Author Topic: MCT Beyond Mars  (Read 25250 times)

Offline LM13

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MCT Beyond Mars
« on: 11/01/2014 05:18 pm »
I hope this is the right place to put this.

Assuming for a moment that MCT is delivered as-advertised:  The figures for MCT performance commonly suggested on this site, derived from statements Musk has made about about 80-100 people per flight for a ~100 day flight, suggest capabilities for the MCT that could make it useful for even more exotic destinations than Mars.  The Trajectory Browser tool at the Ames Research Center website says that there are a few opportunities for such a flight, in the 2030s, that have delta-v requirements as low as 6.5 km/s, so let us say that's the delta-v capability of the MCT.  And the life-support system or consumables would, by the estimates given, give 10,000 person-days of capability. 

6.5 km/s is enough to reach Jupiter orbit and return to Earth, according to the same trajectory database  Some round-trips also come in at under 8 years, though the ones after 2020 come in at 12 years.  That 10,000 person-day figure suggests, then, that 2 or 3 astronauts can make the trip to Jupiter and back using an MCT (though human factors and radiation concerns, I suppose, would make this undesirable).  Pre-positioning consumables (particularly propellant) in Jupiter orbit, or sending multiple MCTs docked together, would increase crew capacity and margins. 

Saturn missions come in at below 7 km/s, but are both much longer and have much shorter stay-times. 

If MCTs are rolling off a production line, is it inconceivable that two or three vehicles might be rented out for such a mission?

I suppose this might be a silly suggestion, but if MCT does come into existence and does work as advertised, can it form the foundation for a whole new human exploration capability for the outer solar system? 

Or would things like radiation hazards or psychological factors make this a non-starter?

Offline xanmarus

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Re: MCT Beyond Mars
« Reply #1 on: 11/01/2014 06:01 pm »
What's the point of manned missions to gas giants?

Offline docmordrid

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Re: MCT Beyond Mars
« Reply #2 on: 11/01/2014 07:53 pm »
More important, how do you handle the radiation environments which are brutal.
« Last Edit: 11/01/2014 07:59 pm by docmordrid »
DM

Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #3 on: 11/01/2014 08:40 pm »
More important, how do you handle the radiation environments which are brutal.
Easier to shield than GCR is. But anyway, just visit Callisto instead which has far lower radiation levels.
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Offline Lars-J

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MCT Beyond Mars
« Reply #4 on: 11/01/2014 09:47 pm »
What's the point of manned missions to gas giants?

Not the gas giants themselves, but Europa, Ganymede and Callisto. Besides Mars, the most suitable places to be in the solar system - and with a lot more resources than Mars. The natural next step if a Mars colony is successful.
« Last Edit: 11/01/2014 09:48 pm by Lars-J »

Offline Clyde

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Re: MCT Beyond Mars
« Reply #5 on: 11/01/2014 09:54 pm »
I wanted to suggest this capacity could enable setting up some robotised mining operations in the main asteroid belt, (eg. propellants production  for in space usages).

Nevertheless http://trajbrowser.arc.nasa.gov says that the DeltaV to eg. Vesta is higher than to Jupiter which somehow suprises me. Is it due to the fact that you need to "slow" down when arriving at Vesta, while there is no such need when caught into Jupiter's potential well?


The exact search criteria I used:
http://tinyurl.com/klrdjnv

« Last Edit: 11/02/2014 03:04 pm by Chris Bergin »

Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #6 on: 11/01/2014 10:09 pm »
Ceres is where we should go after Mars. Much closer, could be really interesting.
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Offline sanman

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Re: MCT Beyond Mars
« Reply #7 on: 11/02/2014 04:21 am »
But do these have to be manned missions? Even if they're the next-best destinations after Mars, the timeline for manned missions sounds like it would be long after MCT is obsolete.

Offline NovaSilisko

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Re: MCT Beyond Mars
« Reply #8 on: 11/02/2014 04:49 am »
Nevertheless http://trajbrowser.arc.nasa.gov says that the DeltaV to eg. Vesta is higher than to Jupiter which somehow suprises me. Is it due to the fact that you need to "slow" down when arriving at Vesta, while there is no such need when caught into Jupiter's potential well?

I believe it's because Vesta has a much higher orbital inclination than Jupiter - 7.1 degrees versus Jupiter's 1.3.

Offline Eerie

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Re: MCT Beyond Mars
« Reply #9 on: 11/02/2014 06:52 am »
Ceres is where we should go after Mars. Much closer, could be really interesting.

Ceres is where we should go BEFORE Mars.

I can't wait for Dawn to arrive, oncee people see some high-definition images there is going to be a lot more interest.
« Last Edit: 11/02/2014 06:57 am by Eerie »

Offline llanitedave

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Re: MCT Beyond Mars
« Reply #10 on: 11/02/2014 05:03 pm »
What's the point of manned missions to gas giants?

