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Ok so we built an ISS with a pricetag of perhaps $1 trillion and it has How many years of useful life expectancy? And then it falls into the ocean just like Mir and Skylab?
I would like to ask: what are the limitations on its useful life expectancy and are these limitations of obsolescence or limitations of wear and tear and consequently of safety and viability?
Because what would be the cost of launching the whole ISS from Earth orbit towards Venus or Mars as an orbiting space station for either of our planetary neighbours? Surely putting it in orbit around Venus is preferable to watching it burn up over the Pacific??
[color=darkred][b]~~Bryan[/b][/color]
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Well, it's a little fragile to be enduring the forces of an interplanetary trajectory injection burn. Other than that, I like the idea.
There are some other shortfalls in its design, relative to the mission you suggest.
We have found out that there is a fuzzy, ill-defined limit to how long humans can endure zero-gee without irreparable damage. It seems to be somewhere over a year. That station needs a huge centrifuge for astronauts to live in and stay healthy for its current mission. It needs the same thing at Mars or Venus.
At either Mars or Venus, there is no protection from either solar storm or galactic cosmic radiation. That protection would have to be added before the station left LEO, or you'll kill the crew in it next solar storm. It's an ugly, miserable death, too.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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So the answer may be to build a new component with a centrifuge and shielding and then tack onto that whatever additional components in the existing ISS may be useful at Venus and launch just that grouping. I am going to say Venus b/c I know we can get there in something like 6 weeks, although getting back is a bit trickier. I am one of the people who favour going to Venus ahead of going to Mars -- we already have the technology and resources and stamina for a round-trip to Venus. Mars can build on that. In fact, most missions out to Mars have a gravity-assist from Venus near the beginning! A glider craft could skim down into the cloud decks of Venus and back out again no problem. A soletta could be attached to the ISS for its trip to Venus to see if that method for cooling is workable.
The journey of 1000 miles begins with a single step. We all keep talking about the big journey to the next planets -- Mars and Venus both -- but we are mostly blind to the steps toward that goal we have already taken. One method of establishing regular contact from Earth to manned stations at Mars and Venus or a surface colony on Mars or the Moon is to establish orbiting space stations at each planet whose function will be to dip down into the planet's gravity-well and back out again with landers. That breaks down the interplanetary problem to getting from Earth's station to the Mars station or the Venus station and back again. That can be a different kind of craft.
[color=darkred][b]~~Bryan[/b][/color]
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Perhaps we could boost it to the Terra-Luna L1 point using an ion drive?
Or just leave it in LEO and periodically reboost it. Perhaps by this time it will be able to be privatised, like they attempted to do with Mir. I wonder how the other partners would respond to ESA selling their share to a private company?
"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony
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Well, let's pursue this a bit farther. What do we have in Earth orbit now that could be repurposed for interplanetary travel and exploration? We talk (and whine!) about the costs of launching from Earth on a trajectory for the Martian surface. What about building a space station with artificial 1gee gravity from centrifugal motion in LEO and then sending it on a slow-boat-to-China trajectory into orbit around Venus or Mars? With modular landing craft included? If we can make 1g by artificial means and if the repositioning cruise itself does not need to be manned all the way, how far can we go? Imagine the Mars or Venus space station on a 2-3yr trajectory to its new home and then a more rapid manned flight launching much later and rendezvousing with the station in time for its final insertion into orbit around the destination planet. Once orbit has been achieved, the manned flight can stay awhile or return from the station to Earth. This is less strenuous than landing in the alien gravity well and returning from there.
[color=darkred][b]~~Bryan[/b][/color]
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When I think about how to that far with what we have (or could have very soon, like 5 years), I have change my model for the expedition. Neither one-launch/one-mission, nor one-mission/one-landing makes any sense at all for voyages further than the moon.
I think of transit vehicles assembled in LEO from modules docked together. These need to be small enough to fit the rockets we have. We did that to build ISS, we can do it again, or rebuild parts of ISS to do it.
