Manned Missions To Jupiter

John Creighton · 2005-12-21 23:47:00

In a predictable pattern no doubt.

Yeah, radially outward from the sun.

GCNRevenger · 2005-12-21 23:48:25

"Yeah but its not just going to scatter evenly around the universe"

Absolutely it is. Why wouldn't it? Its just gas after all.

Dayton Kitchens · 2005-12-22 07:47:17

Yeah but its not just going to scatter evenly around the universe. Its going to go were whatever forces send it. Enless that means directly into the atmosphere, that means its going to float around somewhere in abnormally high concentrations.
In any event, heres Nasa's Human Outer Planet Exploration (HOPE) Mission plan to Callisto info someone mentioned: PDF (3.1MB)

Thanks. While I differ with some of the mission ideas (too short a stay time on Callisto, too small a crew) I am glad that someone is giving such missions serious thought.

Dayton Kitchens · 2006-01-15 19:13:48

Incidentally, I don't want to start yet another thread on the general subject but has any mission architecture work been done on a human mission to Saturn (Titan landing I presume)?

Dayton Kitchens · 2006-02-01 08:11:17

Incidentally, I don't want to start yet another thread on the general subject but has any mission architecture work been done on a human mission to Saturn (Titan landing I presume)?

Note, try as I might, I can't find anything beyond the HOPE site about manned outer planets missions

RobS · 2006-02-03 11:41:37

Figuring out how to keep an astronaut crew in an environment as cold as a liquid oxygen tank is a daunting task and the technology needed is largely undeveloped, so I doubt a serious effort to design a Titan mission can be expected soon.

-- RobS

Austin Stanley · 2006-02-03 16:41:26

Figuring out how to keep an astronaut crew in an environment as cold as a liquid oxygen tank is a daunting task and the technology needed is largely undeveloped, so I doubt a serious effort to design a Titan mission can be expected soon.

I wouldn't worry to much about this. Modern insulation is quite good at trapping heat, and the amount of energy needed to actively heat a habitat is quite small in comparision to other space energy uses (electrolisis, gas seperation, liquifing gasses). Dewars easily hold liquid nitrogen (slightly colder then Titan's atmosphere) in a liquid state for weeks on end with only minor heat losses. Building a larger scale version for an outpost would be more difficult, but even a small nuclear reactor would supply more than enough waste heat to warm the habitat several times over.

I did some calcuations earlier (sorry I can't find the link) and they showed that even in the face of a major leak (inflowing air at like 1L/s) the energy needs to heat it to room temperature were trival.

Commodore · 2006-02-03 18:14:59

They might be able to to keep warm in the cabin, but EVAs would be considerably more difficult. The power supply they'd need to carry would negate just about any advantage of putting boots on the ground. Which is not to say there are not other ways to get the needed level of dexiterity. Mounting a suit to a rover with an arm that can manipulate the suit to any angle while maintaining connections is one.

When it comes to Outer planet exploration, the HOPE mission really has the right overall idea, set up camp on a safe moon, and expand from there. Luna hardware is fine for most of the gas giant satillites. Volitiles are abundant. Odd cases like Titan, Europa, and Io that might require more modified hardware and surface equipment can come later.

GCNRevenger · 2006-02-03 22:09:39

I don't think that a Titan suit would be impractical, since you don't need a pressure suit. All the bulk and mass that would ordinarily go to keeping your blood from boiling could go to insulation and a methane/oxygen burner or fuel cell/heated liner to keep you warm... which could be replenished by local reasources easily.

Commodore · 2006-02-03 23:20:24

Thats true. 1.5 atmospheres is bound to be equivilent to a safe diving depth. And reducing that shouldn't be all that difficult, if we need to at all. The pressure could gradually be stepped up in the transit craft.

The real trick with the heat issue I think is trying to heat the astronaut without unnaturally heating the ground they walk on. Sort of defeats the purpose.

Austin Stanley · 2006-02-03 23:39:15

Thats true. 1.5 atmospheres is bound to be equivilent to a safe diving depth. And reducing that shouldn't be all that difficult, if we need to at all. The pressure could gradually be stepped up in the transit craft.

