Mars Colony?

[Lawnmower Boy]

Re: Mars Colony?

 

Gnaskar:

 

I've been very polite about Zubrin's Mars Direct proposal, the one that you seem determined to push. I even conceded that it might be possible with technology that hasn't been fully developed yet.

 

And that is, indeed, if you're out for blood, a contradiction. But I offered it as a species of rhetorical cover for you to retreat behind. You are not making it easy to stay polite here.

[McCoy]

Re: Mars Colony?

 

Gnaskar:

 

I've been very polite about Zubrin's Mars Direct proposal, the one that you seem determined to push. I even conceded that it might be possible with technology that hasn't been fully developed yet.

 

And that is, indeed, if you're out for blood, a contradiction. But I offered it as a species of rhetorical cover for you to retreat behind. You are not making it easy to stay polite here.

This seems easy enough to resolve. Each of you put up $25 Billion and we'll see who's right.

[Gnaskar]

Re: Mars Colony?

 

What I meant was that while we can go to Mars' date=' given time and effort, the precise details of Mars Direct (that is, a 50 billion dollar project doable with current technology) make it an impossibility. [/quote']

 

I respect that that's your educated opinion as technology historian (hope I got that right). Mine, as an engineer (soon to be, anyway; I finish my first master in about 18 months), is contrary (but see my discussions of the word “technology” later).

 

See Portree' date=' 91ff.[/url'] The ERV was judged too small, a docking manoeuvre in Mars orbit was rejected as too dangerous, and the weight estimate for the Mars landing vehicle was raised by 50%.

 

The weight estimate was increased 50%, and number of crew was raised 50%. There's a bit of a correlation there. The ERV was definitely too small for the increased crew. (He notes that the Mars Direct ERV was too small for 4 "in the options of many", then sources an unpublished section of a report published two years before Mars Direct was proposed. An report infamous for proclaiming the need for giant ships to house a crew of four for a 30 day stay on Mars. Including the construction of "Space Station Freedom" as a construction site for it's assembly.*)

 

6 ESA and Roscosmos astronauts are currently spending their second year in a 200m^2 facility designed to simulate a Martian mission. The Mars Direct ERV is about 80-100m^2 (depending on how much of the rations have been eaten), and is in use for 6 months. The Mars Direct Hab is 200m^2, like the dummy one, but has only four crew.

 

And, though I scarce need repeat it at this point, and Lawnmower Boy only referred to it as NASA’s alternative to expanding the ERV, Mars Direct calls for no docking maneuvers or orbital construction. Hence the name.

 

*Space Station Freedom eventually became the ISS. The original budget estimate for it closely matches the ISS's cost, despite the ISS being a quarter of the size.

 

As usual' date=' that has led to calls to use the more realistic VASIMR and solar-electric drives instead. At which point we're back to relying on orbital infrastructure and working on the International Space Station. And, so, welcome to 2011.[/quote']

 

I'm sorry? MORE REALISTIC? The best Ion Drives in existence require 25kW per Newton. VASIMR (the flagship of the Ion Drive Advocates can manage a whopping 5 newtons. If you feed it 200,000We).

 

By comparison, a metric ton of solar power panels gives off 5,000We. So a solar powered VASIMR ship is 40 tons of panels, half a ton of engine, 100 tons of payload (going by the Design Reference Mission requirements), and 20 tons argon and tankage.

 

A day worth of acceleration provides this ship with 0.27m/s. It needs 3,386m/s to escape Earth gravity from low earth orbit. So, in 34 years or so it will be good to go. (Yes, you can cheat, using tricks to get this down to about 5 years). VASIMR is brilliant when your payload's weight is around a ton or so, and can really benefit from the power available when the engines turn off.

 

The Solar-Electric Transfer Vehicle calls for ultra-thin, self erecting, radiation hardened solar panels 200 meters across. At that point, using the panels as a solar sail would actually increase thrust noticeably. Now who's asking for magi-tech?

 

Nuclear Electric Ion Engines will be the cargo transport of the twenty second century, largely because they can travel between Mars and Earth at any time, rather than waiting for launch windows. They may be able to carry a 50 ton payload to Mars in about a year (with a mega watt VASIMR and reactor). But that would require a vacuum rated nuclear power plant, and those are taboo.

 

And' date=' Chris: minimum nuclear bursting charge [i']still [/i]does not mean minimum radiation. Here. Knock yourself out.

Project Orion still doesn't use off the shelf nukes, Here, see the other side of the story.

 

I've been very polite about Zubrin's Mars Direct proposal' date=' the one that you seem determined to push. [/quote']

 

As I’ve tried to make clear from the start, I only support Mars Direct because it’s cheap enough that you can pitch them to politicians without them running for the hills (50 billion over 15 years sounds a lot better than 150 billion over ten). I’m a Mars to Stay advocate at heart. In fact, my alternative to Mars Direct is published in this very topic (and I’d love to have you take a look at it and point out any weak points. I only sat down to think about a few days ago, there’s bound to be some bugs that should be ironed out before I start seriously spreading it around.)

 

I even conceded that it might be possible with technology that hasn't been fully developed yet.

