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#26 2012-01-07 15:07:56

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Mars Direct 2007

The Mars Semi Direct mission has some pretty good elements I think. 

However I would certainly query the size of the Hab.  210 cubic metres volume is a lot of volume I think.  6x6x6metres near enough. Enough for two rooms of 20 by 20 foot or eight rooms of 10 by 10 foot.  People can live much more closely together than that and still have privacy.  Hygiene and kitchen facilities can be minimised.

That seems pretty excessive to me.  There could be a huge mass saving there - by half perhaps.

Also, is it efficient to take to the surface something with all that landing gear. Wouldn't it be better to pre-land an inflatable hab by robot craft? 

For me the investment priority should be accurate robot landings, so we can be confident of getting equipment into say a 5x5km zone (using ground transponders and satellite tracking).


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#27 2012-01-07 18:56:21

JoshNH4H
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Re: Mars Direct 2007

Rune and Hop, thank you for your explanation of the technical details of the MSD mission.  That seems to make very little sense to me as a mission plan; however optimistic Mars Direct may be, it is simply a better mission plan than MSD. 

Louis- Have you done your research on that?  According to this page of the Atomic Rocket website, citing a NASA report, 17 m^3 per crewmember is the bare minimum in terms of survival.  I believe most Mars missions call for a 6-person crew; This would imply a 100 cubic meter hab.  However, you don't want to be at the bare survival minimum.  Rather, you want to be at a level of space where the crew will actually be able to function properly and get done all of the science and exploration that is absolutely vital for the first mission.  I would say that a 210 m^3 hab is perfectly reasonable for a mission of the length we're contemplating.  It's not going to be spacious or roomy by any standard; for comparison, the average prison cell is about 10 m^3, plus the communal spaces (for which I can't seem to find hard numbers).  Prisoners do not fare very well in prisons; I don't think we want our Astronauts to live in similar accommodations.  That said, does anyone else have input on this one?  I'm no expert in personnel management.


-Josh

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#28 2012-01-07 20:57:09

louis
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From: UK
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Posts: 7,208

Re: Mars Direct 2007

JoshNH4H wrote:

Louis- Have you done your research on that?  According to this page of the Atomic Rocket website, citing a NASA report, 17 m^3 per crewmember is the bare minimum in terms of survival.  I believe most Mars missions call for a 6-person crew; This would imply a 100 cubic meter hab.  However, you don't want to be at the bare survival minimum.  Rather, you want to be at a level of space where the crew will actually be able to function properly and get done all of the science and exploration that is absolutely vital for the first mission.  I would say that a 210 m^3 hab is perfectly reasonable for a mission of the length we're contemplating.  It's not going to be spacious or roomy by any standard; for comparison, the average prison cell is about 10 m^3, plus the communal spaces (for which I can't seem to find hard numbers).  Prisoners do not fare very well in prisons; I don't think we want our Astronauts to live in similar accommodations.  That said, does anyone else have input on this one?  I'm no expert in personnel management.

Well the Apollo lunar module was just over 6 cubic metres for two people - or 3 cubic metres for one.  So in terms of bare survival I don't think your figure can be right.

I am thinking in terms of 6 people as well.

I don't know if you've ever had a garden shed or a tree house. I've had friends from childhood who used to make veritable second homes out of sheds and would stay there happily for hours on end in a space no bigger than 6 cubic metres.  You can pack a hell of a lot into a little shed and you can do even more with 100 cubic metres. There will be plenty of room for sleeping, showering, cooking, food prep and eating. You can incorporate a small gymnasium for two. All the science for the first mission can be pretty miniaturised.

My mission conception would include a farm hab - so there will be other pressurised structures in which people can move.

Most prisoners seem to look pretty muscled up and mean...They're hardly wasting away in modern prisons.

I think with 100 cubic metres - with a floor space of 20x20feet -  you can do a lot.  You can meet all the essential requirements:


Hygiene - 2 toilets/basin and shower  (30 sq ft total)

Food prep, storage  and cooking. (20 sq. feet)

Bunks - 6  (20 sq ft total)

A small dining and meeting area with video screen (40 sq. ft)

A small gym and games area. (40 sq. ft)

Life support, energy storage  and monitoring equipment. (40 sq. ft)

There could be rotas to allow people some additional privacy in using the dining space or games area. E.g. on a rota people might be able to watch a movie by themselves. Such private "downtime" might be helpful, although I am not sure it is absolutely crucial. People can get alot of privacy in their bunk space.

