Yet another Mars architecture

louis · 2015-05-02 13:57:22

I really can't understand why you keep talking about "landing off target". I can't see how that could happen, unless there was a serious malfunction of the lander - the like of which never happened on the Apollo missions. The lander would be tested and tested again - hundreds of times. There is no reason to think it will land off target. Using your logic we would have to started "safety planning" for all sorts of unlikely events.

Keeping the crew alive is a top priority but effort needs to be concentrated where it is effective in guarding against real risk.

There's no reason why a pressurised Rover shouldn't also be provided for use post-landing. But rather than building some huge monster, we could have a small 2 or 3 person vehicle.

Anyway, exploration should not be a major priority for Mission 1. ISRU experimentation should.

We could probably get plenty of exploration value using a pilotless drone - maybe rocket powered - steered by the first colonists.

kbd512 wrote:

Put another way, under normal operating conditions, the crew is aboard the descent/ascent or descent and ascent vehicles for less than 24 hours. The minutes spent during descent and ascent are critical to the outcome of the mission, but should we devote a major portion of available funding to those few minutes because of what might happen afterwards or account for what might happen afterwards with the design of the rest of the mission hardware?
If there's contention about what our general landing accuracy on Mars is or contingency scenarios that have to be accounted for, should we design a propulsively landed solution that necessarily has significant mass and complexity, or should we develop surface transportation solutions that can retrieve our astronauts if they land off target? What solution has the lowest level of technical complexity, small single man capsules with pressured rovers to retrieve astronauts who land off course or a multi-person propulsively landed capsule that lands the entire crew in one operation? What problems or contingency scenarios does landing the entire crew at the same time solve?
Obviously the propulsively landed solution is capable of some degree of course correction to land as near to the target as feasible, but what happens if even that solution lands a little off target? For example, let's say that a propulsively landed multi-person capsule lands 10km from where intended. Does that mean our astronauts have to carry the oxygen and water to walk back to the habitat module? I think you still need a rover of some kind to retrieve the astronauts. You don't need a pressurized rover and perhaps don't even need a rover that carries the astronauts, but you still need a small robotic rover to carry oxygen and water.
For any real surface exploration effort, a pressurized rover that provides some measure of shielding against SPE's is a requirement. Supposedly, we're going to Mars to explore. A substantial pressurized rover is therefore a requirement if we're to accomplish that stated mission objective.
Establishment of a base on Mars is a far future goal that would require some level of cooperation between the various space agencies. It would be really nice to have, but it's not required for surface exploration and shouldn't stand in the way of a surface exploration mission.

louis · 2015-05-02 14:00:29

RobS wrote:

I suppose we can come up with a half dozen scenarios--however unlikely--where the crew might need more than 24 to 48 hours in the ascent or descent vehicle before docking or rescue. So I am very worried about the idea of a minimum-mass vehicle.
I think Zubrin calculated that with a hydrogen-oxygen third stage, a Falcon Heavy could launch 13 tonnes on a Mars trajectory and presumably can land about 8 or 10 tonnes on the surface. That means two Falcon Heavy launches can land about twice that much; one would launch a trans-Mars injection stage and the other would launch a smaller stage and the payload. So even with a non-reusable Heavy, $200 million will get into LEO 18 to 20 tonnes destined for the Martian surface. So we certainly can get a pressurized rover and a good-sized hab on the surface. For that reason, I think we can afford a decent sized rover, a reasonable sized pressurized rover, and a reasonable sized ascent/descent vehicle.
But I may be wrong.

"land about 8 or 10 tonnes on the surface" out of 13 tonnes - really? That sounds a bit counter-intuitive.

RobS · 2015-05-02 14:02:26

I think at this point we are still not certain about the accuracy of landings because Mars has an atmosphere. Apollo 12 could land close to he Surveyor, but the circular error probable of the unmanned Mars probes is tens of kilometers. Zubrin worried about landing accuracy as well. We're still even sure we CAN land larger things on Mars, let alone the accuracy.

RobS · 2015-05-02 14:16:47

I am not sure what you are saying, Louis, but I looked up Zubrin's article and here is a correction:

"The SpaceX Falcon Heavy will have a launch capacity of 53 metric tons to low Earth orbit. This means that if a conventional hydrogen-oxygen chemical rocket upper stage were added, it could have the capability of sending about 17.5 tons on a trajectory to Mars, placing 14 tons in Mars orbit, or landing 11 tons on the Martian surface. . ."

My comment about 13 tonnes launched to TMI comes from Space X's calculations, and I guess they were not using hydrogen-oxygen propulsion. Zubrin figures, with hydrogen-oxygen for the TMI stage, 17.5 tonnes to Mars, 14 tonnes into orbit, and 11 to the surface. That means two could send 35 tonnes on its way to Mars. That's a lot of tonnage for a descent/ascent vehicle. 11 usable tonnes to the surface is a lot for a hab, for a pressurized rover and supplies, etc. So I think it is well worth our while, assuming we can land things reliably and accurately, to land 2 cargo landers before we land people, so they really DO have the equivalent of a base. Or, we might want to think in terms of pairs of Falcon Heavy launches for everything; one large cargo lander, one transit hab and TEI stage, and one ascent/descent vehicle. That'd be 6 Falcon Heavy launches altogether

kbd512 · 2015-05-02 15:44:58

louis wrote:

I really can't understand why you keep talking about "landing off target". I can't see how that could happen, unless there was a serious malfunction of the lander - the like of which never happened on the Apollo missions. The lander would be tested and tested again - hundreds of times. There is no reason to think it will land off target. Using your logic we would have to started "safety planning" for all sorts of unlikely events.

In the context of plans that land the crew together in a combination descent/ascent vehicle, or even individually as my plans call for, landing "off target" means landing them far enough away from a permanently habitable structure or vehicle that retrieval is not practical.

In my plans, the permanently habitable vehicles are electrically driven M113 variants, known as MTVL's, that travel together in convoy for normal exploration operations. For human EDL, the rovers ring the landing area and retrieve individual astronauts after a drastically simplified EDL solution has brought them, individually, to the surface of Mars.

My supposition is that if the human EDL solution is light enough, a simple ringsail, using an inflatable ring to assure deployment of the parachute, is possible. The individual EDL solution forgoes the complexity of propulsively landed multi-person combination ascent/descent vehicle and whatever improvement to landing accuracy that the more sophisticated solution provides.

