Cosmos Magazine has a news bite on SKYLON which reports older news about SKYLON and funding of an engine study by the ESA. Goods news, but no breakthrough. At least the word is out there.
Here’s something to consider: SKYLON’s development is likely to be roughly $10 billion. How does that affect price-tag for LEO services? If 30 SKYLONs are made and each flies 200 times before replacement, then the development cost divided over all those 6,000 flights is $1.67 million, or $139/kg. If 300 SKYLONs are built then it’s just $13.9/kg. That’s development cost, to which we add per unit cost, per flight costs, and fuel costs, then profit. SKYLON uses 66 tons of hydrogen and 150 tons of LOX for propellant, which costs ~ $250,000 total adding $20.8/kg to the bill. Then there’s vehicle costs incurred due to wear and tear of the components of the cryogenic system, SABRE ejector ramjets, landing gear, RCS and avionics every flight. I’m not sure what the best estimate of those would be, but let’s assume roughly comparable to the fuel costs. Thus the bill is up to $55.5/kg. If a SKYLON costs ~$200 million per unit – expensive jet-fighter value – then that’s $1 million per flight over its lifetime, which adds $83.3/kg. That seems excessive and might go down with large production volumes. Perhaps we can halve it. Thus SKYLON might cost $100/kg to deliver payload to LEO.
How much payload do 300 SKYLONs need to carry to LEO to drive costs down? All up they represent 720,000 tons of payload lofted on 60,000 flights. If a 1 GW SPS masses 3,000 tons, including the GEO delivery system for its subcomponents, then 240 GW of SPS power could be installed. To power the whole world to the tune of 24 TW then 30,000 SKYLONs making 6,000,000 flights will be needed. Larger LEO cargo vehicles would reduce this somewhat. The Star-Raker SSTO, designed in the late 1970s as a ramjet/rocket hybrid, was designed to deliver 120 tons per flight, thus reducing the fleet or the flight numbers ten-fold. Alternatively Space-Elevators may eventually be developed, but that’s totally dependent on materials and laser advances that are unpredictable. SKYLON, I would submit, can get the job done.