihelion) + 0.2 km/sec (to fly by the Earth via the moon) + 0.1 km/sec (course correction)
Mercury capture insertion from Earth: 6.9/8.8/10.9 km/sec
Total: 8.4 to 14.4 km/sec; average, 11.3 km/sec (add 1 km/sec to achieve a low Mercury orbit)

Gateway to Venus: 1.0 km/sec (fast trajectory plus Earth flyby via moon plus course corrections)
Venus gravity assist to Mercury
Mercury capture insertion from Venus: 4.6 to 8.3 km/sec, depending on orbital eccentricities (average 6.1 to 6.3 km/sec)
Total: 5.3 to 9.0 km/sec (average 6.9 km/sec) (add 1 km/sec to achieve a low Mercury orbit)

Conclusion: Mercury missions are easiest done via Venus

EQUIPMENT

Ihab (14 tonnes; identical to standard Ihab, but with heavier aerobrake) plus supplies and special equipment

Mercury Shuttle (11 tonnes; identical to Mars shuttle, but with enlarged cargo bay) plus aerobrake for Earth return (3 tonnes) plus crew module (4 tonnes) plus surface payload (typically 30-35 tonnes)

Solar Electric Vehicle (SEV). Insolation is 5 to 10 times greater at Mercury than Earth, so an SEV that can move 19 tonnes of cargo to 4.5 km/sec in six months in Earth orbit can do the same at Mercury in about 1 month. Since a flight from Venus (where insolation is twice as high as at Earth) to Mercury typically takes two to three months, there is plenty of time for an ion engine to work.

OR:

LANTR Tug: A LOX-Augmented Nuclear Thermal Rocket (LANTR) engine consists of a solid-core nuclear engine that heats hydrogen to a high temperature and expels it, with oxygen afterburners. Although LANTR generates an exhaust velocity lower than a solid-core nuclear engine (Isp of 750 rather than 1,000 seconds) it is still better than chemical propulsion (Isp 460 from Lox/hydrogen) and has two advantages: the fuel is six times denser, meaning fewer tanks are needed; and a larger fraction of the lunar water is used, making the fuel six times cheaper.

A LANTR tug consists of an engine, avionics, side-mounted thermal radiators, a thermionic electrical generator, and a cryogenic refrigerator. Fuel tanks (3.4 tonnes dry mass, 34 tonnes fuel; a Lifter-B tank without engines, avionics, and cargo hold) are docked one on top of another to the engine mounting, with the payload (in this case, the shuttle and Ihab) at the far end, shielded from the reactor radiation by the intermediate fuel. Each expedition has a tug with two LANTR engines, to provide redundancy. Tug total mass: 3 tonnes (excluding tanks). The LANTR tug has no heat shield and thus must retain a few tonnes of fuel to place itself into orbit around the Earth.

As Mission 0 shows, SEV is better than LANTR for Mercury travel because of the intense sunlight.

MISSION 0

Ihab (14 tonnes) and 3.5 tonnes consumables (enough for 4 people for 6 months); 3.5 tonnes of communications/GPS satellites (3 total)

Mercury Shuttle (11 tonnes; enlarged cargo bay) plus aerobrake for Earth return (3 tonnes) plus crew module (4 tonnes) plus 30 tonnes cargo: habitat (8 tonnes), van (4 tonnes), consumables (2 tonnes), scientific equipment and TROVs (2 tonnes), and propellant manufacturing plant (2, 7 tonnes each).

Total of above: 64 tonnes; total landed on Mercury: 45 tonnes. If the Mercury shuttle and Ihab enter a relatively low polar orbit, delta-vee to land is 3.2 km/sec and fuel needed to land 45 tonnes is 46 tonnes.

Total mass placed in Mercury orbit: 110 tonnes

Delta-vee from low Mercury polar orbit to high elliptical equatorial orbit: 1.2 km/sec (an equatorial orbit with apoapsis in the planet's shadow will minimize exposure to the sun and keep cryogenic propellant liquid.)

Mission 0 would be uncrewed. After arrival into a low polar orbit, the shuttle will separate and land at the future site of the outpost in an area of permanent shadow with extensive ice deposits (radar evidence indicates possible ice sheets in permanent shadow at Mercury's poles) The fuel-making systems (which include nuclear reactors) would deploy and refuel the shuttle. TROVs would be sent out to explore the area in detail.