I don't think any mission risk reduction benefits will be realized from dragging the mass of a multi-person EDL solution to Mars. It's a plan to spend lots of money and lengthen the timeline for humans to Mars through development of an unnecessarily complicated human EDL solution that will take money from the programs required for transit to/from Mars and the programs required for surface habitation.

louis wrote:

Keeping the crew alive is a top priority but effort needs to be concentrated where it is effective in guarding against real risk.
There's no reason why a pressurised Rover shouldn't also be provided for use post-landing. But rather than building some huge monster, we could have a small 2 or 3 person vehicle.

Each MTVL would sustain a crew of two for approximately 250 days of a nominal 500 day surface stay. A durable rover simply will not be a soda can on wheels. Every attempt to lighten the rover will only defeat the purpose of having them, which would be durable and reliable surface transportation that can sustain the crew and shield them from the effects of solar radiation.

The alternative is establishment of an outpost that our astronauts will never venture very far from. I would prefer that our astronauts actually explore the surface of Mars when they get there. They can only do that if they're mobile.

louis wrote:

Anyway, exploration should not be a major priority for Mission 1. ISRU experimentation should.

NASA is a space exploration agency, not a space colonization agency. We're going to Mars to explore, first and foremost. Permanent human presence is a secondary goal. ISRU is important for the establishment of a permanent outpost, but it's not a justification for going to Mars.

louis wrote:

We could probably get plenty of exploration value using a pilotless drone - maybe rocket powered - steered by the first colonists.

What would another rocket powered robotic vehicle tell us about Mars that all the other rocket powered robotic vehicles haven't already told us? We've done about as much as we can remotely. Sooner or later we need to land some geologists, meteorologists, and microbiologists to try to determine whether or not humans could conceivably live there. After a few mobile surface exploration missions, we can concern ourselves with establishment of a permanent outpost there.

kbd512 · 2015-05-02 16:27:30

Regarding pushing the mass of a M113 to Mars using a single F9H flight, the SEP systems we're developing right now for ARM are more than sufficient for landing ~15t-17t payloads on Mars when used in conjunction with advanced EDL solutions like ADEPT. Without advanced EDL solutions like HIAD and ADEPT, we're not going to Mars.

In very simple terms, we'd need much more powerful and massive propulsion solutions, even with the ISP advantage that SEP provides, for the kinds of mission packages that send the MTV, MDV/MAV, and surface habitation module or rover to Mars together. Eventually we could develop propulsion solutions to send the entire mission hardware package to Mars, but at what cost and on what timeline?

If we opt to use far more economical launch vehicles (F9H) and more efficient propulsion (SEP) we can reasonably afford to put a lot more tonnage on Mars than slightly more capable launch vehicles (SLS) or less efficient propulsion (chemical) would allow for. Sending more tonnage to Mars does far more to lower overall mission risk than skipping orbital assembly or having multi-person combination descent/ascent vehicles.

SpaceNut · 2015-05-02 16:58:21

Going to Mars is not just about lift to orbit of tonnage as its about working back from what we know we need on Mars surface and making the tonnage to orbit line up.

So here is the chance Now, the challenge doors are again open, and the stakes are higher. “The follow-on challenge offers an award of up to $30,000 for design ideas to protect the crew on long-duration space missions,” said NASA. The agency is accepting applications through June 29.

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GW Johnson · 2015-05-02 17:11:17

History over the last millennium says that there are (crudely, and with overlap) 3 phases to “exploring” a new land. The ultimate goal was, is, and always will be, colonization if feasible. Depending upon available technology at the time, some places are feasible, others are not. That situation changes over historical time, just as the transportation technology does.

The 3 phases are (for lack of better names) exploration, adaptation, and colonization.

“Exploration” was, is, and always will be whatever efforts are required to answer two very deceptively-simple questions: (1) “what all is there?” and (2) “where exactly is it?” I mean them exactly as stated, word-for-word. That is not Texas slang. If you have not answered them, you have not “explored”, period. End of issue. That IS the lesson of history.

Our probes have not yet answered these questions on Mars, it generally takes men in-situ to do this, since we cannot yet build intelligent, self-aware robots. We NEVER EVER did it on the moon, although we are getting closer in the decades since Apollo. Apollo was almost nothing but flag-and-footprints nonsense. Almost.

“Adaptation” refers to some sort of base or settlement, where people are trying everything in (or out of) reason to figure out how to survive living off the local resources. A facility like this is invariably “life-supported” from home at first, and perhaps for quite a while.

It takes a long time to figure out how to survive in benign environments, much less the hostile ones. And Mars is nothing if not quite hostile to human life. The success rate in such experiments is historically rather low, but the flip side of that is that we have never failed before.

“Colonization” has an entirely different focus. You cannot do this until “adaptation” is successful. In colonization, what you are looking for is twofold: (1) population growth, and (2) whatever trade basis there might be for a local economy. You simply CANNOT successfully do that until you have successfully learned how to live locally 100% upon local resources.

The best of the colonial efforts half a millennium ago here on Earth successfully solved this trade economy thing. Those former colonies are prosperous nations today. The worst never did solve this economy thing, and so stayed in the resource extraction mode only, and those former colonies are third-world nations or borderline failed states today.

I have previously voiced serious concerns that there will be one, and only one, manned expedition to Mars, that is funded by any or all of the government space agencies on Earth. That’s been the history of the last nearly-a-century of government BS and failure, around the planet.

That being said, that first expedition had better land men on Mars. Screw the flyby and Phobos-only ideas. Period. Or else it will be multiple decades before anybody else ever goes. That’s just an unfortunate fact-of-life in the 21st century. Everybody needs to face up to it, too.

500 years ago, explorations were government-financed entirely, so that is still quite the appropriate model. But, “adaptation” ventures were usually jointly funded, public and private. Two examples are the Dutch East India Company, and the British East India Company. The long-term colonies were almost all privately-financed ventures.

What THAT says is that our first (and only) manned exploration mission had better leave behind some sort of an operating “adaptation” facility, and make joint funding available with the visionary private entities that might go back to Mars and use such a facility. If you do nothing but flag-and-footprints on that first mission, then returning to Mars is nowhere near as attractive to private entities, even the visionary ones. You just delayed things by more decades. Maybe a century. Or more.

