Where exactly is Mars Direct with NASA? - Are they going to do it or not?

SpaceNut · 2004-09-22 19:57:47

Well I have been thinking of the 3 ship senerio and of the time line for each noting that any one that fails puts the mission in jepody and that each ship even if they are somewhat modular are really 3 very different ships in design.

My though would be to spread each of the basic functions across all equally but that also precludes a very acurate landing system such that each could be within meters of each other not miles. If that is not possible then I feel that some means to make them somewhat mobile is in need to get them into closer proximity to each other.

Next thought was on crew size, when we did apollo there was a crew of 3 though 1 was left in orbit. If each is of a balanced design with each having 3 crew mebers then the total on the surface of 9 is very attractive to making the mars base with a high degree of chance for sucess.

GCNRevenger · 2004-09-22 20:44:10

Again, there comes a point where you just have to trust the system not to fail, and take the risk... the astronauts know what they are getting themselves into, spaceflight has never been nor is now a really safe endeavour, and a trip to Mars will be no different. Plus, if any one of the three vehicles fails, some of the crew dies anyway.

Sending multiple tiny ships to Mars isn't all that practical, because the duplicity of hardware will make the whole mission expensive, and the smaller the vehicle becomes the heavier it gets per-size. Have you seen drawings for MarsDirect? It is already very cramped in the HAB and even moreso in the ERV for anyone to live, I don't think it reasonable to pack 3 people into a vehicle about half that size.

You also have to lug along a lander, a nuclear reactor, an ISRU fuel factory (no way you can carry Earth-return fuel), Hydrogen tankage, and Earth-reentry capsule on every mission. Even though these things would be smaller, they would not cost alot less each, and probobly not weigh much less either.

Austin Stanley · 2004-09-22 21:10:12

Mars Direct has some good points and some bad points. As a mission plan I think it is unworkable, but it does set the right mindset for a martian space program. IMO the Mars-Semi Direct takes most of the problems and corrects them. My biggest worry was alway crew size, Mars Direct uses a crew of 4 because that is what the mass allows, not because 4 is what is needed. 6 people is a much better number IMO.

The only infastructure changes I would make is to build up more of a plan to build infastructure at the primary base. A desirable base location should be scouted before the first mission (should not be to difficult to do with unmanned probes), and all subsiquent mission should be direct there. This makes for a small loss in science, but a HUGE gain in mission infastructure.

With a plan like this, it is possible to man the base on a more rotational bases, so that at least some of the time, two teams of 12 people will be there. I would aditionaly launch at least one unmanned cargo flight every launch window, containing vital infastructure equipment. These would allow the (larger) manned launches to focus more of there mass on important safety concurns, while extra base infastructure (which is nice, but not vital to survival), would arrive seperatly.

By infastructure I am talking about things like Rovers, Proplent plants, Greenhouse domes, extra nuclear reactors, air-liquifiers, and (hopefully), a reusable martian assent vehicle. None of these things are necessary for a succesfull mission, but there presence on Mars can multiply the effectivness of later missions. Landing at one site maximises the ability to build up this infastructure and in the long run, allows you to get more science done for your dollar.

--------

Some negative comments have been made about re-using old mission infastructure (habs and such) and later missions. I belive these are unwarnted. The nuclear reactors a mission would bring with them should produce usefull power for much longer than the 3 or so years that would be necessary. Navy nuclear vessles go about 20 years bettwen refulings IIRC. The habs should definetly stay air-tight, and since the missions are dependant upon life-support systems that can function independently for 3 years or so, expecting them to last longer with a little servicing is not to much to ask. In any case early missions can bring the heaviest parts (like the hab shell), while later missions may only be required to bring less heavy replacment parts. Having a team currently on the ground to determine the status of a spare hab should also help (which could happen by the 3rd mission under my plan).

GCNRevenger · 2004-09-23 08:38:12

Early on, particularly when we are in the exploration phase and not the development/colonization phase, building infrastructure shouldn't really be much of a priority, particularly when the cost of getting a pound of anything from Earth to the Martian surface is going to be so high. We should wait to begin real development until later, when launch prices have declined an order of magnetude from what they are now (either by HLLV or RLV), reuseable cargo-carrying MAV vehicles are practical, and ice deposits secured either on Mars or on Phobos & Deimos. Right now with a large HLLV rocket, a beefy/reliable/accurate but expendable lander, and an aerobrake shield on every mission, you are looking at around $1.0-1.5Bn just to get one payload to Mars.