1.5atm isn't an issue at all. People can live indefinetly at those pressures, without any exotic gas mixtures or ill-effects. It coresponds to an ocean depth of about ~5 meters, which is nothing.

The real trick with the heat issue I think is trying to heat the astronaut without unnaturally heating the ground they walk on. Sort of defeats the purpose.

Insulated boots will be necessary. However, since a phase change is necessary to turn the solid surface (which is presumably mostly water) into anything else, the effect will be considerably less than you might anticipate, since the energy necessary for a phase change is considerably greater than that necessary to simply heat the water/ice.

Austin Stanley · 2006-02-04 03:18:50

Ok, I dug out some of my old physics books and did some calculations. The formula for thermal conductivity is:

k=(QxL)/(A*dT) or Q=(A*dT*k)/L
k is thermal conductivity (in W/m*K)
Q is rate of heat transfer
L is thickness
A is area
dT is change in temperature

Silica Aerogell has a very low thermal conductivity, and is so is a good insulator. It is also very light and very strong, and so would be perfect for insulation in a Titan outpost. It has a K value of .017 W/m*K, at room temp, but that value only gets higher as the temperature goes down.

Lets consider then how much heat would be lost at a largeish Titan outpost. A half-sphere 50m in diameter, with .1m of Silica aerogell insulation. It has a total radiating surface area of ~6000m^2 and the temperature diffrence is ~200K.

This means our outpost would lose some thermal energy at a rate of ~200kW. This would be alot if it was eletrical energy, but it is thermal. Any reactor of large enough size to power an outpost of this size, would produce MUCH more than this amount of heat, with most kWe class reactors having megawatts of wasate heat to get rid of.

Austin Stanley · 2006-02-04 03:56:28

Sorry for the double post, but I decided to take a look at the requirments for a Titan space suit. Heat transfer through a plane is governed by this equation:

Q*A=(k*dT)/L which is just a re-worked modle of the one in my earlier post.

The human body has a surface area of <2m^2, so we will use that as an pesimistic estimate of the amount of area we have to deal with. Again, dT is ~200K. Aerogell would also work well for suits, but we might want something a little sturdier, so we will go with a high density plastic. Most of which have k values of ~.5w/(m*K). I figure about 2cm of insulation is the best one could hope for, without the suit becoming to terrible bulky, so we will go with that. This means that heat is lost at a rate of ~10kW.

This may not be so bad. Methane has about ~50MJ/kg of energy so, you would have to burn only .2g of methane a second to get this much heat. And .8g of oxygen a second to combust it with. I'm going to go to bed now, so I'll leave it to you guys to figure out what volume of gas this would require on Titan, to get that much methane.

Austin Stanley · 2006-02-08 06:03:25

Okay, I figured out the necessary volume of Titan Air a methane combustion system would need to provide the necessary heat for our suit. A pretty simple Ideal Gas Law problem actualy.

V=(nRT)/P
V = Volume
n = moles of gas = 1.25x10^-5 mol CH4= .2g CG4
R = Gas Constant = 8.314
T = Temperature = 100K
P = Pressure = 2336 Pa = Partial Pressure of Methane on Titan

Pluging everything in, we get a volume of 5mL. So our combustion system needs to bring in just 5mL of Gas a second, which is easily achievable. So all told, I think dealing with the cold weather on Titan will be pretty easy actualy.

Next, I'll calculate how long someone would have to stand still on the ice for it to melt underneath them.

GCNRevenger · 2006-02-08 19:42:54

Sorry for the double post, but I decided to take a look at the requirments for a Titan space suit...
The human body has a surface area of <2m^2, so we will use that as an pesimistic estimate of the amount of area we have to deal with. Again, dT is ~200K. Aerogell would also work well for suits, but we might want something a little sturdier, so we will go with a high density plastic. Most of which have k values of ~.5w/(m*K). I figure about 2cm of insulation is the best one could hope for, without the suit becoming to terrible bulky, so we will go with that. This means that heat is lost at a rate of ~10kW.

Aerogel is also an inflexible solid that won't bend with the suit very well.