We might experiment with virtual reality headsets as well if they were helpful in confined situations but people will have a lot of personal space with individual Laptops and headphones/sound systems.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#29 2012-01-08 12:49:24

GW Johnson
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Re: Mars Direct 2007

Why not use the experience we have from Mir,  Salyut,  and Skylab,  as well as ISS?  The unique one was Skylab.  Alone of all of them,  there was a huge open space in which to live.  That would be an upper design bound on volume per person.  I'd use Salyut and/or Mir as a lower design bound on volume per person.  ISS falls in-between,  and seems a tad crowded sometimes,  with 6 on board. 

What that says is any crew module for the long ride to/from Mars is going to be a big one.  Not necessarily really heavy,  but voluminous.  There needs to be some real elbow room inside,  like Skylab,  and some spaces where individuals can go to get away from everyone else.  I's suggest a few Bigelow-type inflatables docked together would be the most practical way to launch it,  using Falcon-Heavy at $800-1000/pound.  I'd also suggest recovering it and using it on subsequent missions to Mars and elsewhere. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#30 2012-01-08 15:35:32

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Mars Direct 2007

GW Johnson wrote:

Why not use the experience we have from Mir,  Salyut,  and Skylab,  as well as ISS?  The unique one was Skylab.  Alone of all of them,  there was a huge open space in which to live.  That would be an upper design bound on volume per person.  I'd use Salyut and/or Mir as a lower design bound on volume per person.  ISS falls in-between,  and seems a tad crowded sometimes,  with 6 on board. 

What that says is any crew module for the long ride to/from Mars is going to be a big one.  Not necessarily really heavy,  but voluminous.  There needs to be some real elbow room inside,  like Skylab,  and some spaces where individuals can go to get away from everyone else.  I's suggest a few Bigelow-type inflatables docked together would be the most practical way to launch it,  using Falcon-Heavy at $800-1000/pound.  I'd also suggest recovering it and using it on subsequent missions to Mars and elsewhere. 

GW


It seems to me that we need to keep the descent/ascent vehicle as small as possible. The way I see it, we should think in terms of

A. An MTV Hab (maybe like a Bigelow)

B.  A descent and ascent lander. Perhaps a larger version of the Apollo lunar lander.

C.  A Mars surface hab.



A and B would be assembled in LEO together with the rocket and supply module, forming in total the MTV.  I would have three person MTVs, so for a 6 person mission, there would be two MTVs.


C would be landed robotically.

On reaching the surface,  the Crew of the lander would perform an EVA and activate the inflatable/expandable Mars Hab which would then become the main living space with the landers acting as emergency accommodation.


Of course this proposal depends on fairly accurate landing - we need ground transponders interacting with satellites and teh lander vehicle to ensure we get in the zone.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#31 2012-01-08 16:30:49

JoshNH4H
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Re: Mars Direct 2007

Louis- the difference between the Apollo landers and a Mars mission is quite simple:  Duration.  The longest of the Apollo missions (Apollo 17) were in the LEM for about 3 days, 3 hours, while the shortest (Apollo 11) spent just 21.5 housed there.  A Mars mission is going to last about 550 days, about 180 times longer than the time the Apollo crew spent inside the LEM.

By the way, the LEM had closer to 7 m^3 than 6. 

I had a friend once who accidentally got locked in a locker.  The locker as about 1.5 m high by say .4 meters deep and about the same wide.  That's a volume of .24 m^3.  He was in there for about an hour and he managed to remain relatively calm until the fire department came to get him out (He, a few other friends, and I were volunteering at a gymnastics competition on the weekend so the regular custodial staff was not present to open the locker).  However, this does not mean that I can extrapolate and say that the bare minimum is a quarter of a cubic meter per crewmember.