It’s going to take a lot of time and a sequence of multiple crews at some sort of “adaptation” base, to really and practically solve the problems of “living off the land” on Mars. Expecting to see solutions to those problems, from one early mission, is unrealistic IN THE EXTREME. It NEVER EVER happened that way in the last millennium. And Mars is tougher than anything we ever attempted on Earth.

You will not know what the economic trade basis for successful colonization will prove to be, until those adaptation problems really are fully solved. Talking about that right now is just idle speculation. You gotta go and adapt first, before you know what local resources or products might actually be useful back home.

And, I warn for a second time, DO NOT plan your colony’s economic system on nothing but simple resource extraction. Nothing in history suggests that to be a successful economic model long-term, although nearly all the colonies started out that way.

Having said all that, NOW do you all understand why I have such heartburn with most of the mission architectures I see proposed here, or at NASA, or anywhere else, for that matter?

GW

louis · 2015-05-02 17:51:53

RobS wrote:

I think at this point we are still not certain about the accuracy of landings because Mars has an atmosphere. Apollo 12 could land close to he Surveyor, but the circular error probable of the unmanned Mars probes is tens of kilometers. Zubrin worried about landing accuracy as well. We're still even sure we CAN land larger things on Mars, let alone the accuracy.

That's why you have transponders on the surface and appropriate thrusters on the lander.

IF you have enough retro-rocket thrust there is no reason why you can't land sizeable payloads on Mars.

SpaceNut · 2015-05-02 20:07:13

Well said GW , On Earth there is one other force that compells people to seek out the adaptive and colonizing phases; to get away from ones problems in the grass is greener over there even when it might not be.

kbd512 · 2015-05-02 21:38:00

louis wrote:

RobS wrote:
I think at this point we are still not certain about the accuracy of landings because Mars has an atmosphere. Apollo 12 could land close to he Surveyor, but the circular error probable of the unmanned Mars probes is tens of kilometers. Zubrin worried about landing accuracy as well. We're still even sure we CAN land larger things on Mars, let alone the accuracy.
That's why you have transponders on the surface and appropriate thrusters on the lander.
IF you have enough retro-rocket thrust there is no reason why you can't land sizeable payloads on Mars.

If you generate enough thrust and have enough fuel you can make a refrigerator fly. The problem isn't thrust generation, it's the quantity of fuel required to make the refrigerator fly.

The entire point to development of HIAD and ADEPT is more efficient deceleration to increase the tonnage landed with respect to the mass of the deceleration solution required to soft land it.

louis · 2015-05-03 08:51:59

Well he must be thinking in terms of using some sort of parachute system I guess...I've never seen anything suggest you could land 11 tonnes on 3 tonnes of fuel.

Looks like the Apollo lander (including the ascent stage weighed in at about 15 tonnes) and had over 8 tonnes of propellant on board. So - over 50% was propellant. Are there more powerful propellants now? Maybe that would explain the difference?

http://en.wikipedia.org/wiki/Apollo_Lun … cent_stage

RobS wrote:

I am not sure what you are saying, Louis, but I looked up Zubrin's article and here is a correction:
"The SpaceX Falcon Heavy will have a launch capacity of 53 metric tons to low Earth orbit. This means that if a conventional hydrogen-oxygen chemical rocket upper stage were added, it could have the capability of sending about 17.5 tons on a trajectory to Mars, placing 14 tons in Mars orbit, or landing 11 tons on the Martian surface. . ."
My comment about 13 tonnes launched to TMI comes from Space X's calculations, and I guess they were not using hydrogen-oxygen propulsion. Zubrin figures, with hydrogen-oxygen for the TMI stage, 17.5 tonnes to Mars, 14 tonnes into orbit, and 11 to the surface. That means two could send 35 tonnes on its way to Mars. That's a lot of tonnage for a descent/ascent vehicle. 11 usable tonnes to the surface is a lot for a hab, for a pressurized rover and supplies, etc. So I think it is well worth our while, assuming we can land things reliably and accurately, to land 2 cargo landers before we land people, so they really DO have the equivalent of a base. Or, we might want to think in terms of pairs of Falcon Heavy launches for everything; one large cargo lander, one transit hab and TEI stage, and one ascent/descent vehicle. That'd be 6 Falcon Heavy launches altogether

RobS · 2015-05-03 09:01:33

The Lunar Lander needed a delta-v from low lunar orbit to the surface of 3,500 mph or about 1.5 km/sec. In Mars Direct, Zubrin assumes a landing delta-v of 700 meters per second via propulsion. He assumes the rest is from the atmosphere. In the Mars Society's web page "The Use of SpaceX Hardware to Accomplish Near-Term Human Mars Mission" posted 2011 (I have it saved on my computer; I'm not sure it's still up) Zubrin says this: "Using just its aeroshield for deceleration, the Dragon would have a terminal velocity of around 340 m/s on Mars at low altitude (air density 16 gm/m3). So we could either give it a rocket Delta-V capability of 600 m/s (a 20% mass hit assuming storable or RP/O2 propulsion, Isp~330 s) to land all propulsive, or we could use a drogue to slow it down (a 20 m diameter chute would slow it to ~70 m/s) and then employ a much smaller rocket Delta-V for landing."

I'll still up a copy of the Zubrin article in another posting, if that's of any use to everyone.

RobS · 2015-05-03 09:04:07

This is the 2011 posting. It has been extensively criticized and very risky, but the numbers are useful. He's a reasonably experienced aerospace engineer and thus some of them, at least, should be correct! I mean no offense to anyone, but Dr. Zubrin does strike me as someone who likes his arguments so much, he often ignores some of the facts.