So, in order to maximize scientific return and to generally "take along" the taxpaying public in exploration by proxy... seeing Astronauts taking (multispectrum) photos on the edge of Marineris, the dark sands and microbe hunting at Hellas, taking ice samples from the Martian north pole for analysis. Inspiring stuff... limiting early Mars missions without a reuseable MAV and associated fuel supplies to a single landing site is a bad idea.

"Some negative comments have been made about re-using old mission infastructure (habs and such) and later missions. I belive these are unwarnted."

I disagree, the super-light-weight space nuclear reactors are designed for high fuel burnup rates to keep their weight/size small and decay heat down, they actually do go through their fuel pretty fast and can use it up pretty quickly. A submarine reactor is a bigger, heavier beast where you obviously don't have to pinch kilograms, a small space reactor probobly won't produce full power for much longer than five or six years or so.

I'm also pretty dubious of the usefulness of an old HAB module, which will be fairly cramped, probobly won't have that good a radiation protection, and will already have been lived in for the better part of three years and stored up to two. Later on, when signifigant "Mars-moving" equipment is available and more than basic minimal mechanical facilities are available, then you could bury the HABs and clean them out (disinfect) or patch up old LSS gear, but by then we ought to have a reuseable MAV anyway and won't have any more Earth/Mars transit HABs. Bring & bury purpose built inflatable/rigid foam filled HABs later, big ones with plenty of space designed for long life, and don't bother with the little cramped Explorer HABs scatterd around.

BWhite · 2004-09-23 08:45:54

As for sending cargo to Mars, meaning logistical support for a base, I have a hard time envisioning anything cheaper than deploying a nuclear thermal tug in cislunar space and using it to collect paylaods in LEO, travel to L1 and then do a lunar - Earth gravitational assist fly-by, cutting the payload loose for a slow coast to Mars.

After the tug rounds the Moon, it separates from the payload and slows down for return to LEO.

This minimizes the time your high value nuclear tug isn't pushing something hard. Do some fancy trajectory calculations to minimize the burns needed to achieve Mars insertion and recover the tug to LEO.

'Dem durn banks always want their interest payments and the airlines have learned that letting airliners sit idle (or fly empty) is a great way to bleed money.

Crew? Or at least high value crew? Okay, the nuke thermal tug burns all the way to Mars and flies back more or less empty.

= = =

Using the tug for direct Mars insertion of cargo is wasteful since you need to get it back to LEO ASAP.

Time = Money in the freight forwarding business.

RobertDyck · 2004-09-23 09:14:30

So, GCNRevenger hasn't even read "The Case for Mars". I have it on my bookshelf and read it completely in 1999. I also have "Entering Space", and read it. At this year's convention I bought a couple books directly from Dr. Zubrin, and he signed both. I've just started reading "First Landing" but so far it's good. Those who missed the convention missed a great one; there were more NASA representatives there this time and the president of NSS. Anyone who wants to debate mission plans should really read "The Case for Mars" as well as NASA's Design Reference Mission. For anyone here who hasn't: Pttttt! Ok, that's rude but even someone who isn't a Dr. Zubrin fan would have loved the occasionally caustic debate between the president of NSS and Dr. Zubrin. One other plenary speaker said he was a great fan of Dr. Zubrin's work from the first paper he read; until he met the man. So, if you want to bash our illustrious founder you can't do as well as those who work in the industry and know him. Personally I like Dr. Zubrin; the fact that he isn't perfect just makes him human and encourages me to found a small aerospace firm like he did.

Ps. It was good to meet you Bill; I hope to see you again next year in Boulder.

SpaceNut · 2004-09-23 09:17:55

So it would seem that the Moon to Mars commission hearings have had an impact on Nasa after all for what is out there with regards to research into the Human side of long duration flight.

GCNRevenger · 2004-09-23 13:15:53

This topic of discussion is about the basic design of the MarsDirect mission arcitecture is it not? I think I understand the basics of Dr. Zubrin's plan well enough to talk about them, even though I don't know every little tiny detail listed in his book...

I think that Dr. Zubrin is in a hurry to get to Mars, a biiig hurry, such that he advocates the smallest and cheapest remotely credible mission to gainfully send and retrieve humans from Mars. I think that MarsDirect does not offer enough return either scientificly or with future growth options to be worthwhile. For instance, the maximum crew is limited by the capacity of the launch vehicle in order to save on development; this is the wrong direction to aproach mission design, FIRST you decide what you need to accomplish the mission - in this case, a crew of 6 minimum with large science package - and then design your vehicle and select the launcher to meet these needs. If a direct flight with chemical fuels using SDV is not big enough, then you abandon the idea, not scale back your mission. Adding things like "clusterd habs = base!!!" sounds like a pretty pitiful car salesmen excuse to make the sale too.

