Pratt and Whitney Triton Trimodal Engine

Date: Oct 18, 2004

Pratt and Whitney Triton Trimodal Engine

Date: Oct 18, 2004

I read about this on Friday, and all I can say is: "Yahhooo!!!"

After years and years of sitting on Nuclear Thermal technology, we finally have a usable engine (pending certification). Of primary interest is the fact that the engine lacks the ablation issues that plagued the NERVA/Pheobos/Dumbo/Timberwind projects. The titanium shell is a particularly elegant solution, as it would automatically scram the engine in case of a meltdown situation (which shouldn't happen either). This means that the engine could be rated for atmospheric use!

That leaves one question in my mind, however. How much does this thing weigh? If the engine has a Thrust to Weight similar to that of NERVA NRX (1:1), then it may not be useful for anything but upper or space-drive stages.

Even with a Thrust to Weight of 3:1 or 4:1, it may make a space plane possible. Last time I ran a few space plane simulations with a nuclear rocket, I found that the weight of the craft vs. thrust made it particularly difficult to get off the ground. I actually had to use JATO rockets to get the bird in the air, but I found that the weight cost of said JATOs resulted in the fuel loadout being insufficient to attain orbit. Basically? I needed lighter engines with more thrust.

I agree with the assessment about the longevity of the motor. More than a few hours of operation time will put the turbopumps at risk of catastrophic failure. [...] Long term reuse of the engine however will require the creation of a space version of a 'hot box' for engine component servicing.

While simply yanking and replacing a turbopump module would be far less maintence than we see with the current generation of reusable craft, what exactly is the issue with Turbopumps? Does hydrogen embrittlement eventually cause failure, or does the pump destroy itself during operation? What does NASA do with the SSMEs? Do they replace the pumps after every flight?

Date: Oct 19, 2004

Interesting article.

But IMHO, having two separate coolant circuits in a single reactor (hydrogen for direct NTR thrust and He/Xe for Brayton cycle electrical power production) seems like an awfully complex arrangement.

The designers play up the advantages very effectively -- of course they won't dwell on the technology risk of having such a complex system.

I notice that UFLA (INSPI ?) had some small role in the project. I only regret that big companies like P&W don't show greater imagination by developing INSPI's VCR-MHD instead.

Date: Oct 19, 2004

I notice that UFLA (INSPI ?) had some small role in the project. I only regret that big companies like P&W don't show greater imagination by developing INSPI's VCR-MHD instead.

I think this link sums up their reasons pretty well:

Although ultrahigh temperature gas core reactors (GCRs) or vapor core reactors (VCRs) are the way of the future, these advanced nuclear reactors have not been successfully taken from the drawing board and scaled laboratory experiments into prototype design.

You'll note that this design has nowhere near the power output of the NERVA project. Their goal seems to be to build a Nuclear Rocket with a low chance for failure. When you consider that not even one nuclear propulsion method has ever flown in 40+ years, the wisdom in the decision becomes quite apparent.

Date: Oct 19, 2004

This is no major problema...friends and readers of NS !! Turbopump CBC technology in aerospace has been used reliably for eons this is a big power generator, no 'puny' systems need apply for a human Mars mission with the capability to provide power and cooling features. All TRITON turbopumps will be rated to run under neutronic environments able to handle the thermal stresses in all operational limits.
But for those that express concern there is always the option of added shielding to protect the dual turbopumps at minimal mass penalty.

For efficiency, safety, longevity and adaptability to Mars mission humans and their cargo this is what the doctor ordered- Dr. W. Von Braun of course!

PS. Could you all NS members mention this article online it would help to pass the word to our friends space enthusiasts, business associates and our legislative representatives on capital hill.

Thanks to all NS members for taking the time to read and comment on our production all of us take your constructive criticisms seriously; who knows a suggestion may find its way into actual construction of TRITON.

It's always a pleasure to write for such distinguished readers 'in the know' in our small world.

Date: Oct 19, 2004

PS. Could you all NS members mention this article online it would help to pass the word to our friends space enthusiasts, business associates and our legislative representatives on capital hill.

You know, I did that once before with the Liberty Ship article. I seem to remember that the bandwidth it generated completely took down the NuclearSpace website.