Not the gas giants themselves, but Europa, Ganymede and Callisto. Besides Mars, the most suitable places to be in the solar system - and with a lot more resources than Mars. The natural next step if a Mars colony is successful.

The next natural steps are asteroids and comets.  And those are far more likely to have exploitable resources.
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Offline PerW

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Re: MCT Beyond Mars
« Reply #11 on: 11/02/2014 05:51 pm »
Why not Venus? I have seen intresting suggestions for in air floating hab

Offline inventodoc

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Re: MCT Beyond Mars
« Reply #12 on: 11/02/2014 06:08 pm »
What's the point of manned missions to gas giants?

Exploration of their moons.  Some of those could be excellent human habitats.

Offline inventodoc

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Re: MCT Beyond Mars
« Reply #13 on: 11/02/2014 06:13 pm »
This thread raises a very interesting question.  When you think about it, the requirements to go to Mars are actually much higher than going to various moons and minor planets such as Ceres.   Mars has reentry, resource extraction and launching out of a significant gravity well.   A high-mass deep space exploration ship can do a LOT to change the equation regarding other destinations in the solar system.. 

I'm not sure we are up to solving all the problems of dealing with Mars so soon.  I do think that getting a significant presence on the Moon and exploring asteroids makes more sense to do first.   (I'm not against going to Mars. Mars is cool).

I'm not sure if MCT will ever be built.  If it is, it will represent a new era of human exploration and diaspora throughout the solar system.
« Last Edit: 11/02/2014 06:13 pm by inventodoc »

Offline jsgirald

Re: MCT Beyond Mars
« Reply #14 on: 11/02/2014 06:39 pm »
Why not Venus? I have seen intresting suggestions for in air floating hab

Well, you beat me to it!

The proposed BFR + second stage should be capable of launching a couple of Ba330 or a single [conceptual] Ba2100 to low Venus orbit. After that, a couple of MCTs might handle the logistics of such orbital station.

Not sure if it makes sense for a manned program though, unless it is used for some sort of buoyant station in the atmosphere. I've  seen some speculation on the feasibility of tethering a habitat 80 km above Venus surface, but it sounds far fetched to me. Even more than a Mars colony, in fact.
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Offline francesco nicoli

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Re: MCT Beyond Mars
« Reply #15 on: 11/02/2014 06:56 pm »
What's the point of manned missions to gas giants?

Not the gas giants themselves, but Europa, Ganymede and Callisto. Besides Mars, the most suitable places to be in the solar system - and with a lot more resources than Mars. The natural next step if a Mars colony is successful.

say nothing :D :D

Offline Hyperion5

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Re: MCT Beyond Mars
« Reply #16 on: 11/07/2014 01:20 am »
More important, how do you handle the radiation environments which are brutal.
Easier to shield than GCR is. But anyway, just visit Callisto instead which has far lower radiation levels.

Callisto?  Are you serious? ;)  There's an obvious candidate that everyone in their rush to Europa (too much radiation from Jupiter) and Callisto (too little atmosphere to protect against GCRs) seems to have missed.  The MCT as we know it relies on methane-oxygen propulsion.  With a propellant mixture like that, if you're going to the Gas Giants, why would you ever go anywhere besides Titan?  It's got it all: rivers, seas and lakes full of methane & ethane just waiting for you to "gas up and go" (heck, it even rains methane!), a thick nitrogen-rich atmosphere able to protect against the worst radiation, a thick, icy crust from which you can make water and oxygen, more gravity than Callisto & Europa, and thanks to all that atmosphere landing on it is pretty easy.  Oh sure, it'd take longer to get there and require more delta-v to get off than Callisto or Europa, but Titan is damn near unbeatable when it comes to having the conditions to support a colony. 

Of course it's plenty cold on Titan, but with all that atmosphere, it's the only place in the solar system where you could power the colony via wind energy.  Solar energy is not going to be ideal that far out, but at least on Titan you can get by on something other than nuclear reactors.  You'd need to insulate the MCT pretty good against that thick, cold atmosphere, but we've got experience doing that down in Antarctica.  To be fair though, Titan is still colder on average than even the Antarctic, even near the equator. 

Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #17 on: 11/07/2014 01:31 am »
Why? Because a round-trip to Saturn is much further (more than twice as far from Earth) as Jupiter. And a trip to Jupiter is already a long trip. That's why you'd probably go to Callisto before Titan.
« Last Edit: 11/07/2014 01:33 am by Robotbeat »
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Offline RonM

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Re: MCT Beyond Mars
« Reply #18 on: 11/07/2014 01:34 am »
Why not Venus? I have seen intresting suggestions for in air floating hab

Well, you beat me to it!

