P&W's Nuclear engine... - Wowza article

Rxke · 2004-10-22 17:59:22

http://www.nuclearspace.com/A_PWrussvie … clearspace

Pratt& Whitney have this engine, TRITON, worked out fairly detailed, cost estimate: 800 million...

They're mainly talking about using it for Mars missions, to eventually have some 'train' system of shuttling systems, back and forth between Earth and Mars...

Article/interview, with at the end a bit of -sigh- electoral chit-chat...

Ad Astra · 2004-10-23 23:34:02

The article's formatting detracts from it's readablity. I'll get around to it, as the engine seems interesting. Don't know if it's just a piece of vaporware, of if PW is set on building an NTR. I hope the latter is the case.

Rxke · 2004-10-24 02:05:39

Yes, the gaudy coloours made my head explode

The article is very detailed, though..

Commodore · 2004-10-24 15:51:45

No ones talking about reactors bigger than 500 kilowatts. Why?

Is it just the size and launch weight? Or is there some technical reason?

Were going to need much larger reactors for any long term serface missions, at least at first.

John Creighton · 2004-10-24 15:55:19

No ones talking about reactors bigger than 500 kilowatts. Why?

Maybe they choose redundancy and fault tolerance over efficiency. Perhaps there are not many efficiency gains made by making a bigger reactor. I am just guessing. JIMO uses multiple reactors. See:

http://www.newmars.com/cgi-bin/ikonboar … ;f=24]JIMO disucssion

Terry Murphy of Boeing responded by saying, as Joe said...Prometheus is really divided into three pieces. The RTG and NRA's technologies. Relative to the Brayton we finished our first phase on that contract we're pushing forward, there's still a lot of work to be done but it will look very promising for this type of application. The idea would be to put multiple units on a 'JIMO' and have a fault tolerant approach to it.

As Terry said, you can have several redundant additional units so that in a case there's one or more failures because they run out of 'life' then you can start-up an adjacent unit and you can get to your lifetime and mission reliability that way. Of course, part of the development program would be during this time frame, to test the Brayton to generate as much data as we could on the lifetime performance as part of this certification for space that Terry was talking about. That is sort of what the NRA's are about. To move the technology forward, we understand the closed Brayton data around tailoring it to this application and getting the data necessary to certify the system for space flight.

from:
http://www.nuclearspace.com/A_boeingprofileFIN.htm]An Interview With Boeing

Hmm if you could dump a reactor after it used all its fuel that would save weight. ???

GCNRevenger · 2004-10-24 21:12:11

No ones talking about reactors bigger than 500 kilowatts. Why?
Is it just the size and launch weight? Or is there some technical reason?
Were going to need much larger reactors for any long term serface missions, at least at first.

Both. A small 300kWt/100kWe reactor with cooling and power generator will probably weigh in the ton range, and building a big reactor will be fairly difficult I would imagine.

We don't really need far bigger reactors for early surface missions, small plants with a few hundred kilowatts of electricity should be enough for "McMurdro" sized bases. The only reasons I can think of we would need much bigger plants is for electric propulsion (ion & plasma engines) or for the development/colonization phase of a Moon/Mars base.

PurduesUSAFguy · 2004-10-24 21:17:14

Glad to hear someone is talking about NTRs again, I hope they get funding from NASA for it. That's one uber deal for$800 million, I'd take one less shuttle flight for that.

Rxke · 2004-10-26 09:52:34

Its]http://science.slashdot.org/article.pl?sid=04/10/26/1250259&threshold=2&tid=160&tid=1&tid=14]It's featured on SlashDot

Ad Astra · 2004-10-26 18:43:35

One of the reasons why they want smaller NTR's is for testing purposes. The facilities for indoor testing of large NTR's just doesn't exist, and would be expensive to build.

Back in von Braun's day this was not a problem, because very few people would protest the open-air testing of NTR's. As our understanding of radiation has grown, it has been mandated that NTR's be tested indoors with machines that will filter the radioactive particles out of the exhaust.