 

And that is, indeed, if you're out for blood, a contradiction.

 

If that is a contradiction then we are using different definitions of either technology or develop. I’m not thinking the kind of development you’d need to get a fusion drive here, we’re talking the challenges involved in making a filter that can let 200 tons of Martian air pass without clogging. I’m thinking technology ala making a duel core computer instead of a single core, not building the world’s first computer.

 

You are not making it easy to stay polite here.

 

At the time I started writing my last post, you had just written a blanket denial ignoring the last four pages of debate. You had also used the word “impossible” which has always been a bit of a berserk button when the claim in question doesn’t violate known physics (calling an engineering challenge impossible to an engineer is a good way of making him build it just to prove you wrong). By the time I had posted, you had clarified your view point, making the second half of my post obsolete and inappropriate.

 

I considered removing it, but by the time I had clicked edit you had made your newest post, and it would have been bad form to edit the post. I apologize if this caused you offence. I’ve already apologized for the post itself within the actual post.

 

On the other hand, if I misunderstood you here, and it’s my pigheaded insistence that Mars Direct is possible that’s making it hard to remain civil, then I suggest we agree to disagree. Neither one of us is likely to budge at this point, anyway, and we’ve provided enough of a background to let the others decide on their own opinions on the matter.

 

This seems easy enough to resolve. Each of you put up $25 Billion and we'll see who's right.

If I had 25 billion I’d start the program myself and hope NASA or private investors would provide the other half. As stage one is developing a 140 ton LEO booster, I could fall back to making money on commercial space flight until I had the rest.

[Lawnmower Boy]

Re: Mars Colony?

 

Gnaskar, I think that you continue to underestimate the problems of routine technical development. I single out viscosity, sealing and filtration because they're the classic quotidian problems that get ignored in big picture proposals but which absorb so much engineering work. But they are standing in for a wide range of developmental problems that will have to be overcome to make something like Mars Direct work. Saying, "oh, I'm sure that these kinds of problems are easy to solve" is,well, going against historical experience. Not to mention that delightful RAND study that tried to quantify the process.

 

Notice the "like" here. I appreciate that you disagree with the considered opinion of NASA on whether or not Mars Direct is feasible. I apologise, but I'm going with the authority of NASA over yours. Picking at these considered conclusions is not going to help your case. I just don't believe that you're Smarter Than All NASA. NASA concluded that a direct-to-Mars project was impractical (short of nuclear-thermal rockets). The implication is that we're going to have to assemble any practical Mars mission in orbit. And that we're going to need ion drives.

 

That's how we got to the current schedule:

 

i) Space station (learn how to build stuff in space);

ii) To the asteroids, with ion drives;

iii) Make fuel in space (with lunar ice or asteroidal ice or some other brain storm; but make fuel in space);

iv) On to Mars by, say, 2035, although that date seems to be slipping back.

 

I say, bravo. Each of the intermediate steps are worth doing in their own right. And there's no real need to recklessly hurry to Mars.

 

Finally, on the subject of Project Orion (which, as a one-time effort, properly prepared, I'm fine with), I will only note that your authority does not understand nuclear devices. I'm not an expert, either, but I do know that the floor on the amount of fallout is set by the critical mass, and although you can reduce the critical mass with proper geometries, in the end, low-yield nuclear devices are created by making them burn their charge inefficiently, not by reducing the charge. That's why devices like Davy Crockett, or the W57 in general, have variable yields, and are fairly dirty at low yields.

 

This is, by the way, an argument for making the launching charges for Project Orion as big as possible. Another reason for doing it once, and on a big scale. Build something the size of a city, and launch it into orbit with fusion bombs.

 

Now there's grandiosity for you.

[RexMundi]

Re: Mars Colony?

 

Do Orion once, and the total fallout; based against it's effects and the population as a whole, is an Insignificant Number/Risk, that can be reduced tenfold simply by launch location, and said launch, need happen only once. The Propulsion devices aren't your typical nuclear device, in either function, nor construction.....hate posting links but here's a good one written in english for us non smart people (it has both yes and no's in the comment section as well and even more links spring off it) : http://nextbigfuture.com/2009/02/project-orion-nuclear-pulse-units-emp.html

 

Bigger the charge though the more efficient and the Less "bad things that make the hippies and naysayers run around in circles making the body snatcher noise".....etc etc ....

 

So let's say there will never be the guts or just the sheer SMARTS to do Orion (Cause damn that thing is CHEAP when it comes to Cost per Kg), and we go with a solid, fairly tested, budget confirmed awesome thing like Sea Dragon (and I can already see the Keith Stone Keystone Light Sea Dragon Commercial).....

 

Then if we had a Dollar for every time some Naysayer said something was Impossible since the last time we landed on the moon, we could launch at least half of Mars Direct, and get the rest of the money with one giant Beer Company advertisement. Hells Bells I would cover a Seadragon or an Orion (though I suppose the advertiser there would be Jiffy Pop Popcorn) in Coexist Bumperstickers and Jesus Fish if that's what it takes to get it off the planet.