The proposed BFR + second stage should be capable of launching a couple of Ba330 or a single [conceptual] Ba2100 to low Venus orbit. After that, a couple of MCTs might handle the logistics of such orbital station.

Not sure if it makes sense for a manned program though, unless it is used for some sort of buoyant station in the atmosphere. I've  seen some speculation on the feasibility of tethering a habitat 80 km above Venus surface, but it sounds far fetched to me. Even more than a Mars colony, in fact.

There is an important reason for a manned program at Venus, operating robotic landers or rovers. The surface conditions on Venus are so sever a lander would be lucky to last over an hour. That requires real-time operations. Can't do that from Earth, but you can from Venus orbit.

Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #19 on: 11/07/2014 01:38 am »
You can build long-duration landers and rovers. It's just really hard.

There are two ways: cool the interior where the brains are or just build out of high-temp electronics. I don't think we'll ever bother sending a Venus rover that isn't built using one of those two options.
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Offline Hyperion5

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Re: MCT Beyond Mars
« Reply #20 on: 11/07/2014 02:18 am »
Why? Because a round-trip to Saturn is much further (more than twice as far from Earth) as Jupiter. And a trip to Jupiter is already a long trip. That's why you'd probably go to Callisto before Titan.

Distance is of course an issue with Titan, as is the relative dearth of metals on its surface relative to Callisto.  However it still has the rather massive advantage of possessing rivers, lakes and seas of liquid methane & ethane just waiting for you to stick a suction hose in them and start pumping.  The other major advantage is the fact that you can rely upon wind energy in place of solar energy, which is going to be weak that far out.  Just how much solar energy is there going to be available to colonists at Callisto? 

Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #21 on: 11/07/2014 02:22 am »
I was talking about visiting Callisto first vs visiting Titan. But you're already at colonization??
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Offline llanitedave

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Re: MCT Beyond Mars
« Reply #22 on: 11/07/2014 02:37 am »
I was talking about visiting Callisto first vs visiting Titan. But you're already at colonization??

OK, this time we're really agreeing!  Maybe.  Same with Europa.  Probably the most valuable exploration target we have in the solar system right now, but that doesn't mean it's a good candidate for colonization, either.
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Offline Hyperion5

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Re: MCT Beyond Mars
« Reply #23 on: 11/07/2014 02:54 am »
I was talking about visiting Callisto first vs visiting Titan. But you're already at colonization??

Well considering we're talking about vehicles named "Mars Colonial Transporters" being involved I just assumed that colonization was sort of implied as a long-term possibility.  If we're evaluating "ease of visitation", then sure, go with Callisto.  Titan is still arguably the moon to beat for any colony beyond Mars.  Certainly a better locale than Europa for any long-term base or colony.  You could overcome the metals issue by simply launching off Titan and landing on other, rocky Saturnian moons and doing some mining work. 

Offline llanitedave

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Re: MCT Beyond Mars
« Reply #24 on: 11/07/2014 03:08 am »
You'd overcome the metals issues by simply aiming for the asteroids and comets.  At some point, colonization advocates will realize you don't need deep gravity wells in order to have self-sustaining, productive habitations.  And they'll realize that its the undifferentiated bodies that will have the easiest-to-extract and process resources.

Plus loads of water and deuterium.
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Offline douglas100

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Re: MCT Beyond Mars
« Reply #25 on: 11/07/2014 03:22 pm »
I suggest that the design of any manned spacecraft to the gas giants will depend mostly on the destination chosen. Planetary landers are specialists. A vehicle designed to land on Callisto will be substantially different from one sent to Titan. Any manned lander sent to the gas giants will be substantially different from MCT although it could quite easily incorporate many of MCT's systems. The same sort of "one size fits all" argument came up when people were proposing landing Dragon on the Moon or Venus etc.

On the other hand a spacecraft intended to visit and orbit the moons and smaller bodies would be more generic in its design than any lander. These design trends are already present in current unmanned planetary spacecraft.

I'm with  llanitedave on the matter of gravity wells for human space settlement. Keep away from them. Especially keep away from Titan with its dense, murky almost cryogenic atmosphere that could freeze an unprotected human solid in seconds. A great place to do research, a bad place to live.
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Offline Hyperion5

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Re: MCT Beyond Mars
« Reply #26 on: 11/07/2014 04:37 pm »
I suggest that the design of any manned spacecraft to the gas giants will depend mostly on the destination chosen. Planetary landers are specialists. A vehicle designed to land on Callisto will be substantially different from one sent to Titan. Any manned lander sent to the gas giants will be substantially different from MCT although it could quite easily incorporate many of MCT's systems. The same sort of "one size fits all" argument came up when people were proposing landing Dragon on the Moon or Venus etc.

