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Here's some preliminary thoughts I've had about improving the Mars Direct mission architecture:
1. The capacity of the Ares V can be upgraded by developing 6-segment boosters, and extending the main tank. Once 5-segment boosters have been developed, the addition of another segment should be relatively cheaper. However, such a launch vehicle will be very heavy, and will strain the load capacity of the crawler transporter. The ground-pressure of a fully-laden crawler transporter may be lowered by widening the caterpillar-track segments, and adding a layer of shingle to the crawl-way, to better spread the load.
1b. Another alternative is to develop a much larger booster consisting of 3 Ares V cores side-by-side. This means the environmentally controversial SRB's are not required. Igniting all three tanks at once guarantees the reliability of each engine before takeoff. This means that the middle tank is relatively slow burning. Also, the SRB's, though reasonably safe by themselves, are detrimental in combination with the main tank as a combined system (i.e. Challenger), and under the increased load will require careful evaluation before man-rating. The two first stage main tanks may be kerosene powered if this is advantageous.
2. A more powerful booster should allow a Mars Direct style 4-crew hab and ERV to be thrown direct to Mars with more room for mass uncertainty. However, if such a booster is able, and the final mass requirement is low enough, it would be favorable to launch the hab into a parking earth orbit, where the crew can later board and perform pre-flight checks. However, doing it this way might allow too much fuel in the upper stage to boil off, in which case a purpose built upper stage may be required, further increasing cost. Ultimately, this will probably be decided upon once the mass uncertainty (both of the mars vehicle and the booster) is narrowed.
3. To speed development if necessary, the operational requirements of all systems can be down-graded by sending a crew of 3 on the first mission. This would also allow more supplies to be sent with the Hab: More spares, science equipment, and consumables. This will better accomodate for the contingency of ERV failure on the first mission.
4. From the outset, the martian explorers should be given as many tools as possible to perform a primarily geological science mission. This is to ensure a good science return, and to keep the astronauts stimulated with new discoveries. In order to achieve a leap in science return and mental stimulation, the astronauts should be able to explore as large of an environment as necessary, perhaps and likely larger than what even a large rover may provide. Therefore, the Hab should be able to achieve long-range mobility. This can be achieved without increasing its mass by sending the necessary modifying equipment on a seperate cargo vehicle. The astronauts will then be able to fit this equipment after they have completed the initial exploration of their immediate environment. This additional cargo vehicle may also allow the delivery to the surface of any non-essential equipment that might otherwise be sent with the Hab, like extra consumables, science equipment, tools, and spares.
5. Future launch windows should allow for the launch of double and triple missions. Sending multiple missions in parallel may add a little redundancy, both during interplanetary cruise and once on the surface. The possibility of crews voluntaring to stay for longer periods on the surface should also be allowed for. If two or more missions operate on the surface at the same time, then it is possible for crews to mix, thereby avoiding conflict if there is disagreement within crews.
6. Thorough pre-testing of equipment should be of high-priority. Hopefully, this will be easier as the Mars program will not be a race, and the final deadline won't be as 'hard' as it was during Apollo. The ~2 year launch window should assist, rather than interfere, with this.
As the Mars Direct plan doesn't require space-rendezvous, most pre-testing can be done on earths surface. However, all critical systems should be tested to operate smoothly in zero-g, in case of tether failure during inbound and outbound legs.
The completed ERV should be thoroughly pre-tested, from landing to takeoff, in a mars-proxy environment on earths surface.
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Thats it for now. Feel free to add comments or contribute your own ideas here.
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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Step 1: Bar Robert Zubrin from being anywhere in the same state as the people that make the arcitecture decision.
Step 2: Test all the decision makes with a polygraph if they agree with Bob Zubrin's plan. If they do, ban them too.
Step 3: Burn all copies in the offices and homes of A Case for Mars of the remaining decision makers
Step 4: Ban all use of the word "direct" from strateigic arcitecture planning except when used in the negative sense (eg "not direct").
