So we like landed on Mars, and stuff

[Elukka]

A Stanford Torus and a Mars spacecraft are such wildly different systems they're not really comparable. You don't live in a Mars spacecraft all your life, for one, and a habitat needs shielding against the most hostile conditions the sun can throw at it during solar storms and such while a spacecraft can make do with a small storm cellar as refuge for the crew in the somewhat unlikely event a storm occurs during the mission.

Here are some specifications of a real world nuclear thermal Mars mission study: Mars 1994. It places the habitat between the propellant tanks which provide radiation shielding for essentially 'free'. I'm guessing the engines would also have a shadow shield which is a simple circular plate of metal in front of the reactors that provides shielding in, say, a ten degree cone or whatever is sufficient to cover the habitat.

As a curiosity here's an older yet more potent design that would likely be a political impossibility today... A fairly modest Project Orion vehicle that would take more more payload faster to Mars than even nuclear thermal rockets. This one is small as far as Orions go, and would have been launched on only two Saturn V's. (200 tonne total mass, contrast with the 800 tonnes of Mars 1994.) This would bypass the radiation and EMP issues that atmospheric use of Orion would have.

[Carl]

@Elluka: I'm aware they're different, but that gives a conservative figure. The idea of a single shield that covers a small arc is interesting but again falls foul of the fact that if something goes wrong you just killed the astronauts, plus the constant turning required would require a fair amount of fuel in mars orbit. That Russian design is more interesting, though I question weather there would be enough fuel in the tanks for it to work on the way back, certainly doesn’t work for a VASMIR setup since it’s such a low fuel mass design. A Flare shelter concept might work but I’ve already pointed out the issues. Also it's not a chance of a flare, even with say VASMIR doing 40 days each way and 10 days at mars your going to see several at the quietest part of the suns cycle. At the peak they'll barely get out of the shelter all trip, (not good).

Another issue is that even if you can get the spa crafts shield down, you can't pull the same tricks on mars surface unless you intend to do an Apollo 11 "land, plant flag, grab some rocks, come home" mission. Which really is NOT worth the effort of sending man. That means even if you get the rad shield weight down, you still end up bringing at a minimum several hundred tons of radiation proofed Lander/work area, and another few hundred tons of radiation proofed rovers for getting around. Mars isn’t like earth, it's thin atmosphere and weak magnetic field lets a lot of radiation through. That means suitably rad proofed rovers.

[Elukka]

It gives you an absolute worst case number but fortunately realistic spacecraft shielding is a couple orders of magnitude lighter.

The idea of a single shield that covers a small arc is interesting but again falls foul of the fact that if something goes wrong you just killed the astronauts, plus the constant turning required would require a fair amount of fuel in mars orbit.

What constant turning? What could possibly go wrong with a shadow shield? It doesn't move in any way, it's just a plate of metal between the reactor and the habitat that shields anything in its 'shadow'.

That Russian design is more interesting, though I question weather there would be enough fuel in the tanks for it to work on the way back, certainly doesn’t work for a VASMIR setup since it’s such a low fuel mass design. A Flare shelter concept might work but I’ve already pointed out the issues. Also it's not a chance of a flare, even with say VASMIR doing 40 days each way and 10 days at mars your going to see several at the quietest part of the suns cycle. At the peak they'll barely get out of the shelter all trip, (not good).

It's a detailed real-world design study based on an engine they actually built. Do you think they would get the math wrong on something as elementary as 'how much delta-v does it take to get back from Mars'?
All deep space mission concepts have some radiation shielding. The storm cellar is for especially bad conditions that aren't expected to happen all the time but are possible regardless.

You wouldn't need hundreds of tonnes of radiation shielding on the surface. It's not that deadly. According to this you could spend three years on Mars orbit without any shielding before you'd run afoul of NASA's occupational safety limits. I don't know exactly how much radiation you'd get on the surface but it's bound to be lower than that and you'd certainly have some shielding on your equipment, just not hundreds of tonnes of it.

[Langy]

And you could reasonably make shielding on the surface via the simple expedient of burying it under dirt.