RobertDyck · 2004-09-23 14:59:21

The 90-day report started with "What do we need" and ended with a price tag of $450 billion. A constraint of keeping within your means is a good idea. One of the details from the book was crew roles: two scientists and two technicians. Technicians can repair equipment, scientists would conduct field geology. Two of them would be trained to pilot the ship (any two), and one of the four would be trained as a paramedic in case of a medical problem. Dr. Zubrin pointed out that a medical doctor would be sitting around looking for something to do until a crew member got sick, probably creating projects for himself that get in the way of the others. It's easier to cross train an astroanut to be a paramedic rather than train a medical doctor to be an astroanut, engineer, and geologist. The scientists could specialize in geology and astro-biology. Dr. Zubrin's concern was to create teams with one scientist and one technician who can repair stuff, so there is someone to fix stuff at all times. I would argue that is going a bit overboard; you probably want a career astronaut/pilot, mechanic, geologist, and astro-biologist/paramedic, with everyone trained in firstaid. As for 4 crew members being too small: Apollo only landed 2 on the Moon. If you make the initial mission to large it will be too expensive to get funded.

chat · 2004-09-23 15:39:55

Why design a mars spacecraft to return to earth.

In my opinion if you asked for volunteers to go to Mars to stay, i bet thousands of people would jump at the chance.

And even if you plan for people to return to Earth, they still might decide that running Mars was better option than going back to Earth.

I think NASA should think about all male or all female crews to mars, or the (lets stay) scenario is sure to happen.

Any Mars flight might be the beginning of the mars colony, by chance or choice.

GCNRevenger · 2004-09-23 16:55:55

Ah yes, the tired old "Nasa = Stupid" straw man excuses... Did you know that Bush-I's Space Exploration Initiative was not just a Mars mission? In fact, the SEI was a grand scheme: new infrastructure on Earth, new orbital shipyard/fuel depot, a return to the Moon perhaps for good... and finally about half that $400Bn pricetag for the 8-12 man mega Mars ship, propulsive both ways with no Martian fuel production, no staging, and no aerobraking, topped off with a high-energy Opposition trajectory... But, you get the ship back when you return to Earth, so it could be reused to start developing Mars, not exploring, as soon as possible, which is congruent with the rest of the SEI plan.

The SEI was a big idea, and with it came a big price tag: for all the things that it would accomplish, that $400Bn expense doesn't seem very outrageous now does it? The problem was, Bush-I believed our spaceflight technology more mature than it was (or is today!), and Congress was not willing to put forward such an investment given the long-term nature of the returns, if they felt it was worthwhile at all... The price is not really that unreasonable for what NASA was being asked to accomplish.

Now, MarsDirect... Only two geologists and the spare time of one technition (maybe) for a Mars mission doesn't seem like that many to me, are you sure you are not taking the word of a certain zealous nuclear engineer that this is plenty, in order to save a buck on rockets? And with the Apollo comparisons, please, Apollo was never really intended to do that much serious science because it was intended to beat the Russians to the Moon, which is why Apollo didn't really accomplish that much science. We still don't know if there is ice on the Lunar poles, we still don't know much about the He3, and so on. Two was plenty to take pictures and bring back samples/trophies though... And two is all you will be sending to Mars if the technitions are kept busy.

There is a happy medium between the giant $150-200Bn+ Battlestar Galactia Mars ship and the dinky near-unworkable flags/footprints MarsDirect... and it is dinky and nearly unworkable; if MD is constrained to use chemical engines only, there may not be enough mass to even bring a drill or any heavy science payload because of tight mass margins, MD doesn't leave that much mass margin for radiation shielding, and the ERV is entirely too small to the point of comedy.

RobertDyck · 2004-09-23 18:16:08

I did not at any time say NASA is stupid. In fact at the time Mars Direct was created, Robert Zubrin and David Baker were working for Martin Marietta, a major contractor for NASA. That means one part of the NASA establishment created the 90-day report, after it was cancelled by congress another part of the NASA establishment created Mars Direct.

The 90-day report cost $450 billion in 1989, not $400 billion. Today it would cost more. Those individuals at NASA who were involved with the 90-day report tried for everything regardless of cost, and the extreme price tag left them with nothing. Now you're arguing for that same extreme price? Some people never learn.

The mission plan under the 90-day report was a 2 year mission, with only half the crew spending 2 weeks on the surface. An 8 man crew would still only land 4 on the surface, no better than Mars Direct.

Perhaps you haven't read my mission plan. It's long so I won't get into detail here, but my attempt to tweek Mars Direct resulted in a reusable vehicle for Earth orbit to Mars orbit and back. My design would initially use an expendable chemical TMI stage, but could be replaced with a reusable stage simply by bolting it on. I would also use existing launch vehicles, like Delta IV and Atlas V, rather than relying on developing a new HLLV. RobS has that same approach to launch vehicles.