Step 5: Bring back the guys who did the DRM plans.
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A six-segment super SRB is pushing your luck, the length of the booster starts getting awfully long versus its diameter, and the components under pressure will have to withstand an awful lot of force. This is not an awful way to increase the Ares-V payload though, since a stretch of the core should be fairly easy. The upper stage will have to be a much wider diameter however, and I am worried that the payload will be so much larger that fitting it in the VAB might be a problem.
Still, this is a pretty serious change, and will probably require re-re-designing the SRB, redesigning the engine section and structure of the Ares-V core, and very likely complete redesign of the upper stage. It will easily cost half as much or more to develop as the original rocket.
The three-core "mega Ares" isn't happening either, its too hard to arrange the seperation (Delta-IV Heavy was not a simple upgrade from Medium) and suffers from poor thrust/low altitude Isp like Delta-IV Heavy will. Switching to Kerosene will be as bad as making a whole new rocket. Furthermore, the environmental effects of SRBs are silly and should not be considerd. They are also sufficent reliability as long as people won't be riding on them. The large numbers of engines (17+) pose a real reliability concern.
If you are going to send a third flight for cargo, you might as well stick to semi-direct and go do DRM-III instead of any MarsDirect varient. "Long range mobility of the HAB" is also not happening. Forget about it.
Even four crew is not enough. Probably not even five. Six should be baseline, with option for more in lieu of lab space/science gear.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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FYI, I wrote all of the above before starting related discussion here at newmars. Most of the points are still valid IMO, so I decided to post it here.
You need to watch your fanatical side, GCNR. Over-generalizing the issue doesn't help.
Nevertheless, I agree with you that Mars Direct has a lot of room for improvement.
BTW, GCNR, I haven't really read your email yet. I should really do that... I'll do it now, k?
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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Before someone else posts it first, I should also mention another thought I had: Collapsable crew quarters which fold up into the roof when more floor space is wanted. The crew area can be adjacent to the lounge to extend the living space.
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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The longer and thinner compared to length that a rocket is the more unstable it becomes. A six segment SRB is far too long as well as there is the problem that it weakens as it is used and structural supports to stop collapse increase the weight and reduce payload capacity.
Before someone else posts it first, I should also mention another thought I had: Collapsable crew quarters which fold up into the roof when more floor space is wanted. The crew area can be adjacent to the lounge to extend the living space.
The problem is that Mars direct needs all the spare space it can in the hab for supplies and foldaway accomodation is useless if it has no where to fold out to.
Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.
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Before someone else posts it first, I should also mention another thought I had: Collapsable crew quarters which fold up into the roof when more floor space is wanted. The crew area can be adjacent to the lounge to extend the living space.
Nice idea.
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I also thought about increasing the Hab diameter from 10m to 12m. This would require 20% more sheet-metal, but add 45% more floor area. Seeing as we are using 10m diameter tanks on the Ares V, a 12m payload shroud should be more accomodatable. It'll probably end up looking like Zubrins original Ares with 8.4m tank and 10m shroud (from my understanding)...
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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I tend to think of NASA's DRM III as an improvment to Mars Direct. You really can't upgrade mars direct without losing critical elements of it's design philosophy (ie get to mars cheap and fast).
The DRM incoporates almost all of the important engineering details from Mars Direct (conjunction class missions, some ISRU) the only major diffrence is the use of Mars Orbital Redevous (like Apollo) as opposed to Mars Surface Rendevous (which was considered but discarded by the Apollo program).
He who refuses to do arithmetic is doomed to talk nonsense.
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It would be good if there was a site that explained DRM3 in simple terms. Does Zubrin have a good defense agains DRM3?
Edit: Why don't we lay DRM3 on the table, and we can see if there are any improvements to be made here also (I've changed the topic heading to reflect this).
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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Does anyone know what the maximum volume and mass of any mars landers that we would send to the surface can be?
Also how much of that same lander would be cargo or payload?
