NTR launch escape system concept

[gooddog15]

I've been thinking about the possibility of using a surplus orion launch escape system (if they're ever mass produced ) and modifying it to be used for a NTR, along with a descent module with thrusters, a surplus orion CM heatsheild, inflatable airbags for water/land landings, and a tracking beacon. This could reduce the risk of fallout from a launch failure and some of the development costs by using off the shelf parts (although its still expensive).

However, if there's a launch failure & the NTR landed into the wrong hands..............really bad stuff could happen.

It would look like this:

5. ........____ ____

[>[] [) [____] [___]<]

1.__2.___3.___ 4.

1. NTR

2. heatshield

3. fueltank

4. upperstage from launch vehicle

5. fuel umbilical (periods)

*note*: NTR = Nuclear Thermal Rocket (see http://en.wikipedia.org/wiki/Nuclear_thermal_rocket to get a general idea)

Edited April 5, 2014 by gooddog15

[TechnicalK3rbal]

I've been thinking about the possibility of using a surplus orion launch escape system (if they're ever mass produced ) and modifying it to be used for a NTR, along with a descent module with thrusters, a surplus orion CM heatsheild, inflatable airbags for water/land landings, and a tracking beacon. This could reduce the risk of fallout from a launch failure and some of the development costs by using off the shelf parts (although its still expensive).

However, if there's a launch failure & the NTR landed into the wrong hands..............really bad stuff could happen.

so would this be possible?

Just to be clear....

What's a NTR?

[Nuke]

that would be a nuclear thermal rocket

[sgt_flyer]

the problem with NTRs, is that they have fuel tanks attached to them (with the fuel flow they use, it's hard to have a specially engineered way to shear the plumbing ), and, typically, the payload above them. the planned US Nerva stage weighted 178 tons fully fueled, and 36 tons unfuelled - the planned Orion capsule weight is 8 tons - so that makes a huge difference in the weight to support for an escape system. (you'll have to increase a lot the escape system's solid fuel, which weights a lot )

of course, such an NTR stage would only be used outside atmo - so during ascent, the stage will still be fully fuelled with tons of LH2

the reactor + nozzle itself weights a bit less than the stage's dry mass - but not that much

for the fallout risks in case of booster failure, check out the Kiwi TNT experiment (which was a worst case experiment) - those stages are not bombs, they are nuclear reactors - and those things are built to be tough

[Nibb31]

so would this be possible?

If the question is "would this be possible", then no.

- There is no such thing as a "surplus Orion LES" or surplus CM. Orion MPCV will never be mass produced with the envisioned flight rates.

- There are no available NTRs, nor does anyone have any plans of building one.

- An NTR would be designed to contain any radioactive material in case of a crash, so it wouldn't differ from any other upper stage.

I really don't understand what you're getting at here.

[Kryten]

Multiple nuclear reactors have been launched without anything like this, without issue. One suffered a launch failure, and the only reason anyone even noticed was the US was closely monitoring trace radioisotope levels for nuke test treaty enforcement.

[architeuthis]

As several people have mentioned above, nuclear reactors are relatively safe on the launch pad. Uranium 235, which is the fissile material most often used, has an extremely long half-life (over 0.7 billion years). This means that it is not very radioactive. If the NTR you're thinking of is anything like the old NASA NERVA, then it will have nuclear poison wires inserted in the reactor upon launch. Nuclear poisons absorb neutrons and impede fission reactions. Since there is no fission there will be no neutron radiation, or nasty fission products (short half-lives, highly radioactive) in the core which emit gamma radiation. Once the NTR is in orbit, you send up a space shuttle to pluck out the wires, and boot up the reactor. Only fallout worries in this scenario is if an old reactor has some kind of uncontrolled reentry. That would be messy.