BWhite · 2004-09-23 18:27:01

Ah yes, the tired old "Nasa = Stupid" straw man excuses... Did you know that Bush-I's Space Exploration Initiative was not just a Mars mission? In fact, the SEI was a grand scheme: new infrastructure on Earth, new orbital shipyard/fuel depot, a return to the Moon perhaps for good... and finally about half that $400Bn pricetag for the 8-12 man mega Mars ship, propulsive both ways with no Martian fuel production, no staging, and no aerobraking, topped off with a high-energy Opposition trajectory... But, you get the ship back when you return to Earth, so it could be reused to start developing Mars, not exploring, as soon as possible, which is congruent with the rest of the SEI plan.

Why do you want cargo ships to come back?

Liberty ships were a success if they survived one voyage.

Sending cargo in a multi-billion dollar nuclear ship is simply daft. Using nuclear propulsion to accelerate cargo is an excellent idea, but cut the stuff loose and let it coast, cruise to Mars, aerobrake and pop the airbags.

Goof up once or twice and call the mistake Spam Crater.

Logistics, logistics, logistics. One BIG nuclear tug able to navigate cislunar space can throw payloads to Mars as fast as we can get them to LEO.

= = =

Like I said, crew needs another road. Send crew via Mars Direct =AND= have mountains of cargo waiting for them.

Austin Stanley · 2004-09-23 20:51:49

Early on, particularly when we are in the exploration phase and not the development/colonization phase, building infrastructure shouldn't really be much of a priority, particularly when the cost of getting a pound of anything from Earth to the Martian surface is going to be so high. We should wait to begin real development until later, when launch prices have declined an order of magnetude from what they are now (either by HLLV or RLV), reuseable cargo-carrying MAV vehicles are practical, and ice deposits secured either on Mars or on Phobos & Deimos. Right now with a large HLLV rocket, a beefy/reliable/accurate but expendable lander, and an aerobrake shield on every mission, you are looking at around $1.0-1.5Bn just to get one payload to Mars.

This is why I advocate seperating cargo flights from manned return flights. To help cut costs. The cargo flights do not have to be man-rated, they can take slower orbits (requirering less fuel and a smaller heat-shield). Also cargo flights have a redudency that manned flights cannot match. If they blow up/fail you can just launch the same-stuff at the next launch window and still play with it durring some of the mission. If a crewed flight fails, you can't send those people again, they are dead. Seperating crew and non-vital equipment like this allows you to focus your safety money where it is most effective as well.

I think it is also important to note that reducing the cost to put payloads on Mars will be a gradual process just as the buildup of infastructure will be as well. So these two synergise well with each other. While the costs are high only the most vital and most dramatic cost cutting equiment can be sent (propelent plants, reusable assent vehicles). As the costs come down, more and more infastructure can be pilled up on Mars at both reduced cost AND reducing the amount of stuff you have to send in the long run. Infastructure development may cost more early on, but over the long run you should come out ahead.

The large amount of time inbettwen missions (at least 1.5 years) also makes waiting for cost-cutting less important, as the cost-cutting technology can be developed in tandem with infastructure development. There is no reason to wait for the Nuclear Electric or Solar Sail cargo stage to be developed to send infastructure. Send you first load with the first mission, then later modes can take advantage of the better modes.

So, in order to maximize scientific return and to generally "take along" the taxpaying public in exploration by proxy... seeing Astronauts taking (multispectrum) photos on the edge of Marineris, the dark sands and microbe hunting at Hellas, taking ice samples from the Martian north pole for analysis. Inspiring stuff... limiting early Mars missions without a reuseable MAV and associated fuel supplies to a single landing site is a bad idea.

I agree strongly with this, a reusable MAV vehicle should be the number one infastructure priority. Unfortunatly it is probably the most expensive to develope, and the most inherinetly unsafe. Untill a resuable MAV is deployed however, long range pressurised rovers should still give the crews enourmous amount of area to explore. Mars direct calls for rovers with 500km round trip endurance to give an example. Nuclear powered rovers could do even better, and rover endurce should be extendable with later infastructure investments (towable ISPP, extra tanks, ect). Even without the global mobility a MAV provides, the team should have pleanty to explore, more than enough to last several mission I would think. And stacking infastructure at one location offers a safety net that cannot be beat by solo missions.