On the other hand a spacecraft intended to visit and orbit the moons and smaller bodies would be more generic in its design than any lander. These design trends are already present in current unmanned planetary spacecraft.

Actually I'm pretty sure an unmodified MCT could land on Titan or Callisto without too many difficulties.  The delta-v required would actually be higher with Callisto, as there would be almost no atmosphere to slow it down.  On Titan the atmosphere is so thick the crew would have few problems using the retro-propulsion to merely guide it in and make a last-minute burn to slow down enough.  The modifications you would need to do would be more in terms of insulation for landing on Titan.  You shouldn't need much in the way of modifications to land on Callisto.  The reason why you wouldn't change the MCT lander much is that at the end of the day, it's still expected to be able to land back on Earth.  That requirement means that regardless of which moon it landed upon, it's not going to look much different. 

I'm with  llanitedave on the matter of gravity wells for human space settlement. Keep away from them. Especially keep away from Titan with its dense, murky almost cryogenic atmosphere that could freeze an unprotected human solid in seconds. A great place to do research, a bad place to live.

Going by gravity, gentlemen, would then mean Elon shouldn't bother colonizing Mars at all.  I realize you're counting on artificial gravity for outer space colonization, but the ISS should be a cautionary tale for everyone.  Part of the reason why it cost so much was it required construction in orbit, which took a good long while and involved all sorts of complications.  In contrast, if you're trying to construct something on Mars, at least you can count on good ol' gravity (.375 g of it) to help you out.  It makes construction of all sorts of things far easier, and it also wards off health issues.  Mars also has plentiful natural resources, a thin atmosphere you can build up, and the amount of land you can take hold of is nearly equal to all of Earth's landmasses put together.  The fact that Elon has staked his ambitions on colonizing Mars should tell you everything about whether or not it's worth colonizing an object with a substantial gravity well. 

As for Titan's dangerous cold, it's true it is cold, but you wouldn't be frozen solid in a few seconds.  It would take longer than that, as evidenced by the Antarctic researchers being able to go outside in the buff in mid-winter without clothes on for 5 minutes at a time.  Titan's air may be a better conductor of heat & cold than the air around Antarctica, but it's not so thick that it'd freeze you solid in seconds.  For that sort of issue you'd need to chuck someone into one of Titan's liquid methane lakes or rivers.  Also left unmentioned is that for all of its issues with cold, your blood will not boil on Titan even if your suit springs a leak.  On Callisto, Europa, Ceres and even Mars, you cannot say the same.  The relative dearth of atmospheric pressure on those bodies means a suit leak there could be deadly within a half minute or less.  I am quite confident you would have more time than that to ward off the cold on Titan in contrast.  The margin for error on Titan is, in my opinion, rather higher than on Callisto.

Offline llanitedave

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Re: MCT Beyond Mars
« Reply #27 on: 11/07/2014 05:15 pm »

Going by gravity, gentlemen, would then mean Elon shouldn't bother colonizing Mars at all.

That's another thread, or course, but I'd be tempted to make that argument.  Don't tell Mr. Musk, though, because his big dream, even if I think it's misplaced, is doing us all a whole lot of good in the meantime.
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Offline nadreck

Re: MCT Beyond Mars
« Reply #28 on: 11/08/2014 06:24 am »
I have long thought that an important economic step in establishing a space based economy comes from finding an ice trojan of Jupiter (or Saturn) that could be moved through a series of low energy maneuvers using some of its own mass as reaction mass in an NTR or STR to end up ( taking a fairly long time) in Earth orbit. The value of that resource there would be immense and enabling. If a Muskesque Martian Colony exists, then sending one of these into Mars orbit also makes sense.

Of course we might then go all space opera and have ice pirates too!
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline guckyfan

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Re: MCT Beyond Mars
« Reply #29 on: 11/08/2014 07:20 am »
I have long thought that an important economic step in establishing a space based economy comes from finding an ice trojan of Jupiter (or Saturn) that could be moved through a series of low energy maneuvers using some of its own mass as reaction mass in an NTR or STR to end up ( taking a fairly long time) in Earth orbit. The value of that resource there would be immense and enabling. If a Muskesque Martian Colony exists, then sending one of these into Mars orbit also makes sense.

Of course we might then go all space opera and have ice pirates too!

We may find that in Mars orbit already. Someone should really go to Phobos and Deimos to check. Too bad Phobos Grunt did not work out.

In earth orbit I am not so sure. The sun may slowly disintegrate it and we would left with a VERY massive cloud of debris.

Offline Vultur

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Re: MCT Beyond Mars
« Reply #30 on: 11/08/2014 06:19 pm »
Why not Venus? I have seen intresting suggestions for in air floating hab

Well, you beat me to it!