[Stripe7]

Just look at the Mar's Rovers, how much shielding did we have on them for the entire 8+ months travel to Mars? We do not need to shield the entire ship, just have a bunker for the humans for the big solar flares. NASA workshop on radiation proofing spaceships That paper points to the possibility of using a plasma type shield and different materials for building a "storm cellar".

[Moe]

The idea of a single shield that covers a small arc is interesting but again falls foul of the fact that if something goes wrong you just killed the astronauts, plus the constant turning required would require a fair amount of fuel in mars orbit.

What do you mean "something goes wrong"? It's a non-moving plate of metal. What scenario are you envisioning where something goes wrong that would have otherwise been prevented by encapsulating the entire reactor? And what constant turning?

[Nurizeko]

Hmm, seems interesting, if a bit far fetched for a Dutch TV station.


http://mars-one.com/en/

[Moe]

That's a marketing thing, not a real project.

[CommissarRezail]

Wow thats some nice marketing, well sign me up for mars one as long i get 100 square miles of mars land and 25 percent of its water.

[Carl]

@Eluuka: My bad, quick typing confused you.

I wasn't talking about sufficient fuel for delta V. I was talking about sufficient remaining fuel after Mars exit burn to provide adequate shielding. VASMIR would make this worse since it uses less fuel to start with.

The thing with a shadow shield is 2 fold.

1. Some of the talk in that document stripe links talks about how with magnetic sail shield that particles are capable of moving around it. The technical talk is a littlie over my head so I’m not sure if that’s a result of it's magnetic design or a limitations of the concept of a shield only between the spacecraft and the sun.

2. The spacecrafts angle relative to the sun will be constantly changing throughout it's journey, it will not be flying a straight line to mars and back, it will be a shallow curve, (and an orbit is a circle or an eclipse shape usually), as a result to keep the shield pointing at the sun requires the craft to constantly adjust it's rotation to keep the shield pointing where it need to be.

I also don't think you understand the concept of the suns 11 year cycle. Your STILL talking about flare conditions like their some rarity you will experience once or twice a trip. Even a 90 day round trip will see an average dozen or so at the low point, at the high point your talking several hundred per trip. True not all of these are so bad they'll require a shelter if you build a fairly strong magnetic shield, (some flares are quite weak), but a fair number are quite strong, (with average strength increasing as frequency increases AFAIK), even at the low point they'll be using the shelter several times. At the high point they may well spend more time in the shelter than the rest of the ship.

As I already noted it also creates huge issues because many components that have never been tested at those sorts have radiation levels will now have to be hardened against it and the use of biological methods for food production, CO2 scrubbing, and waste management go straight out the window and care must be taken to ensure they continue to function in such radiation, (it's no good bringing along a great chemical system for waste management if the radiation causes chemical breakdowns that render them useless. All of this also adds to the mission mass, especially on longer missions, that dosen't even come close to making up the difference between the full shield and bunker, but it does means the mission will still have a fair amount of mass. Potential irradiation of parts of the spacecraft also have to be considered. Also the food preservation report highlighted high difficulties with storing food in an environment where high radiation exposures could be expected.

I'm also going to dispute your Mars radiation claim. Not because I think the quoted figure is wrong, (it's sourced), but because the resultant claim of 3 years is not sourced. The specific problem is this:

Apollo astronaut average doses rates where only 6 times higher, (and they suffered no flare events). Whilst the day to day radiation out in open space is dangerous due to heavy ions, (they kill the brain and spinal column off at a high rate amongst other issues), in terms of dosage rates it's quite low. An average Flare, (using a figure drawn from the food paper linked earlier), delivers a 100 years worth of background radiation in a matter of minutes or hours, (5 times the guaranteed lethal dose in fact). As such without seeing the raw data to see what the dose rates where during these events, (and what the magnitude in open space of the event was as they do vary, (duh)), it's not really safe to say mars provides adequate protection. A particular point is that as the particle energy rises the ability of a magnetic field to deflect the particles drops. As such mars with it's much weaker magnetic field might be perfectly adequate at deflecting the low energy background radiation, but it is guaranteed to be significantly worse with the higher energy levels. (i.e. it's fairly certain it isn't going to reduce a solar flare to a sixth it's normal value).