Oops.

Should I do it again?

Date: Oct 20, 2004

good point AKAImBatman...maybe I should ask first if more bandwidth is available for a limited period. I'll post my results here on this thread give me a week to investigate. Thanks for the tip!

Date: Oct 21, 2004

Well, if you can't get the bandwidth I can probably see about a temporary mirror. Maybe somthing like this one:

http://www.nuclearspace.com.nyud.net:8090/A_PWrussview_FINX.htm

(Is that cool or what?)

Date: Oct 22, 2004

Thanks...AKAImBatman, for providing space. Now hopefully people can get access to article/interview without burdening our tiny server...

Date: Oct 22, 2004

Don't thank me, thank Planet Lab. This is their big Coral Cache experiment to provide caching mirrors to any site that needs it. All you need to do is go to .nyud.net:8090, and they'll temporarily cache a copy of the site.

For example:

http://www.google.com -> http://www.google.com.nyud.net:8090/

So feel free to use that mirror whenever you find the need.

Now, without further ado, I'm going to put them to the test.

Date: Oct 22, 2004

Err... that should read:

All you need to do is go to <domain>.nyud.net:8090, and they'll temporarily cache a copy of the site.

I guess I need to be careful when I'm using < & >.

Date: Oct 24, 2004

I think that splitting the shielding into two or more main components would be helpful. The turbo pumps and primary energy conversion systems and valving should be behind some kind of primary shielding. This will cut down on the primary flux damage associated with neutron embrittlement. Something like a multilayer beryllium and boron primary shield.

This primary shielding would provide much of the 'shadow' behind which the rest of the space craft will reside. Secondary shielding could be made by situating the tank containing the liquid hydrogen main propellant on top of this shield stack. Tertiary shielding is provided by the liquid oxygen tankage ahead of the liquid hydrogen tank (this is the afterburn oxygen injection tankage) fallowed by auxiliary propellant tankage (storable hypergolic reaction control system propellants, along with any ion-engine propellant.) Placing the payload or manned modules on a boom extending from this will further reduce radiation exposure to instramanets and crew.

My guess is that by carefully designing the radiation shadows, that a very efficient shielding mechanism could be created.

I'm sure that Pratt and Whitney probably already have done this modelling/design.

Date: Oct 24, 2004

Errr.... you would not want to use beryllium as a primary (neutron) shield -- beryllium acts as a neutron multiplier !!

Neutron shielding is a tricky business, usually requiring a combination of light elements (particularly hydrogen) to slow them down, and then a high-Z material to stop/reflect them.

It really pays to get the most "bang" out of your first shadow shield, since its the smallest one by far, subtending the same angle as any subsequent shields, but with far less area, hence least mass.

Date: Oct 24, 2004

OOps!

I guess that's why they don't have me designing these things!

My advice is to never use neutron multiplyers as shielding--the results will be dissapointing.

Thanks for the correction, Jaro!

Date: Oct 27, 2004

Congratulations everyone! NuclearSpace.com just survived the dreaded Slashdot Effect. Thousands (if not hundreds of thousnds) of people of all professions (including rocket scientists) now know of Pratt & Whitney's Nuclear Rocket. Let's hope that helps get the ball rolling.

Date: Oct 27, 2004

Alright, good job there!

In reply to Jaro's posit about using the Triton for an SSTO--I can't see why the unit could not be used for something like a DC-Y (the big brother to the DC-X Delta Clipper.) Radiation shielding would be the primary concern, and I think this could be made quite manageable. Especially if you use something that is only cargo rated and not man-rated. Eventually, I could see much larger craft using clusters of nuclear thermal/afterburning rocket engines to boost heavy payloads into low earth orbit.
Who knows, maybe even a passenger carrying nuclear-thermal rocket. Possibly a delta-winged lifting body transport--high performance nuclear thermal engines could make things a lot easier to engineer a system that can achieve relatively safe and reliable (almost routine) access to space. Triton is the way of the future.

Date: Mar 10, 2005

I am very excited about this engine. Now it needs a ride to orbit:

http://www.spacedaily.com/news/rocketscience-05i.html