The manned vehicle need not have landers, those can be sent separately as robots. The manned vehicle is unique, it needs to provide long term life support, including both artificial gravity and a radiation shelter or shield. It needs quite a bit of space in which people can either congregate or be alone. You don't do that in a capsule or a small habitat module. You need something about like the old Skylab station for each 3-to-6 folks on board.
That manned vehicle as assembled in LEO has the habitat/supplies, a bunch of propellant modules, and an engine module. It'll need enough propellants to go to Mars/Venus/asteroid and back. You'll have to stage some empties off at each burn, or at least at each end of the voyage. It goes to low orbit about Mars/Venus, or rendezvous with an asteroid, and links up to the landers sent separately (none needed at an asteroid or Venus). You recover this thing in LEO (even if it's just the habitat/supplies, a few empty propellant modules, and the engine module), so you can use the equipment again.
Since it's docked modules, you reconfigure the stack at each staging for the same overall length from habitat to engines. It just gets skinnier at each stage-off. That way, you can just spin it at no more than about 4 rpm, head-over-heels (pitch or yaw, makes no difference), for artificial gravity. 4 rpm is tolerable by just about anyone, and at 56 m radius (cg to hab), that's 1 full gee.
Landers just couple-up to a bunch of propellant modules. Use the lander engines to push that stack to Mars one-way. It doesn't return, the rest of the propellant supports multiple landings with a refuelable, reusable lander. You send more than one lander stack to have redundancy and stranded-crew rescue capability.
But, you make multiple landings at different sites while at Mars. What's the point of going to all the trouble to fly all that way to Mars, and make only one landing? That would be insanely stupid, after all.
Any vehicle fleet design that could accomplish that Mars mission could go to Venus, Mercury, or any near-Earth asteroid. Reuse the maximum part of it that you can. That's how we really do this.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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I think I agree with you .. lol. I am parsing it to try to identify similarities and differences, but I think we're on the same page. If the targets are both Mars and Venus (either/or or both), then we want to build orbiting space stations in LEO lifted up modularly in the same piecemeal fashion as the ISS we have now, for which MIR and Skylab are perhaps examples of 1-module babysteps. But we build them for shielding and g-force habitats. Then we send them away from LEO on a slow-boat to China trajectory. They can take their sweet time getting to where we want them -- 2 yrs or longer if need be. They will be big and heavy and unmanned, so no big rush really. Send the manned capsule separately much later and much much faster -- a few weeks to Venus or 4 months or less too Mars if possible. It can rendezvous with the SS and then unpack/spread out and yes, conduct multiple landings to the surface of Mars or flights through the Venus cloud decks. The SS enables the crew to live in a prepared environment in orbit, versus ekeing out something new and primitive and higher risk on the Martian surface or floating in the Venus clouds. At Venus, chemistry in the upper atmosphere might provide propellant gasses for the return flight or additional flights. At Mars, might be harder. But this converts the problem from How to get from Earth''s gravity-well at the surface to the bottom of some other gravity well and back again to How to get from LEO to low orbit over some other planet and back again. If we can master landing and returning to orbit, then gathering gasses in space and manufacturing propellant off-Earth may come in time and prove to be the long-term solution.
[color=darkred][b]~~Bryan[/b][/color]
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I wouldn't say Venus orbit is safer than Venus cloud deck...
Space travel is always going to remain expensive whilst you continue hauling everything from Terra, because most of what you're going to be hauling is fuel. Just use what's out there (*cough* Luna *cough*). I'm fairly certain Falcon Heavy will actually be built, which gives us 50 tonnes to play with - launch a couple of them unfurnished, maybe with just fuel tanks, engines, and navigation, and furnish and fuel it with Lunar resources. You could maybe then build a 200 tonne dry mass chemical propelled Mars exploration vessel, for 100 tonnes put into orbit. Or for Venus, Mercury, the asteroids...
"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony
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Sorry -- what's Falcon Heavy?
(edit: nvm .. ok I have read up on it. I havent been active in these forums for a cpl years, pardon me! Looks good! Commercial flights at last. Differentiated space vehicles for differentiated purposes is the way to go, plus economies of scale and finding volatiles for fuels in space!)
