Author Topic: Calculating NTR performance curves.  (Read 1002 times)

Offline HlynkaCG

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Calculating NTR performance curves.
« on: 01/13/2012 10:20 pm »
Hello everybody,

I am a developer for Orbiter, a space flight simulator, and I am working on getting NERVA, along with other aspects of the 1968 IPP implimented in the sim. While I have the design studies for the Reusable Nuclear Shuttle and PPMs for VonBraun's Mars Mission (both NERVA powered) I've hit a snag.

NASA's Nuclear Flight definition studies give nominal tempratures and propellant flow-rates for different phases of operation but provide litt-to-no information on intermediate steps.

For instance, I know that...

...the reactors were rated for 1125 mwt output.

...chamber temp was to be around 411 K (280 F) while idleing 23-2500 K under full thrust.

...a propellent (LH2) flow rate of 40 kg/s resulted in a pressure of 4.13 Mpa, 333 Kn (75,000 lbs-f) of thrust, and an impulse of approx 800 seconds.

Now if the relationships were linear knowing the start and points would between temp, prop flow, pressure, etc.. would be enough, unfortunatly they are not.

I need a function (or set of functions) into which I can plug Reactor Temp and Propellant Flow and get ISP (or pressure) as an output.

Likewise I need an Idea of how to calculate reactor temp based on power setting (0-100%) and propellant/coolant flow. Unfortunatly this requires data on NERVA's heat rejection capability/rates that I do not have.  ???

If anyone has any data or sources that can fill in the gaps, the help would be much appreciated.

Heck, I'd settle for some best guesses that I could use in the interim.

-Thank you

Offline nyrath

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Re: Calculating NTR performance curves.
« Reply #1 on: 02/02/2012 08:11 pm »
Sorry I can't help you.

There are a few NTR data points here that might help.
http://www.projectrho.com/rocket/enginelist.php#id--The_Drive_Table

Offline 93143

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Re: Calculating NTR performance curves.
« Reply #2 on: 02/02/2012 08:37 pm »
Uh, that "Drive Table" is very broad-strokes and not super accurate...  I think he's looking for something that would describe the behaviour of a particular engine during throttling...

I need a function (or set of functions) into which I can plug Reactor Temp and Propellant Flow and get ISP (or pressure) as an output.

NASA has a program that may be able to help you.  It probably isn't exactly what you're looking for, but if you combine it with flowpath and transport property data it shouldn't be impossible to generate what you want.
« Last Edit: 02/03/2012 12:12 am by 93143 »

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