I like GWs suggestion much better as a way to figure minimum volume.  I'm going off wikipedia for all these, by the way, if you would like to know my sources.  Interestingly, Mir actually had a pretty significant pressurized volume:  350 m^3 of pressurized volume for a standard crew of 3, though it apparently could hold 6 for up to one month.  I don't think that's necessarily based much on habitable volume, though.  The Salyuts were much more compact, having between 30 and 50 m^3 of pressurized volume per person, some of which would have been used for instrumentation etc.  Skylab had about 106 m^3 per person.  The ISS actually has the most, at 140 m^3 of pressurized volume for each of its 6 crew.  Salyut 6 was one of the smaller Salyuts, and the longest time spent on it was 185 days.  I would say that we would be looking at perhaps 35-40 m^3 per person for the Mars mission.  For 6 people, this gives a total volume of (Get this!) 210-240 m^3.  This is right in line with the Hab as per Mars Direct. 

The differences between a treehouse and a hab to be used in a mars mission are numerous.  The first two that spring to mind are that children are significantly smaller than adults and that you do not have to spend all of your time inside the treehouse.

It sounds like you're suggesting that people spend all of their time in a space that is absolutely tiny.  20 feet by 20 feet is about the size of my dorm room (intended for 3 people to sleep in uncomfortably), maybe including the closet and part of the bathroom.  Maybe.  I can absolutely promise you that you cannot house 6 people in that room every minute of every hour of every day without someone going at someone else's throat.


-Josh

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#32 2012-01-08 17:15:35

louis
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From: UK
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Posts: 7,208

Re: Mars Direct 2007

JoshNH4H wrote:

Louis- the difference between the Apollo landers and a Mars mission is quite simple:  Duration.  The longest of the Apollo missions (Apollo 17) were in the LEM for about 3 days, 3 hours, while the shortest (Apollo 11) spent just 21.5 housed there.  A Mars mission is going to last about 550 days, about 180 times longer than the time the Apollo crew spent inside the LEM.

By the way, the LEM had closer to 7 m^3 than 6.  .

I understand the difference, but you didn't qualify your reference to survival. That said, I see no reason why - in terms of volume - you couldn't survive for a very long in that amount of space.

I think in any case you are misunderstanding what I am proposing. The hab space for the Mars transit can be quite large - connect the lander to the Bigelow style hab. I am not so concerned about that.  But in terms of what we put on the surface, then I think the main hab should not be too large. There will be no shortage of space - they will have the whole planet to explore, and there should be a farm hab as well. 


JoshNH4H wrote:

I had a friend once who accidentally got locked in a locker.  The locker as about 1.5 m high by say .4 meters deep and about the same wide.  That's a volume of .24 m^3.  He was in there for about an hour and he managed to remain relatively calm until the fire department came to get him out (He, a few other friends, and I were volunteering at a gymnastics competition on the weekend so the regular custodial staff was not present to open the locker).  However, this does not mean that I can extrapolate and say that the bare minimum is a quarter of a cubic meter per crewmember..

Did anyone ask him what he was doing in the locker? smile

Anyway, it's a redudant debate in that I am not suggesting they have the bare minimum. I am suggesting they get about  16 cubic metres each.

JoshNH4H wrote:

I like GWs suggestion much better as a way to figure minimum volume.  I'm going off wikipedia for all these, by the way, if you would like to know my sources.  Interestingly, Mir actually had a pretty significant pressurized volume:  350 m^3 of pressurized volume for a standard crew of 3, though it apparently could hold 6 for up to one month.  I don't think that's necessarily based much on habitable volume, though.  The Salyuts were much more compact, having between 30 and 50 m^3 of pressurized volume per person, some of which would have been used for instrumentation etc.  Skylab had about 106 m^3 per person.  The ISS actually has the most, at 140 m^3 of pressurized volume for each of its 6 crew.  Salyut 6 was one of the smaller Salyuts, and the longest time spent on it was 185 days.  I would say that we would be looking at perhaps 35-40 m^3 per person for the Mars mission.  For 6 people, this gives a total volume of (Get this!) 210-240 m^3.  This is right in line with the Hab as per Mars Direct.

The differences between a treehouse and a hab to be used in a mars mission are numerous.  The first two that spring to mind are that children are significantly smaller than adults and that you do not have to spend all of your time inside the treehouse.

It sounds like you're suggesting that people spend all of their time in a space that is absolutely tiny.  20 feet by 20 feet is about the size of my dorm room (intended for 3 people to sleep in uncomfortably), maybe including the closet and part of the bathroom.  Maybe.  I can absolutely promise you that you cannot house 6 people in that room every minute of every hour of every day without someone going at someone else's throat.