In Case for Mars, Zubrin addresses this problem and notes that we do have facilities for testing small NTR's. The strategy is to build small NTR's (~15 Klbf) and cluster them instead of building a large NTR.

GCNRevenger · 2004-10-26 18:55:04

There is another plan, to take an NTR rocket, place the test stand in a building tightly connected to a cave, and vent the exhaust gasses into it. When we get around to building high-thrust thermal fusion or fusion/VCR plasma engines, then cap the cave entrance with concrete.

The Triton engine sounds allright, its nice that it would generate some power, but in thrust mode its specific impulse is a good 100 seconds lower then a thrust-only NTR configuration, and I wonder how much it weighs versus a one-shot throw away graphite NTR like Timberwind as used on NASA DRM-III baseline TMI stage. Two or three ISS solar arrays with advanced cells could probably match the electric output of a Triton engine cluster, I wonder how much they would weigh too.

Martian Republic · 2004-10-26 19:33:26

It look like that TRITON Rocket would also make a good Earth to Moon Rocket too. So we could kill two birds with the same stone. You would want to test the TRITON Rocket out and you would not want to get too far out until you have a certified rocket that you know will work fairly reliably well. If it as good as it looks or as they seem to indicate, I would support building twenty to thirty of them and use them as our primary front line deep space human rockets. It would be the rocket that we would use to go back to the moon with and on to Mars. If that Pratt& Whitney nuclear powered rocket is as far along as that artical seem to indicate, we might be able to bring it on line in a two year government steped up program. We might use a Bigalow type module on the other end with the living quarters and the guidance system and computers as a trip down version. We would probably have to use two Cargo Shuttle that can push 100,000 to 200,000 pounds a piece. Then pull the two External tank in as two cargo bays or as more living quarters depending on what we wanted to accomplish. We would not have the shuttle on it, so it would have to ride the External Tank into space with the engine that would have been on the shuttle on the end of the Externa Tank. So we would have to redesign a new External Tank anyway.

I'm sure there at least someone on this board that does not like this idea and will tear it apart. So have at it.

Larry,

GCNRevenger · 2004-10-26 20:23:02

I don't know about a Lunar shuttle, how many firings is the engine supposed to be good for? Bulk cargo is also better served by ion drive vehicles which still win big considering the amout of propellant you need versus NTR engines (>10,000sec Isp vs 900sec).

As far as manned vehicles go as a Lunar shuttle, how much fuel would be needed to reload the thing and a hypothetical people/cargo reuseable Lunar lander?

And as Shuttle derived vehicles go, no actually we don't have to modify the main tank. In the Shuttle-C arrangement, the tank is the standard one without signifigant alterations, nor is the external tank carried to orbit.

Its also still quite useless to save the main tank, since you would have to make such radical changes to it to make it worthwhile for use as anything else. Cargo doesn't need much of a payload faring beyond what it launches from Earth with, and it is a much much better idea to employ TransHab modules for manned vehicles then remodled Hydrogen tanks.

Commodore · 2004-10-26 21:31:52

Why does it burn out after 30 hours?

Rxke · 2004-10-27 03:04:53

MartianRepublic,

first I was going to react that GCNR was right, go for ion thrusters, but maybe it would be better to use a first Triton after all. As an admittedly more expensive choice, but it might prove to be better to get it through a serious 'dress rehearsal' going to and fro the moon... Iron out the wrinkles. If it proves reliable, fit the 'half used up' Triton with cargo or a unmanned hab etc, and send it unmanned to Mars, to see how stuff works out...

(Dreaming:) Or send it with a RLV (for Mars, not for Earth..) and in-situ propellant plant to Mars... RLV, loaded with props, then comes back (docked to Triton, or on it' own?) with propellant to power tugs working for Luna-Earth...
When this would work, use Triton only for Mars, or other far away places (Dreaming)

John Creighton · 2004-10-27 09:18:34

This thing produces a fair amount of thrust doesn’t it? Could it be modified to land on the moon? How much would the increased weight affect performance? Is the ship to long and slender to sit stable on the moon?