2cm of high density polymer will all but certainly be too inflexible too, you couldn't move in a 2cm thick suit made of solid polymer, some other sort of insulation would be required, perhaps something purpose built. An inch-thick block of polymer is going to be fairly heavy too. Maybe aerogel granuals could be incorporated into a flexible composite outside a woven inner garmet with hot water tubes from the gas burner. The improved mobility and reduced inertia would be valuble.

I would also like to add in some substantial "fudge factors" and modifications:

1: Assume the suit surface area is a little higher, on the account of bulk, the helmet, and the extra heat leakage from thinner spots. Say 2.5m^2.

2: Include an adjustment for heat transport inefficiency; not all the heat produced by the burner will go into keeping the astronaut warm and some of it would go to a thermocouple or infrared photovoltaic to power the suits' electrical supply.

You are also going to need a little energy to boil the LOX supply to feed that burner, and it would be nice to have some extra if it turns out that insulation thickness is a hard problem to fix. I would say double it... so now burn 0.5g methane per second.

2g of oxygen per second just to run the heat/power. Lets say 2.50g/sec if you include breathing gas supply. A five kilo tank would last you a good 33hrs or so, which should do just fine, and burning a little extra LOX would be worth dumping pressurized oxygen tanks I think.

Austin Stanley · 2006-02-08 23:48:45

Aerogel is also an inflexible solid that won't bend with the suit very well.
2cm of high density polymer will all but certainly be too inflexible too, you couldn't move in a 2cm thick suit made of solid polymer, some other sort of insulation would be required, perhaps something purpose built. An inch-thick block of polymer is going to be fairly heavy too. Maybe aerogel granuals could be incorporated into a flexible composite outside a woven inner garmet with hot water tubes from the gas burner. The improved mobility and reduced inertia would be valuble.

The kind and thickness of insulation used can be highly variable, and is the primary factor in the equation given above. Another way to look at this factor is to calculate it's "R" value, which you may be familar with if you have ever delt with home insulation. "R" values are in (K*m^2)/W and is calculated like this:

R = L/k
R = R Value, (K*m^2)/W
L = Length of insulation, m
k = thermal conductance (same as used in above) W/(K*m)

Alternativly, you can calculate the thermal conductance, U, which is the reciprocal of R. U values are in W/(K*m^2) and the formula (obviously) is U=k/L=R^-1

This allows you to final the thermal transfer easily with variable values for insulation. The equation changes to this:

Q = (A*dT)/R OR
Q = U*A*dT

So you can figure out whatever insulation combination you would like. The silicon aerogell I used for the habitat has a value of 5.9, while the suit had an R value of .04. I picked high density plastics (like what is used in Tuperware and milk Cartons), because I thought it would be fairly durable. It's insulating value is less than spectacular, however. Lower density plastics do better, and styrafoam does a lot better, as does fiberglass. All of course would be lighter. Give me an idea what you think the insulation should consist of, and I'll figure it out from there.

Are there any objections for my calculations on the outpost btw?

I would also like to add in some substantial "fudge factors" and modifications:
1: Assume the suit surface area is a little higher, on the account of bulk, the helmet, and the extra heat leakage from thinner spots. Say 2.5m^2.

If we stick with the insulation I used before (high density plastics, 2cm) that brings the heat loss up to 12.5kW. Not signfigantly worse.

2: Include an adjustment for heat transport inefficiency; not all the heat produced by the burner will go into keeping the astronaut warm and some of it would go to a thermocouple or infrared photovoltaic to power the suits' electrical supply.
You are also going to need a little energy to boil the LOX supply to feed that burner, and it would be nice to have some extra if it turns out that insulation thickness is a hard problem to fix. I would say double it... so now burn 0.5g methane per second.
2g of oxygen per second just to run the heat/power. Lets say 2.50g/sec if you include breathing gas supply. A five kilo tank would last you a good 33hrs or so, which should do just fine, and burning a little extra LOX would be worth dumping pressurized oxygen tanks I think.

Hmm, taking my new figure of 12.5kW and adding in 50% efficancy, that brings us up to ~.4g of methane a second, which takes 1.2g of oxygen a second to combust with. Which requires an intake of 10mL of Titan atmosphere a second. All in all, this still seems easily acheivable to me.

