New Mars Forums

There's been speculation on this forum about the US selling its interests in the International Space Station and getting out from under the thing.

I'm curious.  Sell to who?  A consortium?  Stock holders? Another space agency?

Aside from the question of who would actually have enough money to complete the transaction(s), there is the question of motive.  Why would someone buy a share of the ISS?

Assuming you, personally, had enough money to purchase any significant part of the ISS, which part would you want and what would you do with it?

I suppose that it would be more realistic to assume an individual only owned a portion of the station or package aboard it, but if the US really did look to sell out, other ISS partners might try to sell, too.  If you played your cards right, you might end up with the whole thing.

Not only does conservation of energy prohibit getting more power out of the thermal (inert propellant) exhaust than comes out of the fusion reaction, but, if the fusion reaction products must be vented along with the inert propellant, the first and second laws of thermodynamics prohibit getting a working thrust greater than that theoretically available from the fusion reaction alone.  In other words, given a choice between using a fusion rocket engine to provide thrust and using a vented fusion reactor _with the same reaction rate_ to heat any given volume of inert propellant in a thermal rocket engine, the fusion rocket engine provides more thrust.

If thrust is all you’re after, and absolutely nothing else in the universe matters (not mass, complexity, power, or anything), then it’s better just to use a straight fusion rocket engine and forget about all that inert propellant stuff.

However…

Use of an inert propellant can simplify cooling.  All of that inert propellant is potential coolant.  The fusion reactor venting is cooler (having been tapped for power to heat the thermal propellant).  The thermal rocket exhaust is cooler.  Everything’s cooler.    So, the engine mass doesn’t skyrocket as fast.  As long as you were willing to settle for less thrust and specific impulses well below the 2 million Isp expected for a pure fusion rocket engine, using a reactor to heat an inert propellant is the way to go. 

The engine might even ultimately weigh enough less to allow ground launch even with the reduced thrust curve, but don’t quote me on that.  It all depends on whether the engine weight can be made lower than the thrust, and I have serious doubts about whether that’s doable with fusion power.

But I have to admit it’s not _impossible_.  You just have to give up a lot of specific impulse.

Yes, but it's not necessarily a loss to the Marsian economy.

In examining the American example, it's important to know two things:

My Cajun grandmother and my Spanish aunt are both laughing at the suggestion that early cultural influences are obliterated by later influences,

and

The primary influence on US society today has nothing to do with who came out first in the settlement of the country.  The primary influence is the citizens of the United States of America.

Historically, the most famous people in my family tree have been mostly crooks, politicians, and engineers.  In the past, my relatives have often found it convenient to have new places they could re-settle and start decent, productive lives again after making a name for themselves. 

Unfortunately, modern American society is not the place to do this.  There is simply too much insistence on being able to track citizens, particularly financially, and not as much on allowing opportunity.  Starting over after a grave financial error in the States is becoming as difficult as starting over after a prison term.  And starting over, IMHO, is the whole reason to emigrate anywhere.  There has to be room for it on Mars, or you're not going to get anything other than scientists to go live there.

Mars ain't really settled if there's no real characters.

The problem with heat seems to stem from the necessity for confinement.

What if there were no confinement at all, but rather an ablative nozzle/chamber, like the old Orion nuclear pulse propulsion idea?  One could conceivably have an "Orion Lite" vehicle, but then the main limitation becomes the power source. 

If you don't use fission, how do you prime a fusion reaction that isn't self sustaining?

On a more serious note, lack of mutinies on nuclear submarines are _not_ a good indicator of the existence of serious psychological problems in the crews.  Military discipline and cooperation tend to prevent such episodes.

Fortunately, better examples exist in polar expeditions and other groups.  And, while mission-threatening psychological disfunctions are not something that can be ignored, they're not likely, either.

My guess: Not possible.

The kinetic power released by a rocket's exhaust is equal to a half of the thrust times the exhaust velocity.  If you raise the exhaust velocity of the rocket without changing the thrust, all you're doing is making more heat. 

A lot of useless heat.

Fusion powered rockets represent scant gain in efficiency for ground launches even if they work, and they'd run so hot that any current design is as likely to blow up as to actually launch.  Fusion rockets capable of ground launches are a technology for the distant future, if it's possible at all.

When exposed to carbonated water, olivine slowly breaks down to form other iron bearing minerals, like the hematite scattered all over Mars. 

How could the two coexist in the forms seen by Opportunity, over the apparent timescale observed?  You've got me.

Reportedly, the vote split along party lines.

Time to vote Democrat.

Hmmm...  Yes, _that_ could conceivably be within the capabilities of a telepresence "robot", even if a full repair mission is not.

Perhaps something similar could be done for other failed satellites?

Questions, to satisfy my curiosity:

How long can the ISS soak in space without maintenance?  What are the critical components that demand human maintenance, and could they be restarted if shut down for several months?

Also,

What defunct space probes can still be contacted by radio?  The Venus probe Magellan was one of the few shut down while still fully functional, so I know better than to expect full function from every defunct probe.  But what about only re-establishing radio communications?  For example, were the Viking landers on Mars ultimately lost, or were they just shut down?  What's broken, but still has a working radio?

Hmm...

Two important rules of thumb in comedy: Timing is everything, and always tell the audience you're serious.

ESA seems well prepared for this mission.