I disagree, the super-light-weight space nuclear reactors are designed for high fuel burnup rates to keep their weight/size small and decay heat down, they actually do go through their fuel pretty fast and can use it up pretty quickly. A submarine reactor is a bigger, heavier beast where you obviously don't have to pinch kilograms, a small space reactor probobly won't produce full power for much longer than five or six years or so.

If the reactor is turned off (ie. chain reaction inhibited) the fuel supply should last quite a bit longer. Rember if the chain reaction is not occuring, then the fuel source is only subject to normal decay. While earlier reactors may still have limited life spans, it still offers a follow up mission double redudandcy that they could not possibly afford to take with them. This is one of the key benifits of stacking your assets at one site. It offers an increase in safety that solo missions cannot even come close to matching. A later cargo flight could possibly bring a more heavy duty/long term reactor with it which could eliminate the necessity for later missions to bring one. This could saves both weight and cost, and the earlier you do it, the more cost and weight you save, which is why it should be done as soon as possible.

For example, lets examine the advantages of landing a heavy-duty reactor on Mars. Lets assume this reactor weighs 20 tons, cost 500 million to build, and 1.5 billion to deliver on Mars, for a total cost of 2 billion. While a normal reactor weighs only 5 tons is developed for free (since one will have to be developed in any case), and is delivered on Mars at the cheaper cargo rates, which would be 300 milllion. After the big reactor is delivered on Mars and the little reactor no longer have to be delivered it will pay for itself in 7 missions, which would only take about 8~9 years under my schedule. If such a reactor could under such requirments (which doesn't seem to difficult), the economic advantages are clear, everything past those 9 years is just gravy.

I'm also pretty dubious of the usefulness of an old HAB module, which will be fairly cramped, probobly won't have that good a radiation protection, and will already have been lived in for the better part of three years and stored up to two. Later on, when signifigant "Mars-moving" equipment is available and more than basic minimal mechanical facilities are available, then you could bury the HABs and clean them out (disinfect) or patch up old LSS gear, but by then we ought to have a reuseable MAV anyway and won't have any more Earth/Mars transit HABs. Bring & bury purpose built inflatable/rigid foam filled HABs later, big ones with plenty of space designed for long life, and don't bother with the little cramped Explorer HABs scatterd around.

Well the Mars moving equipment will never get to Mars if you don't send it! But seriously the hab structures and life-support systems are going to have to be pretty heavy dutty equipment in the first place, once you reach a certian duration, there is less diffrence bettwen a hab and lss that can last for 3 years and one that can last for 6 or more. But the possible savings in mass here are great, as the hab is the single largest item that has to be sent to Mars. The cost of replacment parts, lysol, heck even an entirely new LSS are small in comparision. If the astronaut can travel in a space only lightweight inflatible hab, and transfer down in a cheap lander a great deal of mass can be saved. And it generaly results in a net increase in living space and safety, as opposed to solo missions. By the 3rd mission when there are 3 habs on mars the living space is greatly increased.

But as far as it goes, building a heavy duty hab on Mars is a great idea. The cost advantage is less dramatic then that of the nuclear reactor I mentioned earleir, but still would pay of in the long run. But again, the sooner you start on the hab, the sooner the astronauts have a safer place to stay, and the more money you can save.

RobS · 2004-09-23 22:58:42

Regarding the size of the ERV, I wish we could see the interior design of it, but my impression is that the cabin is 2 stories and 6 meters in diameter, for a total floor space of 50 square meters. The hab has 100 square meters, but on the flight out the lower floor (50 square meters) is stuffed with cargo and supplies, so I think Mars Direct basically provides 50 square meters of floor space in both directions. This is less than NASA's recommendation, but I am not sure it is impossibly small, especially since one is flying to another planet (or flying home), which gives one an incentive to be patient.

The hab is designed to be covered with sandbags on the Martian surface, so it can be substantially protected from solar radiation and some cosmic radiation.

Regarding the question of multiple landings versus a single base of operations, Zubrin explains the logic based on the exploration of Antarctica: in the first phase, separate missions landed in different places and explored those places. But in the second phase, McMurdo Sound Base was established by the United States, and today all exploration of Antarctica uses McMurdo, which has heavy infrastructure. The problem with exploring Mars is that we don't have a way to get around at first, so we can't establish a Martian McMurdo and see a large portion of the surface. So Zubrin says, start with a series of perhaps four or five missions landing at different places, THEN once one has a sense of the place and the technology for getting around has been developed, emplace a Martian McMurdo and operate from it. He's probably right.

One way of improving the safety of Mars Direct and increasing the crew size would be to fly a pair of missions every opposition; in other words, two habs and two ERVs. If the habs were designed to accommodate 6 in an emergency, one could fly 3 in each and have a total crew of 6. Of course, the down side is the expense. The NASA/ESA report indicates that a normal Mars Direct with 1 hab and 1 ERV will cost something like 4 billion to build and launch.

