In contrast there is limited experience of pumped LH2/LO2 engines anywhere with 4 designs in the US (and the only production design dating from the 1960's) with 2 in Europe and 1 (IIRC) in Russia.
That's $360M to get to first working prototype.
http://en.wikipedia.org/wiki/Jo_Johnson
I notice that Skylon's fuselage is pinched at the middle where the payload bay is. I wonder why they decided not to use a wider payload bay of ~ 6 metres. How much of a payload penalty would that involve.
It's a good guess this pinch is due to Area Rule influencing the design. (http://en.wikipedia.org/wiki/Area_rule)So if you made the payload bay wider, the rest would widen proportionally too.
it would be good to have any kind of company update at this point. How is the work doing?
I feel like they get a trickle of funding from the UK Govt, not enough to do anything much with it, but enough for the politicians to feel good about themselves.
a single rocket launch (I assume they need to test their engines at altitude / hypersonic speed) would eat a lot of that.
At first blush the nacelle/inlet looks reminiscent of other flown configurations such that on the SR-71: it’s axisymmetric with a translating shock cone. But the fact that it can close fully and successfully resist re-entry shock/plasma/thermal conditions is new.
1] The louvres need to be thin to minimize drag during air-breathing (see the attached screen shot) of a REL animation. But this thinness limits the options for thermal protection: there’s no mass/structure to sink heat into, and not much room for active thermal control.
2] The sharp tip of the cone will receive the most severe heating as it’ll be close to the shock wave, and has little volume to sink heat back into. There may be room in the cone for active cooling. Or a more drastic departure would be to swap the actual cone for an aerospike, such as that used on the Trident ICBM. (see picture from http://en.wikipedia.org/wiki/Drag-resistant_aerospike below) During atmospheric ‘forward’ flight the spike is extended to form a simulated cone, but for re-entry it’s retracted leaving the cone blunt and so better suited to face the airflow (which now comes from below).
An aerospike could also be used to alleviate heating on the sharp fuselage nose as it will face similar heating issues.(A pre-emptive note to JohnSmith19: Please don’t take these comments and suggestions to be my dismissal of the Skylon project as impossible. Thinking through engineering challenges like Skylon is a hobby of mine, and I share my thoughts in hopes of hearing corrections when I’m mistaken.)
There are a number of new things that need to be developed. These include ...6. super lightweight tanks that are 1% of the mass of the propellant....