Exterior Survival Bubble?

[Supplement Four]

Reading the Micronauts (and commenting about this in that Random Static thread) got me to thinking about using similar tech in the Traveller universe.

In the Micronauts issue I just read, the Endeavor (their ship) is being attacked by the bio-synthetic drones. The things are like starship termites. They look like little beings--androids--that attach themselves to the hull and start digging, destroying whatever they touch.

At first the 'Nauts resorted to gun turrets, trying to blast these things off the hull, but when that didn't work, they went outside on the hull and started engaging the things.

On the outside of the hull, none of the 'Nauts changed any equipment. Some were in armor (where it can be argued that it is air-tight and fitted with magnetic boots), but most of the 'Nauts were in their regular uniforms or clothes, clearly not wearing a breathing mast or protecting themselves from extreme temperatures.

Sure, it's space opera. It reminds me of that scene in The Empire Strikes Back where Han and Leia are outside the Falcon as it sits inside the belly of a giant space slug on an asteroid. Both Han an Leia wore a mask, but nothing covered their eyes or hands, and they both seemed to not have any problem with gravity.





Besides just saying, "Oh, it's space opera. They didn't concern themselves with realities of being on the outside of a space craft in space," I started wondering how this could be explained--especially since the Micronauts adventure I read earlier where a human from Earth made it to the Microverse and was floating around in space was specifically said to have an atmospheric force field around him protecting him from space and allowing him to breathe.

How could this work in Traveller?

I'm not sure sure it's as far fetched as it at first seems....





If inertial dampeners exist, and artificial gravity, then there's no reason why the exterior of a space craft could be charged to provide a 1G field for those walking on the hull while in space.

Why not?



If the Jump Drive can create a jump bubble around the hull of a ship, then why not a Survival Bubble, too? Where vents open and heat (or air conditioning) along with oxygen are pumped into the bubble to provide an atmosphere in which to breathe and not freeze or fry to death.

What about it?

Maybe it's high tech, but....I think possible using standard Traveller tropes.

Maybe only certain sections of the hull can be fitted this way? Maybe there's a path from a main airlock to a specific exterior piece of the ship that might need attention from outside the ship from time to time.

"The damn fuel scoop is clogged again, and the over-ride isn't working. Engineer, you're going to have to go out there and manually unclog it."

If reactionless drives exists, where the polarity of atomic particles can be changed (from the MT Starship Operator's Manual) to produce thrust, and vector is controlled by a gyroscope locked in a sphere of grav plates, allowing the ship to push off of itself in order to change course, then why not use this same type of technology to keep an atmospheric survival bubble around the external hull of the ship?

-- Just speculating.

 

[Carlobrand]

I'm reading this, and my first thought was, "Uh huh."

Then it tickles at something, and I think, "Hey wait, he's onto something."

I love math, but I've always been weak in the applied physics. However, as I understand it, the basic thing about atmosphere escaping into space is all the little moleculey thingies bumping into each other - except where there's nothing to bump into, they just keep going.

That's my layman-speak. I'm practicing it.

Anyway, when you impose a gravity field, you impose a force that pulls them back down against that tendency to keep going. Now they have to be going fast enough to overcome that gravity field - they have to hit escape velocity. What decides whether they do that is how fast they're traveling (how hot the air mass is) and whether there's something for them to bump into (how much air is above you). There's a table here that shows you the average velocity of oxygen by its temperature, along with a plot of the planetary escape velocities and mean temperatures. Expresses the basic idea, which is that oxygen's a bit too heavy a molecule to easily escape a 1G room temperature world.

http://astro.unl.edu/naap/atmosphere/atmosphere.html

That's not to say some won't escape. Gas molecules don't all run to the same velocity; they average a certain velocity at a certain temp, with some slower and some faster - some a lot faster. As the faster ones escape, the air cools - and thins. I don't have the physics to work that out for the model you're proposing. It's possible that oxygen and nitrogen "like" the gradual pressure drop thing they do on Earth and that the only way to get a breathable pressure hullside is to pump out so much atmosphere that it ends up stacked miles above the hull, like on Earth. Or maybe not, I don't know. If A, then it's impractical; if B, then the basic idea might be workable for enough time to run an errand, especially if you tweak it by dropping the temperature and/or increasing the strength of the grav field and then bleed out gas to replace what's lost. A bit expensive in the atmospheric gas department though. It's a bit like diving by building one big cofferdam instead of just putting on a suit and a tank.

The problem I see is that none of this protects you from solar radiation, at least not enough. A few feet of air is not going to protect you from the fastest and worst sunburn ever. You're protected from vacuum, but you've still got to wear protection from the local sun.

On the other hand, even if the atmosphere has to stack up miles above to give you decent pressure below, you could with enough continuous power and effort make yourself a habitable world on a little asteroid. Unless, as has been speculated, the artificial gravity field tapers off more rapidly than a natural one, in which case anything that gets above the field flies away and there's no way to hold the atmosphere down.

