http://www.scientificamerican.com/article.cfm?id=this-way-to-mars&page=5
so by the time we land on Mars we may have already solved most of these problems with lunar landings.
manned Mission to Mars discussion
- Thread starter jefferiestubes8
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http://www.scientificamerican.com/article.cfm?id=this-way-to-mars&page=5
so by the time we land on Mars we may have already solved most of these problems with lunar landings.
Good heavens, a "private" manned mission to Mars is now being floated for an "older/married" i.e. nonfertile couple.
http://lightyears.blogs.cnn.com/201...d-2-humans-on-mars-mission-in-2018/?hpt=hp_t1
Why do I get the idea that this might just be a scam?
http://lightyears.blogs.cnn.com/201...d-2-humans-on-mars-mission-in-2018/?hpt=hp_t1
Why do I get the idea that this might just be a scam?
http://io9.com/5987372/everything-we-know-about-dennis-titos-2018-human-mission-to-mars
At first I had this down as total madness, I'm prepared to revise my estimate to just "pretty crazy".
They mention inflatable modules that would provide extra living space. Also since it's just a flyby that removes a lot of things that can go wrong with landings and orbital insertions.
Still, we have no experience at all of long term missions that far beyond the safety of earth. If it were to go ahead I would not put good odds on the crew making it back alive.
At first I had this down as total madness, I'm prepared to revise my estimate to just "pretty crazy".
They mention inflatable modules that would provide extra living space. Also since it's just a flyby that removes a lot of things that can go wrong with landings and orbital insertions.
Still, we have no experience at all of long term missions that far beyond the safety of earth. If it were to go ahead I would not put good odds on the crew making it back alive.
IIRC, they also discuss the heat of earth re-entry from such a high speed descent is greater than any current heat shield protection would allow.
I just don't see a "billion dollars" being enough to pay for such a mssion, much less how one would solicit the funding for said mission. That's a lot of "10 dollar" donations, and something wayyyy out of the "Kickstarter.com" experience.
Perhaps "scam" was too strong a word, but I can see a lot of money being spent on prep work/studies to somebody before they decide... "gee, it IS too expensive for us to do."
I just don't see a "billion dollars" being enough to pay for such a mssion, much less how one would solicit the funding for said mission. That's a lot of "10 dollar" donations, and something wayyyy out of the "Kickstarter.com" experience.
Perhaps "scam" was too strong a word, but I can see a lot of money being spent on prep work/studies to somebody before they decide... "gee, it IS too expensive for us to do."
Dragon's heat shield is already designed for Mars re-entry. Using PICA or PICA-X it's not much of a problem.
The entry velocity would be between 15 and 21 km/sec, versus a lunar entry velocity of 11 km/sec or a low-orbit entry velocity of 7.9 km/sec, and the re-entry window is easy to hit even with mid-1960's technology.
1966 NASA report on re-entry from Mars
That makes Dragon look even more like Soyuz--its where that spherical living compartment usually is (except for the Zond circumlunar versions)
If anything, the Mars fly-by dragon looks a bit like the Soyuz 7K-LOK http://www.astronautix.com/craft/soy7klok.htm
The inflatable nose might just be a good idea. There is supposed to be a massive 50 km comet that looks to either hit or just miss Mars in 2014: http://up-ship.com/blog/?p=19134
http://www.economist.com/blogs/babbage/2013/02/comet-headed-mars
So that mini-transhab might just see some use as a meteor bumper.
I don't like the idea of a married couple, in case one gets sick, it is a live tragedy (light delay aside).
I would volunteer for a flyby mission. I have no dependents, so if I croak, it's no big deal. More resources for one--no fights, and I live alone anyway. Moreover, even if I did break down, I would ask mission control not to report it, so as to not cast doubt on manned spaceflight, and suffer in silence if worse comes to worst. Once I pass the point of no return, and there is a leak, I might hope to set the capsule down on the surface as has been contemplated, so I might die on the surface after gathering some rocks. If I crash because the Dragon wasn't prepped to land on Mars, that's fine. If I continue to loop through space, that's fine.
But you don't want a Harlequin romance turning to divorce or a worse tragedy.
We already saw Baumgartner put spaceflight down after his balloon jump.
That I would never do, even if I knew I wouldn't be coming home.
Stoicism and fatalism are required for such a stunt.
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Huh?
The "blogger" suggested it was still quite a problem.
