The Nukespike Engines - An Experimental Stock Part Engine Design

[Horn Brain]

Because it upps the power to the NERVA.....

I don't think you understand. In reality, if you put an aerospike on a NERVA, the thrust will be basically the same. So a NERVA aerospike should have roughly NERVA mass, thrust, and efficiency in vacuum, but better efficiency at lower altitudes than a regular NERVA. It should not have Aerospike thrust with NERVA mass and efficiency. That's just "cheating". By that I mean "not representative of reality" or if you prefer, "a straight upgrade to a stock part".

I think to get a realistic performance out of that arrangement, you should subtract the aerospike's mass from the NERVA's mass, leave it shut down, and just edit the aerospike engine to have:

Low mass (since it's just a penalty)

NERVA thrust (60 kN)

800s vacuum Isp

~500 or ~600 sea-level Isp

Then it will look and perform roughly like what this arrangement could potentially produce in real life.

[Giggleplex777]

What he means is that the aerospike increases the thrust of the NTR at the cost of reduced Isp.