gather oxidiser from an atmosphere?

[fommil]

Is it possible to siphon off some of the oxidiser that my jet engines are not using into an oxidiser tank?

It would be great to be able to fill up the oxidiser tanks on the way up, burn them when the air runs out, then come back down (and not fill up the oxidiser anymore because it's not useful).

Could result in super light spaceplanes!

[Aegolius13]

Not in stock, but maybe there's a mod that can do it.  

We don't really know that the "oxidizer" in  KSP is, but if it's something other than liquid oxygen, it makes sense that it would be hard to make on the fly.  On the other hand, the ease with which the ISRU can make oxidizer out of anything does suggest it really is oxygen. And I would guess the Rapier would run oxygen in closed-cycle mode.

Side note: India's planned Avatar SSTO was supposed to be able to this.  No idea if it is/was feasible in real life, though. 

[sardia]

http://github.com/BobPalmer/Karbonite/releases

Karbonite has atmospheric fuel scoops. 

[Overland]

Modify an engine to run off air intake resource then via alternator turn it into oxidizer resource

I been doing this with LF fuel to monoprop for locomotives for years

[samstarman5]

One thing to remember is with human rockets, oxidizer is stored in a liquid state, which means there is a lot of it in a smaller container than it would be if it were a gas. LOX is produced at a different site, then pumped into the rocket.  It's not something you casually replicate on the rocket itself.

Just about the simplest would be using the likes of a ramscoop to bring in the oxidizer, chill that oxidizer with either a catalyst or subzero cooler, and then store the result.  It would take a few hours of flight time to get a measurable amount, and by then you would have burned more fuel than anything you would have saved by just landing and mining it.

I am sure there are plenty of scifi ideas and even complex actual science ideas to create LOX on a rocket itself, but that's above my paygrade.

[sardia]

6 hours ago, samstarman5 said:

One thing to remember is with human rockets, oxidizer is stored in a liquid state, which means there is a lot of it in a smaller container than it would be if it were a gas. LOX is produced at a different site, then pumped into the rocket.  It's not something you casually replicate on the rocket itself.

Just about the simplest would be using the likes of a ramscoop to bring in the oxidizer, chill that oxidizer with either a catalyst or subzero cooler, and then store the result.  It would take a few hours of flight time to get a measurable amount, and by then you would have burned more fuel than anything you would have saved by just landing and mining it.

I am sure there are plenty of scifi ideas and even complex actual science ideas to create LOX on a rocket itself, but that's above my paygrade.

Most of the benefit is derived from aerobraking. You're already trying to bleed off energy, might as well recoup some of it. Aerobraking often requires hundreds of passes, so it might be worth it. The most obvious example is Jool.

Edited January 15, 2017 by sardia

[KSK]

This sounds like a LACE (for Liquid Air Cycle Engine) which is a thing and has been studied, although it's practical use seems to be a matter of debate still. SABRE (for Synergistic Airbreathing Rocket Engine) is an evolution of certain LACE designs, which compresses and cools, but does not liquify, incoming air to use as the oxidiser in a rocket engine.

[fourfa]

LACE as described above could be an interesting application of a lightly-modded small ISRU converter (certainly it's not much good for mining!) - patch it to convert intake air to liquid oxidizer. If the balance is right, it could be an interesting engineering challenge. Electrical power, extra heat, nonlinear burn rates... sounds fun

Edited January 16, 2017 by fourfa

[Sharpy]

Mining Expansion has scoops for air->oxidizer, and Explodium Sea water -> fuel

(and it's far more lightweight than Karbonite, not putting the whole KSP resource system through a grinder.)

[Grand Ship Builder]

Would be useful, and as seen above, there are mods for it.

Off I go!

[MiffedStarfish]

I think you could go into the config file of an intake, and change the resource from IntakeAir to Oxidiser.

[T.A.P.O.R.]

On 15/01/2017 at 6:05 AM, sardia said:

http://github.com/BobPalmer/Karbonite/releases

Karbonite has atmospheric fuel scoops. 

My search skills are embarrassing. Been trying to find a current version of Karbonite for days!

havent used since 2014.....

[NSEP]

Config files are your friend man!