Question Starting a nuclear reactor without power?

[jedidia]

Here's a hypothetical scenario, that, in view of the add-on I'm currently developing, isn't quite so hypothetical:

A spacecraft is powered by a nuclear reactor. It has some batteries for emergecy power too, of course. Then, for whatever reason, the reactor has to be taken offline. All non-essential systems are deactivated, and the rest runs on the batteries until the problem is fixed. But due to some convoluted reason, the problem can't be fixed fast enough and the batteries go dry. No need to panic, there's still plenty of oxygen, and it will take a while until the vessel heats up enough or cools out enough to make it uninhabitable. Plenty of time to fix the problem in torchlight.

But here's the question: would it be even possible to drive the reactor up again without a single drop of juice? Could a spacecraft reactor be constructed in a way that it ca be manually restarted?

 

[garyw]

If there is no power at all then the reactor will lose cooling so a bad situation all around. I'd expect the reactor to have some sort of backup for issues like that.

 

[jedidia]

If there is no power at all then the reactor will lose cooling

Right. Didn't even think of that. Then again, how much cooling does this stuff need when offline? I know they're never really inactive, but I suppose the heat would be much reduced?

 

[Urwumpe]

Here's a hypothetical scenario, that, in view of the add-on I'm currently developing, isn't quite so hypothetical:

A spacecraft is powered by a nuclear reactor. It has some batteries for emergecy power too, of course. Then, for whatever reason, the reactor has to be taken offline. All non-essential systems are deactivated, and the rest runs on the batteries until the problem is fixed. But due to some convoluted reason, the problem can't be fixed fast enough and the batteries go dry. No need to panic, there's still plenty of oxygen, and it will take a while until the vessel heats up enough or cools out enough to make it uninhabitable. Plenty of time to fix the problem in torchlight.

But here's the question: would it be even possible to drive the reactor up again without a single drop of juice? Could a spacecraft reactor be constructed in a way that it ca be manually restarted?

First of all, this depends a lot on the construction of the reactor. What type of reactor, which coolant, etc.
Second: No.
Third: At least not without a lot of plot devices.

Even if you would have mechanic backup systems for your reactor control - there is no convection in microgravity. You would need mechanic, manually powered pumps to work. A bit of spinning could help producing minimal convection, but how to induce spinning without electricity? What if the reactor is at the CoG?

Next, starting a reactor isn't done in a few minutes. It takes days.


At least in reality. For the two Black Dart reactors, I cheated by assuming high temperature superconductors and He3-fusion to permit a startup of the first reactor in less than 30 minutes - and generous amounts of energy stored in the emergency batteries for getting one reactor online at all since it takes a few pulses at "fat mixture" until the reactor is operating continious.

 

[Artlav]

Sounds like a case of really bad design - there should be an untouchable battery/fuel cell/gasoline generator just for this situation.

If it is a modern day-like fission reactor, then the big problem would be to start circulation of the heat transfer fluid from the core to the steam boiler. Or pumping water into the core/boiler that would drive the turbines.
This could be resolved by provisions for manual pumping.

There would be radioactives on board, so voltaic panels for gamma-rays-to-electricity, or plain RTG-like thermocouples could be used to provide start-up power.
You pull the control rods out of the core manually, the core heats up a bit, the thermoelectric generators power up the pumps, the reactor goes up normally.

And astronauts are supposed to be MacGyvers as a job requirement.
A spaceship must have tanks of compressed air/oxygen, and it must have air circulation fans.
So, blow the compressed air into the fans, wire the fans to the core pump, start the reactor.

 

[Urwumpe]

Right. Didn't even think of that. Then again, how much cooling does this stuff need when offline? I know they're never really inactive, but I suppose the heat would be much reduced?

Again, depends on the reactor construction and the power level. It is fairly high for fission reactors right after shutdown, and drops with the decay of isotopes.

[ame="http://en.wikipedia.org/wiki/Decay_heat"]Decay heat - Wikipedia, the free encyclopedia[/ame]

It is about 5-10% of the last power level of the nuclear reactor one second after shutdown.

 

[jedidia]

Next, starting a reactor isn't done in a few minutes. It takes days.

I'm not modelling in such detail, my reactors don't even have inertia.

Currently I'm merely trying to decide if I should allow the player to restart a reactor that might have been offline due to some hubris) when there is no stored power, or just declare the ship dead until another vessel comes around to provide external power.

.

