Quote from: simonbp on 04/07/2014 09:43 pm but I can't think of any flown vehicles with drop tanks. Proton-M Briz-M uses a drop tank on the Briz-M upperstage.
but I can't think of any flown vehicles with drop tanks.
Quote from: Skyrocket on 04/07/2014 10:36 pmQuote from: simonbp on 04/07/2014 09:43 pm but I can't think of any flown vehicles with drop tanks. Proton-M Briz-M uses a drop tank on the Briz-M upperstage.Did not know that; thanks!
Quote from: Zed_Noir on 04/07/2014 01:30 amCan 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.I'm not clear on terminology. By staging, you're referring to the Boeing proposal, not traditional staging (like I proposed a few posts back), right? Are drop tanks stages? Wiki says no, Boeing (or at least Steve Johnston) says yes...huh.
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.
The launch altitude is probably significant in that at 40,000ft in a near vertical climb the Eagle is still under acceleration so is providing more significantly towards the total Delta-V budget than if it launched at 80,000ft and almost no airspeed or engine thrust left
Quote from: RanulfC on 04/04/2014 07:52 pmThe launch altitude is probably significant in that at 40,000ft in a near vertical climb the Eagle is still under acceleration so is providing more significantly towards the total Delta-V budget than if it launched at 80,000ft and almost no airspeed or engine thrust leftNo. Whether the Eagle is under acceleration or not is irrelevant.
All that matters is the altitude and velocity at the time of separation. And a lower altitude will only be a win if the velocity is enough to reach the higher altitude at a coast -- which it will not even be close to for the 40kft versus 80kft you're talking about. So it would in fact be far better to launch at low airspeed at 80kft than mach 2-3 at 40kft.
The reason they're planning to launch at 40kft is probably that the launch vehicle weighs so much that the F-15 can't get much higher than that while carrying it.
The engines are powered by an unusual mixture of nitrous oxide and acetylene.
ALASA concept Video
Stupid question, I watched with the sound off, but four engines on the first and second stage. Does that mean they are hoping to reduce costs by eliminating the engine gimbals and use differential thrust for steering?Four engines is really cheaper and more controllable than one engine per stage with gimbals?
...As for the change from the drop-tank to intergrated "first-stage" it makes me wonder how long before the rockets get moved to the tail as per "normal"
The ballute looks like a single point failure to me, if that's their way of guaranteeing stability prior to the start of powered flight. Passive stability (when there are two humans a few feet away) shouldn't require an active device like an inflation system. My guess would be before it gets through safety review they'll need to add something like fins (and maybe end up going to 3 stages due to the added weight).
Uhm, it drops off the F-15 and deploys a ballute so it then goes HORIZONTAL where the engine ignites and THEN has to do another PULL-UP manuever?(banging my head on the desk several times)Nope, STILL doesn't make any sense to me.IF (as I suspect is the case) the AF is worried about a "launch incident" with a liquid propellant LV on the F-15 drop the ballute and use a small solid "seperation" stage to allow the F-15 to pull away. The ballute would even be "ok" if they ignited the main stage BEFORE it looses the critical launch AoA but the video doesn't inspire me that this will get much futher as is.As for the change from the drop-tank to intergrated "first-stage" it makes me wonder how long before the rockets get moved to the tail as per "normal"Randy
They probably mix it with another chemical, quite possibly acetone.