[gooddog15]

the problem with NTRs, is that they have fuel tanks attached to them (with the fuel flow they use, it's hard to have a specially engineered way to shear the plumbing ), and, typically, the payload above them. the planned US Nerva stage weighted 178 tons fully fueled, and 36 tons unfuelled - the planned Orion capsule weight is 8 tons - so that makes a huge difference in the weight to support for an escape system. (you'll have to increase a lot the escape system's solid fuel, which weights a lot )

of course, such an NTR stage would only be used outside atmo - so during ascent, the stage will still be fully fuelled with tons of LH2

the reactor + nozzle itself weights a bit less than the stage's dry mass - but not that much

for the fallout risks in case of booster failure, check out the Kiwi TNT experiment (which was a worst case experiment) - those stages are not bombs, they are nuclear reactors - and those things are built to be tough

detaching the NTR from the tank would be a challenge. also the fact that orions escape system as it is has to be modified extensively (I was at first thinking of a modified fairing, which is no biggie) rocks this ideas world.

Multiple nuclear reactors have been launched without anything like this, without issue. One suffered a launch failure, and the only reason anyone even noticed was the US was closely monitoring trace radioisotope levels for nuke test treaty enforcement.

this is for nuclear thermal rockets, not radioscopic thermal generators, which have less radioactive materials. also I think you are talking about Apollo 13's ALSEP rtg which reentered with the LM and is now sitting on the bottom of the ocean

- There is no such thing as a "surplus Orion LES" or surplus CM. Orion MPCV will never be mass produced with the envisioned flight rates.

- There are no available NTRs, nor does anyone have any plans of building one.

- An NTR would be designed to contain any radioactive material in case of a crash, so it wouldn't differ from any other upper stage.

I really don't understand what you're getting at here.

I said that IF parts of orion would be mass produced, and the possibility of using them for a NTR if they became available.

Also I should of said that it would be for a NTR powered transfer stage (that would be launched upside down) for transporting cargo/crews

to the moon or mars for future projects. however I think that a NTR wouldn't survive a impact with the ground (they have actually tested this by strapping a old NTR to a rocket sled and fired it into a thick concrete wall.)

As several people have mentioned above, nuclear reactors are relatively safe on the launch pad. Uranium 235, which is the fissile material most often used, has an extremely long half-life (over 0.7 billion years). This means that it is not very radioactive. If the NTR you're thinking of is anything like the old NASA NERVA, then it will have nuclear poison wires inserted in the reactor upon launch. Nuclear poisons absorb neutrons and impede fission reactions. Since there is no fission there will be no neutron radiation, or nasty fission products (short half-lives, highly radioactive) in the core which emit gamma radiation. Once the NTR is in orbit, you send up a space shuttle to pluck out the wires, and boot up the reactor. Only fallout worries in this scenario is if an old reactor has some kind of uncontrolled reentry. That would be messy.

interesting, I have never heard of nuclear poison wires. Those would make a launch escape system worthless, however the heatshield, thrusters, and parachutes would be handy for a uncontrolled reentry.

Edited March 28, 2014 by gooddog15

[NovaSilisko]

The soviet union and US have both launched actual factual nuclear reactors into space

http://en.wikipedia.org/wiki/SNAP-10A

http://en.wikipedia.org/wiki/RORSAT

[gooddog15]

The soviet union and US have both launched actual factual nuclear reactors into space

http://en.wikipedia.org/wiki/SNAP-10A

http://en.wikipedia.org/wiki/RORSAT

kind off scary thinking there's used radioactive materials flying above our heads that could reenter at any moment

Edited March 28, 2014 by gooddog15

[andrewas]

No. Radioactive material in orbit is not scary. What is scary is radioactive material on an uncontrolled re-entry, or even better, material that was never intended to re-enter and which should be in graveyard orbit. Even then, most of it is safe enough - for instance, the apollo 13 RTG fuel cask, which was supposed to be left on the moon but which re-entered along with the rest of the LEM, coming through re-entry intact and winding up deep in the ocean with, so far as we can tell, no leaks of any kind. Still, there might be something to fear from old soviet hardware.