The proposed BFR + second stage should be capable of launching a couple of Ba330 or a single [conceptual] Ba2100 to low Venus orbit. After that, a couple of MCTs might handle the logistics of such orbital station.

Not sure if it makes sense for a manned program though, unless it is used for some sort of buoyant station in the atmosphere. I've  seen some speculation on the feasibility of tethering a habitat 80 km above Venus surface, but it sounds far fetched to me. Even more than a Mars colony, in fact.

I agree that a Venus floating colony shouldn't be first (more delta-v to leave, harder to build, limited ability to actually explore the planet, sulfuric acid, less ability to get to mineral resources).

It is attractive to those who think that long-term 0.38 g would be bad, though, and the habitat can be at the same pressure as outside so leaks would be slow, not catastrophic.

And I believe it would be ~50km, where temperature and pressure are Earthlike.

Offline Vultur

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Re: MCT Beyond Mars
« Reply #31 on: 11/08/2014 06:20 pm »
Also left unmentioned is that for all of its issues with cold, your blood will not boil on Titan even if your suit springs a leak.  On Callisto, Europa, Ceres and even Mars, you cannot say the same.

While I agree with your point (vacuum is deadly) one's blood doesn't really boil; the body can provide enough pressure to prevent that.

Offline Hyperion5

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Re: MCT Beyond Mars
« Reply #32 on: 11/08/2014 07:54 pm »
Also left unmentioned is that for all of its issues with cold, your blood will not boil on Titan even if your suit springs a leak.  On Callisto, Europa, Ceres and even Mars, you cannot say the same.

While I agree with your point (vacuum is deadly) one's blood doesn't really boil; the body can provide enough pressure to prevent that.

Just looked into this on a NASA page:

Quote from: NASA Goddard Space Flight Center
How long can a human live unprotected in space?

If you don't try to hold your breath, exposure to space for half a minute or so is unlikely to produce permanent injury. Holding your breath is likely to damage your lungs, something scuba divers have to watch out for when ascending, and you'll have eardrum trouble if your Eustachian tubes are badly plugged up, but theory predicts -- and animal experiments confirm -- that otherwise, exposure to vacuum causes no immediate injury. You do not explode. Your blood does not boil. You do not freeze. You do not instantly lose consciousness.

Various minor problems (sunburn, possibly "the bends", certainly some [mild, reversible, painless] swelling of skin and underlying tissue) start after ten seconds or so. At some point you lose consciousness from lack of oxygen. Injuries accumulate. After perhaps one or two minutes, you're dying. The limits are not really known.

You do not explode and your blood does not boil because of the containing effect of your skin and circulatory system. You do not instantly freeze because, although the space environment is typically very cold, heat does not transfer away from a body quickly. Loss of consciousness occurs only after the body has depleted the supply of oxygen in the blood. If your skin is exposed to direct sunlight without any protection from its intense ultraviolet radiation, you can get a very bad sunburn.

At NASA's Manned Spacecraft Center (now renamed Johnson Space Center) we had a test subject accidentally exposed to a near vacuum (less than 1 psi) in an incident involving a leaking space suit in a vacuum chamber back in '65. He remained conscious for about 14 seconds, which is about the time it takes for O2 deprived blood to go from the lungs to the brain. The suit probably did not reach a hard vacuum, and we began repressurizing the chamber within 15 seconds. The subject regained consciousness at around 15,000 feet equivalent altitude. The subject later reported that he could feel and hear the air leaking out, and his last conscious memory was of the water on his tongue beginning to boil.

So I guess you're right that your blood won't boil.  However that is little consolation considering you have about 15 seconds from the time of total exposure to when you lose consciousness.  You would definitely have more than 15 seconds worth of time when dealing with Titan's cold in contrast. 

Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #33 on: 11/10/2014 12:17 pm »
Your lungs can withstand maybe a couple psi, so you can hold your breath in vacuum a little bit (if you're breathing pure oxygen), which could help quite a bit.
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Offline Jet Black

Re: MCT Beyond Mars
« Reply #34 on: 11/10/2014 12:47 pm »
Titan's air may be a better conductor of heat & cold than the air around Antarctica, but it's not so thick that it'd freeze you solid in seconds.  For that sort of issue you'd need to chuck someone into one of Titan's liquid methane lakes or rivers.

contact with the ground would be a bigger problem in the first instance. Have you ever stuck your hand in liquid nitrogen? I have done before for several seconds and it just boils. conversely I picked up a bit of frozen ethanol that we plucked out of the same dewar (we were playing with it) and I got a blister on my finger.
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Offline sheltonjr

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Re: MCT Beyond Mars
« Reply #35 on: 11/10/2014 05:31 pm »

Going by gravity, gentlemen, would then mean Elon shouldn't bother colonizing Mars at all.

