The Trouble of ISRU Refueling NTR Spacecraft

[Spacescifi]

20 minutes ago, YNM said:

Excerpt of the first paragraph of Wikipedia's page about ISRU :

Taking water from asteroids is ISRU.

 

Yes...I know and knew that.

Slightly puzzled with you right now.

[YNM]

49 minutes ago, Spacescifi said:

Yes...I know and knew that.

Slightly puzzled with you right now.

On 5/10/2021 at 11:26 AM, Spacescifi said:

To get LH you must travel to a source, and extract and cool the hydrogen gained into LH.

If hydrogen is NOT available you run the chance of melting or damaging your reactor from heat overload from using a denser atomic chemical...unless you go super slow....which has issues of it's own due to crew health.

 

Seems to me one easy solution is to keep spare LOX in storage and use regularLH/LOX chemical rocketry or anu other chemical with LOX when you do ISRU and hydrogen is not reasily available to mine.

 

So using known tech, any spacecraft exploring our home system will need BOTH nuclear and chemical rockets.

NTR for orbit to orbit and hydrogen ISRU when available, and stored LOX to use for chemical rockets if hydrogen is not available.

You need hydrogen and oxygen.

Water is dihydrogen monoxide - two hydrogens, one oxygen.

On 5/10/2021 at 11:26 AM, Spacescifi said:

Locations hydrogen is hard to come by:

1. The moon....we hope it has enough but it is limited.

Mercury: I dunno. I think it may have low if any ice at all.

Venus: Would be easier to die trying to mine hydrogen here than to mine it.

 

Places Hydrogen IS available in other than Earth:

Jupiter, Neptune. Uranus, icy comets and asteroids. Likely several outlying moons farther from sun.

2 hours ago, Spacescifi said:

One design I think could work well is an oblong vessel with an inflatable bladder at it's center of mass.

Ideally it would find an icy comet or icy asteroid, extract as much water as possible and fill up the bladder balloon.

Read again. Emphasis mine but is otherwise completely your own writing in your own post.

Edited May 11, 2021 by YNM

[FleshJeb]

  

2 hours ago, Spacescifi said:

Consider....are they prepped for boiling cadavers and using them as propellant?

No.

Which means....the boiler they do have is too small for a cadaver, let alone two. Which means some poor guy or gal is going to have to 'disassemble'  them...piece by piece. IN ZERO G! Messy and gross is an understatement.

Do they have medical saws aboard? Hope so. Otherwise we are talking cutlery.

Don't envy this person...at all. Probably will suffer from PTSD after. Even worse if they lack medical training and or the cadaver is opposite gender and they had a romantic relationship with them in the past or were developing one. Even if they were not, how do you explain to your significant other back home on Earth what you did to survive.? You don't....not easily probably.

If you've got a week, stuff them in the wastewater treatment system, let the microbes do the work and decant the results. On a sufficiently large spacecraft, the maintenance hatch will be man-sized.

If you must disassemble the body, freeze it first--There's plenty of cold to go around. Hacksaws should be in abundance.

I used to design and inspect wastewater systems, so I'm hard to gross out and ruthlessly pragmatic. The first step to solving any problem is believing that a good solution exists and then going from there. There's no room for fatalists in space.

If we were to approach this realistically, you wouldn't start a journey with insufficient propellant. So, we're probably looking at mid-transfer propellant loss from a micrometeroid in at probably one tank. Which means you have a braking/capture problem at your destination. The solution to that is to start hacking dry mass off the ship that's not strictly required. That will get you a lot further than 70kg of meat soup. For a similar situation, I'll refer you to The Cold Equations. I'll spoil the TV version by saying they ripped out everything from the ship they possibly could and everybody lived. The book version is FAR more satisfying.

[kerbiloid]

The ship just should have a ISRU incubator to produce as many human slaves  (from the neighbor thread) as needed, use them to mine and refine, then spend as NTR propellant.

Did I miss something?

(Using Civilian Population and Kethane mods, for example).

[sevenperforce]

On 5/10/2021 at 4:49 PM, Spacescifi said:

Hahaha! You may regret saying that. Because we are about to boldly go where probably no scifi has gone before.

[gross, snipped]

So how much ISP and what kind of thrust or disassociation can we get out of a half liquid ton of milk, a half ton of orange juice, and 3 gallons of blood plus whatever is left of the cadavers that was boiled into mush and burned as propellant LOL?

Humans are mostly water so just run the numbers with water.

 

[kerbiloid]

Humans are water polluted with at least three kilograms of calcium carbonate and phosphate.

[sh1pman]

On 5/12/2021 at 7:23 AM, kerbiloid said:

Humans are water polluted with at least three kilograms of calcium carbonate and phosphate.

Out of what, 60-80kg? Might decrease ISP by a few seconds. Not significant.

[kerbiloid]

26 minutes ago, sh1pman said:

Out of what, 60-80kg? Might decrease ISP by a few seconds. Not significant.

May pollute the chamber and cause explosion.