[gooddog15]

No. Radioactive material in orbit is not scary. What is scary is radioactive material on an uncontrolled re-entry, or even better, material that was never intended to re-enter and which should be in graveyard orbit. Even then, most of it is safe enough - for instance, the apollo 13 RTG fuel cask, which was supposed to be left on the moon but which re-entered along with the rest of the LEM, coming through re-entry intact and winding up deep in the ocean with, so far as we can tell, no leaks of any kind. Still, there might be something to fear from old soviet hardware.

I found some stuff on incidents with RTGs:

http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Safety

maybe I should repurpose this thread... something like "risks of nuclear power in space"

edit: don't know If I can do that

Edited March 29, 2014 by gooddog15

[Brotoro]

kind off scary thinking there's used radioactive materials flying above our heads that could reenter at any moment

There isn't any up there that is going to "reenter at any moment." We know where the stuff is.

But the Soviet Union did inadvertantly crash a few of their satellites containing RORSAT reactors to Earth. A couple went down into oceans, but one spread debris over Canada in 1978. The Soviets paid Canada three million dollars for the necessary cleanup that followed.

[gooddog15]

There isn't any up there that is going to "reenter at any moment." We know where the stuff is.

But the Soviet Union did inadvertantly crash a few of their satellites containing RORSAT reactors to Earth. A couple went down into oceans, but one spread debris over Canada in 1978. The Soviets paid Canada three million dollars for the necessary cleanup that followed.

the question is, we know where the stuff is?

[NovaSilisko]

the question is, we know where the stuff is?

http://n2yo.com/?s=1314

Most of the soviet ones have reentered by now, I believe. If any are left, though, they can be tracked. Anything much bigger than a tennis ball can be easily tracked from the ground.

Edited March 29, 2014 by NovaSilisko

[Brotoro]

As I recall, most of the RORSAT reactors are still in orbit. After the end of the operational lifetime of the nuclear powered radar reconnaissance satellite, the reactors were boosted into high orbits for longterm storage. It's only when the mechanisms for boosting the reactors into high orbit failed that the reactors reentered (or one was a launch failure).

[gooddog15]

RORSATs reactor ejection mechanism doesn't really fix the problem for proper disposal of the reactor though, as all it does is delay the reactors eventual reentry. Actually, it doesn't make sense to have a RTG on a spacecraft in low earth orbit if solar panels can do the same job while being cheaper.

[NovaSilisko]

RORSATs reactor ejection mechanism doesn't really fix the problem for proper disposal of the reactor though, as all it does is delay the reactors eventual reentry. Actually, it doesn't make sense to have a RTG on a spacecraft in low earth orbit if solar panels can do the same job while being cheaper.

To properly conduct their spying, RORSATs needed to be in an ultra-low orbit - so low that they needed to be somewhat aerodynamic. As such, they elected to use a nuclear reactor instead of solar panels, because it has less drag. Bit overkill if you ask me.

[architeuthis]

To properly conduct their spying, RORSATs needed to be in an ultra-low orbit - so low that they needed to be somewhat aerodynamic. As such, they elected to use a nuclear reactor instead of solar panels, because it has less drag. Bit overkill if you ask me.

It also means that they don't need carry infeasibly massive batteries to maintain constant operation. The RORSAT orbit was so low they were occulted by the Earth for half of each orbit, and those big radar arrays were power hungry beasts.

I read an interesting article recently. Orbit characterization done by amateur astronomers in the U.K. back in the 80's suggests that RORSATS maintained their orbits with ion engines. The RORSAT program is still classified by the Russians, but if true then this development scooped the design used by ESA's GOCE 'Ferrari of space' by several decades.

[architeuthis]

interesting, I have never heard of nuclear poison wires. Those would make a launch escape system worthless, however the heatshield, thrusters, and parachutes would be handy for a uncontrolled reentry.