That's another thread, or course, but I'd be tempted to make that argument.  Don't tell Mr. Musk, though, because his big dream, even if I think it's misplaced, is doing us all a whole lot of good in the meantime.

200-220 MT of refined high grade material to LEO at a time with a fully reusable launcher and in space manufacturing with concepts like spider-fab and 3D electron beam welding printing changes the equation. Makes one wonder what could be built.

A 10 meter center cylinder with 2 6 meter diameter torus's at 75m and 150m radius and 8 spokes, 1 cm thick would require 6 200 MT BFR Launches and provide 62X the interior volume of the space station.  0.5G on the inner ring and 1.0G on the outer ring.

Another thread perhaps. Does anyone know a good one to discuss this?

Offline RanulfC

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Re: MCT Beyond Mars
« Reply #36 on: 11/10/2014 11:35 pm »
Your lungs can withstand maybe a couple psi, so you can hold your breath in vacuum a little bit (if you're breathing pure oxygen), which could help quite a bit.

Uh, no... Not unless you want to have your lungs blown out your nose and explode :)

You let it ALL out or your in serious trouble. You should have a about half a minute or so of conscious activity available if you were pre-breathing pure O2.

Randy
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Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #37 on: 11/13/2014 12:04 am »
Your lungs can withstand maybe a couple psi, so you can hold your breath in vacuum a little bit (if you're breathing pure oxygen), which could help quite a bit.

Uh, no... Not unless you want to have your lungs blown out your nose and explode :)

You let it ALL out or your in serious trouble. You should have a about half a minute or so of conscious activity available if you were pre-breathing pure O2.

Randy
You ignored what I said. Your lungs and nose, etc, can withstand 1-2 (perhaps 3 for some) psi of pressure differential. That's a verifiable fact. It can be shown with a simple experiment.
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Offline guckyfan

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Re: MCT Beyond Mars
« Reply #38 on: 11/13/2014 07:54 am »
Your lungs and nose, etc, can withstand 1-2 (perhaps 3 for some) psi of pressure differential. That's a verifiable fact. It can be shown with a simple experiment.

How do you retain 1-3 psi in your lungs? Sounds risky.

Edit: Fixed quote
« Last Edit: 11/13/2014 07:55 am by guckyfan »

Offline inventodoc

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Re: MCT Beyond Mars
« Reply #39 on: 11/13/2014 12:31 pm »
The point remains that once you've got a big spacecraft, there are lots of good places to go.   Titan is in fact the only other terrestrial surface where humans can go outside without a spacesuit. You will need arctic like gear, possibly electric heat and oxygen and you are good to go. Stay out of the lakes, though.

Offline sghill

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Re: MCT Beyond Mars
« Reply #40 on: 11/13/2014 01:37 pm »
Your lungs can withstand maybe a couple psi, so you can hold your breath in vacuum a little bit (if you're breathing pure oxygen), which could help quite a bit.

Or breath out steadily as the pressure drops on the outside- an old SCUBA procedure for coming to the surface with no tank (or escaping a submarine!). The expanding air in your lungs still has lots of O2 in it. We used to practice this in shallow water dives.

I think "2001" got this one right; "Gravity" certainly didn't...
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Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #41 on: 11/13/2014 02:44 pm »
Your lungs and nose, etc, can withstand 1-2 (perhaps 3 for some) psi of pressure differential. That's a verifiable fact. It can be shown with a simple experiment.

How do you retain 1-3 psi in your lungs? Sounds risky.

Edit: Fixed quote
Have you ever blown up a balloon? About 1psi.
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Offline douglas100

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Re: MCT Beyond Mars
« Reply #42 on: 11/13/2014 02:57 pm »

I think "2001" got this one right; "Gravity" certainly didn't...

Yep, Clarke believed that humans could survive for a short time in a vacuum as far back as "Earthlight" in 1955...
Douglas Clark

Offline dror

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Re: MCT Beyond Mars
« Reply #43 on: 11/13/2014 06:29 pm »

200-220 MT of refined high grade material to LEO at a time with a fully reusable launcher and in space manufacturing with concepts like spider-fab and 3D electron beam welding printing changes the equation. Makes one wonder what could be built.

A 10 meter center cylinder with 2 6 meter diameter torus's at 75m and 150m radius and 8 spokes, 1 cm thick would require 6 200 MT BFR Launches and provide 62X the interior volume of the space station.  0.5G on the inner ring and 1.0G on the outer ring.

Another thread perhaps. Does anyone know a good one to discuss this?