-- RobS

RobertDyck · 2004-09-24 07:55:01

Each year, there are new projects formed at Mars Society convention. This year we started the Mars Homestead project. http://www.marshome.org]http://www.marshome.org

This project is intended to design the first Mars settlement. Not the first manned mission, but the first permanent settlement. The project does not address any robotic or manned precursor mission, but I have suggested just a single manned scientific mission before settlement. How many science missions before settlement is a matter of debate so no one else has even addressed it. Mars Homestead is intended for 12 individuals and use of local resources to build everything necessary for permanent habitation. I myself am working on extracting bulk gasses, and materials from Mars air and soil. This includes air for breathing as well as metals, plastics, fibreglass, etc. Someone else is working on bricks and masonry; another member is working on water, a university student who is studying nuclear reactor engineering is designing the nuclear reactor, etc.

Perhaps we need to emphasize the various phases of Mars exploration. We need to build a small and affordable vehicle for the first manned science mission, and keep the crew small. I still recommend 4 astronauts for that one. Then we need a construction crew for the base, again Mars Homestead is planning on 12. The science mission needs a lot of equipment, including a laboratory and rover; that can be delivered by an expendable cargo lander. The modification of Mars Direct that I have in mind would use a reusable Interplanetary Transfer Vehicle (ITV) that would travel from Earth orbit to Mars orbit and back. Use an expendable chemical TMI stage at first, then use the MAV itself with oversized fuel tanks as the TEI stage. Replace the MAV with a reusable one based on DC-X once a permanent base is established, but that requires a reusable TEI/TMI stage and some sort of fuel tanker to deliver fuel to Mars orbit. That definitely isn't for the first mission. I also advocate a reusable crew taxi for Earth surface to Earth orbit. There are many designs possible, but that is the last piece to make the entire tip with reusable vehicles.

Oh, GCNRevenger, one of the plenary speakers at this year's convention presented NERVA as the ideal TMI stage. He argued the nuclear package could be used as a power generating reactor when not used for propulsion. I asked him about Timberwind since it has higher Isp and much lower engine mass. He claimed Timberwind would burn itself out after a single use. I argued it's lower mass would make a single use engine useful. This is one reason I designed the ITV with a bolt-on propulsion stage: there are many propulsion designs possible. Nuclear/VASIMR is another option. Do you want to jump into that argument and claim it has to be a Gas Core Nuclear Rocket?

GCNRevenger · 2004-09-24 10:54:39

Alot of material here, this might require more than one post...

"The 90-day report started with "What do we need" and ended with a price tag of $450 billion." ...sounds alot like saying NASA is dumb to me. That since NASA came up with the figure, and since the figure is absurd for any any Mars mission short of all-out colonization, to me this says that you therefore think that NASA is absurd... I do recall your plan to small degree, and I think you are aproaching the mission from the wrong direction too, making the mission fit the launcher instead of the launcher fit the mission. Even such a plan with the uprated 40MT EELV+, such an arcitecture... I have doubts.

I would also like to note a little more about the SEI Battlestar Galactica, which I think is a really really bad idea by the way... it was not so much a ship as an interplanetary cycler, nuclear power plant, perhaps greenhouses, maybe even a spinning section for short-term artifical gravity doses... not a cargo ship.

"This is why I advocate seperating cargo flights from manned return flights. To help cut costs. The cargo flights do not have to be man-rated, they can take slower orbits (requirering less fuel and a smaller heat-shield)... Seperating crew and non-vital equipment like this allows you to focus your safety money where it is most effective...

...Untill a resuable MAV is deployed however, long range pressurised rovers should still give the crews enourmous amount of area to explore. Mars direct calls for rovers with 500km round trip endurance to give an example... Even without the global mobility a MAV provides, the team should have pleanty to explore, more than enough to last several mission I would think. And stacking infastructure at one location offers a safety net that cannot be beat by solo missions."

In the long run, cargo and crew probobly ought to be separated as you say... but this is not the long run. You really have to weigh the extra expense of developing two different vehicles. Plus, a cargo mission and a human mission, without the aid of heavy tugs, do share alot of hardware in common. They would anyway probobly use the same launch vehicle at least to reach orbit, they will probobly use similar landers as the airbag landing aproach is not good enough for cargo, they will use the same OMS engines & aerobrake shield most likly... Putting some of the cargo and humans together saves having to send an additional cargo flight, and for pure cargo missions a HAB-less HAB lander/shield on the same launcher makes sense.

