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#1 Re: Human missions » Mars One » 2012-07-31 14:20:37
but what when you're over 60 or 70 or even 80 years old and living on Mars?! It's certain that old people would be a huge drag for other people living there.
Not as much as you would think. The Mars colonists would be young (20s-30s) on arrival; meaning that when the first colonist hits 80 years of age, there would already be well over a hundred colonists (sending a group every two years), with the infrastructure to support them. It's still a stupid idea, and the very old would indeed be "dead weight".
#2 Re: Life support systems » Greenhouse - hydroponics vs soil » 2012-07-30 20:34:27
Then I said once the settlement is rich they could transport livestock; he didn't like that.
Win
Also, has there been any research done on Aquaponics systems for Mars? To over simplify it - it's like a hydroponics system, however under the plants (in the water) are fish (usually fast breeding fish like Tilapia). The fish waste serves as food for the plants while the plants generate oxygen and filter the water for the fish to survive and breathe. The fish just keep breeding, and once they "over populate" you just take the extra and eat them. Atleast then we wouldnt be stuck with just plants.
#3 Re: Life support systems » Greenhouse - hydroponics vs soil » 2012-07-30 13:37:48
I'm in agreement with Rob on using soil; the mineral water isn't necessarily reusable; new water would have to replace the old water over time. Seems to require extra resources that you may not have readily available.
On another note:
Quote from the second article down:
"Last year, PETA made headlines with a request to SpaceX to make their planned colonies on Mars all-vegan. Well, here’s a start: NASA is working on a vegan menu for their astronauts’ mission to the red planet in 2030."
All I have to say is... no. PETA should stay out of it. If you want to accelerate bone loss in lesser gravity, and rise the food production cost, just cut out meat.
#4 Re: Unmanned probes » Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT » 2012-07-27 12:40:29
No, it means that none of the instruments on MSL are capable of definitively identifying the presence of the type of microorganisms that we might expect to be in Gale crater if there is life on Mars. If there is life near the surface of Mars, MSL will very likely pick up chemical signatures of it. But in this hypothetical situation, the data would be inconclusive until we get a sample back or send an even more capable rover.
We know that - that answer doesn't have anything to do with the question (which was whether or not NASA would actually say anything); it was not at all a serious question, just idle speculation.
#5 Re: Unmanned probes » Official MSL / Curiosity Rover Thread | Aug 5, 2012 10:31 p.m. PT » 2012-07-26 23:05:37
Food for thought:
NASA has stated that MSL is seeking signs of life but that it's not a life detection mission. Does that mean that if NASA detects life on Mars it won't say anything since it is not looking for life to begin with? Sounds an awful lot like a repeat of Gil Levin's labelled release experiment from the Viking landers.
#6 Re: Human missions » Elon Musk: ticket to Mars for $500,000. » 2012-07-26 11:31:13
The only functioning economic model would constitute a "fully" closed system where one planet would not have to rely on the other; they would both still be supporting the growing in-space infrastructure, but Mars would have to not just be an outstretched hand of Earth. There is no Mars-Earth, only Mars* and Earth*, but as you VERY correctly say, it's far off. You could say that's the end goal, a Mars* and an Earth* if one is lost the other lives on; an act of charity indeed.
#7 Re: Human missions » Starlite » 2012-07-26 06:41:55
Here is Ward's blog:
http://mauricewardstarlite.blogspot.com/
Reading the posts (which end in 2009), you'll find some references to the tests carried out on Starlite. I also see that most of the comments (under the posts) are from this year, what was it this year that pushed people to find out more about it? I guess someone should tell all the commentors that Ward died in 2011 and that their questions and comments will go unanswered.
#8 Re: Human missions » Elon Musk: ticket to Mars for $500,000. » 2012-07-25 17:24:15
If you don't think production is part of an economy there is no hope for you.
Please show me where I said anything remotely close to that
However, this could be considered close to that - I don't think unpractical* types of production is part of a functioning economy.
a misguided game of Monopoly
Thats what you get for making him the banker.
Also - can I have Boardwalk?