You should take a look at the slums of Manila for close living. People there live day in day out in very cramped conditions. They survive quite happily most of them. Obviously our crew are going to have the best nutrition and hygiene systems. 

I am really not sure what you think the problem with close living is. As long as you have heat, light, food, water, hygiene facilities etc there's no problem, as long as you have the right pyschological attitude. We would of course favour compact individuals - probably no taller than 5-5 and no heavier than 140 lbs.  That's good all round as they eat less.

I am not a fan of looking at previous space habs as  a model.   I prefer the Musk approach. Identify the minimum that has to be done - the most cost effective approach and create something new out of that. Besides you really need to sort out your thinking between transit hab, lander hab and surface hab. They are not necessarily the same and in my view should NOT be the same.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#33 2012-01-08 20:22:06

SpaceNut
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Re: Mars Direct 2007

So what is the volume of the Mars Analog sites run by Mars Society? How does it compare to what is proposed for long duration living?
Another place to look at for size to people and duration you could also look at a submarine.....

Have a look at this Mars Life Support Systems paper by Donald Rapp
http://marsjournal.org/contents/2006/00 … 6_0005.pdf

http://spaceclimate.net/Mars.Life.Support.combo.pdf

Last edited by SpaceNut (2012-01-08 20:47:13)

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#34 2012-01-08 21:04:22

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Mars Direct 2007

SpaceNut wrote:

So what is the volume of the Mars Analog sites run by Mars Society? How does it compare to what is proposed for long duration living?
Another place to look at for size to people and duration you could also look at a submarine.....

Have a look at this Mars Life Support Systems paper by Donald Rapp
http://marsjournal.org/contents/2006/00 … 6_0005.pdf

http://spaceclimate.net/Mars.Life.Support.combo.pdf

That's a v. good point SpaceNut...I am fairly confident that submarine personnel get by on far less volume space than ISS personnel  and for months on end.

Thanks for reminding me about the example of submarines. smile


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#35 2012-01-09 06:13:51

Glandu
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Re: Mars Direct 2007

There's far more place available in modern submarines, especially nuclear ones; staying stacked like sardinas Uboot fashion is tough but doable for week-long missions. It is no more for month-long missions.

My uneducated preferences goes to inflatables, both for travel & on site.


[i]"I promise not to exclude from consideration any idea based on its source, but to consider ideas across schools and heritages in order to find the ones that best suit the current situation."[/i] (Alistair Cockburn, Oath of Non-Allegiance)

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#36 2012-01-09 07:45:33

GW Johnson
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Re: Mars Direct 2007

The thing the crew will spend the most time inside will be the habitation module of the orbit-to-orbit vehicle.  That's the one that needs to be voluminous,  and it does not ever need to land.  If it's at one end of a long ship,  just spin it end-over-end nd you have artificial gravity.  That solves a whole host of life support problems if you have artificial gravity.  That approach does require de-spin for maneuvers,  but that's no real problem.

I like the submarine example,  too.  The old diesel electric boats,  particularly German U-boats and the 1920-vintage US S-class,  were very cramped,  not intended for more than a month or so at sea.  They were called pig boats for a very good reason.  The larger fleet subs were still cramped,  but livable for a nominal 3 month war patrol.  60-70 men inside a 300 foot ship that was chug full of machinery.  Crawl through one sometime.  There's several on display as memorials.  The new nuclear attack boats are better still (see Nautilus,  on display),  and the missile boats are very spacious by submarine standards.  6-9 months possible in them. 

Here is something to consider:  it's not the gross volume but net,  after subtracting off for machinery and equipment that occupies spaces.  When you do that,  the various space stations don't look so very spacious inside,  excepting the old Skylab.  You can see this effect in photos.  It is very significant to psychology. 

What you take to the surface of Mars,  you really don't have to live inside-of for so long,  plus you can go outside!  An inflatable pitched near the descent vehicle makes a lot of sense. 