GCNRevenger · 2004-10-27 12:08:19

There are a few issues to consider...

As safe as the engine might be to the astronauts, and as harmless it will be when its first launched, will the risk of a NTR rocket returning to Earth and failing to enter orbit then reentering be unacceptable?

How much will the engines with the more complex cores and plumbing and turbines and radiators cost compared to a simple pebble-bed one shot arrangement like Timberwind? It will cost signifigant money to launch fresh fuel for an NTR vehicle, the weight of the engine is a fairly small componet.

That is, is it cheaper to launch a reuseable NTR rocket and spend lots of money to refuel it by launching more liquid Hydrogen, or simply launching a brand new TLI/TMI stage fully fueled with cheap one-shot engines? This would preclude using the engine to return though unless you brought more engines.

Keep in mind, that throw-away engines will weigh quite a bit less and have ~100sec higher Isp, which could reduce your fuel bill substantially. Its also not so much of a loss to simply throw the engines away if returning to Earth orbit is with a hot reactor too risky.

The amount of electricity generated by a bimodal reactor can also be made up pretty easily with solar pannels probably without adding too much mass compared to the mass of the radiators/turbines/pumps/etc.

The Triton engine doesn't have that much thrust, probobly not enough for a Lunar landing vehicle. You need more thrust.

John Creighton · 2004-10-27 13:25:39

The Triton engine doesn't have that much thrust, probobly not enough for a Lunar landing vehicle. You need more thrust.

Not to digress too much but did anyone ever see the movie chicken run?

Rxke · 2004-10-27 13:56:24

:laugh:

You're trying to change the subject?

GCNRevenger, so you're not too hot about the Titan?

GCNRevenger · 2004-10-27 14:25:21

I have mixed feelings... it depends alot on the mission arcitecture...

Pro:
Has double the performance as LOX/LH
Produces energy in nontrivial amounts
Restartable, probobly enough for half a dozen firings, maybe a few more
Does not rely on much new technology except for complex fuel elements (a con)

Con:
Heavier, possibly heavier then throw away engines paired with solar panels for similar electrical output
Lower performance, a full 100-200sec Isp lower then Timberwind
Possibly much more expensive then throw-away engines
Might present unacceptable political/percieved risk for Earth reentry if used on a Earth/Moon Earth/Mars cycler
Much more complex then a throw-away engine in general

The baseline NASA Mars SemiDirect/DRM-III mission, which I conceptually favor, uses a smallish throw-away NTR TMI stage of maximum Isp which keeps the fuel needed pretty small and cuts the mission up into three pieces. Here, aerobraking is employed for orbital insertion and the return trip by chemical propellants

A mission where TRITON would be useful would involve using the same ship for Earth return as well as getting to Mars. You will have to either put a substantial lander that carries the Mars-acent fuel or a rover (so you can reach the ERV/MAV in the event of a landing error) on the vehicle or place it into Mars orbit on a seperate vehicle. This scheme would permit some reuseability, but you will have to launch signifigant quantities of fuel for the vehicle (plus the lander if its reuseable) and I think it will take some serious on orbit construction & manpower to ready/re-ready the thing for the next trip. Plus, the fuel bill for each trip will be pretty high either to push the Cycler + Lander or Cycler and Lander separatly, and that will take big bucks to haul from Earth, though how much I don't know. It starts sounding like Battlestar Galactica in a hurry.

John Creighton · 2004-10-28 12:51:28

Anyway on chicken run the smart chicken is trying to figure out how to fly out of the coup and he says the problem is thrust. We need more thrust. Anyway the thrust of the engine is
334KN
F=ma
Thus the mass the rocket could hover is:
F/a=334 KN/9.8 m/s^2
Which is 34.08 k-N-s^2/m
Which I believe is 34.1 tons
Thus if the vehicle weighed 34.1 tons then it could lift off earth.
Now doesn’t the moon have a tenth the gravity?
That would be 341 tons that the engine could hover. I don’t think it is out of the question that this thing could land on the moon. Granted it will be kind of tall and slender and maybe fragile.