 

Impossibility is just a degree of difficulty that means it hasn't been done yet. Not that it can't be done. It should be done to just for being able to run up to the haters and go "PhPpHPHTPpPTHtTT!!!!!! Nayh Nayh Nayh Told You So!".....They get told that a lot, you just have to look back a generation or so to the folks that actually used to DO things instead of just Refine crap others built 30 years ago......

 

~Rex

[Gnaskar]

Re: Mars Colony?

 

I just don't believe that you're Smarter Than All NASA. NASA concluded that a direct-to-Mars project was impractical (short of nuclear-thermal rockets).

 

The assumption here is that NASA decides what to do with it's budget. Except Nixon was the one to shut down Apollo and started the Shuttle Program, Bush senior killed the 90-day plan but started the ISS, Bush junior started Constellations, which was then canceled by Obama (who's also shutting down the other two). And the senate is keeping Orion (the Multi-Purpose Crew Vehicle, not the Pulsed Plasma Propulsion variant) alive, despite NASA's desires.

 

With Apollo or the 90-day plan we'd have a man on Mars already, with a total price for the project equivalent to the ISS (and the Shuttle for the Apollo). With Constellations we'd have had a heavy booster (190 ton class) and a crew launcher (25 ton class, Shuttle Derived) by the time the Shuttle went offline, allowing it to be cheaply replaced by a more traditional launch architecture. We'd also have a Moon Return Mission by 2020. They were too expensive for the presidents' PR advisers, so were cancelled. But, except for Nixon all of these guys increased NASA's budget. With or without Mars Direct, NASA isn't the problem. NASA loved Constellations, but it was cancelled for being "lacking in innovation" and "over budget". Lacking in innovation was the whole point. It's what one would call incremental development.

 

That's how we got to the current schedule:

 

i) Space station (learn how to build stuff in space);

ii) To the asteroids, with ion drives;

iii) Make fuel in space (with lunar ice or asteroidal ice or some other brain storm; but make fuel in space);

iv) On to Mars by, say, 2035, although that date seems to be slipping back.

 

And Ion Drives will not be used for anything but light satellites for a long time. No one seriously suggesting using them for crewed flight. The Solar-Electric Transfer Vehicle mentioned in the 50 years of planning document is spending months in the Van Allen belt (which is like being in a constant solar flare). Obama's "flexible path to Mars" basically means spend money randomly (design a 21 ton crew vehicle, discontinue your only crew rated launch vehicle with a capacity over 20 tons, continue the ISS zero gee health studies and micro gravity production studies, but stop all orbital assembly and refueling studies. Vaguely point at the asteroid belts [but no money toward a space-rated EVA suit that allow any flexibility, no system to leave the Orion space for EVAs, and no actual way to do anything but an asteroid flyby]).

 

So, yes, the current plan vaguely pointed at an asteroid. Not in the belt, though, but a Near Earth Asteroid. There is no plan of mining them, either, and the crew vehicle runs on a propane chemical rocket. The original plan was for a methane rocket, but it was changed at the last minute. No plan has called for making fuel in space (here defined as in vacuum) since O'Neill’s Island Three plan.

 

If you’re going to use NASA’s current plan as an argument, look at it first. The Space Station is finished; scheduled to crash in 2020. No new NASA modules will be added, so no more building in space. Current Schedule is thus:

 

i) Deorbit Space Station, after spending another 100 million or so getting our last crews up on Russian rockets. Research human research, space medicine, life sciences, physical sciences, astronomy and meteorology in the last few years of the program.

ii) Decide in 2015 what to do about the lack of crew rated boosters and heavy lift vehicles. Cancel all half finished projects relevant to this.

iii) Do an asteroid flyby sometime in the next decade. Maybe. If a booster is made.

iv) Make light Ion Satellites with RTG power for exploring the outer solar system.

 

None of this is relevant to the question of how to send a crew to Mars.

[RexMundi]

Re: Mars Colony?

 

Sea Dragon!

 

~Rex

[Lawnmower Boy]

Re: Mars Colony?

 

The assumption here is that NASA decides what to do with it's budget. Except Nixon was the one to shut down Apollo and started the Shuttle Program, Bush senior killed the 90-day plan but started the ISS, Bush junior started Constellations, which was then canceled by Obama (who's also shutting down the other two). And the senate is keeping Orion (the Multi-Purpose Crew Vehicle, not the Pulsed Plasma Propulsion variant) alive, despite NASA's desires.

 

With Apollo or the 90-day plan we'd have a man on Mars already, with a total price for the project equivalent to the ISS (and the Shuttle for the Apollo). With Constellations we'd have had a heavy booster (190 ton class) and a crew launcher (25 ton class, Shuttle Derived) by the time the Shuttle went offline, allowing it to be cheaply replaced by a more traditional launch architecture. We'd also have a Moon Return Mission by 2020. They were too expensive for the presidents' PR advisers, so were cancelled. But, except for Nixon all of these guys increased NASA's budget. With or without Mars Direct, NASA isn't the problem. NASA loved Constellations, but it was cancelled for being "lacking in innovation" and "over budget". Lacking in innovation was the whole point. It's what one would call incremental development.