I'd be very careful comparing a Mars lander design to the Apollo LEM design.  The velocity requirements are very much higher at Mars,  plus you have entry heating and ascent drag to deal with.  Likely 3-4 stages if chemical.  I'd go nuclear - single stage is possible with NERVA-type technology,  which we could still resurrect (not quite all those guys are dead yet). 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#37 2012-01-09 08:03:39

Dayton3
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Posts: 137

Re: Mars Direct 2007

Mark Friedenbach wrote:

Mars Direct is simpler, safer, and easier to pull off than DRM 3.0. The DRM was in response to MD, but added the complexity of a transfer vehicle left in Mars orbit. IIRC Zubrin spends a section in the Case for Mars discussing the problems of this approach that I won't reiterate here, but another big one that Rune didn't mention is the lack of artificial gravity on the way out. One can only speculate as to why.

.

There is one factor in favor of Mars Semi-Direct.

It allows for a mission to be salvaged without being redesigned if fuel production on the Martian surface fails for some reason.   Because the Mars Ascent Vehicle is small enought that a "bare bones" one but fully pre fueled can be delivered to the Mars surface.

I have a feeling that NASA to this day is still not convinced of the viability of fuel production on the Mars surface for the first missions to Mars.

Last edited by Dayton3 (2012-01-09 08:04:02)

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#38 2012-01-09 12:24:52

GW Johnson
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From: McGregor, Texas USA
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Re: Mars Direct 2007

Thinking like suspenders-and-belt is how you survive in space.  I would definitely try some fuel production on the first landing.  I would not count on it in any way for the return from that first landing. 

Question:  why is everybody still focused on one trip-one landing?  Why not make one trip and several landings?  It's a lot of trouble to go there.  Why not make it really worthwhile?

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#39 2012-01-09 13:00:34

louis
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From: UK
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Re: Mars Direct 2007

GW Johnson wrote:

Thinking like suspenders-and-belt is how you survive in space.  I would definitely try some fuel production on the first landing.  I would not count on it in any way for the return from that first landing. 

Question:  why is everybody still focused on one trip-one landing?  Why not make one trip and several landings?  It's a lot of trouble to go there.  Why not make it really worthwhile?

GW


I favour two landings - three people in each lander (total  six people). I'd like to see a doubling up in Mars inhabitants every two years with each new wave of settlers buiding habs for those that follow.

I also favour several pre-landings with robot craft.  These would land supplies and I think a fuel production unit if that could be operated robotically (obviously that would need a lot of research, but I don't see why not. Alternatively, land some fuel.

I certainly don't think Mission 1 should rely on ISRU fuel production, but it should begin fuel production. There must however  be a guarantee of getting off the planet.


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#40 2012-01-09 13:51:34

Mark Friedenbach
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From: Mountain View, CA
Registered: 2003-01-31
Posts: 325

Re: Mars Direct 2007

GW Johnson wrote:

Thinking like suspenders-and-belt is how you survive in space.  I would definitely try some fuel production on the first landing.  I would not count on it in any way for the return from that first landing. 

Question:  why is everybody still focused on one trip-one landing?  Why not make one trip and several landings?  It's a lot of trouble to go there.  Why not make it really worthwhile?

GW

Because it's easier, simpler, safer, and more productive to just include a 1,000km-range rover and all the scientific/prospecting gear to go with it. Why burn all the fuel and carry the risk of moving the whole hab around?

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#41 2012-01-09 16:19:13

JoshNH4H
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Re: Mars Direct 2007

First off, there seems to me to be little reason why something so well-tested and checked out as the fuel production system (will be) would fail.  That said, in the event that it does I see no reason why we couldn't just send up a nice big fuel tank to fill up the ERV, along with the rest of the mission (One of the wonderful perks of Mars Direct is that all of the fuel will be made by the time the humans have to launch).

GW, I absolutely agree that the space that is not filled up with instruments is a much better measure of the space actually available to the astronauts.  If I had that on hand I would absolutely have given that.

It is my understanding that inflatables are actually not lower mass than solid habs.  Their primary benefit is in that they take up less space while in transit.  That's a big benefit, so I agree with their use as well.


-Josh

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#42 2012-01-10 10:52:29

GW Johnson
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Re: Mars Direct 2007

Josh:

What I had in the paper at last August's Dallas convention in part called for a single stage NERVA-propelled lander,  a big rover with a drill rig on it,  a swarm of small robots to assist 3 persons on the surface,  and an inflatable Quonset hut to live in.  You erect the hut and base your activities at a safe distance away from the NERVA,  not in the lander.  But the lander makes a better shelter if a solar flare occur.  Surface time was a week or two.  You leave a transponder at each site,  to enable future precision landings. 