#9 Re: Human missions » Starlite » 2012-07-25 14:29:05
After reading this thread, I assumed Starlite to be an elaborate hoax, so I decided to look a little bit deeper into its history and current status. Here's what I took away from it:
1. Maurice Ward - the inventor - was tremendously secretive of his "invention". He wouldn't let even a peice of it leave his sight, refusing to patent the product, or give potential buyers/investors a sample; out of fear that someone may reverse engineer it. He even went so far as to bringing his daughter with him when he went to a testing facility to grab up any flakes that may fall off the material in a hoover vac.
2. There are a fairly large number of well-documented tests by agencies of various governments and first-hand reports from numerous scientists and engineers attesting to Starlites validity; aparently it was able to withstand the force of 75 hiroshimas without breaking a sweat.
3. After 20 years of holding the product he was never able to meet the terms set down by the various interested parties (goverments, private companies ect.).
4. Ward was a very greedy man, always demanding greater and greater amounts for his "invention" - when agencies/buyers/investors met his price, he would just jump it up higher, leading the price up to unrealistic heights.
5. Maurice Ward died in 2011, all updates on Starlite "talks" stopped in 2009, his website even losing it's domain name. Ward NEVER wrote down the "recipe" for Starlite; it's not lost, because aparently his close family knows what it is now.
Ward always raved about how Starlite could save endless lives (obviosly it could if it could do what it claimed), it's my opinion that it was ethically wrong not to release it, as it would have gone to the betterment of mankind.
I'm still a bit skeptical of Starlite, and doubt it will ever see the light of day; after twenty years of Maurice Ward dragging it along without a single investor/buyer, there were questions as to whether or not he even posessed the skill to replicate it. (maby it's just a peice of material he got off an alien crash ooooooo 
)
The implications this material would have on the aerospace industry are profound. It would be great for a heat shield or blast barrier - I would also like to see if it could be used as radiation shielding.
#10 Re: Human missions » Elon Musk: ticket to Mars for $500,000. » 2012-07-25 09:51:38
I know, you might point out that some of the people going to the Sahara could sell other things to the kazoo makers. True. A little local service economy in the Sahara. Still, how do you pay the service economy if the kazoo makers aren't making any money? Poor little kazoo makers.
:'( No! not the kazoo makers!...
Maby they could start a kazoo band and sell tickets.
As soon as you arrive on Mars and fold out your PV panels, you have an economy.
Wrong
When people grapple with these ideas they often get confused between different concepts e.g. profit and revenue, ISRU utlitisation, trade surplus, serivces/manufacture, Mars GDP, subsidised and unsubsidised activities, money cost/energy cost/labour cost, Mars money and Earth money, per capita wealth, personal wealth, transit costs etc etc Really, you need to have a good grasp of all these different concepts.
Exactly
All your silly buzzwords aside, producing something does not make an economy. I'm sorry that my poor metaphor failed- i really can't make this any plainer.
But I digress, go make your kazoos- afterall, production = economy.
This is dead on with what I have been trying to say.
#11 Re: Human missions » Elon Musk: ticket to Mars for $500,000. » 2012-07-24 14:37:10
2500????
I second that
I very much doubt Space X will donate material free to agencies. They will have to pay one way or the other. It might not be a straight commercial transaction, it might be a donation to the Mars project.
I was only referring to the very first Mars mission - in post 16 - in reply to your post (post 15) which was also about the first Mars mission.
In terms of the first mission, it won't only be SpaceX; NASA will have very heavy involvement - SpaceX just provides the cheap efficient transportation (which NASA helps pay for a large fraction of the development cost), there is no doubt that NASA will have priority access to anything gathered on the martian surface, which means the sale of anything is most likely out of the question, as NASA doesn't have to make money - the taxpayer provides that for them. Also, I didn't say agencies, I said museums - again I am ONLY referring to the very first mission.
Obviously the initial development costs are not going to be recouped any time soon but what is important is if Mars can pay its way in terms of revenue thereafter. I think it can, ferrying scientists, space agency staff etc, putting experiments on Mars, returning regolith and meteorites (or maybe fossils! - imagine how much they will cost)...