 

 

 

And Ion Drives will not be used for anything but light satellites for a long time. No one seriously suggesting using them for crewed flight. The Solar-Electric Transfer Vehicle mentioned in the 50 years of planning document is spending months in the Van Allen belt (which is like being in a constant solar flare). Obama's "flexible path to Mars" basically means spend money randomly (design a 21 ton crew vehicle, discontinue your only crew rated launch vehicle with a capacity over 20 tons, continue the ISS zero gee health studies and micro gravity production studies, but stop all orbital assembly and refueling studies. Vaguely point at the asteroid belts [but no money toward a space-rated EVA suit that allow any flexibility, no system to leave the Orion space for EVAs, and no actual way to do anything but an asteroid flyby]).

 

So, yes, the current plan vaguely pointed at an asteroid. Not in the belt, though, but a Near Earth Asteroid. There is no plan of mining them, either, and the crew vehicle runs on a propane chemical rocket. The original plan was for a methane rocket, but it was changed at the last minute. No plan has called for making fuel in space (here defined as in vacuum) since O'Neill’s Island Three plan.

 

If you’re going to use NASA’s current plan as an argument, look at it first. The Space Station is finished; scheduled to crash in 2020. No new NASA modules will be added, so no more building in space. Current Schedule is thus:

 

i) Deorbit Space Station, after spending another 100 million or so getting our last crews up on Russian rockets. Research human research, space medicine, life sciences, physical sciences, astronomy and meteorology in the last few years of the program.

ii) Decide in 2015 what to do about the lack of crew rated boosters and heavy lift vehicles. Cancel all half finished projects relevant to this.

iii) Do an asteroid flyby sometime in the next decade. Maybe. If a booster is made.

iv) Make light Ion Satellites with RTG power for exploring the outer solar system.

 

None of this is relevant to the question of how to send a crew to Mars.

 

No, NASA doesn't decide what to do with its funding. Congress does. There was this big thing in 1776--83 about that. (The advantage of being a historian is that you know obscure stuff like that.)

 

Okay, snark over. Congress appropriates, but the executive advises. Yes, Nixon ended Apollo. Because he was advised that it was time to end it. Evil old Bill Clinton/George Bush didn't decide not to go with Mars Direct because he/they hate Mars. He/they decided not to go with it because NASA felt that it wouldn't work. NASA mustered devastating criticisms, and instead of dealing with the criticisms, Zubrin and his cultists have been been picking and carping, shuffling and sliding, ever since.

 

Please don't go down that road.

 

As for the ISS, as I'm sure that you know, notwithstanding plans to defund it in 2020, there are also plans to extend its life past then, and three nations have been invited to sign on to further extension. In spite of being "finished," one new module is still being planned for addition next year. In the mean time, there are still at least nine years of experimentation, experience, and maintenance to go, including VASIMR testing.

 

Speaking of VASIMR, I see that Charles Bolden has singled it out as a potential drive for a manned Mars flight. I knew that I wasn't hallucinating that. Yes, it will require a nuclear reactor. But all feasible Mars manned missions do. (Just to review, outside Heaven's Gate, or whatever Doctor Zubrin is calling his cult today, Mars Direct is not feasible. Oops. Sorry. Too much caffeine= too much snark.) It is even the chosen technology to boost the ISS ahead of 2020 deorbit. We'll see.

 

As to what happens after 2020, well, it won't be a manned Mars trip, because those are currently not feasible. But VASIMR development (and other ion engines) will certainly continue, and there's that asteroid mission. Then? Who knows. I don't expect plans for the 2030/2040 framework Mars mission to come to fruition. They're unrealistic. Again; no matter how hard you will them to exist, manned missions to Mars are not currently realistic.

 

Development, time, blah blah blah. Either this is because everyone who has looked at the question seriously agrees with this. Or, it's because NASA (or possibly a mind-controlling potted plant in the Oval Office) harbours a secret anti-Mars bias. I know which option I'm going for.

[McCoy]

Re: Mars Colony?

 

Evil old Bill Clinton/George Bush didn't decide not to go with Mars Direct because he/they hate Mars. He/they decided not to go with it because NASA felt that it wouldn't work. NASA mustered devastating criticisms, and instead of dealing with the criticisms, Zubrin and his cultists have been been picking and carping, shuffling and sliding, ever since.

 

[snip]

 

Development, time, blah blah blah. Either this is because everyone who has looked at the question seriously agrees with this. Or, it's because NASA (or possibly a mind-controlling potted plant in the Oval Office) harbours a secret anti-Mars bias. I know which option I'm going for.

As a historian, have you never come across a case where the fatal flaw of a plan was that it wasn't developed in house? An idea that was killed for no other reason than it wasn't invented here?

[McCoy]

Re: Mars Colony?

 

Sea Dragon!

 

~Rex

You might want to see a doctor. You may have caught Rudy Giuliani's 911 Tourette.

[Gnaskar]

Re: Mars Colony?