 

[aramis]

Carlo - pretty much - but there are two other big factors in atmosphere loss.

1. Solar Wind impact accelerates the uppermost gasses IF it hits them
2. atmospheres do sort by gas density (just like any mixed fluid).

So, if you've a deep and not very highly stirred atmosphere, it's going to sort by density. (Even if well stirred, the lightest stuff will separate from the heaviest. One of the laws of fluid mechanics.)

Nitrogen Gas is atomic mass 14; Oxygen gas is atomic mass 16. In a truly still and deep air, you're going to get more oxygen at lower altitudes.

Now, as for solar wind - unless you have a strong magnetic field, you're going to lose atmosphere to solar wind. And you'll lose the lightest isotopes first.

2300AD has a good set of tables for minimum molecular mass retained; any world smaller isn't going to retain lighter gasses than the world's mass allows retention of; chemical (especially biological) processes can release them from heavier compounds.

http://www.universetoday.com/101325/more-evidence-that-mars-lost-its-atmosphere/

 

[mike wightman]

So the question boils down to how far does the 1g artificial gravity field extend from the ship?

Maybe this is how the jump drive was discovered by Earth, research being done on an oversized manoeuvre drive designed to attach itself to an asteroid and tow it, the attachment provided by the external gravity field generator. They turned it up as high as it would go and were very surprised when the field reached a certain critical energy density and opened a rip into jump space.

 

[Lycanorukke]

"The damn fuel scoop is clogged again, and the over-ride isn't working. Engineer, you're going to have to go out there and manually unclog it."

Or from the Blakes 7 episode "Stardrive" where they created a small forcefield bubble over a hull hole and pressurised it for repairs.

There was another one with Mass Effect where a 'membrane' of SF₆/gravity fields was used to prevent leakage of the N₂/O₂ atmosphere in conjunction with centrifugal force holding the air 'down'.

In Trav you could probably do it with one of the globes (white/black/etc) but grav alone couldn't do the required air pressure without winding the G's up beyond what a person could stand to keep the 'air column' within reason.

 

[Timerover51]

Nitrogen Gas is atomic mass 14; Oxygen gas is atomic mass 16.

Nitrogen Gas is N2, so molecular mass is 28. Oxygen gas is O2, so molecular mass is 32. Carbon Dioxide is CO2, so molecular mass is 44, the heaviest if you are talking about breathing a straight oxygen-nitrogen gas mixture.

 

[Carlobrand]

Carlo - pretty much - but there are two other big factors in atmosphere loss.

1. Solar Wind impact accelerates the uppermost gasses IF it hits them
2. atmospheres do sort by gas density (just like any mixed fluid).

So, if you've a deep and not very highly stirred atmosphere, it's going to sort by density. (Even if well stirred, the lightest stuff will separate from the heaviest. One of the laws of fluid mechanics.)

Nitrogen Gas is atomic mass 14; Oxygen gas is atomic mass 16. In a truly still and deep air, you're going to get more oxygen at lower altitudes.

Now, as for solar wind - unless you have a strong magnetic field, you're going to lose atmosphere to solar wind. And you'll lose the lightest isotopes first.

2300AD has a good set of tables for minimum molecular mass retained; any world smaller isn't going to retain lighter gasses than the world's mass allows retention of; chemical (especially biological) processes can release them from heavier compounds.

http://www.universetoday.com/101325/more-evidence-that-mars-lost-its-atmosphere/

Nitrogen Gas is N2, so molecular mass is 28. Oxygen gas is O2, so molecular mass is 32. Carbon Dioxide is CO2, so molecular mass is 44, the heaviest if you are talking about breathing a straight oxygen-nitrogen gas mixture.

All agreed, but this is a question of numbers, and that's where my awesome powers fail me. The question on the deck is: can you establish a breathable atmosphere around a ship, presumably using the tech available in Traveller, long enough for a person to do useful work?

The question breaks into two parts. One: can you establish the envelope using Trav tech and a reasonable supply of air, or is the air going to "stack up" the same way it does on Earth, with the result that you'd need miles of it overhead before you could provide a breathable pressure at the level of the hull? Two: if you can establish the envelope, how long will it last before solar wind and other effects cause it to thin beyond healthy limits?

Questions of stirring and settling only become practical if we get a good answer to question one. One presumes there will be stirring in the course of making it; settling and loss only become issues if we can make it in the first place. So, what is that answer to question one? One possible answer might be:

...In Trav you could probably do it with one of the globes (white/black/etc) but grav alone couldn't do the required air pressure without winding the G's up beyond what a person could stand to keep the 'air column' within reason.