The tyranny of the rocket equation means it may simply be too expensive in terms of launch mass to bring all that stuff along. This is why we use graveyard orbits (not just for nuclear reactors even, but also for geosynchronous satellites). For less than 100 m/s of dV you can throw space junk into an orbit that will be stable for over a 1000 years. Sure it's not exactly a "permanent solution", but its not terribly short term either. You could also dump stuff into a heliocentric orbit for just a bit more dV and then you don't even have to worry about tracking radioactive debris, and worrying about it interfering with future missions (same goes for ditching it in the Lagrangian points, except in that case you will know where stuff is without having to actively track it). Ideally we could launch the stuff into a solar system escape trajectory, but that is too expensive in terms of dV.

[gooddog15]

The tyranny of the rocket equation means it may simply be too expensive in terms of launch mass to bring all that stuff along. This is why we use graveyard orbits (not just for nuclear reactors even, but also for geosynchronous satellites). For less than 100 m/s of dV you can throw space junk into an orbit that will be stable for over a 1000 years. Sure it's not exactly a "permanent solution", but its not terribly short term either. You could also dump stuff into a heliocentric orbit for just a bit more dV and then you don't even have to worry about tracking radioactive debris, and worrying about it interfering with future missions (same goes for ditching it in the Lagrangian points, except in that case you will know where stuff is without having to actively track it). Ideally we could launch the stuff into a solar system escape trajectory, but that is too expensive in terms of dV.

the heatshield, thrusters, and parachutes were for a launch failure in the upper atmosphere, in which the NTR and the rocket were on a ballistic trajectory.

also I found a way for the plumbing part to work, using a umbilical on the side to connect the fuel lines to the NTR. It would act just like the Apollo CSMs umbilical between the service and command modules, detaching after a abort.

[sgt_flyer]

Hum, an umbilical would be hard to do here - a Nerva engine turbopumps would pump aproximately 1700l of LH2 per second. (Not taking into account the effects of such a high fuel flow in ducts - of cryogenic stuff )

(Based on the known nerva dry / empty weight and burn times) - the umbilical between the reentry module and the csm needs waaaay lower fuel )

The known specs for a nerva stage :

Dry weight : 34019kg

Full weight : 178321kg

Burn time : 1200s

Lh2 mass / L : 0.07 kg.

So you get : fuel weight : 144302kg - divided by 1200 : 120.7kg/s.

This multiplied by 14.28 (approximately the number of liters of lh2 /kg) you have 1717l/s

[architeuthis]

the heatshield, thrusters, and parachutes were for a launch failure in the upper atmosphere, in which the NTR and the rocket were on a ballistic trajectory.

What would the point be? I assumed you had meant a reactor reentering after a very long stay in orbit. Are assuming that the NTR was powering the stage in question? Because otherwise the environmental and public health impact of lowly radioactive (e.g. Uranium 235) debris crashing to Earth may be less than the potential impact of a upper stage failure of a common rocket such as the Briz-M upper stage for the Proton-K which uses toxic hypergolics dimethyl hydrazine (UDMH) and nitrogen tetroxide as fuel and oxidizer respectively. Should we put parachutes on those?

Edited March 31, 2014 by architeuthis

[gooddog15]

It would be used in the case the NTR powered upper stage couldn't be fired to get itself into orbit (think of the public outrage over firing a nuclear powered rocket engine in the atmosphere. It would problably crush any space agency to its breaking point). also I think the Russians can care less about the failure of their Briz-M upperstage, as they already have a lake were by just standing around it you instantly get cancer.

Edited April 5, 2014 by gooddog15

[Nibb31]

An NTR would only be fired in orbit anyway. It would not be used to get to orbit, because that would mean firing in the atmosphere.

There is no need for extra hardware. You would just launch it exactly as the Russians and Americans launch payloads that contain RTGs:

- Any radioactive material is contained in a high-impact shielded compartment

- The launch trajectory would go over the ocean so if it fails, the payload ends at the bottom of the ocean where it can do no harm.