Some looking at high altitude aircraft also shows that at typical flight altitudes the earths atmosphere is significantly less effective, with average does being around a fifth that of LEO. Atmospheric pressure at 40'000Ft is some 20% of earth sea level normal, (Approximate, varies with a few factors). Mars surface is 0.5% of earth sea level normal so it's going to provide even less, (though it's high CO2 content may make it more effective than the simple pressure comparison implies). Suffice to say I would be VERY surprised if a lethal dose at orbit did not produce at least a dangerous dose at surface.

@Langly: that works ok for the habitat, (subject to you bringing something with you to do that covering and having the ability to drop the habitat and cover it over before the astronauts descend), but the rovers aren't likely to be anywhere near as easily solved, (they'd get too big in volume terms).

@Stripe: Nice link . Seems my source on the whole weight savings differences is wrong, but then that was dealing more with high end nuclear waste storage. They are different types of radiation, i just hadn't figured on it being that different shielding wise. I am having issues with some of the technical terminology, (most of it i get but some goes straight over my head), but it's nice to read up on it. It does however point out the same high mass issues with the use of physical shields and notes that we don't currently have a completely workable design for any level of energy shielding. I'd also point out, (because someone is going to read the whole thing and bring their recommendation up), that their recommendation vis a vis lunar rock assumes the use of rockets for shipping, a fairly low ISP engine, compared to some of the options now discussed anyway, (good pessimism though), and assumes no oxygen extraction for fueling and life support needs. All of those basically change the math on the cost calculations. Though the fuel mass to other mass ratio figure it gives is nice to have . They also missed off an electrostatic variation oddly enough.

Though i should point out my mass figures where way off. I knew using the surface area to mass of the Stanford torus shield was not perfect as the curved nature produces a 3D trapezoid shape rather than a true 1MX1Mx1.8M box, (1.8M is 6 Ft, to within a few cm). But i drastically underestimated the effect. That link gives lunar soil a mass of 1.5 grams per cubic cm. So actual mass is about half what i assumed for lunar rock and somewhat less for more ideal earth shipped materials.

The biggest flaw with the whole premise of their study however is that they're running on the assumption that the space weather system can provide warning to the mars craft. That’s simply a false assumption. The system is composed of earth orbit and earth ground based instruments. This means a whole hemisphere of the sun is completely unwatched, and signal lag means even if we see a flare, we may not be able to get a warning to the spacecraft in time. The spacecraft will have to do it's own watching which adds a far range of complications to both the shelter design and the overall spacecraft design, as well as demanding more from the crew.

Also I’d like to point out that the original point of the high mass shield design was: What can we build with our current tech. A physical shield is pretty much the only choice in that situation as our current energy shield tech simply isn't even flight ready for background shielding, let alone a full shield. By the same token we currently have no method of storing food in a high radiation environment, and the current range of long term space modules such as those used on the ISS are not proofed for a high radiation environment. Considerable development would be needed to make them ready for such an environment and sort out the food problem.


That said having done the math earlier on just how much supplies mass you'd need I worked out that, (assuming mass per module rather than volume is the limit on module payload limits), that you could store 5 years of supplies for 20 people with a 20% safety margin in approximately 25 modules. Add on 10 more for living quarters and another 10 for other stuff and you have a total of about half the modules of my smallest example. Thus the radiation shield is likely to be under 10,000 tons in that case, (factoring in all my prior mistakes ). Total mass including a fairly heavy lander and module mass is therefore only around the 8,000 tons mark, (the shield drops to a meager 5000-6000 tons with lunar materials). Fuel mass makes that a LOT larger, and theirs still engine and structural mass to add on. But it adds upto a lot less than my initial estimate, the entire spacecraft would be under a third the old shield mass. And the extreme 200'000 ton shield design could probably transport a good 200 people along whilst being a LOT lighter than my estimate.


@Moe: Where talking about using the reactor shield to do dual duty as a limited arc solar radiation shield .

