NASA announced a draft RFP for a vehicle that launches a 60 kg payload to orbit. This is a fairly exciting prospect for the NewSpace companies that are interested in providing launch services as government funding is often seen as an effectively free investment, and I imagine that NASA is hoping to launch a new, more robust commercial small satellite marker. I just hope that the contract works a little better than the NEXT program in 2013 which hasn’t gone anywhere yet, at least as far as anything public.
I thought I might go ahead and do a bit of a quick sizing just so we could see what sort of vehicle might work for the mission. Now, first we need a DeltaV, as there is no orbit given in the draft, we will assume a slightly elliptical inclined low earth orbit so we’ll just go ahead and assume a 9400 m/s budget. And for the sake of simplicity, let’s do a 2 stage LOX/RP-1 vehicle with a pressure fed upper stage and a gas generator turbopump first stage. And we will assume aluminum 2014 propellant tanks with Ti 6AL-4V pressurant tanks. And everything else pretty bog standard for a small launch vehicle.
-First Stage – 1200 psi engine with 94% efficiency give an Isp = 282 s mission average and a 92% propellant mass factor – This has a 20% mass margin.
-Second Stage – 150 psi engine with 94% efficiency and a 50-1 expansion gives an Isp = 313 s, and a 88% propellant mass factor – This has a 10% mass margin.
Overall, the vehicle has a total mass of 11,100 lbm GTOW and an 820 lbm dry. It is also 36″ in diameter and 33′ long, or roughly 1 meter diameter and 10 meters long. This is actually a pretty convenient size to move around in a 40′ container and around a standard shop with standard tools.
The engine for the first stage has a 7″ diameter chamber and a 15″ diameter exit, 10″ to the throat and 30″ long. Just a bit big for the chamber to be 3D printed, but if you used 2 chambers, you might be able to print the chamber with a machined nozzle extension.
The engine for the upper stage has a 5″ diameter chamber and a 16″ diameter exit, 8″ to the throat and 33″ long. You should be able to print the chamber with a machined nozzle extension.
So that is just some rough sizing; I should add a little bit more about the mass budgets later this week.