Home > Press Center > Mars News >
The Use of SpaceX Hardware to Accomplish Near-Term Human Mars Mission
posted May 16, 2011 6:50 AM by Michael Stoltz [ updated May 20, 2011 11:12 AM ]
Robert Zubrin, Pioneer Astronautics, 05.15.11
The recent announcement by the entrepreneurial Space Exploration Technologies Corp. (SpaceX) that it intends to field within two years a heavy lift rocket capable of delivering more than twice the payload of any booster now flying poses a thrilling question: Can we reach Mars in this decade?
I believe the answer is yes. In this paper, I will lay out a plan to make use of the soon-to-be-available SpaceX systems to accomplish near-term human Mars exploration with minimal technology development. First, I will layout a baseline mission architecture and plan. In the next section, I will discuss various technology alternatives available within the selected mission architecture. Then, in the following section, I will discuss alternative mission architectures. I will then conclude with some overall observations bearing on the question of sustained exploration and settlement of Mars.
It may be noted that the author is not an employee of the SpaceX company, and does not have detailed knowledge of the SpaceX systems. It will take the hard work and ingenuity of the SpaceX engineers to develop configurations and systems that can make these ideas a reality. Nevertheless, it is apparent that if an approach such as that recommended here is adopted, the requirements and capabilities numbers can be made to converge. We can reach Mars in our time.
1. Baseline Mission Plan

Here’s how it could be done. The SpaceX Falcon Heavy will have a launch capacity of 53 metric tons to low Earth orbit. This means that if a conventional hydrogen-oxygen chemical rocket upper stage were added, it could have the capability of sending about 17.5 tons on a trajectory to Mars, placing 14 tons in Mars orbit, or landing 11 tons on the Martian surface. The same company has also developed and is in the process of demonstrating a crew capsule, known as the Dragon, which has a mass of about 8 tons. While its current intended mission is to ferry up to 7 astronauts to the International Space Station, the Dragon’s heat shield system is overdesigned, and is capable of withstanding reentry not just from Earth orbit, but from interplanetary trajectories. It’s rather small for an interplanetary spaceship, but it is designed for multiyear life, and if we cut its crew from 7 to 2, it should be spacious enough for a pair of astronauts who have the right stuff.
Using these basic tools, a Mars mission could be done utilizing three Falcon Heavy launches. One would deliver to Mars orbit an unmanned Dragon capsule with a kerosene/oxygen chemical rocket stage of sufficient power to drive it back to Earth. This is the Earth return vehicle (ERV).
A second launch will deliver to the Martian surface an 11 ton payload consisting of a Mars Ascent Vehicle (MAV) employing a single methane/oxygen rocket propulsion stage, a small automated chemical reactor system, 3 tons of surface exploration gear, and a 10 kilowatt power supply, which could be either nuclear or solar. The MAV would land with its propellant tanks filled with 2.6 tons of methane, but without the 9 tons of liquid oxygen required to burn it. This oxygen could be made over a 500 day period by using the chemical reactor to break down the carbon dioxide that composes 95 percent of the Martian atmosphere. Since the reactor and the power system together only weigh about 2 tons, using such technology to generate the required oxygen in-situ rather than transporting it saves a great deal of mass, and offers the further benefit of providing copious power and unlimited oxygen to the crew once they arrive. Combined, the 11.6 tons of methane/oxygen propellant is sufficient to deliver a 2 ton crew cabin (equal in dry mass to the lunar ascent vehicle used during the Apollo missions) from the Martian surface to high Mars orbit where it can rendezvous with the ERV.