And astronauts are supposed to be MacGyvers as a job requirement.
A spaceship must have tanks of compressed air/oxygen, and it must have air circulation fans.
So, blow the compressed air into the fans, wire the fans to the core pump, start the reactor.

As much as I would love stuff like this, I don't plan to get so detailed

 

[Urwumpe]

I'm not modelling in such detail, my reactors don't even have inertia.

Well, you should at least include reactivity. :lol:

Otherwise, you would then have in the simplest way just one dependency on electricity: The pumps.

A radiation cooled nuclear reactor would be possible BTW, at least after some days to cool down. No pumps needed there, just structure. But once you start it and need more power, extra radiator surfaces will be needed with pumps. A few solar arrays as "spaceflight ram air turbine" might be a choice there.

 

[csanders]

I just had a funny vision of an MMU holding jumper cables.

 

[jedidia]

Well, you should at least include reactivity.

Even that would get too complicated at this stage. I have to wrap this up, and people are already going to have enough trouble with the fairly accurate thermodynamic aspects of design, I decided to leave power at a very basic level currently. You have it, or you don't.

A few solar arrays as "spaceflight ram air turbine" might be a choice there.

Well, it's up to the player wheather he wants to build some into his ship or not... I just have to decide on a course of action what to allow or not allow should someone be incompetent enough to run out of power completely, be it by bad design or bad handling...

A radiation cooled nuclear reactor would be possible BTW, at least after some days to cool down. No pumps needed there, just structure. But once you start it and need more power, extra radiator surfaces will be needed with pumps.

This part actually works...

 

[Urwumpe]

Well, if you just simplify things over and over again, it is just "Throw a switch and the reactor goes from deep hibernation to full power in a second". That doesn't really feel well, but might be more realistic in some considerations: The reactor is a closed system, keeps itself alive, does manage its own internal power levels and has its own emergency power supply to shutdown or power up at will.

 

[jedidia]

does manage its own internal power levels

it does, actually. I don't like micromanaging large vessels. Feels odd, and gets old after a few times.

and has its own emergency power supply to shutdown or power up at will.

Yes, I'm beginning to think that might be the best way to do it.

 

[Urwumpe]

it does, actually. I don't like micromanaging large vessels. Feels odd, and gets old after a few times.



Yes, I'm beginning to think that might be the best way to do it.

Same here, not even for small vessels. No problem with manual backups, but a modern spacecraft should be capable of managing itself.

 

[toddhisattva]

Maybe it should be an RTG-style reactor?

 

[Quick_Nick]

How much power do you need? How much can you get with solar panels before you're dead?

 

[Linguofreak]

For a small spacecraft with a small reactor, might it be possible to have emergency pumps driven (either with a direct mechanical linkage or an intermediate generator and motor) by a crewmember (or multiple crewmembers) on an exercise bike type setup?

In fact, with a generator powered this way, your batteries only need to be able to power cooling for start up or shutdown alone, rather than both, and as long as you have batteries capable of handling a full startup (or shutdown, whichever needs more energy for cooling), a single crewmember need not be able to provide the full power requirements of the pumps, but rather only be able to fill the batteries in a reasonable amount of time.

For larger spacecraft where such a scheme would be impractical, I'd anticipate that efforts would be taken to provide multiply redundant reactors and never shut them all down at once.

 

[jedidia]

For a small spacecraft with a small reactor, might it be possible to have emergency pumps driven (either with a direct mechanical linkage or an intermediate generator and motor) by a crewmember (or multiple crewmembers) on an exercise bike type setup?

That is quite fun to imagine :lol:

For larger spacecraft where such a scheme would be impractical, I'd anticipate that efforts would be taken to provide multiply redundant reactors and never shut them all down at once.

That's what I'll officially recommend in the manual, but I still have to decide how to handle the situation if the player doesn't care. Or just tries it for the fun of it... :shifty:

 

[Andy44]

Do your spacesuits have batteries? Any power tools? How about auxillary craft? Rig those batteries up to power your reactor start-up. That's how Apollo 13 got home alive.

 

[Nexiss]

How about auxillary craft?

Now there's an idea jump start from a Delta Glider or XR ship.

there's that MMU with the jump leads thing again :lol:

 

[NukeET]

Next, starting a reactor isn't done in a few minutes. It takes days.

No it doesn't.

A S5W with a S3G core 3 shutdown for 2 months takes about 2 hours for startup.