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Replying to GCNR's post at the top: I think we have to accept now that any manned mars mission will come well after 2020, once the lunar program has ended. I think we should consider that a clean-sheet booster might be on the cards by then, or at least NASA might be willing to make a larger investment.
SpaceNut, I also wonder whether there is a size limit of a Mars lander. If there is, perhaps it is dictated by the maximum size of parachute, due to limits of materials. Also, I imagine the heat-shield will have to be bigger to protect a larger volume. Perhaps the RCS system plays a minor part too.
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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Extreme fanatic? The problem is that Bob Zubrin is the extreme fanatic, rejecting his looney plan that is pushed as gospel truth by himself and others isn't fanatical, its bringing back saner consideration. If Bob's plan isn't obviously bad, then there is no such thing, and people pushing it either don't understand how bad it is or are only interested in "sticking up for Bob" and not really considering anything. MD doesn't just have "room for improvement," I think the design philosophy that dictated many of the details about the mission is total baloney.
The basic idea, direct flight with 2+ separate vehicles with aerobraking and ISRU is a huge improvement over Battlestar Galactica certainly, but the plan as advertised is equally bad in the opposite extreme. Equally bad.
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I don't like "folding staterooms" idea, its trying to cheat the need for real contiguous space, and does so at the expense of any persistent person space. Contiguous space should be there whenever any crewmen needs it, not when the others fold up their walls/bed/furniture, and if personal spaces are temporary it discourages crewmen from rightly considering them "their" space. Both of these are essentially for crew health over such a long time.
The MarsDirect and DRM-III HABs are already 8m wide give or take, 10m would be quite a large upgrade and consume considerable payload mass. 12m would be awfully overkill, and would require consideration for aerodynamic interference on launch.
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DRM is pretty simple and not too dissimilar from MarsDirect conceptually. The two major differences are that a fully fueled ERV is placed in Mars orbit instead of the surface with an additional payload flight bringing an ascent vehicle to reach it and an ISRU plant to fuel it. Both would be ready to go before people leave for Mars.
The second major difference is size, the vehicles themselves are double the mass and volume of MarsDirect's vehicles. As such, they require either a massive 250MT super-HLV (DRM-I) or a separate HLV launch for each vehicle to bring up fuel/engines to LEO to push each ship to Mars (DRM-III).
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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What would MarsDirect look like with two launches per vehicle; one for the vehicle and one for the final stage?
Let's try to compare apples with apples here. Whats the mass-per-man of MD vs DRM?
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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But they aren't, and the real performance of the mission - what we get out of the deal - doesn't vary linearly with the mass per crewmen. The only thing that does, up to a point, is the safety of the crewmen per mass/volume.
DRM provides for almost two and a half times the volume during transit, and also importantly provides enough mass to actually accomplish things when we get there. Considering the tonnes-per-crewmen DRM is about 50-75% better, but will have mass to carry real equipment unlike MarsDirect, so it will be able to accomplish far far more.
DRM-III also provides a clear path for upgrade to a partially reuseable system with the aid of a light Mars RLV and aerobraking on the Earth end of the trip.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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How does DRM3 compare with Mars Semi-Direct in its original iteration?
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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The MarsDirect and DRM-III HABs are already 8m wide give or take, 10m would be quite a large upgrade and consume considerable payload mass. 12m would be awfully overkill, and would require consideration for aerodynamic interference on launch.
Just took a quick look at the scale of the analog stations and they are twice that it appears...
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The MarsDirect and DRM-III HABs are already 8m wide give or take, 10m would be quite a large upgrade and consume considerable payload mass. 12m would be awfully overkill, and would require consideration for aerodynamic interference on launch.
Just took a quick look at the scale of the analog stations and they are twice that it appears...
Really? And thats for people who can go outside, have a surface/horizon/gravity, and day/night cycles too. All the more reason to ditch Plan Bob.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Check out DRMIII here: http://exploration.jsc.nasa.gov/marsref/contents.html
As for a comparision with Mars Semi Direct, IIRC the two are pretty similar. Mars Semi Direct trades a surface rendevous for an orbital redeveous ala DRM III, other than that DRM III is just simply a bigger more robust mission.