Once these elements are in place, the third launch would occur, which would send a Dragon capsule with a crew of two astronauts on a direct trajectory to Mars. The capsule would carry 2500 kilograms of consumables, sufficient, if water and oxygen recycling systems are employed, to support the two-person crew for up to three years. Given the available payload capacity, a light ground vehicle and several hundred kilograms of science instruments could be taken along as well.
The crew would take six months to reach Mars, after which they would land their Dragon capsule near the MAV. They would then spend the next year and a half exploring Mars. Using their ground vehicle for mobility and the Dragon as their home and laboratory, they could search the Martian surface for fossil evidence of past life that may have existed in the past when the Red Planet featured standing bodies of liquid water. Going further, they could set up drilling rigs to bring up samples of subsurface water within which native microbial life may yet persist to this day. If they find either, they will prove that life is not unique to the Earth, but is a general phenomenon in the universe, thereby answering a question that thinking men and women have wondered upon for millennia.
At the end of their 18-month surface stay, the crew would transfer to the MAV, take off, and rendezvous with the ERV. This craft would then take them on a six-month flight back to Earth, whereupon it would enter the atmosphere and splash down to an ocean landing.
2. Technical Alternatives within the Mission Architecture
a. MAV and associated systems
In the plan described above, methane/oxygen is proposed as the propulsion system for the MAV, with all the methane brought from Earth, and all the oxygen made on Mars from the atmosphere. This method was selected over any involving hydrogen (either as feedstock for propellant manufacture or as propellant itself) as it eliminates the need to transport cryogenic hydrogen from Earth or store it on the Martian surface, or the need to mine Martian soil for water. If terrestrial hydrogen can be transported to make the methane, about 1.9 tons of landed mass could be saved. Transporting methane was chosen over a system using kerosene/oxygen for Mars ascent, with kerosene coming from Earth and oxygen from Mars because methane offers higher performance (Isp 375 s vs. Isp 350 s) than kerosene, and its selection makes the system more evolvable, as once Martian water does become available, methane can be readily manufactured on Mars, saving 2.6 tons of landed mass per mission compared to transporting methane, or about 3 tons per mission compared to transporting kerosene. That said, the choice of using kersosene/oxygen for Mars ascent instead of methane oxygen is feasible within the limits of the mass delivery capabilities of the systems under discussion. It thus represents a viable alternative option, reducing development costs, albeit with reduced payload capability and evolvability.
b. ERV and associated systems.
A kerosene/oxygen system is suggested for Trans-Earth injection. A methane/oxygen system would offer increased capability if it were available. The performance improvement is modest, however, as the required delta-V for TEI from a highly elliptical orbit around Mars is only 1.5 km/s. Hydrogen/oxygen is rejected for TEI in order to avoid the need for long duration storage of hydrogen. The 14 ton Mars orbital insertion mass estimate is based on the assumption of the use of an auxiliary aerobrake with a mass of 2 tons to accomplish the bulk of braking Delta-V. If the system can be configured so that that Dragon’s own aerobrake can play a role in this maneuver, this delivered mass could be increased. If it is decided that the ~1 km/s Delta-V required for minimal Mars orbit capture needs to be done via rocket propulsion, this mass could be reduced to as little as 12 tons (assuming kerosene/oxygen propulsion). This would still be enough to enable the mission. The orbit employed by the ERV is a loosely bound 250 km by 1 sol orbit. This minimizes the Delta-V for orbital capture and departure, while maintaining the ERV in a synchronous relationship to the landing site. Habitable volume on the ERV can be greatly expanded by using an auxiliary inflatable cabin, as discussed in the Appendix.
c. The hab craft.
The Dragon is chosen for the primary hab and ERV vehicle because it is available. It is not ideal. Habitation space of the Dragon alone after landing appears to be about 80 square feet, somewhat smaller than the 100 square feet of a small standard Tokyo apartment. Additional habitation space and substantial mission logistics backup could be provided by landing an additional Dragon at the landing site in advance, loaded with extra supplies and equipment. Solar flare protection can be provided on the way out by proper placement of provisions, or by the use of a personal water-filled solar flare protection “sleeping bag.” For concepts for using inflatables to greatly expand living space during flight and/or after landing, see note in Appendix.
3. Alternatives to the Selected Mission Architecture
a. Direct Return.
In an ideal world, direct return from the Martian surface using in-situ produced propellants is the way to go. This, of course, is the basis of the Mars Direct plan, which other things being equal, would be my preference. However, under the assumption that this is a near-term mission using soon-to-be-available systems with minimal technology development, that is not feasible. For example, direct return of a Dragon capsule from the Martian surface in one stage using hydrogen/oxygen propellant produced from Martian water would require about 50 metric tons of propellant. This would require 50 kilowatts of 24-hour power to produce, which, assuming a nuclear reactor is not available, means a solar array of about 5000 square meters. Such an array would likely weigh at least 10 tons, thereby blowing the mission mass budget, and be difficult to deploy by automated systems as well. In addition, assuming a water concentration of 4% by weight in the soil, obtaining 50 tons of Martian water would require mining 1200 tons of soil, which is a non-starter. Using Martian water in combination with atmospheric CO2 to produce methane/oxygen instead of hydrogen/oxygen would cut the power requirement by about 40% and the mining requirement by 60%, but the plan still remains unfeasible within the limits of the available systems. Thus the use of a lightweight LEM-type vehicle to perform Mars ascent and rendezvous with a Dragon placed in a highly elliptical Mars orbit is necessary if the mission mass requirements and delivery capabilities are to converge.
b. Double rendezvous
An alternative to the plan described here might be to fly the crew to Mars in the same Dragon used for the ERV (i.e., a “mothership”), and fly another Dragon to the Martian surface to provide a surface hab. The crew would then rendezvous with the MAV, and take it down to land near the surface hab, which they would live in for 1.5 years, after which they would ride the MAV back up to the ERV. This architecture is feasible in principle, but inferior to the one selected because it requires two orbital rendezvous per mission instead of one, does not allow the ascent propellant to be made in advance of the launch of the crew, and lands the crew separate from substantial living quarters or extended life support capability, without any countervailing advantages.
4. General Observations
The proper goal of a human Mars mission program should be sustained exploration followed by settlement. This can only be done if costs are kept low. This plan creates sufficiently low cost mission architecture to enable sustained exploration. Falcon Heavy launches are priced at about $100 million each, and Dragons are presumably even cheaper. Adopting such an approach, we could send expeditions to Mars at half the mission cost currently required to launch a Space Shuttle flight. In addition, both Dragons employed in the mission are re-used: one remaining on site to contribute to the growing Mars base, and the other returned to Earth. It will be observed that no orbital infrastructure, advanced orbital operations, advanced propulsion, or even surface nuclear power systems (although the 10 kilowatt Topaz demonstrated by the Soviet program would fit the bill) are required to enable the mission. This, plus the fact that the mission can be done using a booster soon to be available minimizes development cost and time, and moves the potential timeframe of the mission from the indefinite future to the near-present.
For settlement, cheap one-way transportation to Mars is required. In addition, cargos larger in scale both in mass and in dimension need to be delivered. This will require development of a true heavy lift vehicle, with at least an 8 meter and preferably a 10 meter fairing, and launch capabilities of over 100 tonnes to orbit. Furthermore, if costs are to be lowered, reusability is desired. However reusability needs to be placed in perspective. The most important part of a space transportation system to make reusable is the lowest stage, since this is the most massive (therefore offering the greatest reusability savings), and adding mass to it (to make it reusable) does not cause any increase in the mass of the stages above it. On the other hand, making upper stages or interplanetary transfer systems reusable only saves a small amount of hardware, but causes the mass of the stages below them to increase. Thus reusability needs to be implemented in steps from the bottom-up, rather than from the top-down (as was unfortunately done in the Shuttle.)
Using the mission architecture described here, and the soon to be available Falcon Heavy and Dragon, the first human missions could be done and an initial outpost could be established on Mars during the present decade. With the advent of a heavy lift vehicle capable of delivering ~9 m diameter hab modules in the 30 ton class one-way to Mars, the subsidized settlement of Mars could begin, with such return flights as remain necessary continuing to be conducted by the FH/Dragon-derived systems. If the heavy-lift vehicle can evolve to reusability, starting with its lowest stages, costs of one-way transport to Mars could be lowered further, eventually reaching the point where individuals of fairly ordinary means would be able to pay their own way, freely venturing forth to start new lives on a new world.
Appendix: Notes Concerning Various Mission Issues
1. Zero Gravity Health Effects.
There is no need for zero gravity exposure. Artificial gravity can be provided to the crew by tethering the Dragon off the TMI stage, in the same way as is recommended in the baseline Mars Direct plan.

2. Radiation.
Cosmic ray radiation exposure for the crew is precisely THE SAME as that which would be received by those on any other credible Mars mission, all of which would use the six month Conjunction class trajectory to Mars, both because that is the point of diminishing returns (the "knee of the curve") where Delta-V trades off against trip time, and because it is uniquely the trajectory that provides a 2-year free return orbit after launch from Earth. Assuming the baseline mission, the total cosmic ray dose would be no greater than that already received by a half-dozen cosmonauts and astronauts who participated in long duration missions on Mir or ISS, with no radiation induced health effects having been reported. (Cosmic ray dose rates on ISS are 50% those of interplanetary space. The Earth's magnetic field does not shield effectively against cosmic rays. In fact, with a crew of six, the current planned ISS program will inflict the equivalent of 30 man-years of interplanetary travel GCR doses on its crews over the next decade. This is an order of magnitude more than that which will be received by the crew of the mission proposed here.) There are enough consumables on board to provide shielding against solar flares.