I also think that LEO is the place to go with the first MCTs.
Even befor mars, the MCT vehicle will have to be proven in LEO for at least the duration of a one way trip.
 I'd say that a mct based space station in LEO is a mandatory milestone in SpaceX's roadmap.
Space is hard immensely complex and high risk !

Offline Hyperion5

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Re: MCT Beyond Mars
« Reply #44 on: 11/13/2014 08:21 pm »
Your lungs can withstand maybe a couple psi, so you can hold your breath in vacuum a little bit (if you're breathing pure oxygen), which could help quite a bit.

Uh, no... Not unless you want to have your lungs blown out your nose and explode :)

You let it ALL out or your in serious trouble. You should have a about half a minute or so of conscious activity available if you were pre-breathing pure O2.

Randy
You ignored what I said. Your lungs and nose, etc, can withstand 1-2 (perhaps 3 for some) psi of pressure differential. That's a verifiable fact. It can be shown with a simple experiment.

The pressure differential you're talking about would only be possible if you were breathing in air about as thick as that found at 40,000 ft (2.71 psi).  Since the human body shuts down due to oxygen deprivation on Everest (sub-30,000 ft), I would say you would have to let most of the air out of your lungs.  Even pure oxygen would only get you so far, and oxygen can turn poisonous in the right pressure conditions.  See this site for a list of air pressures at differing altitudes on Earth: http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html
« Last Edit: 11/13/2014 08:22 pm by Hyperion5 »

Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #45 on: 11/13/2014 08:25 pm »
Hyperion: oxygen pressure at Everest is 1psi. Oxygen is only toxic at very high pressures (multiple atmospheres), ie while diving, so isn't relevant to this discussion.

Speaking of, this is off-topic. What was supposed to just be a drive-by comment derailed the thread. I've proven my point so will say no more.
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Offline TrevorMonty

Re: MCT Beyond Mars
« Reply #46 on: 11/13/2014 09:05 pm »
It is partial pressure of gases that effects their toxicity. That is why air purity is critical for scuba air fills. That 1% of CO on surface ends up being equivalent to 5% at 40m. Still 1% of air breathed but partial pressure is now 5x surface partial pressure which increases its absorption rate.

Offline Hyperion5

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Re: MCT Beyond Mars
« Reply #47 on: 11/13/2014 09:41 pm »
Hyperion: oxygen pressure at Everest is 1psi. Oxygen is only toxic at very high pressures (multiple atmospheres), ie while diving, so isn't relevant to this discussion.

Speaking of, this is off-topic. What was supposed to just be a drive-by comment derailed the thread. I've proven my point so will say no more.

Your point was meant to emphasize that surviving the near-vacuum of Callisto is not as bad as it seems, especially relative to Titan's cold.  I remain dubious about that premise, not least because to get yourself out of that dangerous situation you would probably have to scramble to get to safety.  Scrambling and exerting oneself without an active oxygen supply sounds extremely dangerous.  We're talking maybe 10-15 seconds of leeway time before it's lights out.  Once that happens it doesn't matter if the vacuum doesn't immediately kill you because you being unconscious in a vacuum environment will kill you anyways.  So in my book, Callisto is still more dangerous a place for crew than Titan. 

Offline Hyperion5

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Re: MCT Beyond Mars
« Reply #48 on: 11/13/2014 09:45 pm »
Titan's air may be a better conductor of heat & cold than the air around Antarctica, but it's not so thick that it'd freeze you solid in seconds.  For that sort of issue you'd need to chuck someone into one of Titan's liquid methane lakes or rivers.

contact with the ground would be a bigger problem in the first instance. Have you ever stuck your hand in liquid nitrogen? I have done before for several seconds and it just boils. conversely I picked up a bit of frozen ethanol that we plucked out of the same dewar (we were playing with it) and I got a blister on my finger.

You do know that 98% of Titan's atmosphere is gaseous nitrogen, right?  It's not so cold that even nitrogen will freeze.  There are ways to protect MCT crewmembers in climate-controlled suits, and nobody's suggesting that the crew will regularly be sticking unshielded hands into liquid methane or ethane lakes. 

Offline Robotbeat

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Re: MCT Beyond Mars
« Reply #49 on: 11/13/2014 10:02 pm »
Hyperion: oxygen pressure at Everest is 1psi. Oxygen is only toxic at very high pressures (multiple atmospheres), ie while diving, so isn't relevant to this discussion.

Speaking of, this is off-topic. What was supposed to just be a drive-by comment derailed the thread. I've proven my point so will say no more.

Your point was meant to emphasize that surviving the near-vacuum of Callisto is not as bad as it seems, especially relative to Titan's cold. ...
No, that wasn't my point.