[/QUOTE]Besides life support for the crew, one of the biggest challenges would be the return into the Earth's atmosphere. Heat shielding for a high speed re-entry hasn’t been tested. NASA isn’t even testing its new system on the Orion spacecraft until next year at the earliest. Orion is in development to take astronauts back to the moon and on to Mars.[/QUOTE]
Oh, PICA heat shielding on the Stardust sample mission worked fine at a re-entry velocity of 12.6 km/sec and a heating rate of 1,200 W/cm^2. The Dragon's PICA-X heatshield is already 3 inches think and only about a half-inch burns off during re-entry from orbit, so they have a huge margin. Re-entry from Mars might get into the 3,500 W/cm^2 range, and PICA hasn't been experimentally tested at those heating rates, but it's not predicted to be a serious issue. They would have to conduct such testing, though, and might have to switch to a different material. If need be, they can go up to 10 inches thick with the PICA shield.
Probably the main issue is that they'll want to very accurately model the aero-thermodynamics so they don't waste mass on an unnecessarily thick shield. Getting a heat-shield to survive a re-entry is obviously possible since meteors make even more extreme entries with an accidental shield. Their existence made Robert Goddard suggest an ablator back in the 1920's.
Besides, heat shield design is fun.
Probably the main issue is that they'll want to very accurately model the aero-thermodynamics so they don't waste mass on an unnecessarily thick shield. Getting a heat-shield to survive a re-entry is obviously possible since meteors make even more extreme entries with an accidental shield. Their existence made Robert Goddard suggest an ablator back in the 1920's.
Besides, heat shield design is fun.
Oh, PICA heat shielding on the Stardust sample mission worked fine at a re-entry velocity of 12.6 km/sec and a heating rate of 1,200 W/cm^2. The Dragon's PICA-X heatshield is already 3 inches think and only about a half-inch burns off during re-entry from orbit, so they have a huge margin. Re-entry from Mars might get into the 3,500 W/cm^2 range, and PICA hasn't been experimentally tested at those heating rates, but it's not predicted to be a serious issue. They would have to conduct such testing, though, and might have to switch to a different material. If need be, they can go up to 10 inches thick with the PICA shield.
Probably the main issue is that they'll want to very accurately model the aero-thermodynamics so they don't waste mass on an unnecessarily thick shield. Getting a heat-shield to survive a re-entry is obviously possible since meteors make even more extreme entries with an accidental shield. Their existence made Robert Goddard suggest an ablator back in the 1920's.
Besides, heat shield design is fun.
Hey, ya gotta find your fun where-ever you can.
W/cm square... watts?
Fairly useless except as a technology demonstrator, but it at least does give something for appearance to human beings, and we need that sort of thing. Eventually we'll mark any landing as a milestone towards colonization, but I doubt the first landing will reveal anything the landers haven't already shown us.
RAMA
RAMA
Hey, ya gotta find your fun where-ever you can.
W/cm square... watts?
Yep! So if your heat shield has to survive a peak heating rate of 1,300 Watts/cm^2, it's like aiming a 1,300 Watt hair dryer on each square centimeter of the heat shield surface.
What they generally do for testing is to hit the heat shield material with a plasma arc, sort of like what you'd find in a welding shop. I'm not sure how good a job a propane torch would do, but it would be a similar testing concept.
The other parameter is the total heat soak, which is in Joules (a Joule is one Watt for one second) per square centimeter. Your shield might survive a brief period at 1,300 Watts/cm^2 but erode away before re-entry was completed, so you have to check the total energy the shield can take. For example, one minute (60 seconds) at 1,000 W/cm^2 would be 60,000 Joules/cm^2. In older units common to NASA's early days, they'd have expressed this in BTU's/square inch.
So to test a heat shield material, you take a block of it and heat it with a torch, starting the burner on low, then cranking it up to eleven, then slowly backing off to simmer. As the heat soaks into the shield material the shield could start to melt internally or it might crack, both of which would be very bad.
For some applications you might just use a heatsink material, like a thick titanium skin which will heat up as you re-enter. The test there would be to hit it with the simulating heating it would experience and make sure its temperature never exceeds your design limits. For the Shuttle, the idea was that the tiles should never let the aluminum skin of the shuttle get too hot.
There are lots of links online that show pictures from testing the Apollo heat shield, where you can see the ablation and burning in various test blocks they tried out.
^^Ahhh, now I see why you find heat shields fun. You get to play with welding torches! ;-)
Thanks for the tutorial.
Thanks for the tutorial.