After the communications satellites are deployed in a high polar orbit, the LANTR/SEV tug would move the Ihab and tanks into a high elliptical equatorial orbit to minimize exposure to the sun, establishing "Portal Station." The tug would need fuel (delta-vee 2.5 km/sec) for transport to the high elliptical orbit, back (in case of emergencies), and station keeping (10 tonnes for the LANTR tug, less than 2 tonnes for the SEV tug).

Transportation System Choices:

LANTR tug: 3 tonnes. Delta-vee one way: 7 km/sec. Fuel needed to push 120 tonnes payload plus 3-tonne tug plus 20 tonnes tanks: 220 tonnes LOX/LH2 (eleven Lifter-B flights from the moon). TOTAL MISSION MASS: 363 tonnes

SEV tug: 23 tonnes (much larger than the SEV tugs used in Earth orbit). Delta-vee to enter low Mercury orbit: 10 km/sec. Xenon propellant needed to place 112 tonnes payload plus 23 tonne SEV tug plus 2 tonnes tanks: 55 tonnes. LOX/LH2 fuel to push complex to Venus (delta-v 1 km/sec from Gateway): 48 tonnes (some in the shuttle, some in an extra tank). TOTAL MISSION MASS: 240 tonnes

MISSION 1

Ihab (14 tonnes) and 7 tonnes consumables (enough for 4 people for 12 months)

Mercury Shuttle (11 tonnes; enlarged cargo bay) plus aerobrake for Earth return (3 tonnes) plus crew module (4 tonnes) plus 30 tonnes cargo: habitat (8 tonnes), greenhouse (4 tonnes), van (4 tonnes), consumables (4 tonnes; enough for four crew for 18 months), scientific equipment and TROVs (3 tonnes), and manufacturing equipment (3 tonnes).

SEV tug: 23 tonnes

Total landed on Mercury: 45 tonnes
Fuel for landing: 46 tonnes
Total staying in orbit: 44 tonnes (Ihab, 4 tonnes consumables, SEV tug, shuttle aerobrake)
Fuel for orbit change and maintenance: 5 tonnes
Fuel to return to Earth via Venus: 24 tonnes
Total of above: 164 tonnes

Ion engine propellant: Payload (164 tonnes) plus 6 tonnes tanks times 0.4: = 68 tonnes (4 EELV flights from Earth)

Trans-Venus Injection Propellant: 238 tonnes times .25 =60 tonnes (3.5 Lifter-B flights from the moon)

Mission 1 would include four crew. It would depart from Gateway using chemical propulsion, fly past Venus, and the SEV would progressively match the vehicle's speed to Mercury's during the two-month flight, placing the craft into a low polar orbit less than three months after passing Venus.

Mission 1 lands at the future Outpost, deploys the habitat, greenhouse, and van, explores the high-latitude region, and operates TROVs exploring the rest of the planet. It collects samples to return to Earth. Finally it takes off and rendezvous with Portal Station in a high elliptical orbit. It brings the crew, crew module, 2 tonnes of samples, and up to 15 tonnes of fuel with it (if needed). The SEV sends the IHab and shuttle back to Earth via Venus. At Earth the shuttle and IHab aerobrake while the SEV tug inserts itself into orbit and arrives at Gateway.

Returning to Earth via Venus: Ihab (14 tonnes), consumables (4 tonnes), samples (2 tonnes), Mercury shuttle (11 tonnes), aerobrake (3 tonnes), SEV tug (23 tonnes); total, 57 tonnes
Fuel needed (57 x 0.4) = 23 tonnes

Subsequent launches can launch to Mercury without landing fuel because fuel can be orbited and stored in the tank farm at Portal. They involve about 90 tonnes of payload (Ihab, shuttle, SEV tug, cargo). The mission arrives in Mercury orbit, fuels up, and lands, then makes the fuel for the return and the next mission.

Rxke · 2004-03-28 13:22:28

RobS, the more I read about your plan... The more realistic it looks.

It is scalable, would be perfect for NASA... You can decide where you end the program if funds run out, but given the timeline it is very well conceivable it *wouldn't* end with Mars... As you pointed out in the last posts.

A lot of the hardware you describe for 'phase 1' (the Moon) is off the shelf stuff (imagine a shelve with launchers, heh, but you know what i mean)

3rd parties could become involved fairly easily, for supply missions etc, so it could give a boost for private companies and new partners etc...

What strikes me the most: it won't break the bank, if done gradually, no it would/could be the start of a whole new blossoming industry.

Hope some NASA guys visit these boards, grin... And read your novel-in-the-making as an additional inspiration, too, it gives the whole scheme even more 'flesh'

Even Dr. Zubrin might like the idea...

EDIT: Looks like this thread's broken, posted msgs after this one , but it doesn't show...

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