As regards Venus: my understanding about the space shuttle program is that NASA began working on the next generation shuttles almost before the first generation got launched and that was 30+yrs ago. The next generation is supposed to use aerodynamic lift to get it up to the edge of space and *then* kick in rockets to carry it to LEO, while the first generation used one big long glide to return to Earth and needed rockets all the way up. An aerodynamic craft capable of lifting us from Terra into LEO should function *in principle* in the cloud decks of Venus as well, for dipping down in and then back up out again. The viscosity of that atmosphere will work in our favour to give lots of lift for the wingspan, but, yes, I understand the materials of the craft's skin must resist sulphuric acid and the engines must work without oxygen .... No small problem there!
BUT: Is Mars any easier? Thin atmosphere, therefore aerodynamic transport would require enormous wingspan to body ratio plus, again, anaerobic atmosphere mostly CO2. A duststorm could flip the plane -- a big span gives wind lots to grab hold of, vs Venus where wings tighter to the body should be an advantage against wind. Mars requires more conventional rocket-powered landers trips down to the surface. And how has that been working for us? How many Mars landings have been crash landings? It's a poor track record.
Last edited by StarDreamer (2013-04-04 09:35:37)
[color=darkred][b]~~Bryan[/b][/color]
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The iss swims in the sky at an inclination of 51.6° that's pretty useless as a way station. It would be useful if we could assemble multi launch missions in orbit or have non direct entries from luna or countless other things we all want to do. Only problem is that dam orbit. Why don't we just change it.
Take a falcon heavy cargo and turn it into a big extended fuel tank for its second stage, dock with the station and just boost. Falcon heavy has a capacity of 53,000 kg, you don't need a faring so the extra tank weight will probably cancel out giving you 53,000 kg of spare fuel. With a specific impulse of 342 you will only need 388,197 kg of fuel to boost a fully loaded ISS to an equatorial orbit. That's about 7 falcon heavies, probably get by with five if you ditch a few modules and do a deep clean first. At $100m a pop that's just $500m-$700m for the whole move, well within the NASA budget.
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That much more fuel eh? Ok, so by now everyone can see I am no rocket scientist or engineer myself, but I like to think that helps me think outside the box, right up to where reality intervenes ....
May I ask: how much gravity is still felt at the LEO altitude of the ISS? If it takes that much fuel to lift the ISS, then obviously it's not as far up the Earth's gravity well as I thought, even if we see ppl floating around there. But perhaps the real comparison is to how much fuel it would take to lift the whole ISS off Terra in its current fully-laden state? (Never mind the ballistics of it -- just the fuel for the mass over the distance to orbit against our gravity.) At an equatorial orbit, does that start wreaking havoc with the economics of getting to/from the ISS from Earth? And does that kill the idea of using aerodynamic lift to get payloads off Terra up to the ISS, as per next-gen shuttles? Probably less natural shielding out there for astronauts too.
Grrr -- why does it all need to be so difficult? LOL
[color=darkred][b]~~Bryan[/b][/color]
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The ISS has a mass of 450 tonnes (9 launches of Falcon Heavy... in a few years we'll be able to do the same project on a lower budget and have more functionality). Ignoring all the extra mass involved (fuel tanks, engines etc) and using H2/LOX, you'd probably need about 2500 tonnes of propellent.
If it's in an equatorial orbit, it will be easier to get to. The reason the ISS isn't is because of politics (the Russians need access).
If you're changing it's orbit, why not use a lower thrust, higher Isp effort that the structure can actually handle? You might be able to get away with only a single Falcon Heavy launch for propellent.
"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony
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I have been watching this thread.
I think the idea of recycling hardware could be a good one.
I am going to offer this. Suppose you put a habitation on Phobos (Or demos).
http://en.wikipedia.org/wiki/Phobos_(mo … cteristics
Spectroscopically it appears to be similar to the D-type asteroids,[13] and is apparently of composition similar to carbonaceous chondrite material.[14] Phobos's density is too low to be solid rock, and it is known to have significant porosity.[15][16][17] These results led to the suggestion that Phobos might contain a substantial reservoir of ice. Spectral observations indicate that the surface regolith layer lacks hydration,[18][19] but ice below the regolith is not ruled out.
I am not sure carbon is available on that moon, but I hope it is.
