Anyways, a. who would be operating the Skylons servicing the ISSb. ISS servicing is only a stepping stone for Musk. He wants to go further than LEO in bigger pieces than 15 tons.c. The ISS will be near its end by the time Skylon is on the market.d. What says Skylon will not go the way of HOTOL, Space Shuttle, Concorde or SR-71?
Quote from: BobCarver on 11/29/2012 03:16 amOne of the major drawbacks to the SSME was the fact that it had to be disassembled and examined after every flight.I have not found any reference to these kinds of problems/solutions on the REL website. This could be a show-stopper for the reusability of the SABRE engine.That was the early SSME. They haven't had to rebuild the engines after every flight for a long time. In fact IIRC the Block III (that was planned to come online in 2005 before Columbia changed everything) didn't need to be so much as removed from the orbiter for ~10 flights. It also had a radically decreased probability of catastrophic failure compared with the Block II.Also, the difficulties tend to scale very steeply with main chamber pressure, and SABRE uses a significantly lower chamber pressure than the SSME (about half, I believe).
One of the major drawbacks to the SSME was the fact that it had to be disassembled and examined after every flight.I have not found any reference to these kinds of problems/solutions on the REL website. This could be a show-stopper for the reusability of the SABRE engine.
Quote from: Rocket Science on 11/29/2012 01:54 amExotic engines aside my concern with Skylon is one of directional stability. All hypersonic vehicles had a lager vertical stabilizer ala X-15 to Shuttle. Skylon looks like an X-3 redo with all its inherent problems. I guess we’ll see the final configuration....http://www.456fis.org/DOUGLAS_X-3.htmOne important difference is that while the X-3 had fuselage-mounted engines, Skylon has them on the wingtips which should give a bit more stability.Skylon should really be counted as a 'hypersonic' vehicle as it doesn't get into hypersonic flight & stay there, it merely passes through that part of the speed range as it accelerates (out of the atmosphere) up to orbital velocity.
Exotic engines aside my concern with Skylon is one of directional stability. All hypersonic vehicles had a lager vertical stabilizer ala X-15 to Shuttle. Skylon looks like an X-3 redo with all its inherent problems. I guess we’ll see the final configuration....http://www.456fis.org/DOUGLAS_X-3.htm
The thing is full of liquid hydrogen, and it has a very light structure. The control surfaces do indeed look too small if you're used to kerosene-fueled vehicles, but these are not "artist's impressions"; they represent the results of actual analysis.
One important difference is that while the X-3 had fuselage-mounted engines, Skylon has them on the wingtips which should give a bit more stability.
Actually, if SABRE works as planned, governments may decree that it replace conventional fossil fuel engines on airliners in order to cut down on CO2 emissions. In that case it would make a profit by government decree. There seems to be a high likelihood of this happening considering the deteriorating state of the environment. It's a straightforward fix for the pollution from airliners.
Isn't crack growth now prevented by having a turbine balde grown from a single crystal, complete with ventilation channels. Part of the improvment in commerical engines such as the Trent is that they now operate at a higher temperature than the melting point of the fan. I would assume that only Rolls Royce, GE and Pratt and Whitney have really mastered this technology.
$20m also conveniently enables complete payback on the $2bn investment in only 100 missions or half the airframe's life, opening the window for the Skylon operator to make profit.
That raises the question of who will be RE's elusive partners in manufacturing the engines and the spacecraft. If you eliminate US companies for ITAR reasons, it doesn't leave *that* many options. Has RR been involved in space propulsion recently ?
Has RR been involved in space propulsion recently ?
Quote from: Kharkov on 11/29/2012 02:09 amOne important difference is that while the X-3 had fuselage-mounted engines, Skylon has them on the wingtips which should give a bit more stability.It is the exact opposite. Then there are engine out considerations.
If you sell your flights at 40m that is, otherwise it will only cover operating costs.I think RE plan to produce a vehicle for only 190m, so they make a big plus is they sell at 2bn. Which they have to.
Is ITAR so restrictive? I mean there is cooperation between american and european companies in aerospace...
It's not a monocoque fuselage. It's a spaceframe, supporting a non-structural skin and internal non-structural tanks. It's more similar to a Zeppelin than an aeroplane or rocket.
Quote from: Crispy on 11/29/2012 11:10 amIt's not a monocoque fuselage. It's a spaceframe, supporting a non-structural skin and internal non-structural tanks. It's more similar to a Zeppelin than an aeroplane or rocket.I would appreciate a link for that if you have one handy...
Material ConstructionSKYLON's fuselage and wing load bearing structure is made from carbon fibre reinforced plastic and consists of stringers, frames, ribs and spars built as warren girder structures. The aluminium propellant tankage is suspended within this, free to move under thermal and pressurisation displacements.The external shell (the aeroshell) is made from a fibre reinforced ceramic and carries only aerodynamic pressure loads which are transmitted to the fuselage structure through flexible suspension points. This shell is thin (0.5mm) and corrugated for stiffness. It is free to move under thermal expansion especially during the latter stages of the aerodynamic ascent and re-entry.
In the event of an “unstart” with the engines sitting so far from the center of gravity you would have a massive asymmetrical thrust and yaw.
QuoteIn the event of an “unstart” with the engines sitting so far from the center of gravity you would have a massive asymmetrical thrust and yaw.I would assume that these engines are able to deep throttle like jet engines. So they would probably start them throttled down all the way. But I admit that I may be way off the mark there.
Unstart is an inlet issue and not related to starting the engine