You've got my support. I would be concerned with thrust-to-weight ratios though. For large rocket vehicles the GLOW (Gross LiftOff Weight) is typically only 25% less than the sea level thrust. The Apollo/Saturn 5 appeard to 'crawl' up from the launch pad because the vehicles GLOW was about 6.9 million pounds, but the sea level thrust was 7.5 million pounds. So only an excess of 600,000 pounds of thrust was used to accelerate a 6.9 million pound vehicle--it starts to move slow. Of course, the Saturn 5 was expending propellant at 15 tons per second, so it naturally get's lighter. Still, it barely had enough thrust to move, let alone takeoff!

An afterburning nuclear thermal rocket engine could possibly (probably) develop enough thrust to lift the bulk of a fully fueled/loaded vehicle. But I'd have to do the numbers.

Most likely, an NTR freighter will probably have to use some kind of boosters to suppliment the thrust generated by the nuclear engines. This allows the vehicle to gain some speed and altitude while lightening itself--eventually, if the calculations are done right, the vehicle will have gained enough speed and altitude that once the boosters burn out, the nuclear sustainer could carry it the rest of the way up. It's just a matter of tayloring the thrust and Isp levels to a dynamic launch point (a position in space and velocity) where it can achieve orbit from there. Then it becomes an engineering problem to design a booster system that can achieve those required vehicle dynamics. It's complicated, but not insurmountably so. Analysis of staging with boosters just involves careful accounting of the masses expended, and then carefully applying the concept of 'staging' to the basic rocket equations. I've even done some rudimentary simulations (although it's been a while) involving basic shapes and aerodynamics. I tweaked the models and managed to achieve similar numbers for Apollo/Saturn vehicles for orbital heigh, velocity and propellant mass consumed. But I admit, this was about 15 years ago!

Anyways, if I can be of any assistance, please feel free to e-mail me at orionspulse@yahoo.com