It might be that air needs some sort of ceiling against which to press, and if the only ceiling is more air, then it might need to stack up many miles in a 1G environment to build up the weight needed to give you a breathable pressure at the hull surface. Or you'd need such high levels of gravity that you'd end up in a specialized suit anyway just to be able to stand. So, without the black globe or a plastic bubble or some other means of exerting a "ceiling", you couldn't do it.

What I'm trying to ferret out is the numbers.

Earth escape velocity is 11.2 KPS. That little table's hard to see, but it looks like average molecular velocity for oxygen at room temperature's somewhere between 4 and 5 KPS. That's not enough to escape, but a projectile launched straight up at 4 to 5 KPS can go quite a ways before it starts coming back down again. As we vent air out, the molecules are bumping into each other and spreading out - and going up. The ones that don't bump into another molecule are going to keep going up until, like that projectile, they run out of steam and start falling down. My weak math says that's 800 kilometers for a 4 KPS mass.

So, great, the molecules go out 800 klicks and fall back, but near as I can tell that doesn't mean the gas behaves any differently in 1G on a space hull than in 1G on a planet. What's going to determine the pressure at the hull is the weight of air above the hull - which is to say you end up with air to the same height you'd have here on Earth. Why? I'm not sure, that's where my learning fails me. However, the good news seems to be that I can build Kobold - my little asteroid tribute to Niven - but I need enough air to fill an atmosphere that might go 80 kilometers up even if I aim for pure oxygen at a quarter atmosphere, and the same would apply to Four's spaceship atmosphere bubble. (On the positive side, if I start from Earth and move slowly, I can maybe take some of that atmosphere with me instead of having to bottle and then vent it.)

And of course all bets are off if my artificial gravity field only extends a meter or two.

And then we get to how long such an atmosphere would last. However, if it's already impractical without some sort of ceiling, then the answer to question two depends on what manner of ceiling we adopt, since it then becomes a question of the interaction of the atmosphere with that ceiling and of that ceiling with the solar wind and suchlike. That black globe could hypothetically hold in whatever atmosphere you put out for however long you needed, considering that the ship has to make port and turn the thing off every week or two. White globe probably same. I can't think of anything else in Trav that fits the need without importing a trope from some other sci fi source.

 

[mike wightman]

Here is a little experiment to try.

Tie a rope to a bucket and half fill bucket with water.

Now spin around and the water will stay in the bucket.

Next experiment - fill a bucket with smoke and repeat your spinning at the same rate as before.

Watch what happens to the smoke.

if it stays in the bucket then the artificial g field on a ship will hold an atmosphere.

If the smoke escapes from the bucket forget it.

And no, I haven't tried it.

 

[aramis]

All agreed, but this is a question of numbers, and that's where my awesome powers fail me. The question on the deck is: can you establish a breathable atmosphere around a ship, presumably using the tech available in Traveller, long enough for a person to do useful work?

The question breaks into two parts. One: can you establish the envelope using Trav tech and a reasonable supply of air, or is the air going to "stack up" the same way it does on Earth, with the result that you'd need miles of it overhead before you could provide a breathable pressure at the level of the hull? Two: if you can establish the envelope, how long will it last before solar wind and other effects cause it to thin beyond healthy limits?

Well, given gravitic focusing of lasers in TNE, maybe. But....

Ok... Gross simplifications following, because I don't do integral calculus...

standard air density is roughly 1.2kg/m³. and standard pressure is roughly 1.03 kg/cm²

An ideal mass column of 1cm² is 10km per m³.

We know that we are looking for the length of a non-ideal column with two pressures:
T is target pressure in kg/cm².
E is End Pressure in kg/cm². E axiomatically = 0.
D is STP density
V is volume in m³
L is length of column in m units (thus making V*10000m=L)


We know that the density decreases with the pressure, roughly linearly.

This means we can calculate based upon the midpoint, and it's average density.

So V= (T+E)/2D.
And thus
L=10000(T+E)/2D
L=5000(T+E)/D
And since E = 0...
L=5000T/D

A pure O2 atmosphere is breathable at 0.1 kg/cm - but thats survival level.
Standard pressure is 0.2 kg/cm² PPO2 - so that's a safe level (NASA uses 0.3kg/cm² - because they want a safety margin.)

So T=0.2 D=1.3 (O2 STP density).
L=5000*T/D
L=5000*0.2/1.3
L=1000/1.3
L=769

So, for this to work, we need 769m at 1G....
But then, to know the drop off, since gravity is a force measure -
and we know that men don't function much above 2G's... 3G's for short periods. (One can walk on a plane during a coordinated 2G turn - but at 3G, it's pretty damned hard.)

Which means you need to have ≤2G at work site, and ≥0.5G at the far end (because, according to the potentially wrong tables in T2300, which I have to hand, 0.47G at surface is the minimum to hold an Min Molecular Weight 31 atmosphere, and earth's still at ≥0.98G at 100 miles up, so, for simplicity, close enough to still 1G, and that's vacuum.)