My paper said send 3 down while 3 monitored and did science from orbit.  Then alternate crews and landers.  I put enough delta-vee into the 20% inert 10% payload landing boat to land 25 degrees out of plane and return,  with rocket braking all the way down.  That's no aerobraking credit,  but a gravity and drag penalty on the way up,  so its a very conservative size-out.  Having at least one lander ready in orbit at all times for a rescue trip was one of my mission requirements. 

You could do that with any mission making multiple landings.  My design was 6 persons,  and 3 landers so that the loss of one did not terminate the mission.  The three landers pushed all the landing propellant supply unmanned to Mars orbit.  I sent the manned vehicle with enough propellant to return,  in case rendezvous failed for any reason.  Suspenders-and-belt. 

The prime design called for fast trip zero-gee manned ship,  but the backup was a "slowboat" NERVA,  which would be spun end-over -end for artificial gravity.  No more than one year at microgravity,  and set right at 1 gee for artificial,  again suspenders-and-belt,  based on what has already been done.  That's probably what we really want to do. 

My paper's design made 16 widely-separated landings in the one trip,  plus a visit or two to Phobos.  A real planetary ground truth survey.  There were 3 unmanned vehicles sent one-way to Mars plus one manned vehicle that goes two-ways and is recovered in LEO to be used again.  All 4 were in the 600 metric ton class as assembled by docking 34-ton modules in LEO. (That was based on Spacex's projections for Falcon-Heavy before they settled on 53 tons.)  It true exploration based from orbit (what all is there?  where exactly is it?)

The return from that trip would be the critical ground truth information for selecting one or two experimental base sites.  These would be the places where you set up the real ISRU that you tried out on the first mission.  Some of those first examples will have worked,  most won't.  But that experience takes "theoretical" designs and turns them into machinery you can rely on,  for the second trip.  Again,  suspenders-and-belt.  This second trip is surface-based work,  and "looks" more like what people are proposing in these forums and most of the papers I see.  But the chances of success are much smaller,  if you don't do what I suggest for a first survey mission. 

The experience and supplies generated by those couple of well-sited experimental bases is what enables a more permanent settlement,  that could blossom into a real colony if some trade commodity could be identified.  Done right,  this could happen fairly fast.  Done  wrong,  the inevitable failures and fatalities might well kill the process. 

Suspenders-and-belt.  And an armored codpiece!

GW

Last edited by GW Johnson (2012-01-10 10:57:54)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#43 2012-01-10 11:36:43

Rune
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From: Madrid, Spain
Registered: 2008-05-22
Posts: 191

Re: Mars Direct 2007

You know what? Dismounting from a cooling NERVA has to be a frightening experience. All that cooling melted glass on the ground and such wink. How far from the unshielded bottom and sides of the engine did you mean to have the astronauts go through? Because I am assuming the lander is a tail-sitter, and even after it is cool, it is still an already-activated 400MW reactor...


Rune. Otherwise, nice plan. Solid and with room to grow. Can I see it somewhere?


In the beginning the universe was created. This has made a lot of people very angry and been widely regarded as a "bad move"

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#44 2012-01-11 14:47:06

GW Johnson
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From: McGregor, Texas USA
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Re: Mars Direct 2007

I suppose you take your time before dismounting,  and then move away quickly,  once you clamber down.  I envisioned a crane arm that makes a nice personnel and cargo elevator.  Proximity is bad (inverse square),  but really it accumulates over time.  What you don't want to do is stand near the thing any longer than necessary.  (One of the reasons I like gas core concepts better is faster thermal and radiational cooldown:  essentially an empty chamber.)

A few dozen meters away is a pretty good distance temporarily for unload trips.  Pitch camp maybe a km or two away.  You're pretty safe up in the lander cabin with the propellant and structure for a shield.  Nice shelter for solar flares if it's built tough as an old boot,  and you have a couple of water and/or wastewater tanks to hide beneath. 

The Mars Society archives on-line have my original paper.  A version of it is posted on "exrocketman" dated 7-25-11.  Some second thoughts about using NERVA vs electric as the backup scheme is posted 9-6-11.  That site is http://exrocketman.blogpot.com   If you click on the identifier "space program",  then it shows only those articles with that identifier. 