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I often don't see why there is so much anger and debate over Mars Direct vrs DRM III. Mars Direct certianly deserves credit in being revolutionary change in thinking about Mars Mission architectures, however it is very much a back-of-the-envelop set of calculations, and not as fully formed mission plan as DRM III is. And even DRM III is only a design reference mission, not a completely worked out plan in it's own right (though much more complete than Mars Direct).
Some of the arguments still have merits such as the necessary size of the cabin or crew size, ect... but advocating Mars Direct (at least in the incarnation seen in the book) over DRM III is like advocating a car you drew on the back of a napkin vrs fully formed bluprints from GM.[/url]
He who refuses to do arithmetic is doomed to talk nonsense.
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I disagree,
There is a world (or two) of difference between MD and DRM, primarily because the former is not capable of doing what is advertised safely and effectively in any practical evolution of the design (without scrapping the design).
Furthermore, MD has "defined down" what is possible beyond any reasonable threshold, whether this is by ignorant folly or willful deception by Zubrin I don't know, but that is what is entailed with believing the design can live up to its billing.
MarsDirect terminally and fatally suffers from unrealistic assumptions, while DRM-III in either nuclear/80MT or chemical/130MT versions does not.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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I have been reviewing the many documents on the Mars Homestead Project and making some attempts on there review not only here but over on Re colony as well.
The base of documents are all on the premise of going though the exploratory stage as put forth through the utilization of Mars Direct plans. There are several images as it relates to the plan and its intent to build the first base.
Building the first permanent base using building material from the Martian soils.
I am not sure that even using the DRM III would get any easier for an initial base building start but if the mass are as you indicate it would not hurt.
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*cough* They copied Ben Bova *cough*
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
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The site reminds me of perhaps the single greatest flaw of Mars Direct, here given as an advantage:
The Mars Direct plans calls for landing sites about 300 kilometers apart...
I remember reading this in The Case for Mars. Not sure about that number though. Is this a real limitation or just a suggestion to improve redundancy?
Any recurring mission should be free to explore anywhere we want, and should not be limited to exploring swaths of land near previous landing sites.
How does DRM or Semi-Direct compare with MD on this issue?
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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Amen
This is since Bob thinks a few old HABs are a "base"
DRM doesn't address this
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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This is covered in page 9 of The Case for Mars, btw. I'll explain the gist of it:
Once the Hab lands next to the first ERV, they are comitted to using this ERV. If the first ERV fails, then the next missions ERV is within 800km, so they can use that instead (forfeiting the next manned mission opportunity in the process).
So it is a contingency in case the first ERV fails after both the Hab and second ERV have landed (i.e. if it fails half way through the 1.5 year human habitation period).
Allowing the second mission to take place at an unlimited distance from the first eliminates this contingency. However, the book mentions that "if the worse came to worst [the second ERV also fails], the four could just tough it out on Mars until additional supplies and another ERV could be sent out [in the next window opportunity]"
So it can be seen that keeping follow-up missions close to the previous mission sites isn't absolutely necessary, but it would come at the cost of significantly less redundancy.
In my opinion, succeeding missions absolutely must be able to land wherever they want. So if you have any ideas to restore this sort of redundancy, let us here it.
- Mike, Member of the [b][url=http://cleanslate.editboard.com]Clean Slate Society[/url][/b]
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Simple answer: don't have this redundancy.
Complicated answer: in theory, the MAV/ISRU payload called for in DRM-I had enough payload capacity to fully fuel the MAV with fuel from Earth if it were stripped down to the bone. So no ISRU plant, no rover, no reactor, no science gear, just fuel tanks for the MAV.
Put this thing in polar orbit around Mars, build it well so it can stay in orbit a long time. If the crew's assigned MAV fails, bring the "spare" down from orbit to their location so that they can launch and get home that way.
Fuel boiloff might be a problem though.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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