 

Let me just reaffirm the framework for this debate. The question is whether Mars Direct, as proposed by Robert Zubrin and David Baker and advocated by the Mars Society, is feasible using NASA’s human exploration budget with a human landing within, let’s say, 10-15 years. For the sake of argument we’re assuming that politics are not involved in the decision at any level, meaning no side project clambering for a share of the funding, no interference from the senate or the POTUS, no budget increase. 3.5 billion a year for the next 15 years is 52.5 billion, allowing 200 million a year for the next ten years to continue NASA’s involvement in ISS at a reduced rate.

 

With this in mind, I’m going to deliberately ignore that the current NASA director is good friends with the CEO of the private company designing the VASIMR, and consider the engine under its own merits. I’m going to keep in mind the lesions NASA has learned from ISS, and only point out in passing that the last module to be added to it, Nauka, is designed, built, tested, launched and attached by Roscosmos, and thus not much of an orbital assembly test bed for NASA (just to not be called on ignoring that argument). I will also note the VASIMR is, objectively, a fantastic station keeping device, capable of boosting the station up several hundred meters a month on virtually no propellant, or ramping up the mass flow and doing a short, 3 week, boost of almost a kilometer.

 

So, let us address NASA’s concerns about Mars Direct as described in Portree, 91ff:

 

1: ERV is too small to transport a crew of 4, let alone 6, back from Mars.

2: A crew of four is too small.

3: A Mars orbit rendezvous is risky for a human crew.

4: Zubrin’s weight estimate for the hab is optimistic.

5: The Ares booster described by Zubrin is too small to handle the above concerns.

 

I’m not adding the ISRU to the list of concerns, because every NASA plan since then has called for it. The Design Reference Mission (both scrubbed and not) and the Solar Electric Transfer Vehicle called for it. NASA has set up a facility to test ISRU, implying that they expect to use it at some point. So while I agree that the compressor is a weak point, it is not in and of itself a show stopper. If we want, we can organize a robotic Mars Sample Return Mission based on it (this would fit under the robotic exploration budget, which is due for a new mission anyway) before sending the first ERV. The cross feeding of these two missions adds a tiny but exploitable leniency in the budget for ISRU development.

 

Now then. To work.

 

Let’s start by noting that concern 1, 4, and 5, and indirectly 3, can be solved with the same solution. They all point towards either a bigger booster or orbital assembly. We don’t really have a choice here, as it would no longer be Zubrin’s Mars Direct with orbital assembly. So to start with we have to look at the Ares Booster.

 

Now, the Ares Booster is not the brainchild of Robert Zubrin. It was designed David Baker and Sid Early of Martin Mariette in the early nineties. It was designed around the following concept: place four Space Shuttle Main Engines (SSMEs) under a modified Space Shuttle External Tank, add two Space Shuttle Solid Rocket Boosters (SRBs), and put a standard H2/LOX upper stage on top of it. The idea was that since all components already existed, the Ares would be cheap to design.

 

What immediately strikes me as wrong with the Ares design is the SSMEs. The Space Shuttle’s engines were designed to be reusable, driving up their cost and complexity, while decreasing the efficiency. I would have used some older, cheaper engine, like the RL10 (Saturn V’s second stage engine, still used today in Delta IV rockets) or the RS-68 (another Delta IV rocket). As it turned out, NASA agrees with me. Meet the Ares V. The Heavy Launch Booster of the Constellation program replaced Baker’s 4 Space Shuttle Main Engines with 6 cheaper RS-68s, increasing capacity significantly (by 34%, in fact, for 188 tons to LEO).

 

Constellation was, of course, cancelled a year ago, and it was noted that the Ares V would only be ready sometime in the mid to late 2020s under Constellation and the Constellation project would cost 100 billion by then. This has to be addressed before I claim the possibility of using the Ares for a 2020 manned mission.

 

So here is where Constellation went wrong. The Constellation program was designed around the following parameters: First design a crew launch vehicle with a 25 ton payload, the Ares I, to allow continued ISS operations after caning the Shuttle. Then develop a spacecraft akin to the Apollo spacecraft (the combination service module and command module), known as Orion or the Multi-Purpose Crew Vehicle, first as an ISS life boat and later as a transport for Moon/Mars missions. Then develop the Ares V along with an Earth Departure Stage and a Moon/Mars Hab (Altair).

 

My proposed alternative is as follows: Ares I’s tasks can be done by a Falcon 9 (expected to be crew rated by 2015) with a Dragon capsule. At 56 million per launch, SpaceX’s Falcon is cheaper than the Ares I’s construction cost alone. Orion is useless of this kind of mission, especially if we want to rule out orbital rendezvous (concern 3). Altair is designed for Moon operation, and thus is mostly fuel (as the moon has very limited ISRU capability). Cut all of those from the budget and development plan.

 

Shutting down Orion gives us another billion a year, but using them would be going away from our framework (total cost of up to 50 billion), so that money goes to ISS.

 

So, under this new framework, an accelerated design process for the Ares V combined with an increased budget for it can allow us to get it ready within the 8 years before we first need it. One can also argue that we could share the design costs of this particular vehicle with other projects given the obvious usefulness of a heavy booster. The Lunar Quest Program, New Frontiers, Space Technology, and Space Launch Systems programs, for example.