[GeoffS]

Carl, you seem to be assuming that everything would need to be taken on the same trip/spacecraft with the crew. Logically, you wouldn't even think of doing that. Send the stuff you need on the surface ahead of time on unmanned flights, land it all in the chosen area, and then as the last flight you send your crew/settlers on a ship that is assembled in Earth orbit and is designed for a one-way trip to Mars orbit. You don't even need to take a lander on that crew flight, send it on ahead and park it in Mars orbit. All you take on the crew flight is sufficient fuel and provisions for the one-way trip. That cuts the shielding required down drastically.

[Carl]

@Geoffs: Not really. Weather you bring it on the main rocket or send it ahead the main rocket still needs the same shielding. All sending the lander and rovers ahead does is reduce the mass of the main rocket. My estimates assume the payload bay with the lander and rovers is un-shielded.

p.s. in case it's unclear we've moved on from the one way trip assumption to "can we (money issues aside), sends a manned mission to mars to do science and, (presumably), bring them back with current tech"? I.e. could we do a mars vershion of the apollo missions today if money was no object?

[Moe]

Not really. Weather you bring it on the main rocket or send it ahead the main rocket still needs the same shielding.

Many big differences. Lighter landers are easier to bring down. Multiple launches means you get to make sure that everything is in place and working before you send people. Remember, you have to land all this shit, and Mars doesn't have much of an atmosphere, so parachutes are only of limited use. Setting down a huge lander containing habitat modules, a mars rover, and all the golf equipment they'll need presumably is a lot more challenging than sending several smaller ships.

[Carl]

Many big differences. Lighter landers are easier to bring down. Multiple launches means you get to make sure that everything is in place and working before you send people. Remember, you have to land all this shit, and Mars doesn't have much of an atmosphere, so parachutes are only of limited use. Setting down a huge lander containing habitat modules, a mars rover, and all the golf equipment they'll need presumably is a lot more challenging than sending several smaller ships.

Yes but the total mass to transit to mars and thus the total spacecraft mass to bring them there is the same, (it does have advantages in terms of simplifying many things as you state, but it doesn’t help the mass issues which is what Geoffs seemed to be implying).

[CommissarRezail]

Its the same? so they bringing all the equipment back?

[Moe]

Yes but the total mass to transit to mars and thus the total spacecraft mass to bring them there is the same,

It'll probably be larger but that doesn't matter because a single large ship carrying all the crap that you lot want to shoot up there is problematic at least. Your shielding calculations are off though. There's a 1992 paper that estimates the mass of a manned mars vehicle to be 500-550 tons. NASA's latest design document from 2009 lists 350 tons for the vehicle, including shielding.

Allow me to quote this part: "Two cargo flights are used to pre-deploy a cargo lander to the surface and a habitat lander into Mars orbit where it remains until the arrival of the crewed MTV during the next mission opportunity."
In other words, everyone, including NASA, agrees that we need more than one ship. Pre-deploy is much preferred over all-up, which by the way would most probably still consist of multiple vehicles that could potentially rendezvous on the outbound flight.

That document is worth a read by the way because it addresses all of the questions in this thread and was written by people who actually know what they're talking about. It's 100 pages, but it has actual numbers instead of armchair theorycrafting.

PS: Regarding storm shelters:

The amount of radiation [in case of a solar flare] can be so large that the dose the explorers, if unprotected, would receive significantly exceeds all limits, and can result in rapid death. However, to protect the explorers for limited periods, “storm shelters” can be constructed in the most heavily shielded areas of the spacecraft and habitats, and can be provisioned with sufficient consumables to maintain humans for the maximum estimated duration of an SPE (from a few hours to several days).

[Carl]

@Moe:

I'm going to have a read but just up front:

1. From a preliminary look, (read a couple of minutes), this document seems to involve a great many technologies we do not currently have. By far the most obvious that NASA hasn't solved yet that the storm shelter concept requires is a viable means for storing and transporting food for the trip. Currently if you don't shield the food from Solar Flares to the same degree as the crew it won’t last the trip. At that point for even a 20 crew spacecraft the effective number of modules you need to shield for food storage and the shelter ends up being the majority of the modules, (some quick thinking says you could get 20 peoples to mars with as littlie as 28 modules: 20 storage, 3 bedroom modules, 1 Control Module, 1 Observatory Module, 1 Waste Processing, 1 Dining room/Kitchen Combination Module, 1 Exercise Module). At that point you might as well shield the whole thing and be done with it. The main point however is that I’m hypothesizing my way along something that could be built right now. Not something we need 10 years and a trillion dollars worth of research to pull off.