Maybe tomorrow I will run the figures for boot meltage, but I can tell right now that it won't be signifigant. It's going to take quite alot of energy to bring the ice up to the melting point, and even more to melt it.

::edit skipped a decimel place::

Austin Stanley · 2006-02-10 00:46:46

Okay, I've done some more research, and I still think that some sort of thermoplastic would be our best bet for a Titan cryosuit insulation. It's requirments are pretty diffrent than that of anyother suit ever designed, so it makes sense that it would be made out of something diffrent. A cryosuit must be tough, resist cold temperatures, and be a good insulator. It does not have to withstand or withhold extreme diffrences in pressure like a spacesuit or mars suit would. It's chemical enviroment is rather safe as well with little to no UV radiation, few reactive compounds, and a very cold temperature which discourages those reactions. The extremely low gravity means weight continues to be less of an issue.

Given these conditions, I think that some flourine containing thermoplastic would probably be one of our best bets for a Titan cryosuit insulation. PFA, PVDF, FEP, PTFE, or some such. I'll focus on PTFE (polytetrafluoroethylene) more commonly know by it's trade name Teflon, here, since it is a pretty good fit of the properties we need. It's a good insulator, fairly strong, chemicaly reistant, and can easily withstand the temperature extreams on Titan (it good down to ~70K).

Anyways, Teflon has a Thermal conductance of .25 W/K*m. That means to get the same thermal resitance by previous suit design had, it would only need 1cm of the plastic. Or you could double the the insulating factor. I'll assume we halve the thickness, so I don't have to recaluate the heat transfer :-)

One of GCRN's concurns over a plastic insulator was it's weight. Teflon has a specific gravity (density) of 2.15 g/cm^3, which is pretty high for a plastic, so 1cm of it over the entire surface area of the suit (25,000cm^3) is only 53kg. However, on Titans, .17g surface, that's only 7.5kg which is easily managable. On the plus side, a suit with ~1cm of Teflon coating would be very difficult to damage.

GCRN, I realy would appreciate any other input you have on this, since I know you deal with plastic chemistry on a profesional basis.

GCNRevenger · 2006-02-10 10:20:18

At Titan temperatures, many hydrogenated polymers will be as hard as a rock and not flexible in the slightest. Some fluropolymers (relatives of Teflon) retain some flexibility, but I don't think any centimeter-thick polymer layer will be flexible enough for a soft suit. At least not at the joints.

Is this thing going to be a soft suit, or a hybrid hard/soft suit? If the latter is the case, thick hydrogenated polymer would do for the hard body parts (torso, thighs, calves, upper and fore arms, feet) with bellows style joints (ankles, knees, midriff, shoulders, elbows, wrists, neck) made from a fluropolymer with extra insulation or heating tubes. Hence one reason to have an extra margin for burner capacity.

Weight is not the only concern, inertia is still present and would still make moving around hard the more mass you pack into the suit. Using solid blocks of polymer for body pieces will be pretty heavy, so I would look into using a composite of some kind (fiberglass/aerogel based?) to cut the weight down.

RobS · 2006-02-10 11:24:18

Of course, there's still the problem that you couldn't use your fingers very efficiently on Titan because of extensive insulation needed to pick up cold objects. I suspect astronauts will spend most of their time inside running telerobots.

Then there's the problem of designing telerobots to work at cryogenic temperatures. . . not an easy challenge to make electronics function, joints move, wheels to roll, etc. No doubt it can be done, but I imagine a very expensive test facility will be needed (maybe at the Martian south pole?) and possibly some very irritating and potentially dangerous glitches will have to be handled the first year or two.

-- RobS

GCNRevenger · 2006-02-10 11:39:28

Thats where the heater comes in, dedicated coolant lines from the heat exchanger would run up the arms to the gloves, so these would be fairly thin. If digging for rocks without passing heat onto them is a problem, a simple metal/plastic digging tool and tongs would do just fine.

Tele-operated robots are too slow... if we are bothering to send people, then they will be infinatly more efficient.