I also disagree with you that a 500km exploration radius from the landing site is good enough; we want to explore Mars, ALL of Mars, and that means going almost anywhere on the entire surface. Not 500km, but 5,000km would be a good figure if you are going to limit yourself to one site. A rover with that kind of range short of nuclear powerd would be impractical.

There is finally a question, how safe is safe enough? How much safer does "stacking" old HAB modules, ISRU plants, and reactors make the mission? Is it not safe enough without this option? Is it worth the huge loss of science and inspiration of exploring Mars to be just that little bit "safer?" I think that it is not... Somewhere, sometime, you simply do have to trust that a system will work, and I think that one set of equipment with an anytime-return ERV is safe enough. Nobody said this would be a safe endeavour.

As for the reactor... I know that the fuel is conserved when you shut the thing down, but the cooling system will have to keep running for months to take care of decay heat anyway, and you will have to get power to operate the cooling system, so the reactor will have to be operated at low power levels even "shut down" anyway... as for using it as backup, it will have been operating for about four years (two to make fuel, two to power HAB) and on "idle" for another two, which brings you pretty close to the ~5-6 year practical limit for fuel loading in a compact reactor. A large reactor like you have mentioned will be a top priority when we do start building a base, and it will preferably be refuelable unlikly the little "Exploration class" plants.. Not to mention much more powerful.

Again, as far as building a heavy-duty surface HAB and also a light-weight one-way Earth-Mars HAB, thats redundant... build only one that serves both missions instead, and the Earth-Mars HAB should be pretty spacious and have heavy radiation shielding anyway, so for exploration missions I don't see a big enough bennefit to send a dedicated surface HAB using a MarsDirect or SemiDirect style arcitecture. Since they will be scatterd across Mars, then recycling them doesn't make loads of sense.

More to come later...

RobertDyck · 2004-09-24 11:16:46

The interplanetary vehicle must have a micrometeor shield, deal with extreme heat of space, vacuum (only radiant cooling), and mono-atomic oxygen in Earth orbit. It must also be engineered to operate in zero gravity. The Mars Direct hab has rotation for artificial gravity, but the ERV doesn't have either artifical gravity or exercise machines. That's my one criticism of Mars Direct, the ERV isn't good enough. A dedicated surface habitat can be designed to be entirely inflatable. The landing vehicle only needs a capsule with one seat per astronaut and as much interior space per crew member as Gemini. The surface habitat doesn't need a micrometeor shield, the largest part of TransHAB. It does need protection from dust storms and the salty, alkali soil of Mars. Thermal protection in space is usually multiple layers of aluminized Mylar with a loose mesh spacer between layers. This uses the vacuum of space to form a thermos bottle. It doesn't work on Mars; the atmosphere may be only 0.7% of the pressure on Earth, but it is enough to cause convection. Interior architecture is quite different for zero-G and gravity. Bottom line: we need separate habitats.

A permanent base/settlement can be made with local resources so you can use heavy material. The question of what tools & equipment must be brought to start the settlement vs. manufactured on Mars is a key question of the Mars Homestead project. Expect the science mission to use a different surface habitat than a permanent settlement. The design of the science mission surface habitat could be used as a construction shack for the settlement team, but expect the settlement itself to be much more.

SpaceNut · 2004-09-24 11:39:44

NASA scientist says manned Mars flight planned for 2025
According to NASA's timeline, the first piloted mission to Mars should be sometime in 2025. It will be a 30-month mission.

http://www.daily-chronicle.com/articles … news04.txt

snipet:
A group of Northern Illinois University students heard detailed plans Thursday night about how NASA plans to organize manned flights to Mars.

Mike Greenisen, NASA scientist and NIU graduate, presented his talk "International Space Station: Transitional Platform for Moon and Mars."

"Sometimes we have to stop and say, 'We're really going to Mars, we're really going to do this,'" Greenisen said about himself and others at NASA.

GCNRevenger · 2004-09-24 11:56:26

"Perhaps we need to emphasize the various phases of Mars exploration. We need to build a small and affordable vehicle for the first manned science mission, and keep the crew small. I still recommend 4 astronauts for that one."

Again I have to ask, why do you think four is enough? Because Dr. Zubrin says so? Because that is all you can send using Ares/Shuttle-Z each? The mission design must be aproached from the other direction, that we decide how many people are needed to accomplish real results, then build an efficent vehicle around that need, and then select the launcher around that vehicle. In that order more or less. Thus far, NASA wants six people; as they are aproaching the problem from the right direction, Dr. Zubrin in his Mars fever is not, and the vehicle needed for six is only marginally bigger/heavier then for four... I really don't see the support for a science mission with less then six people, and sending a double-batch of 3-man MarsDirect ships will get expensive because of duplicity of hardware... as for that being a redundancy, how safe is safe enough? Will both ships be able to land close enough together? Won't that be a waste of scientific capability to double-up on landings? Can KSC launch two MD flights that close together?