3. Aerocapture.
The preferred method of Mars capture is aerocapture, rather than direct entry. This means that the Dragon aeroshield, which has some lifting capability, may well be adequate. This is a complex problem, but a back of the envelope calculation indicates that the Dragon’s shield size is in the ballpark. Thus, consider a loaded Dragon system with an entry mass of 17000 kg, an effective shield diameter of 4 meters, a drag coefficient of 1, coming in with an entry velocity of 6 km/s at an altitude of 25 km, where the Mars atmospheric density is 1.6 gm/m3. Setting drag equal to mass times deceleration, it can be seen that that the system would decelerate at a speed of 42 m/s2, or a little over 4 gs. It could thus perform a 1 km/s deceleration in about 25 seconds, during which time it would travel about 140 km. This deceleration is sufficient to capture the spacecraft from an interplanetary trajectory into a loosely bound highly elliptical orbit around Mars. If the perigee is not raised, the craft will reenter again, and again, progressively lowering the apogee of its orbit, until either a desired apogee for orbital operations is achieved or the craft is committed to entry for purposes of landing. That said, if a larger aerobrake were desired, this could be created by adding either a flex-fabric or inflatable skirt to the Dragon core shield.
4. EDL.
Using just its aeroshield for deceleration, the Dragon would have a terminal velocity of around 340 m/s on Mars at low altitude (air density 16 gm/m3). So we could either give it a rocket Delta-V capability of 600 m/s (a 20% mass hit assuming storable or RP/O2 propulsion, Isp~330 s) to land all propulsive, or we could use a drogue to slow it down (a 20 m diameter chute would slow it to ~70 m/s) and then employ a much smaller rocket Delta-V for landing.
5. Living Volume.
The habitable volume of the Dragon capsule is admittedly lower than optimal. However it should be noted that with 5 cubic meters per crew member, it is 2.5 times higher than the 2 cubic meters per crew member possessed by Apollo crews. Alternative comparisons include 9 cubic meters per crew member on the Space Shuttle, or 8 cubic meters per crew member on a German U-Boat (Type VII, the fleet workhorse) during WWII. This would be uncomfortable, but ultimately, workable by a truly dedicated crew.
However these limits can be transcended. The Dragon has a 14 cubic meter cargo area hold below the aeroshield. Into this we could pack an inflatable hab module, in deflated form, but which if inflated, could be as much as 6 m in diameter and perhaps 8 m long, thereby providing an additional three decks, with added useful volume of 226 cubic meters and a total floor space of 85 square meters, 85% as much as that in the Mars Society's MDRS or FMARS stations, which have proved adequate in size for crews of six. After Trans-Mars injection, the Dragon would pull away from the cargo section and turn around, then return to mate its docking hatch with one in the inflatable. It would then pull the inflatable out of the cargo hold, much as the Apollo command module pulled out the LEM. The inflatable could then be inflated. The other end of the inflatable would be attached to the tether, which is connected to the TMI stage, for use in creating artificial gravity.
Upon reaching Mars, the inflatable could either be expended, along with the tether system and TMI stage, prior to aerocapture. Alternatively, and optimally, the tether and TMI stage alone would be expended, but the inflatable deflated and retained for redeployment as a ground hab after landing.
Extra space could be also be provided on the ground by using a 4th launch to pre-land another Dragon loaded with supplies, including one or more inflatable modules which could be set up by the crew after they land.

6. Overall Risk.
The mission architecture is much safer than any based on complex mega systems requiring orbital assembly, since the quality control of orbital assembly does not compare with that which can be accomplished on the ground. It would be better to have a crew of four, but if we are to do it with Falcon Heavys, a crew of two is all we can do. While such a crew size lacks a degree of redundancy otherwise desirable, it also offers the counter benefit of putting the fewest number of people at risk on the first mission. It's quite true that not flying anywhere at all would be safer, but if you want to get to Mars, you have to go to Mars.
[Image: SpaceX]

louis · 2015-05-03 09:17:50

I agree with most of what you say GW.

A few areas of disagreement:

1. Historically, exploration was a kind of survey of what was there. Even at the beginning of the 20th century maps of our planet still had substantial areas of "terra icognito". There is nothing like that on Mars now. We have a good, if rough idea of what is there already. But that is not to underplay the importance of a human presence to take exploration further - for one thing humans could control robot vehicles in near real time and speed up that whole process.

2. 100% self-sufficient is unlikely and not very desirable. My own studies suggest that the Mars colony could probably without too much effort sustain itself on a 95% (tonnage basis) i.e. importing 5% of the stuff it uses. Construction can use ISRU materials. Agricultural needs would be taken care of pretty quickly - so food and clothing could be taken care of in-situ. Power could be supplied from ISRU steam engines used steel or similar reflectors to concentrate solar power on boilers, which would then feed steam to engines to power the settlement. Things like turbines could be manufactured from 3D printers.

They would just need to import things like computers, 3D printers, space suits, medicines and medical technology. But after the initial wave of importation, these would reduce to maintenance levels. Probably most people on Mars would never get in a space suit - except in a touristy sort of way. They will probably just live in pressurised habs and pressurised vehicles.

That said, I think the colony will make so much money that it will be able to afford high levels of importation, so the real figure could be closer to 50-70%.

3. Let's take a hypothetical "Mission 2" - just think of all the opportunities for revenue earning from returned regolith and meteorites. Universities all around the planet will be desperate to get their hands on it. Then there are all the mini experiment packs they could take out on behalf of researchers around the planet...$100,000 per Kg. of experiment. Why not? That's before we discuss sponsorship - how much would Coca Cola or Toyota pay to sponsor the Mission and or an exploratory journey? How much would car companies pay to have mock-ups of their cars placed on Mars? How much would Mercedes pay to brand a Mars Rover?

I'm not a great fan of sponsorship, but in the absence of government funding, please don't underestimate the revenue that could come in.

Longer term the colony I think will be able to make huge amounts of money by: providing life support for a university campus near the base; hosting explorers from the various Space Agencies on planet Earth; exporting precious metals;
developing Mars-based industries e.g. Rolex watch assembly, luxury goods manufacture (e.g. gossamer like clothing and jewelry); supporting film and documentary crews; assembling art works (e.g. sculptures - possibly using 3D printers) on Mars; providing data storage e.g. maybe digitised versions of the World's Great Libraries; and "gap year" tourism.

