Comments on the article.
I've only commented on the bits I disagree with. The rest you can presume I go along with.
"Air is taken in at the front of the SABRE and almost instantly cooled down to the point at which it is almost liquid, using terrifically powerful freezer kit employing a liquid-helium loop."
And driven by a pair of oversize liquid Hydrogen tanks. A very cold thing makes a fairly warm thing substantially colder.
>>The supercold air takes the place of liquid oxygen in the combustion chamber, reacting with liquid-hydrogen fuel to produce thrust in much the same way as the space shuttle main engines. Heat sucked from the intake air is dumped into the fuel.<<
The amazing spaceplane is expected to be able to repay those big investment cheques, as it will be able to deliver payloads – admittedly, at first quite small ones of only 10 tonnes or so compared to its own substantial mass of 275+ tonnes – at low cost.
That's a payload which is c3.6% of GTOW. In the launch biz that's pretty good.
It's better than a Delta IV and on a par with an Atlas V. This counters the traditional whine that SSTO's can't deliver as much payload (as a portion of GTOW) as expendables.
The shuttle manages about 1.25% of GTOW. It has an SSTO payload fraction *without* the actual benefits of SSTO.
REL's engineers have been compelled to shave everything to the limit to produce a design which seems to show that SABREs and the fuel they need to reach orbit can fit into a re-entry-capable airframe along with some cargo.
In a word. No.
The ceramic aeroshell is to be just 0.5mm thick.
Slightly thinner than some part of the SR71 wing structure (which were *also* corrugated BTW).
Skylon's skin is only designed to carry the *thermal* load. Mechanical loads are carried by the geodesic truss framework. The technique was proposed for the X20 DynaSoar.
The undercarriage has had to be lightened too,
Below *common* state of practice, *not* state of the art as far back as the late 1958s (and not a CAD/CAM workstation in sight).
"so that a Skylon won't be able to land on just any runway"
Wrong. This thing might take off like Michelle McManus but it'll land like Britney Spears. Weather or not it'll be *allowed* to use ordinary airports, as it is technically a UAV, is something to be thrashed out.
" – it will need a special reinforced one able to cope with heavily loaded wheels moving rather fast."
On *takeoff* only.
If the craft itself should gain just a few per cent in fueled-up weight during the development process, this would wipe out its entire payload margin.
No. SSTO's are vulnerable to growth in the *dry* weight. In principle the wings make it *less* vulnerable in this area than vertical takeoff designs.
"There are those who would argue that operations using liquid hydrogen fuel will simply never be economical:"
Mostly they argue its a pig to handle. Liquid oxygen freezes out water on top of the insulation if it's not good enough. Hydrogen liquefies *Oxygen* out of the air.Insulation has to be *very* good. It's a PITA.
However *all* alt-space advocates agree the fuel cost is "In the noise".
The *real* cost is the manufacturing and "standing army" of managers, safety inspectors, managers of safety inspectors, document management team etc. Cost is strongly proportional to *complexity* and *weakly* proportional to size.
" the stuff takes up so much room that hydrogen aircraft – including the Skylon – are always made up mainly of fuel tanks."
*All* launch vehicles are mostly fuel tank.
" It is so troublesome, potentially dangerous and expensive to handle that it will infallibly destroy any business model based on it other than that of government-funded military or scientific projects."
No.
Regarding RE's business model it's *strictly* for profit.
They build a vehicle. It's up to *other* people to operate it.
It's like building a taxi. Someone *else* operates it. If they don't make a profit *they* go out of business. Just like a *real* transport systems, not the insane 1 shot ticket-to-ride/govt cost++ system expendables foist on the users.
TBH there were a few moments when I was tempted to flag the article as Troll.
If this is Lewis on a subject I know something about what is he like on subject I don't know anything about?
<sigh> There goes my shot at the Reg spaceplane desk.
Biting the hand that feeds IT