I agree 100% with that, however for the taxpayer* to get a return on investment (not SpaceX - as they would be getting paid to "ferrying scientists, space agency staff etc, putting experiments on Mars, returning regolith and meteorites" primarily by Govt. (at first)) there would have to be some sort of Martian economy like clark stated, stimulating growth and putting money in the private sector via tourism and practical* exports.
- and no, an economy can't be soley based of a place "devoted to peace and science" as the Antarctic Treaty reads.
cheers!
#12 Re: Human missions » Elon Musk: ticket to Mars for $500,000. » 2012-07-24 11:47:19
We ought to take those words and put them up on a plaque in the first Mars base in 2022.
Second off, what you bring back will have a huge saleable value: regolith and meteorites will be selling for hundreds of dollars a gram. Not just that - but virtually any item from the first mission will have high value to science based museums around the world who again will be paying hundreds of dollars a gram. If a museum gets just an extra 10 people per day through the doors because of a Mars related exhibit they might raise over $30,000 a year. Over ten years that's an extra $300,000 revenue. That's why they can afford to splash out $100,000 on a little selection of objects that have been to or come from Mars.
If we used your Mars base in the next 10 years date,
The first Mars mission lander will not have the ability to bring back vast amounts of rock; what little rock will be brought back will be used for scientific study, and even if it was sold along with any "first mission tech" (unlikely; it seems more approprate / probable that after the "artifacts" are studied to the fullest extent, they'll be donated to the high profile museums of the participating countries (Smithsonian, State Hermitage ect.) )- the money made from the few peices brought back would be insignificant compared to the price of the actual launch - using only the first mission - you would never break even from the sale of Mars rocks, so you would never make any money. Very unlikely that you would get an absolute return on your investment right away (definitely not from the first), unless a better technology is used - which may not happen for the next 4 or 8 years due to political and economical contraints.
#13 Re: Human missions » Elon Musk: ticket to Mars for $500,000. » 2012-07-24 07:28:44
There is no money to be made on Mars, not in 10 years and not in 20 years. There have been a lot of fanciful ideas, but there is no economy that makes any sense.
Wish it were otherwise. The economy needed is 50+ years out.
Agreed; the companies that help us get there might make money on the taxpayers dole via NASA/Govt, but growing the right economy and generating anything from Mars itself is a long way off - especially if using "flag and footprint" schemes with chemical engines to get there.
SpaceX looking into other propulsion systems does show promise, and could change things (especially if it's something that can be refueled at Mars (water NTR) or doesn't need much fuel at all (SEP)).
#14 Re: Human missions » Comparative Mission Archetecture » 2012-07-22 18:09:44
[(by "tricks" I mean aerobrake, basing at high mars orbit instead of low, departing form a Lagrange point/HEO...).
Just wanted to give my take on aerobraking/aerocapture, what I think is important to remember, and how it relates to manned SEP missions.
So first, aerobraking: its been used on half a dozen (non re-entry) missions, slowing down the craft over the course of a few hundred passes. So far its been done via craft with solar panels, using the large panels as drag brakes. The craft is moved into an elliptical orbit, and using the atmospheric drag at the lowest altitude portion of its orbit, it lowers the altitude of the "high end" of its orbit.
The problem with aerobraking (as I see it) is that it takes a long time: velocities between 1-2km can take upwards of 50-100 days; this couldn't be shortened for a manned mission, because - keeping safety in mind - you have to assume the worst possible atmospheric density (there is currently no way to accurately predict the exact atmospheric density on mars at a certain date and time - at altitudes where the aerobraking would take place [100+ km], atmospheric density varies (2-3x on each pass). Spending this long in transit would expose you to un-needed radiation; and on the return trip to earth, while aerobraking here, you would be aerobraking (100+ passes) through the van-allen belts.