Rxke · 2004-10-28 13:20:58

1/6th gravity.

John Creighton · 2004-10-28 13:52:14

So 34.1 tons divided by 1/6 is 204 toons. So does the vehicle weigh more then 204 tons?

GCNRevenger · 2004-10-28 13:59:57

That depends mostly on how much margin you need. You need signifigantly higher thrust then weight in order to escape gravity quickly, so you don't spend so much time in the high gravity field. If you didn't, you would simply run out of gas before reaching orbit.

I have doubts that the "RL-10 class" Triton engine could produce enough thrust to lift the vehicle and TEI fuel from the Moon, and landing would be difficult with such a big bulky vehicle anyway.

John Creighton · 2004-10-28 14:30:16

Well if the thrust to weight ratio was one, the escape velocity of the moon is 11.2 km/s so you would need roughly an 11 000 s burn or a 3 hour burn. Yeah that sounds like a lot of fuel. How long can the engine fire at maximum thrust for? Of course if you circulize at some point you won’t have to fight gravity all the way. I agree landing the vehicle should be tricky.

GCNRevenger · 2004-10-28 17:50:26

Obviously a multi-hour burn isn't practical at any thrust level.

The Apollo LM acent module had about 200% the thrust compared to its Lunar weight, or about 35% as much thrust versus its mass.

The decent stage had a ratio around 30% as much thrust then mass.

So I guess it isn't all that bad, but I still think landing or launching an NTR vehicle of any substantial mass won't be easy.

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#1 2004-10-22 17:59:22

Re: P&W's Nuclear engine... - Wowza article

#2 2004-10-23 23:34:02

Re: P&W's Nuclear engine... - Wowza article

#3 2004-10-24 02:05:39

Re: P&W's Nuclear engine... - Wowza article

#4 2004-10-24 15:51:45

Re: P&W's Nuclear engine... - Wowza article

#5 2004-10-24 15:55:19

Re: P&W's Nuclear engine... - Wowza article

#6 2004-10-24 21:12:11

Re: P&W's Nuclear engine... - Wowza article

#7 2004-10-24 21:17:14

Re: P&W's Nuclear engine... - Wowza article

#8 2004-10-26 09:52:34

Re: P&W's Nuclear engine... - Wowza article

#9 2004-10-26 18:43:35

Re: P&W's Nuclear engine... - Wowza article

#10 2004-10-26 18:55:04

Re: P&W's Nuclear engine... - Wowza article

#11 2004-10-26 19:33:26

Re: P&W's Nuclear engine... - Wowza article

#12 2004-10-26 20:23:02

Re: P&W's Nuclear engine... - Wowza article

#13 2004-10-26 21:31:52

Re: P&W's Nuclear engine... - Wowza article

#14 2004-10-27 03:04:53

Re: P&W's Nuclear engine... - Wowza article

#15 2004-10-27 09:18:34

Re: P&W's Nuclear engine... - Wowza article

#16 2004-10-27 12:08:19

Re: P&W's Nuclear engine... - Wowza article

#17 2004-10-27 13:25:39

Re: P&W's Nuclear engine... - Wowza article

#18 2004-10-27 13:56:24

Re: P&W's Nuclear engine... - Wowza article

#19 2004-10-27 14:25:21

Re: P&W's Nuclear engine... - Wowza article

#20 2004-10-28 12:51:28

Re: P&W's Nuclear engine... - Wowza article

#21 2004-10-28 13:20:58

Re: P&W's Nuclear engine... - Wowza article

#22 2004-10-28 13:52:14

Re: P&W's Nuclear engine... - Wowza article

#23 2004-10-28 13:59:57

Re: P&W's Nuclear engine... - Wowza article

#24 2004-10-28 14:30:16

Re: P&W's Nuclear engine... - Wowza article

#25 2004-10-28 17:50:26

Re: P&W's Nuclear engine... - Wowza article

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