2. NASA gets thing wrong, (just like have a few times in this thread). That whole situation with the space weather system is just one examples. Their figures for shielding a single module with lunar rock in the same document are wrong by the documents own facts on thickness required and density, they forgot to add on the end caps on the hollow tube that would encase the modules. It's quite possible their math is faulty on some critical component.

3. I'm being fairly conservative across the board because of the aforementioned tech limitations, I’m not using the ultra efficient module layout of stacking them end to end, that way if there's a problem in one module it doesn’t cut the whole craft in half. I'm also being fairly pessimistic on the crew size, assuming we'll require a fair number of people to run all the instruments and such like. NASA's study probably works on a 4-8 crew baseline, which knocks 6-10 modules off my spacecrafts minimum. I'm also assuming that to aid with psychological issues it might be best to make the spacecraft a littile on the over-large side so there's plenty of nooks and crannies for crew to go get some solitude if they need it and have no duties to attend to. It also allows far more volume for recreational facilities and other coping mechanisms as well as a fair degree of backup in other area's. I'm also assuming the use of existing stuff re-purposed as much as possible. That equates to higher average masses no matter what, since using existing modules rather than a single custom one as the papers spacecraft seems to assume is rather inefficient in terms of materials.

Now to go reading.

[Stripe7]

1. You don't store food in a storm shelter, other than for a week or so. Food for space will actually be irradiated to sterilize it. More radiation will not bother it.

2. End caps? Use lead shielded doors.

3. NASA has experience with having 6 people in space for a years. It is called the ISS.

[Carl]

Stripe:

1.the paper you linked on food for a mars trip says it will. All but a couple of items, (not sufficent to cover all dieteary needs), saw degredation from high dossage rates.

2. Dosen't mater if it;s an end cap or a lead sheilded door. it's still mass that has to be added

3. I'm talking about doing the actual science and what have you when they get to mars

Edit: Still reading.

[Nurizeko]

That's a marketing thing, not a real project.

yes. Marketing going to Mars. Which is why I posted it here.

Whether it can actually do it...well...that's a point of discussion for the thread isn't it?

[GeoffS]

@Geoffs: Not really. Weather you bring it on the main rocket or send it ahead the main rocket still needs the same shielding.

But according to you the food for the entire stay on the planet would need to be shielded, as well as the rovers and habitat modules themselves, making the shielding required much more than for just the crew and enough provisions for the journey.

Also, you misunderstood what I meant by "a ship that is assembled in Earth orbit and is designed for a one-way trip to Mars orbit" and "All you take on the crew flight is sufficient fuel and provisions for the one-way trip". I'm not talking about not bring the crew back, just not bringing the outbound ship back. To minimise weight on the manned flights, you cut out all unnecessary stuff. Anything that is not needed during the actual trip you send on ahead on unmanned flights. That includes the ship for the return journey with its own fuel and provisions, or at least the fuel and provisions.

If you do it that way (which is similar to the proposal in the NASA document that Moe linked) then you make it easier to establish a longer term or even permanent base on Mars. You just lift all the stuff out of Earth's gravity well into something like a "warehouse" in Low Earth Orbit, assemble what you need in modular ships for the trip to Low Mars Orbit, stick it in a "warehouse" orbiting Mars, and take it down to the surface as you need it. The same process could then be used later for missions to Mercury, Titan, Europa, or anywhere else. The manned ships would only need to be large enough and heavy enough to take the crew and the minimum provisions for the journey one way.

[Trinity]

http://upload.wikimedia.org/wikipedi..._of_Terror.ogv
by NASA (NASA), from Wikimedia Commons

Pretty complicated just landing a rover. Imagine a manned landing.

[LoCo]

Trinity: Why would it be that much more complicated doing manned landings?

Were you under the impression that humans would die from being shaken up a little?