This brings me to my next point regarding the ability to aerocapture - Solar panels can't survive too large of a dynamic pressure (which is the pressure on the craft by the atmosphere) or heat flux (the heat (that is convected/radiated into the aerobraking/aerocapture craft) from the shockwave caused by hitting the gas particles at hypersonic velocities) too large (obviously) before seriously degrading the performance, or damaging the panels; putting aerocapture (only one pass through - as that is considered true aerocapture) with solar panels out of the question. The Mars Odyssey had an estimated heat flux (during some of the worst passes of the aerobraking) of 500 W/m^2; any higher, and it would have damaged the efficiency of the panels. However take this aerocapture point with a grain of salt, as solar panels have improved since 2001 (launch date of Odyssey - and how outdated the information I found on the subject is); not sure how durable (i'm sure its increased significantly) current solar panel tech is (hopefully someone can provide info on the state of current solar panels).
My first thought was that one could fold in the solar panels (no clue how it could be done) during aerobraking, saving the panels. However, the problem with this is that it increases the ballistic coefficient; meaning you have to go further down into the atmosphere, which in turn would create a higher heat flux, damaging the solar panels (at least those used on the Odyssey); facilitating the need for an apropriate heat shield.
Then there's the matter of whether or not spending the time aerobraking is even feasable for a manned mission (50+ days), as turn time on a mission can save alot of money - the more missions you can fly in the same time increases any given mass throughput. It's my opinion that aerocapture would be the best option (as Zubrin's Case for Mars suggests (note that's using chemical propulsion, so I guess it's not really relevant) - one pass through; which as of 2001, was impossible for solar panels. The only other option would be to flip the craft around and point the "exhaust" in the opposite direction - however being the low thrust system it is, you have to wonder how much time it would add / how viable even that is.
On a second note:
GW's mission also provide 1g artificial gravity to crew during transit I'm a bit doubtful on this as first we don't know what the minimum therapeutic g is.
The point GW made was that we don't know what the minimum therapeutic g is (like you said), so to be safe and have 100% certainty that we could without a doubt "hold up" during the long flight, just have the craft provide a full 1g of gravity.
My personal preference is for a centrifuge inside of an inflatable
Something like an inflatable ring sounds promising - see Natilus-x [ http://en.wikipedia.org/wiki/Nautilus-X ]
The more recent research on RPM's humans can withstand that I posted over in the "landing on Mars" thread would directly relate to an inflatable ring. Reposted below.
http://www.ncbi.nlm.nih.gov/pubmed/1102 … t=Abstract
Small excerpt from the abstract:
"Early studies suggested that 3 rpm might be the upper limit because movement control and orientation were disrupted at higher velocities and motion sickness and chronic fatigue were persistent problems. Recent studies, however, are showing that, if the terminal velocity is achieved over a series of gradual steps and many body movements are made at each dwell velocity, then full adaptation of head, arm, and leg movements is possible. Rotation rates as high as 7.5-10 rpm are likely feasible. "
And Finally:
I apologize for being so objective Impaler - Common sence can tell you that a very well designed fully reusable manned SEP vehicle could be the cheapest way to go; it's also an option that will never go away regardless how the political winds shift, because it is the (arguably)safest - without requiring any mega-infrastructure (microwave/laser sail ect). My only question is how feasible it is.
#15 Re: Martian Politics and Economy » Creating the Cis-Lunar economy » 2012-07-20 15:53:37
I'm trying to teach you how the worldwide economic model of price determination works, i'm not making any assumptions, just trying to get you more informed.
I'm not making any predictions or assumptions on who will buy what. I'm also not setting concrete prices (especially ones that seem too optimistic)
If your argument were true, the huge increase in meteorite finds in recent decades (thanks to commercialisation of searching and improved technology) would have led to a collapse in prices, but there is no evidence of that. On the contrary interest in private collection of meteorites, increased per capita wealth, more opportunities to trade and the huge growth in higher education have cancelled the effects of increased supply. What is your explanation for the healthy state of the meteorite market on Earth?
Repeatedly asserting something is not the same as arguing it.
You're right, I feel like i'm beating a dead horse; Mark and I have reinforced how supply and demand works via our previous postings.
There is no reason to suppose that demand for lunar regolith will continue indefinitely at high levels.