This flawed philosophy also seems present when designing crew accomodations: I really don't think that 50m^2 is enough, particularly when it is going to be devided up into staterooms, toilet room, shower, possibly a storm-cellar, and contain cooking equipment, furnature, some of the LSS system, and dry goods storage. An advanced version of the TransHab technology offers a roughly 80-100% more diameter then a rigid structure for similar mass and ought to be 10-12m in diameter over three decks wrapped around a central core, possibly with a "bilge hold" for dry goods, equipment bays, etc. Enough space to comfortably fly six people and not a square centimeter less, no cramped HAB modules... Relying on the crew keeping mentally glued together because of "anticipation" sounds to me like Dr. Zubrin is trying to play Psychologist! A six-month ISS stint is a stretch as it is, and they get all the space they want... It would be far longer if there were a free-return abort too.

Overall, I see too much forcing the crew to "shut up and deal" all to save a buck on the vehicles, this is the wrong way to go about building space ships... There ought to be a water/polymer/aluminum "inner core" the astronauts would sleep in, doubling as storm cellar and reducing flight radiation doseage... Heavier? More expensive? Sure, but its this kind of thing thats worth it... You won't have Mars dirt to shield you to and from where cosmic rays are strongest.

An all-reuseable Mars arcitecture is still a long ways off, and at the moment the high development cost even makes it undesireable... Reuseable MAV, reuseable Earth/LEO launcher, reuseable transfer stage... $$$ Today we go with a HLLV rocket, with an expendable Timberwind TMI if that can be done cheaply, to deliver large payloads directly to the Mars surface with expendable landers to accomplish full-planet exploration, start initial base(s), and still serve to deliver large componets later (reactors, large habs, etc). The GCNR engine would be a waste until we are ready to develop and colonize Mars, its a waste for early missions or for building/tending a small base.

Palomar · 2004-09-24 12:01:39

So, GCNRevenger hasn't even read "The Case for Mars". I have it on my bookshelf and read it completely in 1999. I also have "Entering Space", and read it.

*I found _Entering Space_ to be a bit on the technical side... :-\ Unfortunately I purchased it online (something I rarely do; I always like to have a book in hand and browse through it before purchasing). I expected it to be written more along the lines of _The Case for Mars_.

Will have to give it another "go"; since participating at this message board, I've been reading and posting about subject matter I wasn't overly familiar with previously (aside from amateur astronomy stuff and "general" history of space exploration).

--Cindy

P.S.: Robert, being the mega-brain you are, I'm sure you zipped through ES overnight.

SpaceNut · 2004-09-24 12:13:06

Is leaving the Earth return vehicle in orbit around Mars such a good thing, since the time frame for it being unmanned and unattended is quite long.

GCNRevenger · 2004-09-24 12:39:59

"Bottom line: we need separate habitats"

No, no we don't. The TransHab concept can fulfill both roles nicely, as its micrometeoroid shield is a thick layer of hard and soft foams, wrapped with Polyaramide or Ultrahigh quality Polyethylene fabrics. Spray the outter layer a fabric with a Teflon or Aluminum coating and you are good to go. The weight and money savings of eliminating the surface HAB, the dedicated lander, and some of the cargo flight will more than make up for needing a larger landing engine I would imagine.

I think that leaving the ERV in Mars orbit is not that great of a risk, as it will be in "storage" mode and not really active. You can fill the thing with inert nitrogen and leave all the LSS gear turned off and everything. It will probobly be powerd by storable chemical propellants, so you don't have to haul them up from the Mars surface, like Kerosene and Catalyzed Peroxide or maybe LOX & Methane if boiloff can be controlled.

Palomar · 2004-09-24 12:56:29

Is leaving the Earth return vehicle in orbit around Mars such a good thing, since the time frame for it being unmanned and unattended is quite long.

*Yeah. Good question. Wish I could answer it.

I need to re-read _The Case for Mars_; first read it 3 years ago.

--Cindy

John Creighton · 2004-09-24 13:06:49

I think it is a good point that inflatable could allow for a larger hab. It also must be a saving to store the earth return vehicle in orbit. If it doesn’t have to land on mars it should be easier to bring the necessary fuel for both ways. GCNRevenger do you think it makes sense to produce locally the fuel for the mars assent vehicle. It seems like a good way to save mass to me. What if the mars assent vehicle produces more fuel then it needs to just get out of orbit? What should be done with the extra fuel? Will it improve any safety margins?

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