[Paladin]

Actually yes. If there had been humans aboard that lander, they'd all be dead. The opening of the parachute would have killed them all.

[LoCo]

I'm sorry. I seem to have given the impression that I was advocating the exact same method of landing.

I'm not.

I'm just saying that it wouldn't be much more complicated.

[CommissarRezail]

Actually yes. If there had been humans aboard that lander, they'd all be dead. The opening of the parachute would have killed them all.

Soup or jello?

[GeoffS]

Actually yes. If there had been humans aboard that lander, they'd all be dead. The opening of the parachute would have killed them all.

Actually no. Since the peak deceleration during the EDL was about 15g, and the parachute opening only gave about 9g, and even untrained humans can tolerate upto 17g without loss of consciousness or long term harm, trained astronauts would certainly have survived.

[Stripe7]

The primary reason for the fancy sky crane approach to landing Curiosity on Mars is that the rocket exhaust for a rocket landing would have kicked up so much dirt and rocks that there was a chance of damaging it. If we ware landing people on Mars and send robots ahead to prep the area, they can build a landing pad and clear it of most debris before the landing of a heavy lander. That way the Mars lander just makes a rocket landing all the way down.

[Paladin]

GeoffS: Meh... I can't be bothered to go back and watch the videos over again, but I could swear one of the engineer guys or whatever the fuck they were interviewing about the landing said that some stage of it would have killed humans. *shrugs*

[The Unbound]

Not a word. They do talk about potentially killing the rover.

[Harper]

I think the phrase you are looking for is "A neck breaking 9 G's", which is what the rover was experiencing when the parachute opened.

[CommissarRezail]

I believe you can prevent kneck snaping if you brace the people in braces no?

[mlai]

Have we found Martian microbes yet? I need creationists to shut up already. Ppl here who aren't Americans can't understand our mental anguish.

[Jonny]

I don't know, religious dumbfuckery transcends borders. Only this morning I saw a Scottish guy on the news seriously stating that 1 man, 1 woman marriages were a "universal right" and that same sex marriages were trying to "change reality".

I think the phrase you are looking for is "A neck breaking 9 G's", which is what the rover was experiencing when the parachute opened.

Possibly if a normal parachute snapped open like that, but wouldn't astronauts in a landing capsule have all sorts of deceleration couches and support systems?

[CommissarRezail]

Have we found Martian microbes yet? I need creationists to shut up already. Ppl here who aren't Americans can't understand our mental anguish.

Tbh we already shut them up, it just they don't want to shut up. I mean really a whole universe of galaxies, and we are the only living things here, that's so doubtful that its funny.

[Carl]

@Geoffs: Ahh get where your coming from now. Agree that it helps complexity, TBH the concept i was thinking of looked something like this, (basic layout, i decided aginst a complex 3d object in wings):



Each section would in effect be itself modular as much as possible. That would make making the entire thing payload, or removing the payload, or whatever reletivlly simple. I never envisaged a fixed unchangeable design. Indeed the whole requirement of building it as much as possible out of existing pats modified slightly for the job dictates a very modular style to the whole thing.

I think you got the wrong end of the stick on the whole shielding thing though.

1. The trip time to mars (from Moe’s link), is approx 180 days, (give or take a small amount). Taking the average flare rate from wiki and the average dose rate from the nasa food document stripe linked that works out at around 900Gy at solar minimum. Which was enough to cause serious issues in the food paper studies. So even if mars is perfectly fine radiation wise you still need to shield it on the way out.

2. NASA's mars paper can't agree with itself on mars surface condition. One section claims more research is needed, another claims it's 50% of open space, (so still deadly in flare conditions), another fails to give a specific value but talks of flare conditions like their an issue. With the level of uncertainty and what we know about mars's magnetic field and atmosphere if we where to go right now i'd prefer to assume it is going to be an issue. (Remember we where talking about doing it right now, so nowhere near sufficient time to get our answers unless curiosity can provide them). This leads to the problem that with unshielded rovers you need to limit maximum distance to base to the minimum distance that can be covered on foot, (in case of a broken down rover), in the minimum time, (30 minutes, again from NASA's mars paper). That’s a not a great exploration range, (a few KM at the most), and duststorms could make it worse as if it's not safe to step out in one someone in a broken down rover caught in a flare in a dust storm is basically dead. Shielded rovers basically mean you can go anywhere you please within limits of supplies. So long as there's always a backup plan for getting them home through a flare in the event of a rover failure your fine, (but that’s what spare rovers are for ).