Yup
#16 Re: Martian Politics and Economy » Creating the Cis-Lunar economy » 2012-07-20 09:06:54
That market would implode or become inaccessible the moment you bring back a sample with the promise of more on the way. Meterites are fetch high prices because they are a rare, naturally limited product. *cut* Either the entire collectors market will disappear, or more likely it will be come like diamonds: only 'natural' meteorites will continue to have value, and rigorous documentation of the fall is required to sell one.
Agreed
Meteorites are rare on Earth and will be rare on the Moon, but more accessible. Also, ordinary regolith will have value.
On the Moon meteorites of types never found on Earth will be found.
One very rare meteorite may be worth million of dollars though weighing only a kg or so.
The regolith will have value, but as stated before, "the market would implode or become inaccessible the moment you bring back a sample with the promise of more on the way" - especially when you're bringing atleast 20 tonnes yearly (I stand by this view unless that 20 tonnes number that was put down is fixed - it's the only thing that's making you wrong)
There's too many assumptions here (hypothetical meteorites that weigh only a kg and are worth millions); you can't fix prices.
#17 Re: Human missions » Landing on Mars » 2012-07-19 19:41:37
I accomplished my purpose of showing how easy it can be to incorporate 1 full gee of artificial spin gravity.
First, I went over, and read through your mission design - very impressive; interested in seeing your lander designs (maby then we can keep the thread on-topic), any questions - please ask.
Second; I would have posted this as a reply on your site, however - was on my phone and didn't have time to create a typepad (or any of the other accounts needed to post) - i'll do that later when i'm at work and feeling lazy. (I think you'll find this of interest)
All you need is a radius exceeding 56 m from the center of gravity of a long, slender orbit transport to the habitat at one end. The gee level achievable this way is 1 full gee at 56 m for a “fuzzy” maximum rotation rate speed limit of 4 rpm. Longer radii allow lower, even more tolerable, rotation speeds.
The research stating that anything over 3 RPM is intolerable for humans (some even getting sick at 3 RPM) is outdated (as i'm sure you know) - (in the trials, subjects went from 0 RPM to 3 RPM immediately), however, more recent research suggests that rotation rates up to 10 RPM are possible, with no adverse effects- As long as the RPMs are incrementally increased, to allow adequate adaptation.
http://www.ncbi.nlm.nih.gov/pubmed/1102 … t=Abstract
Small excerpt from the abstract:
"Early studies suggested that 3 rpm might be the upper limit because movement control and orientation were disrupted at higher velocities and motion sickness and chronic fatigue were persistent problems. Recent studies, however, are showing that, if the terminal velocity is achieved over a series of gradual steps and many body movements are made at each dwell velocity, then full adaptation of head, arm, and leg movements is possible. Rotation rates as high as 7.5-10 rpm are likely feasible. "
#18 Re: Human missions » Landing on Mars » 2012-07-18 08:48:31
GW I recommend you start a new thread on your NTR based mission profile as it's not really on topic and it is getting some interest as you pointed out.
Agreed - this thread is supposed to be specifically addressing how to land - that being said, I find discussing GW's mission profile much more interesting.
I might make a counter proposal with SEP which is think blows NTR out of the water on both performance and feasibility grounds but I'll need to get your exact figures to make an apples-2-apples comparison.
For a manned Mars mission? A manned SEP ship wouldn't be feasible for anything further out in the solar system, and in the inner solar system it would take too long to get anywhere; not to mention how heavy it would be - especially with all the extra radiation protection equipment it would have to have from the multi-day soak it would need to take in the Van Allen Belts, before it gained enough speed to break out of orbit.
Edit: didn't see there was another thread on SEP - however I would like to see some comparison stats addressing the concerns I mentioned, and how it compares to other propulsion methods. I want numbers!
I used the old NERVA data because that's the only design that ever got any significant testing, to the best of my knowledge.
The pebble bed NTR project (Project Timberwind) ran for 6-8 years (mid 1980's - early 1990's). Various prototypes were under construction (that's why I used that design).
DoE nuclear/lh2 rocket engine. 2451.6 kN. Development ended 1992. Isp=1000s. Used on Timberwind launch vehicle.
Thrust (sl): 1,912.300 kN (429,902 lbf). Thrust (sl): 195,000 kgf. Engine: 8,300 kg (18,200 lb). Thrust to Weight Ratio: 30.1204819277108.