I would like to suggest that a station be established for mining. I also suggest a tethered rotating station in orbit of Mars to provide 1/3 gee, to find out what the effects of Martian gravity are on humans.
So personal could rotate between these two stations to try to maintain a tollerable degree of health.
As for the Phobos or Demos station, I suggest a facility that could manufacture very small devices to be launched to Mars using a linear accelerator (Magnetically).
They might be hollow and have a lifting air body configuration.
They might be filled with a pressurized liquid, solid, or slush of CO2. They would need some type of navigational device including sensors, and data processing capabilities.
They might require heat sheilding beyond the latent cold that they would contain (CO2 Liquid or solid or slush) in their interior.
They would require course correction abilities, presumably using lifting body methods.
The motive force for course corrections would be venting the expanding gasses of CO2. I presume that to some degree they would warm the liquid, solids or slush within during the entry to atmosphere of Mars.
It is presumed that some type of GPS would aid their navigation.
A small body size means more surface area to mass. This could be played to an advantage. On Earth Spiders can fall from great heights, but use the viscosity of air to break their fall and escape serious injury.
I do not intend that these vehicle will land intact however.
I am hoping that they could provide scrap metals and perhaps silicon to a location advantagious to habitation.
So I suggest that they would re-enter, heat up, use the expanding gasses within as motive force to actuate navigational devices, and that they would then do a lifting body flair, and perhaps even impact a cliff with nose extreemly up, and then fall to the ground below the cliff, prividing scrap metals for human settlers.
The advantage of this is that a site could be chosen on the basis of needs not directly connected to needing metal mines, but other requirements.
So the mining would occur at first on Phobos or Demos.
Upon impact, the small bottle like devices would behave to a degree like air bags, but rupture, and that venting of CO2 volitiles would dissapate some of the heat of impact.
I do not discount the potential of associated exploritory landings by humans prior to this manipulation, but associate it with a compresensive plan to settle Mars.
Last edited by Void (2013-04-06 13:32:09)
Done.
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Why tether a 1/3g rotating station in orbit when you have a 2/5g planet available nearby? With more radiation shielding? Just rotate the crew between the planet and orbit; no problem if you have in-situ fuel production.
"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony
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Fair enough Terraformer, that's another option. If you can maintain such a rotation of persons, then you have it.
Done.
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If you're changing it's orbit, why not use a lower thrust, higher Isp effort that the structure can actually handle? You might be able to get away with only a single Falcon Heavy launch for propellent.
I calculated the mass of propellant to move the ISS to an equatorial orbit using an isp of 342 (merlin vacuum). You certainly wont be able to change your orbit to equatorial with one falcon heavy using ANY chemical propulsion And there is no feasible way to generate enough power for electric thrusters to do the trick.
It was simply placed in a bad orbit and it will take a ton of fuel to correct that. Well I wish it would take just a ton, its more like 200 tons.
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My original line of inquiry though, went something like this:
1) The ISS has a terimination date of useful life expectancy. Is this date set by: probable orbit deterioration? probable infrastructure degradation due to the hostile environment of space? or probable obsolescence -- the toy becomes less fun to play with over time. Cause 1 can be remedied by shifting it to a new orbit and cause 3 is just psychological on our part. Cause 2 would be the only insurmountable.
2) Rather than let this $1T toy degrade into space junk or let it make a hole in the ocean on Earth, what would it take to lift it the rest of the way up out of Terra's gravity well and send it towards Venus or Mars for use as a LVO/LMO space station there? What's the cost/benefit equation look like for using it to gain a toehold on another world versus letting it go into the night and building something new from scratch?
[color=darkred][b]~~Bryan[/b][/color]
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It would take about 1,200,000 kg of fuel to move the iss from LEO to mars transfer assuming the fuel had an isp of 342. Reboost only requires about 4000 kg of propellant per year, going to mars would take 300 years worth of reboost fuel.
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The real cause of finite life out of the ISS is related to "stardreamer's" cause #2: infrastructure degradation. The systems inside, and the structure of the thing, will wear out and cease to function. It is inevitable.