GW Johnson wrote:

History over the last millennium says that there are (crudely, and with overlap) 3 phases to “exploring” a new land. The ultimate goal was, is, and always will be, colonization if feasible. Depending upon available technology at the time, some places are feasible, others are not. That situation changes over historical time, just as the transportation technology does.
The 3 phases are (for lack of better names) exploration, adaptation, and colonization.
“Exploration” was, is, and always will be whatever efforts are required to answer two very deceptively-simple questions: (1) “what all is there?” and (2) “where exactly is it?” I mean them exactly as stated, word-for-word. That is not Texas slang. If you have not answered them, you have not “explored”, period. End of issue. That IS the lesson of history.
Our probes have not yet answered these questions on Mars, it generally takes men in-situ to do this, since we cannot yet build intelligent, self-aware robots. We NEVER EVER did it on the moon, although we are getting closer in the decades since Apollo. Apollo was almost nothing but flag-and-footprints nonsense. Almost.
“Adaptation” refers to some sort of base or settlement, where people are trying everything in (or out of) reason to figure out how to survive living off the local resources. A facility like this is invariably “life-supported” from home at first, and perhaps for quite a while.
It takes a long time to figure out how to survive in benign environments, much less the hostile ones. And Mars is nothing if not quite hostile to human life. The success rate in such experiments is historically rather low, but the flip side of that is that we have never failed before.
“Colonization” has an entirely different focus. You cannot do this until “adaptation” is successful. In colonization, what you are looking for is twofold: (1) population growth, and (2) whatever trade basis there might be for a local economy. You simply CANNOT successfully do that until you have successfully learned how to live locally 100% upon local resources.
The best of the colonial efforts half a millennium ago here on Earth successfully solved this trade economy thing. Those former colonies are prosperous nations today. The worst never did solve this economy thing, and so stayed in the resource extraction mode only, and those former colonies are third-world nations or borderline failed states today.
I have previously voiced serious concerns that there will be one, and only one, manned expedition to Mars, that is funded by any or all of the government space agencies on Earth. That’s been the history of the last nearly-a-century of government BS and failure, around the planet.
That being said, that first expedition had better land men on Mars. Screw the flyby and Phobos-only ideas. Period. Or else it will be multiple decades before anybody else ever goes. That’s just an unfortunate fact-of-life in the 21st century. Everybody needs to face up to it, too.
500 years ago, explorations were government-financed entirely, so that is still quite the appropriate model. But, “adaptation” ventures were usually jointly funded, public and private. Two examples are the Dutch East India Company, and the British East India Company. The long-term colonies were almost all privately-financed ventures.
What THAT says is that our first (and only) manned exploration mission had better leave behind some sort of an operating “adaptation” facility, and make joint funding available with the visionary private entities that might go back to Mars and use such a facility. If you do nothing but flag-and-footprints on that first mission, then returning to Mars is nowhere near as attractive to private entities, even the visionary ones. You just delayed things by more decades. Maybe a century. Or more.
It’s going to take a lot of time and a sequence of multiple crews at some sort of “adaptation” base, to really and practically solve the problems of “living off the land” on Mars. Expecting to see solutions to those problems, from one early mission, is unrealistic IN THE EXTREME. It NEVER EVER happened that way in the last millennium. And Mars is tougher than anything we ever attempted on Earth.
You will not know what the economic trade basis for successful colonization will prove to be, until those adaptation problems really are fully solved. Talking about that right now is just idle speculation. You gotta go and adapt first, before you know what local resources or products might actually be useful back home.
And, I warn for a second time, DO NOT plan your colony’s economic system on nothing but simple resource extraction. Nothing in history suggests that to be a successful economic model long-term, although nearly all the colonies started out that way.
Having said all that, NOW do you all understand why I have such heartburn with most of the mission architectures I see proposed here, or at NASA, or anywhere else, for that matter?
GW

RobertDyck · 2015-05-03 21:40:04

louis wrote:

We could probably get plenty of exploration value using a pilotless drone - maybe rocket powered - steered by the first colonists.

NASA's Helios HP01 was an electric pilotless drone that had solar panels on its wings. During the day it would charge batteries, running off battery power at night. It could remain airborne for months. And the HP01 operated so high that air pressure was equal to Mars. Ceiling was 96,863 feet (29,523 metres) according to wikipedia. An altitude calculator says that's air pressure of 3.16 mbar. Mars Pathfinder recorded surface pressure varying between 6.77 and 7.08 mbar. That implies this aircraft could fly at descent altitude. Mars has less sunlight, but Mars has less gravity and solar cells have improved. Solar cells for Helios were installed in year 2000, from a company called SunPower. Their website today says their E-Series has 15% conversion of sunlight to electricity, X-Series 21.5%. Don't know which one Helios had, but Spectrolab XTJ cells for space are up to 29.5%.

louis · 2015-05-04 10:50:43

kbd512 wrote:

NASA is a space exploration agency, not a space colonization agency. We're going to Mars to explore, first and foremost. Permanent human presence is a secondary goal. ISRU is important for the establishment of a permanent outpost, but it's not a justification for going to Mars.
...
What would another rocket powered robotic vehicle tell us about Mars that all the other rocket powered robotic vehicles haven't already told us? We've done about as much as we can remotely. Sooner or later we need to land some geologists, meteorologists, and microbiologists to try to determine whether or not humans could conceivably live there. After a few mobile surface exploration missions, we can concern ourselves with establishment of a permanent outpost there.

We could cover thousands of square kilometres very easily and quickly with pitoless drones. They can land and take samples, and return them to base for detailed analysis. Much quicker and more effective than having big human crews in rovers (I presume you know how difficult and draining doing an EVA is) .

I realise NASA isn't a space colonisation organisation. That's why they are not going to be the ones to get us to Mars. Space X is. The most likely scenario is that Elon Musk will get us there - possibly with a "NASA badge" on the front.

RobS · 2015-05-04 11:03:43

While we may have much of Mars mapped to close to one-meter resolution, that does not complete the "exploration" phase. We don't know where there are buried glaciers near the surface, or readily available water. We don't know which craters were carved out by nickel-iron meteorites or, even better, meteorites rich in PGMs. We don't know whether Mars is littered with rich gold deposits or has none at all. Where will a settlement get its copper? Chromium? Uranium? These will require a lot more study and lots of rock samples.