 

So, with a 188 ton booster in hand, let’s see what we can do to deal with our concerns.

 

Concern 2: Crew Size.

The only concern that is independent of booster sized, so it has to be addressed first. NASA generally wants a 6 man crew for its Mars missions. NASA generally also wants one of those crew members to stay in orbit over the planet to keep an eye on the orbiting return vehicle Mars Direct rules out. So, given no orbiter, we could do a five man crew.

 

The one thing Mars Society is doing to promote its plans is leaving a crew of four in the middle of nowhere to look at how that works out in practice. The answer is that it works out quite well. To be fair, I’ll look at the feasibility of the mission with both a 4 and a five man crew.

 

Concern 1: ERV is too small.

The ERV cabin weighs 11.5 tons. With the increased load of the Ares V, that can be increased 34%, to 15.4 tons. Can this be shown to be a significant improvement in cabin size?

 

The cabin mass is broken down thusly:

• Structure, furniture, shielding, control systems and spare parts: 5.7 tons
  
• Life support, power and consumables (scales with number of crew): 5.8 tons
  

So, if we keep the four man crew the increase in size for the cabin is from 5.7 tons to 9.6 tons. That’s a 68% increase in size. If I had to estimate its size based on ISS modules of a similar weight I’d say it was around 75m^3-100m^3 in pressurized volume. Enough to give each crew member a private 10m^3 room and still have a spacious common area. Note that the ERV would be a micro gee environment, meaning cubic meters are more descriptive of size than square meters.

 

But what about a 5 man crew? Increasing the consumables by 25% gives us 7.2 tons of non-structure, and 8.2 tons of structure. A 43% increase in size, or a 15% increase in size per crew member. Note that it’s just 1.4 tons smaller than the four man version, so still has somewhere between 50m^3-75m^3 of interior space. That still allows a 6m^3 private room for each of the crew.

 

In conclusion: The Ares V allows the use of an expanded ERV capable of handling a crew of four in conditions equivalent to current standards, or a crew of five in conditions that aren’t too rough. The analysis is extremely sensitive to the weight of the life support systems, a field that has seen advances since the proposal of Mars Direct (for example, we’re carrying 500 kg of washing water per person on this trip, which could be halved with a 5% improvement of the recycling, giving us a ton of more space).

 

Concern 3: Mars orbit rendezvous is risky.

We don’t need orbital rendezvous around Mars. We do do one in Earth orbit, as the Ares V isn’t crew rated, so we need a Falcon 9 to load the crew onboard.

 

Concern 4: Zubrin’s weight estimate for the hab is optimistic.

The Ares V gives us a capacity of 33.9 tons for the hab, compared to Zubrin’s 25.2 tons; an increase of 8.7 tons.

 

The Hab’s landing mass, by the original plan, is as follows:

• Structure, furniture, shielding, control systems, science kit and spare parts: 11.2 tons
  
• Life support, power and consumables (scales with number of crew): 11.8 tons
  
• Rovers brought along: 2.2 tons.
  

 

This allows us to increase structure by 8.7 tons (with a four man crew), or 5.8 tons (with a five man crew). At worst, that’s a 50% increase. Assuming Zubrin wasn’t off by more than that, we’d still have 200m^2 to divide amongst a crew of 5, and ESA studies seem to show that 200m^2 is good enough for a crew of six for this kind of mission. We can also further increase the ratio by going with the NASA standards for rations, for 2 tons less food brought along, but better rations give us a happier crew so that’s a worst case option.

 

Concern 5: The Ares booster is too small.

We’ve upgraded to the Ares V, making use of the research that has already been done on it, and reducing development time by cutting the crew capable requirement.

 

Can we do it for 50 billion?

That is the million dollar question. It also requires a financial background to determine with any certainty, so unless there is someone with that background and access to a budget breakdown of the Constellation program on these forums we could argue ‘til the cows come home. With typical NASA launch costs for the Ares V we lose 10 billion for the heavy six launches required and 0.2 billion for the Falcon 9 launches. If the Ares V launch costs were at market standard instead, launch costs would only be 3 billion total (keep in mind that bigger boosters tend to be cheaper per kilo than smaller ones).

 

Is waiting for the VASIMR to be capable of Crewed Mars Missions a viable option?

The VASIMR engine is a) far more expensive than a chemical rocket, about ten times the weight of a chemical rocket for the same weight class craft, c) requires a heavy power plant. Given a potential near future power density of 2kg/Watt, a VASIMR capable of transporting a mission of this type (50 tons to Mars orbit) in less than 180 days would have a payload fraction around 3%.

 

The result is a requirement of a 1600 ton monstrosity the size of four International Space Stations to move the payload to Mars. This battleship is reusable, but this really doesn’t help it’s case much. A smaller SETV type craft could be used (it would spend a year bringing the payload into Earth escape velocity before the crew dock from a smaller chemical rocket), but these can only be used twice and require four launches to put together (plus one per payload).

 

When Charles Bolden talks of a manned 39 day flight to Mars, he’s assuming a power density of 0.5kg/Watt. That would be optimistic if he was talking about an unshielded nuclear reactor with no cooling system. But he’s talking about solar panels, which currently do about 20kg/watt. That kind of improvement is nanotech age stuff that we might find sometime next century, not the stuff of near future Mars missions.