GW

Last edited by GW Johnson (2012-01-11 14:49:32)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#45 2012-01-12 05:00:32

JonClarke
Member
From: Canberra, Australia
Registered: 2005-07-08
Posts: 173

Re: Mars Direct 2007

Mark Friedenbach wrote:

Mars Direct is simpler, safer, and easier to pull off than DRM 3.0. The DRM was in response to MD, but added the complexity of a transfer vehicle left in Mars orbit. IIRC Zubrin spends a section in the Case for Mars discussing the problems of this approach that I won't reiterate here, but another big one that Rune didn't mention is the lack of artificial gravity on the way out. One can only speculate as to why.

Zubrin came up with MSD in response to a number of criticisms of MD.  The main disadvantage of MSD as opposed to MD overal is more launches and mission critical rendezvous in Mars orbit.  The main advantage is much less propellant needs to be manufactured.  Not mentioned by Zubrin is the fact that, as conceived, the ERV in MD was too small by a factor of two or three.  lso, as originally written, MSD had less optomistic assumptions about mission masses.  Overall there are good easons why almost all subsequent mission studies have used MSD.  Including Zubrins latest concept (too sketchy to be called a proposal) for a two person mission based on Dragon.

It is just as feasible to use spin gravity with MSD as with MD.  Whether it is needed is a different story.  I am inclined to think not.

It's all moot though as they way this works is that every few years some engineers working under political pressure at JSC come up with a reference mission, and then anyone within the agency or government has to use this mission as the bible for what a minimum human-to-Mars programme would look like. The current DRM is unpublished Constellation-era framework that called for multiple (!!) Ares V launches per mission, with some crazy number like 300-400 tonnes to LEO, and all for just a few weeks at a single spot on the surface. Unfortunately it's unpublished (unfinished?), but of course being the JSC-approved reference mission, it was taken at face value the only design considered by the Augustine commission, who of course said it was ridiculously expensive and put Mars off the table for the foreseeable future.

There have been five DRMs, two are (2.0 and 4.0) unpublished as separate studies, but the details are available in other published report reports, including 5.0.  None are "minimum" misions.  None involved 300-400 tonne launches to LEO.  None spent only a few weeks on Mars, all were 500-600 stay missions.

I am not a fan of DRM 5.0 either, as it basically scaled 4.0 up to 5.0 rather than taking advnatage of a large booster (130 tonnes vs 90 tonnes) to reduce the number of launches.  But it still contained useful information and is well worth reading.

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#46 2012-01-12 12:44:55

Mark Friedenbach
Member
From: Mountain View, CA
Registered: 2003-01-31
Posts: 325

Re: Mars Direct 2007

The post-VSE mission designs were not published in DRM format. These Constellation-based mission (which looks more like the 90-day report than Mars [Semi-]Direct) is now the "official" plan. It's the one the Augustine commission used to cost (and reject) a Mars mission.

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#47 2012-01-12 14:48:15

JonClarke
Member
From: Canberra, Australia
Registered: 2005-07-08
Posts: 173

Re: Mars Direct 2007

Mark Friedenbach wrote:

The post-VSE mission designs were not published in DRM format. These Constellation-based mission (which looks more like the 90-day report than Mars [Semi-]Direct) is now the "official" plan. It's the one the Augustine commission used to cost (and reject) a Mars mission.

Yes it is, e.g: Human Exploration of Mars Design Reference Architecture 5.0 Addendum.  NASA/SP–2009–566-ADD

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#48 2012-01-12 16:46:59

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Mars Direct 2007

Part of NASA's problem has been a failure to be simple and consistent in its branding. A confusion of visions, programmes and missions, means that the general public have no real connection with what is going on (contrast with Apollo which had brilliant branding). Of course that confusion reflected a higher level confusion about strategic aims and delivery.

There should have been a single Mars programme. 

It might have been named Mars Apollo.  The first phase could have been robot missions. But the branding is important, so people can feel the momentum of what is going on.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#49 2012-01-12 17:44:28

Mark Friedenbach
Member
From: Mountain View, CA
Registered: 2003-01-31
Posts: 325

Re: Mars Direct 2007

@JonClarke, I stand corrected. Somehow I never saw the addendum published.

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