GW Johnson · 2015-05-04 11:20:37

RobS is entirely correct. We have excellent mappings of the surface at close to 1 meter resolution, include mineral distributions of various kinds. But none of those probes has ever scratched but a few inches below the surface. Massive ice deposits don't show in things like that, they have to be under meters of overburden in order not to sublime away.

You find stuff like that with men, drill rigs, shovels, and backhoes. It's just like prospecting for oil and gas in the sense that you must look "deep", and in a lot of places, to find anything truly useful. Deep may not be kilometers like with oil and gas, but it's going to be at least a few to tens of meters anyway. Like here, every site will be wildly different in detail, as to what's really down there. Been that way for millennia here. Important lesson too often ignored.

The exploration expedition that sends men needs a rover with a decent drill rig on it. We're talking about something with a real pipe string-and-replaceable-bit arrangement designed by someone with actual experience in the oil drilling industry, not some Mickey-Mouse toy out of some NASA lab somewhere (nobody there ever worked in a real drilling outfit, to my knowledge). The backhoes can wait for the adaptation missions. Better take picks and shovels, though. And space suits supple enough to use all this stuff effectively.

You've only got about 10 years left to make that suit ready for a mission in the 2030-35 time frame. What's the point in sending men who are so crippled by their suits that they cannot truly explore in the sense we are discussing here?

I still recommend setting up the first adaptation facility on that first (and likely only) exploration mission. Leave it running on automatic making propellant, or oxygen, or water, or whatever actually works in-situ for us. The private entities like Spacex are more likely to return sooner on their own nickel if there's assets like that left in place.

I'd like to put my foot in my mouth again, and say we'd better land at multiple sites before we pick one for that adaptation base facility. That's what it took 500 years ago (exploring multiple sites before picking one thought "best"), and nothing has changed since. Every site will be vastly different on, and especially under, the surface. Only the atmospheric gases are the same at every site.

Not all your ISRU/ISPP stuff can be gas-based, though. Sorry, output rates will be too slow because the gases are so thin. Inconvenient little fact of life regarding process equipment design -- higher inlet density equates to higher throughput rates, whatever they are. Applies to compressors, too.

GW

Last edited by GW Johnson (2015-05-04 11:31:05)

RobertDyck · 2015-05-04 13:08:47

Congress has spent decades and billions of dollars in unmanned probes. They aren't going to start over from scratch. That has to be used, that has to reduce the cost of Mars exploration. "Old Space" companies will always try to maximize cost by saying everything spent so far is useless, we need to start over. Congress won't pay for that. We have the current zombie, dragged out nothing that isn't complete destruction but doesn't achieve anything either. This will continue as long as you try to start over.

Yes, we need a bit more. But you have to leverage what has been done by dramatically reducing any further exploration. I have proposed a robotic sample return. That's primarily technology demonstration of ISPP, but also brings back to Earth a sample. Pick a spot, start the permanent base with the first human mission. But that has to include rovers to explore beyond base, and eventually a rocket "hopper" for planet-wide exploration.

Do you want me to post images from MGS Mars Odyssey for thorium concentrations? Thorium is an indicator mineral for uranium, but more importantly thorium can itself be used as nuclear fuel. Shallow radar (SHARAD) on MRO has mapped glaciers at mid-latitudes.

We also need an orbiter as a technology demonstrator for aerocapture. What would that orbiter do? There has to be a science mission. What do we need to pick a spot for the human base?

Last edited by RobertDyck (2015-05-04 18:55:57)

RobS · 2015-05-04 16:48:38

I'd love to see the thorium concentrations. How do they compare to terrestrial bedrock units?

SpaceNut · 2015-05-04 17:58:42

No need as its already here RobS in this topic http://www.newmars.com/forums/viewtopic.php?id=7052
We would not want to have ITAR issues....

RobertDyck · 2015-05-04 18:53:37

ITAR! We don't have anyone enforcing ITAR on us. Besides, we're quoting figures publicly available.

That forum SpaceNut linked regards radiation. Here is a surface map of Thorium. Sorry, it was made by Odyssey, not MGS.
Map of Martian Thorium at Mid-Latitudes

And a paper published in Lunar and Planetary Science XXXIV (2003)
EVOLUTION OF THE MARTIAN CRUST: EVIDENCE FROM PRELIMINARY POTASSIUM AND THORIUM MEASUREMENTS BY MARS ODYSSEY GAMMA-RAY SPECTROMETER

And a paper published in 43rd Lunar and Planetary Science Conference (2012)
ANALYSIS OF URANIUM AND THORIUM LINES IN MARS ODYSSEY GAMMA SPECTRA AND REFINED MAPPING OF ATMOSPHERIC RADON

GW Johnson · 2015-05-05 11:04:23

For some reason, too many misunderstand the point I am trying to make about exploring for resources. Of course we take advantage of everything we have learned and done so far.

Just for one example, consider buried ice.

RobertDyck said (and I agree) that "Shallow radar (SHARAD) on MRO has mapped glaciers at mid-latitudes." Those locations are all good candidate sites. There's water there.

My point: "how much and how easy to recover?" You cannot learn the answer to that by remote sensing with today's technologies. You have to drill.

If it's big monolithic layers, you can drill and use steam injection to extract water "the easy way". If it's in thin layers interspersed with dirt and rock layers, you have to do some amount of strip or open-pit mining (risk of collapse in loose regolith rules out deep mining). That's a lot harder. If's it's well-dispersed as simple water content in the regolith, you have strip mine in a gigantic scale to process enough regolith to get significant water (that's the problem with lunar water).

Only the big monolithic deposit scenario is easy enough to take advantage of on that first visit. So, now the question becomes: "which of the buried glaciers fits the bill?" Where do we actually land?

You won't know until you get there, with a drill rig. Simple as that.

Just like 500 years ago, you will likely need to visit multiple sites before you find the one you really want. Murphy's Law.

GW

RobS · 2015-05-05 11:10:49

And we will never find everything a base needs in one place. The main things a base needs, I think, are water, nickel-iron meteorite, and perhaps copper (which is a widespread ore associated with basalt lava flows). The nickel-iron may be widepsread at the sand size and can be separated magnetically, so water is the key ingredient. I'd look for an equatorial spot with buried ice (easier to fly to Phobos and Deimos. easier to fly to any orbital inclination) and start there. There was a recent article about buried glaciers that appear to be sublimating away in Valles Marineris, so they are at an extremely low altitude, plus are on the equator.

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