Liquid oxygen rocket

[darthvader15001]

hello there. in theory, could a rocket fueled solely by liquid oxygen generate enough thrust to lift off? just a weird idea that I thought of.

[darthgently]

37 minutes ago, darthvader15001 said:

hello there. in theory, could a rocket fueled solely by liquid oxygen generate enough thrust to lift off? just a weird idea that I thought of.

Sure, if the LOX were highly pressured it could launch like a water rocket.  But having something to oxidize would be the more performant avenue

[JadeOfMaar]

1 hour ago, darthgently said:

Sure, if the LOX were highly pressured it could launch like a water rocket.

And if the rocket itself isn't much larger than a 2L bottle.

If it's big enough then it's too heavy and you just have a controlled, very powerful leak.

[darthvader15001]

1 hour ago, darthgently said:

Sure, if the LOX were highly pressured it could launch like a water rocket.  But having something to oxidize would be the more performant avenue

 

14 minutes ago, JadeOfMaar said:

And if the rocket itself isn't much larger than a 2L bottle.

If it's big enough then it's too heavy and you just have a controlled, very powerful leak.

Sorry I wasn’t clear. What I meant was that the theoretical rocket burns only lox.

[magnemoe]

LOX would work as an cold gas thruster if turned into oxygen gas. SpaceX uses this for control of their Starship rocket and booster. You use the gas for trust with the liquid is your fuel reserve. 
So you need to make it gas for trust. Now if you had an over pressure of oxygen on top you could use it as an very impractical bottle rocket as it would have pretty similar performance to an water an compressed air one. 

Edited July 7 by magnemoe

[NFUN]

You can't burn only lox. That's like trying to start a fire with lots of air but no fuel

[kerbiloid]

Or use the quasistable liquid ozone, which exothermically turns into normal oxygen.

Edited July 8 by kerbiloid

[DDE]

At that rate we can start thinking about lOx NTRs and such.

[farmerben]

I suppose its possible for an ISRU project to generate excess O2.  In which case we would be looking for uses for it.  Most other gasses are lighter and thus better for propulsion.

In the case of Mars it might be possible to build an SSTO that runs on carbon monoxide and oxygen.

[JadeOfMaar]

10 minutes ago, farmerben said:

I suppose its possible for an ISRU project to generate excess O2.  In which case we would be looking for uses for it.  Most other gasses are lighter and thus better for propulsion.

In the case of Mars it might be possible to build an SSTO that runs on carbon monoxide and oxygen.

It's nice that you mention that. Per a nerd friend's advice I had made a test config for engines to burn CO + Oxidizer at 90% the original (LFO) Isp. And I believe CO is produced by merely using electrolysis so yeah, this may be quite possible IRL.

15 hours ago, DDE said:

At that rate we can start thinking about lOx NTRs and such.

I don't think we can. If you dare to make concentrated Oxygen hot enough to produce thrust you're making it hot enough to react with its heater. There's a reason an incandescent bulb's filament is sealed in vacuum or inert gas.

[DDE]

1 hour ago, JadeOfMaar said:

If you dare to make concentrated Oxygen hot enough to produce thrust you're making it hot enough to react with its heater.

Counterexample: oxygen-rich staged combustion.

[JadeOfMaar]

9 minutes ago, DDE said:

Counterexample: oxygen-rich staged combustion.

I bet that doesn't burn as hot as an NTR does so that would probably be plenty safe.

[DDE]

5 hours ago, JadeOfMaar said:

I bet that doesn't burn as hot as an NTR does

Well, in general, counterintuitively, NTRs aren't as hot as LRPEs.

According to http://www.lpre.de/energomash/RD-170/ on an RD-170, turbine inlet temperature is 772 K.

Quote

In an oxidizer-rich staged combustion engine, protection of the turbopump oxygen tract units from combustion under the influence of accidental ignition initiators is of particular importance. Due to extremely high pressure in the path of 11D520 and 11D521 engines, as well as high mechanical loads characteristic of a powerful engine, the problem of protection against combustion during their creation was particularly acute.

To prevent combustion due to the breakage of structural elements or friction of rotating parts against stationary ones (due to the selection of gaps from deformation or riveting on mating surfaces from vibration), the gap between the blades of the nozzle apparatus and the rotor is made relatively large, and the edges of the blades - relatively thick.

In order to exclude fire and destruction of turbine gas path parts, nickel alloys are used in the design, including heat-resistant alloys for hot gas lines. The turbine stator and exhaust path are forced cooled by cold oxygen. In places of small radial or end gaps different kinds of heat protective coatings are used (nickel for rotor and stator blades, metal-ceramic for rotor), as well as silver or bronze elements, which exclude fire even in case of possible touching of rotating and stationary parts of the turbo pump unit.

To reduce the size and mass of foreign particles that can lead to fire in the turbine gas path, a filter with a 0.16x0.16 mm mesh was installed at the engine inlet.

Translated with DeepL.com (free version)

Meanwhile NERVA was in the high 2000s to 4000s... whoops. RD-170 does reach 3676 K, but only in the combustion chamber where there's film cooling et cetera.

Edited July 8 by DDE

[kerbiloid]

15 hours ago, JadeOfMaar said:

I don't think we can. If you dare to make concentrated Oxygen hot enough to produce thrust you're making it hot enough to react with its heater. There's a reason an incandescent bulb's filament is sealed in vacuum or inert gas.

In the Glushko's encyclopaedia it's called "rocket engine on metastable fuel", and expects 25 km/s of exhaust speed.

So, at least it was studied.