@Paladin: as others say it was probably that comment, the real issues are:

1. whats the instantaneous loading there, if it's high enough it could be difficult or impossible to get the astronauts through in one piece.

2. Even if it isn't the stated max G load is really on the high side by NASA standards, by quite a bit actually. Even if it's survivable that doesn’t means it's advisable.

@Stripe: The problem is you'd still have to get some very hefty robots down to do the clearing. That said it may not be such an issue. My guess is that a habitat wouldn't be so heavily affected by the dust cloud as a rover. They're probably worried about it gumming up curiosity’s workings and internals whereas a habitat would have to be sealed against. Also sticking the rockets on the top of the habitat should help reduce down blast from them. Very much an area of consideration though.

@Trinity: that was linked earlier in the thread, still a cool video though. Pity there isn't an equivalent for the Galileo decent probe from several years back. We threw that thing into Jupiter at 11 times the speed. To say we put the probe through hell isn't much of an exaggeration.

[CommissarRezail]

Why do the habitat have to be bubble tent form, why not conjoin the buildings with linking tubes, thus reducing the need to take off space suit , put on space suit, take space suit again? Every building would have a sanitation station anyway. I mean seem to save time to me, it would be a space station on the ground, just have it lock out a section if something would to happen.

[Croaxleigh]

Have we found Martian microbes yet? I need creationists to shut up already. Ppl here who aren't Americans can't understand our mental anguish.

They'll just say that the devil put them there.

[GeoffS]

I think you got the wrong end of the stick on the whole shielding thing though.

1. The trip time to mars (from Moe’s link), is approx 180 days, (give or take a small amount). Taking the average flare rate from wiki and the average dose rate from the nasa food document stripe linked that works out at around 900Gy at solar minimum. Which was enough to cause serious issues in the food paper studies. So even if mars is perfectly fine radiation wise you still need to shield it on the way out.

??? I was using your criteria for required shielding, so...

Let's try this once more... you claimed that the rovers and provisions would all require shielding during the outbound flight. I said that was the reason why you would send them on ahead on unmanned flights, to reduce the mass of shielding required for the manned mission. You then claimed that doing that would not reduce the shielding required on the manned flight. So, unless you plan on carrying shielding on the manned flight for cargo that is not there, you are the one with the wrong end of the stick.

@Paladin: as others say it was probably that comment, the real issues are:

1. whats the instantaneous loading there, if it's high enough it could be difficult or impossible to get the astronauts through in one piece.

2. Even if it isn't the stated max G load is really on the high side by NASA standards, by quite a bit actually. Even if it's survivable that doesn’t means it's advisable.

The instantaneous loading was 15g. That's what "peak deceleration" means.

And 15g is approximately 100% higher than the decelerations experienced during Apollo missions, that's true. But it's also true that it is only 25-50% more than military and aerobatic pilots routinely tolerate, and they tolerate it through the vertical axis of their body, not the more resilient horizontal axis. It is also some 300% less than the estimated human tolerance level for sustained eyeballs-in g levels, and some 650-700% less than the estimated eyeballs-out g suffered by some racing drivers who walked away uninjured from accidents.

So yeah, 15g is a long way short of any dangerous level for trained astronauts on properly designed crew seats.

[Nurizeko]

Have we found Martian microbes yet? I need creationists to shut up already. Ppl here who aren't Americans can't understand our mental anguish.

yes we can, thanks to America's need to vocalize their opinions quite loudly we hear it over the pond.

[mlai]

Who here would actually be shocked if, let's say, the big rover found indisputable Martian microbial fossils during its mission time?
I mean shocked at the existence of ET life. Not at the rover being lucky enough to strike gold.
I'd probably just say, "Well, it's about time. Cool, happened within my lifetime." To me it's a forgone conclusion, just a matter of when. I'd be as interested in the social reaction, as in the details of the fossil findings. It would be like reading a sci-fi trope that we finally caught up with.