If we aassume 2G at near end (1 diameter) and 0.5G at far end (X diameters)...
2G=D
1G=D(√2)
0.5G=D(√4)
and
768+D=D√4
768+D=2D
768+D-D=2D-D
768=D

Your AG needs to make the air think it's between 768 and 1536m from a source that generates 2G at 768m...

You can tweak the numbers elsewise, and I'm not doing the math to calculate the actual proportional effect of the gravity on the column size; I'll just note that my column length is undoubtedly too short for this application.

And I'll note further - I find it implausible - not impossible, just implausible - to do this at TL≤15

 

[Lycanorukke]

Thinking on it a bit, instead of using gravity generators to 'pull' the air down and hence increase the pressure, Aramis's mention of colums gave me an idea. Instead of trying to suck the air down into the bottle to boost pressure, why not cork the bottle and pump the air in.

In T5 at least the Nuke dampers at higher levels can manipulate kinetic energy (kinetic option). Set one up and all material inside the field will be pulled towards the damper, including air. The air pressure will rise unil it exceeds the dampers tractor effect. The average nitrogen molecule speed at 20C is about 510 m/s or 1836 kph. A TL15 Damper can negate 5kph, while a TL25 can handle 2000kph.

By cancelling any molecules trying to get out (aka the equivilant of hitting a wall, and other molecules bank up behind them creating pressure) you get pressure build up inside the projected globe. Sooo - at TL 25 you could plop an Nuke damper "atmosphere dome" down anywhere and it would be leak proof. Lesser tech ones would leak badly but may last long enough to do some good, esp if you reduced the pressure it has to hold and the temperature.

If you needed an excuse to lower the tech level further just say it only works on gasses and not solid masses, can only negate energy (a tractor only, not a pressor), only performs this function with no other damper functions, etc.

 

[Carlobrand]

...In T5 at least the Nuke dampers at higher levels can manipulate kinetic energy (kinetic option). ...

Kine-wha? A T5 nuclear damper can damp a molecule's movement? Directionally?

... By cancelling any molecules trying to get out (aka the equivilant of hitting a wall, and other molecules bank up behind them creating pressure) you get pressure build up inside the projected globe. Sooo - at TL 25 you could plop an Nuke damper "atmosphere dome" down anywhere and it would be leak proof. Lesser tech ones would leak badly but may last long enough to do some good, esp if you reduced the pressure it has to hold and the temperature...

Ummm, I think you're lowering the gas temperature. You're removing energy directionally, but any removal of energy is going to lower the gas temperature since a gas' temperature is its movement. You are in effect confining the gas by dropping it to very low temperatures - directionally. You're creating a directional temperature and pressure situation: the gas feels warm laterally but frigid to up-and-down surfaces, and it exerts more pressure laterally than up and down.

My guess is the temperatures needed to confine the gas may be dangerous to tissue. Even if not, I'm not sure how the alveoli would handle having normal pressure on the horizontal plane and little pressure on the vertical plane. At the very least, you're not getting as much oxygen because the alveoli are in effect dealing with half their surface facing air at normal pressure and half their surface facing air at reduced pressure. I'm not really sure it is healthy to breathe under those circumstances.

 

[Lycanorukke]

Kine-wha? A T5 nuclear damper can damp a molecule's movement? Directionally?

Yup. It essentially can become a Tractor/Pressor at T15+ if the kinetic option is selected. I paid a lot of attention to the tech in the T5 BBB and the new ways to twist it. And dampers have a lot of "fun potential"

You are not exactly removing energy, but redirecting it. All molecules constantly are pulled towards the damper. As these molecules bunch up the pressure and temperature increases. The heat is vented as IR to space, so as long as the damper keeps adding energy as motive force you have a constant temp. The reason you need the 2000kph is to prevent leakage. You could have the same effect with a lesser damper, but the lower the 'attraction speed' the greater the leakage due to the molecules thermal energy exceeding the 'boundry speed'..

Another way would be to have two dampers - one projecting a small sphere, and one projecting a sphere slightly larger, with the small sphere inside the big one (like a Russian doll). The inner sphere is a "repeller" and the outer sphere is a tractor. Sandwiched in between the two spheres is a dense gas (denser means lower velocities, hence lower tech levels to contain it). As long as the air (O2/N2) pressure inside the inner sphere is less that the pressure of the dense gas 'membrane' you have a contained atmosphere.

 

[Patron Zero]

Just my interpretation but almost seems like a personal force field is being discussed in theory much like the life-support belts depicted in Star Trek-The Animated Series.

If nothing else, than maybe a man-portable force-field projector that will contain atmosphere and 'screen' out harmful radiation but there's the rub of not so harmless radiation (weapons fire) exiting said bubble.