Status: Development ended 1992.
Unfuelled mass: 8,300 kg (18,200 lb).
Diameter: 8.70 m (28.50 ft).
Thrust: 2,451.60 kN (551,142 lbf).
Specific impulse: 1,000 s.
Specific impulse sea level: 780 s.
Burn time: 493 s.
You are correct though in that unlike NERVA, it wasn't flight ready.
Also...
I used 8.5 months 1-way, and a 27 month round trip to estimate supplies. I was using about 15 kg food+water+makeup O2 per person per day, but that's just a wild guess.
This may help you with estimating consumables:
http://www.5596.org/cgi-bin/mission.php
#19 Re: Unmanned probes » Great panorama of Mars » 2012-07-17 19:26:45
Let's go...
I'll race ya
- this gets me excited for Curiosity, awesome view.
#20 Re: Life support systems » Livestock » 2012-07-17 19:19:00
Thought this could be relevant:
http://www.youtube.com/watch?v=O9XtK6R1QAk
Mammals don't seem to take to zero g very well ^ watch above video, so there would have to be serious thought put into hibernation/ stasis - or better yet just spin the ship and produce artificial gravity (which is the most likely outcome).
louis also brings up an excellent point with the chickens - infection and hygiene in a closed life support system would be an issue
he also brings up another great point in using small mammals - mammals with a high reproduction rate - rabbits, guinea pig ect. are more likely to be the first livestock on mars (very minimal space needed, very easy to breed, and in the case of guinea pig - tastes like chicken (don't take my word for that; never tried it))
#21 Re: Martian Politics and Economy » Creating the Cis-Lunar economy » 2012-07-17 18:36:34
A simple google search will bring up the article about the Atlas Summit where the exact quote is mentioned. - and yes this quote is referring to current tech, but this hypothetical current lunar colony was also shown to be "near term"
http://shortformblog.com/post/266330740 … sm-profits
http://www.motherjones.com/mojo/2012/07 … usk-spacex
Don't forget that the price of lunar rock is affected by it's availability. The prices can't be set. Dumping a lot of it into the market (in this case 20 tonnes a year - Terraformer's number not mine) would without a question de-value it over the years, even to the point where it's lower then the return req. The "rare lunar regolith" you mentioned would no longer be rare.
However, dispite all this you are right that "lunar jewelry" could be worth alot, and worth the costs like you stated it would be (with regulation): the issue is dumping 20 tonnes a year into the economy, which is not the way to do it.
Then there is lunar tourism - which I think will be the biggest money spinner of all.
In agreement 100% with that ^^^^
- If you want a source for planetary resources stating that they are focusing on providing resources for in-space infrastructure, rather than bringing it back to earth, I can provide a video link.
- Also, mining the moon for water is profitable - that's the main thing planetary resources is mining for anyways. - the idea that was put forward saying it wouldn't be is another indicator that this hypothetical base/colony is very very near term - if that's the case I disagree with the launch + return costs.
#22 Re: Martian Politics and Economy » Creating the Cis-Lunar economy » 2012-07-17 13:29:22
Gathering moon rocks and sending them back to make jewlry would not be profitable at all. Quoting SpaceX's Steve Davis "If the entire moon was made of solid gold, it would be unprofitable for any company on Earth to go mine it and bring it back, if the entire moon was made of heroin, it would still be unprofitable." The cost alone of the fuel + lander (every time the lander spashes down / lands on the earth, it will have to be completely stripped down and refurbished after taking the extreme thermal stresses) to get them back to earth is much greater (using your optimistic return cost) than the moon rocks (100/g - your price, which would significantly drop if you tried introducing 20 tonnes/year of the stuff into the world economy) are even worth. This is why planetary resources won't be sending anything back to Earth (as they said), instead they will be catering to the growing space infrastructure.
#23 Re: Human missions » Landing on Mars » 2012-07-17 08:11:52
I do think I need to re-run those calculations. I think I messed up reconciling available volume with contained mass for the LH2 propellant tanks. The concept is still "in the ballpark", though.