I was merely correcting the common misconception that the lungs can't withstand ANY pressure when you're in a vacuum. As far as we know, they can probably withstand 1-3 psi while you are still conscious (because, again, you can blow up a balloon). That is all I was trying to say. And I really will shut up now.
« Last Edit: 11/13/2014 10:04 pm by Robotbeat »
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Offline Patchouli

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Re: MCT Beyond Mars
« Reply #50 on: 11/13/2014 11:04 pm »
Back on topic I don't think MCT could handle the thermal environment or the duration of missions much beyond Mars.

Going to the asteroid belt probably would be pushing it as far as the capabilities of the vehicle go.

Missions to Jupiter you're pretty much looking at something like the large nuclear electric version of Nautilus-X as the minimum.
Going to Saturn would require an even more capable spacecraft though MCT in a highly modified form could be used as  a lander on Titian.
« Last Edit: 11/13/2014 11:19 pm by Patchouli »

Offline Lar

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Re: MCT Beyond Mars
« Reply #51 on: 11/13/2014 11:07 pm »
Do we need a thread split to discuss breathing vacuum?

Did making this suggestion deflate someone's balloon?
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Vultur

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Re: MCT Beyond Mars
« Reply #52 on: 11/14/2014 04:26 am »
Back on topic I don't think MCT could handle the thermal environment or the duration of missions much beyond Mars.

Thermal, maybe, but if MCT can carry supplies for 100 people for 3-4 months, it could probably support a small crew for several years.

I think the bigger problem will be power - I expect MCT to be solar powered, which is fine for Earth-Mars and might even work out to the asteroids (a smaller crew might mean less power needs) but beyond that...

Also, delta-v needs and refueling. MCT will probably depend on aggressive aerobraking and refueling at the Mars end.

Offline JasonAW3

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Re: MCT Beyond Mars
« Reply #53 on: 11/14/2014 01:18 pm »
As the MCT is pretty much designed and will be buyilt for one mission, getting people to Mars, I seriously doubt that it would be of that much use much beyond Mars.

However, this does not preclude it from being a starting point for designs that can be used for both inner and outer system space craft.
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Offline CyclerPilot

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Re: MCT Beyond Mars
« Reply #54 on: 11/15/2014 08:45 pm »
Thermal, maybe, but if MCT can carry supplies for 100 people for 3-4 months, it could probably support a small crew for several years.
 

Agreed.  MCT's have all the right pieces to support a small crew on longer 'exploration' missions.
 
Quote

I think the bigger problem will be power - I expect MCT to be solar powered, which is fine for Earth-Mars and might even work out to the asteroids (a smaller crew might mean less power needs) but beyond that...
 
Agreed.  Anything further out needs nuclear power.
 
Quote

Also, delta-v needs and refueling. MCT will probably depend on aggressive aerobraking and refueling at the Mars end.
Delta-v will really limit destinations.  MCTs will probably only be capable of 7-8 km/s dV max.  There are some near earth asteroids where it is barely possible to make the round trip on that, but the options will be limited.  Gravity assists could help, but add transfer time.  Any non-Mars mission would probably be refueled and launched from a higher Earth orbit to maximize dV.  Binary asteroids would have a slightly lower landing and return dV penalty.  The heat shield would still have to be drug along for earth return, so not much can be trimmed mass-wise.

For main belt roids, ISRU becomes a must.  Since there is no atmosphere, all water and carbon will have to be mined and processed.  More solar or a nuclear reactor would have to be brought along to power ISRU.  It becomes quite a project that 1 MCT could probably not do alone.

I could see the asteroid mission designed such that only a small handful are doing any science while most of crew is cocentrating on getting back alive.  With that said, I think such a mission sounds exciting and would love to be a part of one. ;D

Offline Vultur

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Re: MCT Beyond Mars
« Reply #55 on: 11/15/2014 11:11 pm »
Thermal, maybe, but if MCT can carry supplies for 100 people for 3-4 months, it could probably support a small crew for several years.
 

Agreed.  MCT's have all the right pieces to support a small crew on longer 'exploration' missions.
 
Quote

I think the bigger problem will be power - I expect MCT to be solar powered, which is fine for Earth-Mars and might even work out to the asteroids (a smaller crew might mean less power needs) but beyond that...
 
Agreed.  Anything further out needs nuclear power.

Or at least a radically different design - I could see a solar-powered mission to Jupiter with modern solar cells.

Offline Krevsin

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Re: MCT Beyond Mars
« Reply #56 on: 11/16/2014 06:06 am »
I'm wondering whether the lack of resources needed to make methalox in the destination (when talking about destinations requiring high dV, ofc) could somehow be overcome by adding expendable tanks.

It seems like a straightforward addition, but the MCT will likely need a pretty impressive mass fraction and you'd most likely start seeing diminishing returns when adding expendable fuel tanks to it.

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