Austin Stanley · 2006-05-23 01:17:16

At Titan temperatures, many hydrogenated polymers will be as hard as a rock and not flexible in the slightest. Some fluropolymers (relatives of Teflon) retain some flexibility, but I don't think any centimeter-thick polymer layer will be flexible enough for a soft suit. At least not at the joints.
Is this thing going to be a soft suit, or a hybrid hard/soft suit? If the latter is the case, thick hydrogenated polymer would do for the hard body parts (torso, thighs, calves, upper and fore arms, feet) with bellows style joints (ankles, knees, midriff, shoulders, elbows, wrists, neck) made from a fluropolymer with extra insulation or heating tubes. Hence one reason to have an extra margin for burner capacity.

The answer to your first question is the secound. A hybrid hard/soft suit. Hard pecies for most of the body area (torso) with flexible joints. I figured that 1cm+ of Teflon is not going to be flexibile, especialy at these temperatures.

Weight is not the only concern, inertia is still present and would still make moving around hard the more mass you pack into the suit. Using solid blocks of polymer for body pieces will be pretty heavy, so I would look into using a composite of some kind (fiberglass/aerogel based?) to cut the weight down.

A composit of some kind will probably be the solution. The outer layer could be made from some sort of tough thermaly resistant polymer (like Teflon), with more fragile less thermaly resistant layers underneath (aerogel, fiberglass, others). Small pockets of air/gas tramped bettwen these layers will only increase the R value.

An intresting aspect of Titan's non-toxic/non-corosive atmosphere is that the suit (aside from the head-peice) does not necessarily have to be air-tight. So long as the gas is heated before it intrudes the fabric mesh, it will likely be harmless.

Then there's the problem of designing telerobots to work at cryogenic temperatures. . . not an easy challenge to make electronics function, joints move, wheels to roll, etc. No doubt it can be done, but I imagine a very expensive test facility will be needed (maybe at the Martian south pole?) and possibly some very irritating and potentially dangerous glitches will have to be handled the first year or two.

The obvious answer is again to insulate and heat the robotics. Possibly with nuclear elements, or with combustion or eletric heaters. Like I demonstrated above, with modern insulation the energy requirments to keep objects at decent temperatures is not actualy all that great.

GCNRevenger · 2006-05-23 06:37:47

I'm still a bit skeptical about the added bulk of insulation like aerogel, which despite being very light might need to be awfully thick.

Robots would need RTG power anyway if they were going to operate any length of time, since there is no light for solar power.

cjchandler · 2006-07-02 09:33:15

Getting back to the propulsion method to actually get to jupiter, if your nuculer rocket ideas are not as robust as you hope, you can always use a tether to slow down and then leave jupiter. You'll have a nuculer reactor for electricity/propulsion anyways and the tether wouldn't add much weigh. Plus, you could recoupe lost energy while breaking. With no reaction mass, it might be nice for moving into other orbits around the different moons as well.

GCNRevenger · 2006-07-02 10:43:49

Tether for orbital capture? I don't think so, far too slow, especially from transit velocity. The maximum linear speed a tether could generate would be waaay too low for transit back to Earth too.

If we don't have high-power/high-efficiency propulsion of some kind, we aren't going anywhere anyway, there is no point even bothering. Chemical engines can let us visit Mars, but a visit to any of the outter planets would be pushing it.

Austin Stanley · 2006-07-02 14:58:05

I'm still a bit skeptical about the added bulk of insulation like aerogel, which despite being very light might need to be awfully thick.

I don't think you are correct about this. The k values I used for thermal conductance constants are in W/(K*m) in other words, the measure the amount of thermal energy they transfer per unit of thickness. Aerogel, having an incredibly low thermal conductance (or a very high thermal reistance, depending upon how you look at it) requires LESS thickness to achive the same level of insulation then praticaly any other material might. My earlier calculations show this.

Don't let it's low density fool you in to thinking it must be bulky to be effective, when dealin with insulation the opposite is generaly true. In fact, vacume (which is as low density as you can get) is the best insulator possible, air is likewise a excelent insulator, provided you do not allow it to circulate (bringing convention effects into play).

Robots would need RTG power anyway if they were going to operate any length of time, since there is no light for solar power.

Totaly agree.

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