[RexMundi]

Re: Mars Colony?

 

Is there a reason to stick with the yet to be built Constellation/ARES stuff as opposed to going Back to a better Idea like the Sea Dragon? (I actually liked a lot of the stuff on the heavy end of the Constellation family, it was the lighter end stuff and the Orion that irked me....) and why the Falcon over the Delta IV workhorse and it's Variants?

 

~Rex...is taking notes....

[Gnaskar]

Re: Mars Colony?

 

The Ares V doesn't require the design of a new engine. The Sea Dragon requires two new engines. It's a simple matter of the Ares V being cheaper and faster to develop.

 

The Delta IV isn't crew rated while SpaceX has a capsule and a launcher. They're ready to go, and Boeing isn't. And there's the matter of a Delta IV launch costing about 50% more than a Falcon 9 (which, at 56 million, is a bargain).

[RexMundi]

Re: Mars Colony?

 

Ah! That makes sense then. Still the development of the Sea Dragon Engines shouldn't be that big of a deal. It seems they know right where to go with it.

 

I do like the Constellation stuff at the upper end though, and the Falcon stuff looks more interesting now that I found some info to digest about it. SpaceX has far less Union issues then Boeing does as well that would be another factor in the end and it's still an in house company (what can I say, I don't want to share with the other countries for tons of reasons, they can rent space on our boat.....)

 

It still seems that Mars Direct is very workable with a minimum amount of tweaks. So why all the serious witchhunting naysayer stuff about it nd the push for all this little remote controlled flyby this or that stuff? It's almost like there is a concerted effort to keep Feet OFF of something, in favor of being able to stare at pixels on a plate for decades, even though having those Feet on the Something, would generate the public interested needed to toss more little Robots out there in the Big Black.....

 

~Rex....doesn't understand Haters.......

[Gnaskar]

Re: Mars Colony?

 

A major part of it is Robert Zubrin himself. The cult leader metaphors flying around are entirely fair. "The Case for Mars" is occasionally painful to read, especially when he moves away from his area of expertise or launches off into inappropriate historical comparisons to the frontier life or the old sea trading routes. He's gotten better over the years, but his early stuff is the most famous (and he was louder back them).

 

Another problem is that 50,000,000,000 $ looks like a lot of money when you state it like that instead of as 15% of NASA's budget for the next 15 years. People don't like anything that looks like they have to pay more taxes. Everyone wants to explore the universe, no-one wants the bill. The end result is that NASA's budget is ten pages of relatively small budget projects that occasionally add up to something grand. The ISS budget is spread over eight or nine posts, which is part of why no-one knows the full cost of it.

 

Robotic missions are cheaper, and can do a lot of science when you can guess what experiments you'll want to do. There's also a push towards robotics from the military side of things. They're really fond of semi-autonomous units they don't have to send "deeply regrets to inform you" letters to the next of kin of.

 

It's an evil circle of no-one wants the bill because the public isn't interested enough, because there's no grand manned missions to draw their attention, because the grand missions are cancelled due to lack of funding.

 

A Sea Dragon isn't a grand engineering challenge, but it's still a (worst case) 20 year, 80 billion program. No one is willing to pay for that, because there is not enough stuff going into space to support it, because there is nothing that can launch big stuff into space, etc. That's the reason why the Romulus Project calls for their development and use, opening the way for the really cool stuff in space.

[RexMundi]

Re: Mars Colony?

 

Yeah I like the Sea Dragon inclusion in your Romulus Project. In my Hard Sci Fi game I went with a (At the Front End_) Constellation set up combined with a bunch of off the shelf stuff ala Stephen Baxter SF. Seriously though non game realted it just seems common sense that if we want to do it right we do it BIG. Not this podunk piddly repetitive LEO stuff....

 

There's whole piles of ways the money can be raised as well. Everyone out there would want a piece of it so who cares if the suits and vehicles end up plastered with sponsor stuff ala NASCAR, if you could get the sheer public Interest that something like NASCAR, or the NFL, or World Cup Level Soccer garners for the project and all it's related spin off's. Toss in some competitive Us vs Them and it looks pretty doable. Even more doable when you look at all the graft and crud getting wasted on stuff at the moment.

 

Looks like such a simple thing once you are past the hater body snatcher squeee of disapproval.

 

~Rex

[Sociotard]

Re: Mars Colony?

 

This doesn't deserve its own thread, but I thought people might like to see this picture of a crater on mars with some kind of skylight to an underground cave in the center. It could be a site for some kind of 'quick and dirty' settlement. Go in the hole, seal it and pressurize. (it can't possibly be that easy, but it could in fiction)

 

[RexMundi]

Re: Mars Colony?

 

So using that picture for the folks in my Hard Sci Fi game that are stuck on Mars. Great find, thanks much, have Rep.

 

~Rex

[L. Marcus]

Re: Mars Colony?