They have already had troubles with most of the life support systems inside, only repeated repairs and replacements keep it functional. The same will prove true of the solar PV panels outside. There's already been one repair.
Eventually, the shells of the modules themselves will degrade, as will the docking structures that hold them together. They were fragile enough to begin with, just to be light enough to fly at all. Only a low-thrust thing like some sort of plasma device would be feasible, to move a fragile thing like that to another orbit, and it would take years to accomplish such a move. Same for leaving LEO, just longer still (bigger delta-vee).
My bet is that it will be a race to see whether the life support gear inside, or the solar PV gear outside, will become unrepairable first. Once that happens, the station becomes uninhabitable and therefore useless, and also a falling-debris threat wherever it might be located. The projections for that outcome vary, from about 2020 to about 2030. But it will occur, and sooner than anybody wants.
I would not bet any money at all on it surviving to 2030. But that's just me.
Same thing was just beginning to happen to Mir, when it was deliberately crashed in the Pacific, just before ISS construction started. It wasn't quite finished deteriorating, but the Russians wanted to participate in ISS, and could not afford to participate in both.
GW
Last edited by GW Johnson (2013-04-06 16:11:11)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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I don't dissagree, but can some parts be reused, even if they have a refirbished life exptancy of 5 years, they might fit into some type of a space mission. I would not like to totally dismiss the notion of reusing orbital hardware.
For instance I believe that there are plans to obtain and reuse antenna from old sattelites.
I would think that some justification might occure (Not in the case of the space station), by removal of space junk that is going to disintigrate through collisions and make a greater space junk hazzard. While minining asteroids may be on the surface more proffitable, capturing and recycling mass in orbit might have an economic benefit where it releives the amount of space collision hazards.
Most plans intend to burn that stuff in the atmosphere, but in some cases would value be obtained by harvesting parts from it?
The value of the part, and the value of clearing the orbits that we depend upon for certain operations such as communications for our Earth infrastructure?
I understand that in the case of the ISS, the constrictions on cost caused it to be constructed in a very narrow fashion, specialized for a single purpose, but can the pressure shells be stripped of life support, but junctioned with a new module, and used for some type of semi-automated manufacturing facility, where humans only occasionally and with personal life support equipment enter? Would that hold any value?
Last edited by Void (2013-04-06 23:05:18)
Done.
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Ok -- fair enough!
Then this has highlighted yet another issue over the long haul: If we are talking about setting up shop permanently on other planets, what needs to be done to prolong the serviceable life of our missions and colonies. Something that barely lasts from one mission to the next is obviously a non-starter. I am guessing its not that we dont know how to prevent this kind of degradation, but the cost and the politics. Are we ready, now, technologically, to overcome the problem of material degradation in space?
As some comedian once said: if the black boxes in planes are indestructible, why cant they make the whole plane out of that stuff????
The real cause of finite life out of the ISS is related to "stardreamer's" cause #2: infrastructure degradation. The systems inside, and the structure of the thing, will wear out and cease to function. It is inevitable.
They have already had troubles with most of the life support systems inside, only repeated repairs and replacements keep it functional. The same will prove true of the solar PV panels outside. There's already been one repair.
Eventually, the shells of the modules themselves will degrade, as will the docking structures that hold them together. They were fragile enough to begin with, just to be light enough to fly at all. Only a low-thrust thing like some sort of plasma device would be feasible, to move a fragile thing like that to another orbit, and it would take years to accomplish such a move. Same for leaving LEO, just longer still (bigger delta-vee).
My bet is that it will be a race to see whether the life support gear inside, or the solar PV gear outside, will become unrepairable first. Once that happens, the station becomes uninhabitable and therefore useless, and also a falling-debris threat wherever it might be located. The projections for that outcome vary, from about 2020 to about 2030. But it will occur, and sooner than anybody wants.
I would not bet any money at all on it surviving to 2030. But that's just me.
Same thing was just beginning to happen to Mir, when it was deliberately crashed in the Pacific, just before ISS construction started. It wasn't quite finished deteriorating, but the Russians wanted to participate in ISS, and could not afford to participate in both.
GW
[color=darkred][b]~~Bryan[/b][/color]
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