[Langy]

I'd be shocked that there had been life on Mars, but not that there's ET life. I'm pretty positive ET life exists; the only real question is 'where is it,' and I'd be surprised if the answer was 'in the solar system' rather than 'in Alpha Centauri' (or wherever).

[Nurizeko]

Yeah it's pretty much a given somewhere out there, there is life, from microbial to intelligent.

It would be pretty cool to find proof of life on Mars though, not only would it be the first instance of extraterrestrial life, but to find a second instance of life within our solar system?

It would raise important questions, like should we revise how common we think life is out there, and other questions like was this an instance of panspermia? If so what seeded what?

[SpitfireMK461]

It needs to be noted that Curiosity does not have the instruments capable of detecting life that may be there, it only has instruments to detect environmental factors that would make life possible. To see any fossils, it would have to just accidentally stumble upon one on the surface and just happen to get a picture of it.

[Moe]

I'd be shocked that there had been life on Mars,

We may actually be from Mars. It's not inconceivable that asteroid impacts blasted fragments upwards with enough force to reach escape velocity and to later hit earth, seeding life here.

[CommissarRezail]

Yeah, considering we are finding meteors that came from mars.

[Carl]

@Geoffs: Sounds like I’ve confused you. Terrible communication on my part I guess. Let me go through each piece of shielding and why it's there:

1. Radiation Shelter: Basic manned flight requirement if your not shielding the whole thing, (though if enough is shielded for other reasons it may be of littlie difference weight wise to shield everything).

2. Food Supplies for the Trip out: Food degrades under radiation exposure and more research is required before we can solve this. As such at the current time we need to shield this food or it will be ruined by the time of arrival.

3. Food for Mars Surface: Since it has to cover the same environment as the food in point 2 just to get to mars it too requires shielding if we want it to be viable upon reaching Mars

4. Food for Return Trip. Same issues in point 3, if we want it edible by time it gets to mars, never mind gets back to earth it needs shielding.

5. The habitat will need a Radiation Shelter at the minimum. Though if the technical limitations can be overcome covering it with Martian Soil instead would be far more efficient weight wise as you don't need to ship the shielding out from earth.

6. If we want the landing group to be able to go more that 30 minutes walking distance from the base we need to provide shielding on the rovers.


Shipping stuff out all at once or separately doesn’t change what needs to be shielded or how much shielding each piece needs. (Though grouping it all together can invoke square cube law and make the shielding mass to payload mass better). Yes shipping most of the food on the cargo rocket with the lander and Rovers means you don't have to carry it on the manned craft. But you still have to move that mass to mars which means the same weight to LEO. That was what was being shot at when you came into the thread. People where pointing out how horrifically expensive it would be to lift all that stuff to LEO. (Minimum of 3 Million US Dollars per ton).

Does that clarify anything?

Also don't want to derail the thread but:


Raises his proverbial hat to Mr Armstrong.

[mlai]

Point taken that the Mars Lab rover isn't specifically designed to find fossils.
However, my point is that IMO life is so inevitable that if the planet had hospitable conditions for it for any appreciable length of time, it would have been there. To me it's as inevitable and routine a chemical process, as diamonds on a planet with carbon. The "bio-" prefix does not make it anything special or difficult.
I not only expect Mars to have it, I also expect it on Europa.

[Carl]

@Mlai: If it was that simple scientists would have re-done it in the lab. So far they haven't. Despite having a very good idea of the chemical soup they can't get them to combine into even the simplest life forms in the lab. There's clearly some extra environmental factor scientists haven't worked out yet, until we know what that is predictions about Mars or Europa are premature. Even titan is just a high probability spot, (and strictly because it has the right chemicals in complex sequences in huge abundance, if that extra environmental factor happens at all on titan it's probable it has life. if it doesn’t it never will have life unless we start it off. Until we can say for sure the Mars once possessed those conditions or Europa did, (and the radiation hasn’t fried them), we won’t be able to make a prediction.

[mlai]

They haven't had it yet because it takes a lot of time and a lot of room, "a lot" in human terms.