 

This doesn't deserve its own thread, but I thought people might like to see this picture of a crater on mars with some kind of skylight to an underground cave in the center. It could be a site for some kind of 'quick and dirty' settlement. Go in the hole, seal it and pressurize. (it can't possibly be that easy, but it could in fiction)

 

That's not a hole ...

 

... That's an eye!

[Sociotard]

Re: Mars Colony?

 

"What's it looking at?"

 

"What isn't it looking at?"

[McCoy]

Re: Mars Colony?

 

So' date=' let us address NASA’s concerns about Mars Direct as described in Portree, 91ff:

 

1: ERV is too small to transport a crew of 4, let alone 6, back from Mars.

2: A crew of four is too small.

3: A Mars orbit rendezvous is risky for a human crew.

4: Zubrin’s weight estimate for the hab is optimistic.

5: The Ares booster described by Zubrin is too small to handle the above concerns.

Is "two launches per launch window" a defining characteristic of Mars Direct? If we launch three or even four rockets every time Mars is in the right position, two or three uncrewed for each one with people, can we still call it Mars Direct? Seems like many of those objections can be overcome with additional launches.

 

1: ERV is too small to transport a crew of 4, let alone 6, back from Mars.

2: A crew of four is too small.

 

OK, design the ERV for a crew of three, and have two of them on Mars and fueled up before we launch the crew of six.

 

4: Zubrin’s weight estimate for the hab is optimistic.

 

Send the Rovers on ahead. In fact, design them so they can made operational, fueled, and driven by remote control in case the crew ends up more than a four hour walk from the ERV's.

 

Yes each launch adds to the expense, and this may take the progect over budget, but that's a political problem, not a technical one.

[RexMundi]

Re: Mars Colony?

 

I don't think it's that much of a political Issue. Not if you get the public behind you.

 

~Rex....says it worked for the other stuff....

[Gnaskar]

Re: Mars Colony?

 

Is "two launches per launch window" a defining characteristic of Mars Direct? If we launch three or even four rockets every time Mars is in the right position' date=' two or three uncrewed for each one with people, can we still call it Mars Direct? Seems like many of those objections can be overcome with additional launches. [/quote']

 

Depending on how stringently you want to follow it; yes, two launches is part of the requirements. For one thing, launch cost doesn’t scale linearly with rocket size (which is why Sea Dragons and Orions get proposed), so launching 3 rockets is generally more expensive than launching the same payload in two. For another, there’s a limited number of launch pads, and getting a heavy launch rocket in place, fueled up, and ready to go takes quite some time. Depending on the number of pads available (currently one for this scale launch), and the size of the ground crew, there’s only so many launches you can do before the window closes.

 

The fewer the pads you need to build, and the smaller the ground crew you have to hire, the cheaper the mission is. And the 50 billion budget is a defining characteristic.

 

OK, design the ERV for a crew of three, and have two of them on Mars and fueled up before we launch the crew of six.

 

That would certainly help, and, although no one ever likes to talk about it, would allow the mission to succeed even if one of the ERVs should blow up in transit or crash. Not putting all your eggs in one basket and all that.

 

Send the Rovers on ahead. In fact, design them so they can made operational, fueled, and driven by remote control in case the crew ends up more than a four hour walk from the ERV's.

 

The rovers weigh about 4 tons, so this could be launched by a Titan or a Delta if required. Which doesn’t take up valuable super-heavy launcher pad space, making it a viable option. On the other hand, it’s limited how much help adding 4 tons to the hab is going to be if 3.5 of that is required as supplies for the increased crew size.

 

I don't think it's that much of a political Issue. Not if you get the public behind you.

 

~Rex....says it worked for the other stuff....

 

Therein lays the problem. As of now, there really isn’t enough of a public interest in something like this. The days when Werner Von Braun could appear on national TV and inspire a generation are long gone. The Cold War is over (and has been my entire life span). There are very few things that could excite the public into supporting this kind of thing today.

[Michael Hopcroft]

Re: Mars Colony?

 

I don't think it's that much of a political Issue. Not if you get the public behind you.

 

~Rex....says it worked for the other stuff....

 

The public wasn't completely behind Apollo. There were many circles in which it was disparaged or even ridiculed. Tom Lehrer commented on the US "spending twenty billion dollars of your money to put some clown on the Moon", and there were serious debates over funding it. There were also concerns about the involvement in the program of of ex-Nazis like Werner von Braun (who had been smuggled into the US on false papers in the late 1940s to keep him out of Soviet hands, as opposed to being tried for war crimes related to the V-2 program). There are some accounts that say Kennedy himself might have scaled back the program in reaction to the cost of the enterprise had he lived.

 

There were so many other things going on in the country at the time that Apollo was almost a distraction, with the people involved living in their own little world.

[RexMundi]

Re: Mars Colony?

 

Enough of them were behind the program. Enough of them were actually interested in pushing boundries, and turning impossible into just a degree of dificultiy that just means, hasn't been done yet.

 

When the naysayers got loud enough though, and Loud is something they do very well, then we screeched to a hault figuratively speaking, and it became more about keeping said Naysayer happy and smiling then actually doing something. Unles you're the lead dog the view never changes.

 

~Rex