Not sure if you answered this: Is there an altitude limit? I'd guess takeoff from Denver would not be feasible.
Patchouli “I wonder will Skylon use something similar to what ULA is proposing for their Integrated Vehicle Fluids concept to solve the problem of on orbit power and supplying GOX and H2 to the RCS system? One thing that seems would be fitting is use of a hydrogen oxygen fueled ICE for the APU. Of course with Skylon being reusable the high cost of fuel cells is probably less of an issue then it is with an expendable upper stage.Basically the answer is yes. There is a gaseous feed created from the orbital propellant tanks which sends hydrogen and oxygen to the RCS thrusters, fuel cells and APU (although the APU might be replaced by bigger fuels cells and a more electric design approach to actuation).
On costs I was hoping it would possible to give some idea of how much of that c£10Bn cost would be needed to separate out the cost of setting up the mfg plant and first flight vehicle from the cost of the test programme.
Believe it or not that is very close to the same energy use per km over an antipodeal trip as for a commercial jet.
Hempsell has mentioned that a Skylon on suborbital trajectory would carry about 30 tonnes although he seemed doubtful there would be much use for one. BTW last time I checked LH2 was about $5/lb and LO2 $0.15/lb. However the takeoff noise may well be a killer. Takeoff noise for the Shuttle was c 170dB (well above the human pain threshold). Most of it was provided by the SRBs. Modern turbofans are *much* quieter (and larger) than the old turbojets because they mix a *lot* of low speed air in from the outside with the small fast moving core. *If* SABRE does the same at ground level then the noise level will be more the difference between the *bulk* airflow through the engine and the surrounding atmosphere will set the noise level. If SABRE accelerates that flow to near *core* velocity then it's likely to get loud.
Quote from: adrianwyard on 08/04/2012 09:47 pmI've wondered if the takeoff will look a bit more rocket-like than how it's depicted in the animations. In those the exhaust plume looks rather like a Concorde take-off where the reheat just added those nice Mach diamonds. However, with Skylon we need to picture eight rocket engine bells with an exhaust similar to that of the Shuttle SSMEs... Quite impressive! And it's probably a good thing the runway is re-inforced as these engines are pointing at it... Now I think about it the rockets could presumably be gimballed to point directly aft until V1 speed, and only pointed Earthward at the last minute to get airborne, and at that speed the plume doesn't hit much runway area for very long. And getting back to noise: my suspicion is that anyone who buys a ticket for a Skylon passenger module will be handed some nice heavy duty noise-canceling headphones for the takeoff.
I've wondered if the takeoff will look a bit more rocket-like than how it's depicted in the animations. In those the exhaust plume looks rather like a Concorde take-off where the reheat just added those nice Mach diamonds. However, with Skylon we need to picture eight rocket engine bells with an exhaust similar to that of the Shuttle SSMEs... Quite impressive! And it's probably a good thing the runway is re-inforced as these engines are pointing at it...
There is also the little matter that core gas velocity is that of a LH2/LO2 rocket, *not* a turbine.
Quote from: john smith 19 on 08/18/2012 11:14 amThere is also the little matter that core gas velocity is that of a LH2/LO2 rocket, *not* a turbine.Well... in airbreathing mode it's a hydrogen/air rocket, not a hydrogen/oxygen rocket. So I would expect that to be a bit lower.
Of course. How do you suppose they'd get past Mach 5 with subsonic exhaust?Using CEA, with a chamber pressure of 2000 psia, an oxynitrogen surrogate atmosphere (okay, I was lazy) at 123 K, and a 1:6 mix of 200 K hydrogen to oxygen by mass, the exhaust velocity appears to be in the vicinity of 2500 m/s at altitude, or 2240 for ideal expansion at sea level. Probably around Mach 6 in the ambient air over the runway, even for the real system...SSME seems to be in excess of Mach 10 ambient at sea level...
I'd thought SABRE in air breathing mode was running at around 100 atm c1500psia.
Incidentally did that run give any idea what the plume size would be?
Incidentally did that run give any idea what the plume size would be? People has expressed concern over plum impact on Skylons tail. I think this is highly unlikely given the engine locations on Skylon *unless* the plume is huge.
New Alan Bond interview from Farnborough talking about the precooler test program http://www.rocketeers.co.uk/node/2370
So I guess we're looking at press release or site update in a couple of months.