GW
The 20 ton NERVA module you stated factors in the idea that it would have to be a bimodal NTR correct? So when it's not on a burn, it's also generating power (also keeping the NTR warm so it can be burned at any time, without having to start up a cold reactor to get moving - incase an emergency manuever is required ect.) I also think the weight can be decreased and lsp increased by taking up a particle bed design for the NTR (if we are intent on using proven, previously tested designs) - bringing the lsp up to around 1000 with a thrust:weight ratio of 30:1; this also allows the particle core to be dumped after full use, reducing the shielding required. Also, pebble bed reactors are inherently safe, active safety systems aren't needed as there is no active piping in the core (this would the case for a pebble/particle bed NTR (the core would spin, pushing the pebble-like fuel to the edges, allowing a clear path for the hydrogen)), and the cooling system uses a fireproof inert gas, making it impossible to explode (this would also help make a case for on-earth testing)- I imagine an active cooling system for the pebble-bed NTR's (even though a cooling system isn't really needed for a NTR as all waste heat is carried away - not the case for bimodal NTR, which would benefit from one), could be employed throughout the length of the ship, which could double as solar radiation protection... then again heat radiators would still be needed for a bimodal NTR to take away any excess heat (they wouldnt have to be that big) - (right? - they are needed anyways since humans generate alot of heat) adding to the weight - the particle bed NTR itself would be much lighter than the NERVA, so adding the heat radiators could possibly cancel it out. Then again you have to wonder the effect aerocapture has on heat radiators, and what interplanetary debris has on them - which brings us to the next point:
Bigelow inflatables have a lot of armor because there's so much junk in low Earth orbit. Does anyone know the danger in interplanetary space? I bet its one or two orders of magnitude lower than in LEO. It may be that it'd mass less to send two light inflatables than one armored one, and switch if there's a puncture.
There are alot of interplantary dust particles, from comets and asteriod collisions that could possibly be a problem, however I imagine it wouldn't be as bad as it is around earth (although interplanetary particles would be moving much faster than the space junk around earth). So I second this question "Does anyone know the danger in interplanetary space?"
Bigelows were designed only to function while in a planets magnetic field, so additional shielding is needed anyways to protect it from the added thermal stress of interplanetary flight, and cosmic radiation - however as you said they do have a lot of armor - much more protected than the ISS, still don't think it will be quite enough though; yet I could be wrong.
#24 Re: Human missions » Landing on Mars » 2012-07-16 22:18:48
Ah thats what you meant - makes a lot more since now, and correct on all accounts.
It's also a very good point - in the case with inflatable hab + storage modules, you wouldn't need all 98 launches that GW suggested; making it somewhat cheaper. If inflatable heat shield tech is perfected, then could aerocapture be used?(in conjunction with a rocket burn) as aerobraking at mars isn't efficient.
#25 Re: Human missions » Landing on Mars » 2012-07-16 21:50:30
What about the use of inflatables?
In terms of what exactly? If you mean inflatables inorder to land - currently, inflatable landing systems employ the approach of surrounding the lander with non-vented airbags where the lander bounces on impact a number of times until the impact energy is dissipated (this obviously wouldn't work for a human landing), and as i'm sure you know, there is also current testing on inflatable heat shields - NASA is launching one for testing on July 21st (I'm going to watch the launch as it's only 30mins away). Or do you mean inflating some sort of balloon structure while in the upper atmosphere using onboard hydrogen, then gradually releasing it to land? Does anyone know how much propellant it would take to inflate such a thing? You could take it a step forward and inflate yourself a large aerostat for more manueverability. Either way - it could be cost effective for landing depending on how it's set up, however it needs to be completely inflated and it would have to me massive - a hot air balloon sctucture would not work - but if it takes just as much hydrogen to inflate such a thing in the upper atmosphere as a NERVA would take to land, then I don't think it would be worth it because you would still sacrafice control with any inflatable (on mars anyways), unless we come up with a suitable air breathing propulsion system for it.
In terms of taking off theres still alot of problems asociated with getting it from its max altitude into orbit (rockets?), and then theres whether or not it would be able to carry a human payload up and dock with the "mother ship".