Any idea about the kind of propellant used? Liquid would probably need to be pumped to the top of the rocket, but swapping from one solid motor compartment to another with the same nozzle seems complicated.
If you really wanted to use solids, maybe you could use the same trick as Orion's LAS: essentially have the solids fire forward into a U-shaped duct.
If you had to pump it 2 m forward at 10 Gs acceleration, the hydrostatic head would be on the order of 2 atm.
Another illustration by Boeing
Off-Topic note: Those engines are stolen from KSP! I recognize the "radial" engine set!On-Topic: I thought I'd suggested such a set up before and seem to recall that I was told it wouldn't work "well" for an LV. I was under the impression that "tractor" rocket designs had some significant issues?Randy
I don't see how that can put 100lbs into orbit and considering how much even an AIM-120 costs, how they expect to do it for $1mil/flt. Article mentions a launch at 40,000ft (well below an F-15's ceiling) with the first two stages using common tractor engines. There's a lot missing here, including an adequate payload bay, so I can only conclude Boeing through Phantom Works got a chunk of cash to do some PR shots (like with the CST-100).In that regard, this is a success as I've always dug the McDonnell Douglas F-15
Well if you put them close to the fuselage you have to put them at an angle, which is less efficient (you have "cosine losses"). An interesting aspect of tractor configuration is that you can save mass on structural elements since you pull instead of pushing, so you don't have to worry about buckling.
Are all four engines burning after it drops the drop tank? I hope the payloads are rated for 10+ g acceleration...
Can the 1st stage burn be pump-feed and the 2nd stage burn be pressure-fed? Presumably the pump gets discarded with the 1st stage. It would be something like the propellants gets pumped from the 1st stage tankage to the 2nd stage tankage to the combustion chambers for the 1st stage burn.
but I can't think of any flown vehicles with drop tanks.