Routing the hot bypass air does sound like the thorniest problem. It may not be worth it, and instead you dump it through bypass doors - a la SR71. But that comes with a performance penalty (no thrust from bypass burners, plus maybe drag) and complexity.
It's a good guess that Bond et al considered this sort of configuration in depth after the HOTOL cancellation, before coming up with Skylon.IIUC the only thing that's a little different now is the temperature/pressure of the cooled air is less extreme with SABRE 4.
You're missing the point. I wasn't calculating the performance of the vehicle. I was calculating how badly wrong REL's estimates would have to be to kill their idea completely. Saying "yes, but their numbers might not be right" doesn't engage the actual question.
{snip}Can't access the reddit article but stating a "life-expectancy" for an air frame in years is odd to say the least. Even "200 launches" is based on a ton of assumptions and airframe life is most often expressed in hours (of flight time) not years. (BTW? That would be over 80,000 hours ) And is dependent on component and materials versus stress and maintenance factors which are not known until you actually do the testing required to gather the data.The statement would appear to have about as much validity as the claims that the Falcon-9R first stage can fly "10 times" which is unproven and un-provable until after you actually FLY the airframe at least 10 times...Randy
Quote from: RanulfC on 03/24/2016 04:44 pm{snip}Can't access the reddit article but stating a "life-expectancy" for an air frame in years is odd to say the least. Even "200 launches" is based on a ton of assumptions and airframe life is most often expressed in hours (of flight time) not years. (BTW? That would be over 80,000 hours ) And is dependent on component and materials versus stress and maintenance factors which are not known until you actually do the testing required to gather the data.The statement would appear to have about as much validity as the claims that the Falcon-9R first stage can fly "10 times" which is unproven and un-provable until after you actually FLY the airframe at least 10 times...RandyExpressing the life expectancy of an air frame in years may be odd but it is normal to express the shelf life of silicon chips in years. 10 years is about the maximum shelf life of a Flash Memory.Ref: http://www.wdc.com/WDProducts/SSD/whitepapers/en/NAND_Evolution_0812.pdfWhether the entire Skylon needs replacing after 10 years or only its electronics would need investigating. Things like the hydraulics and seals may also need replacing.
Mark said they were aiming for 10 year lifespan for Skylon and rapid reuse
To be clear the exact quote I'm referencing is :QuoteMark said they were aiming for 10 year lifespan for Skylon and rapid reuse
Quote from: A_M_Swallow on 03/24/2016 05:26 pmQuote from: RanulfC on 03/24/2016 04:44 pm{snip}Can't access the reddit article but stating a "life-expectancy" for an air frame in years is odd to say the least. Even "200 launches" is based on a ton of assumptions and airframe life is most often expressed in hours (of flight time) not years. (BTW? That would be over 80,000 hours ) And is dependent on component and materials versus stress and maintenance factors which are not known until you actually do the testing required to gather the data.The statement would appear to have about as much validity as the claims that the Falcon-9R first stage can fly "10 times" which is unproven and un-provable until after you actually FLY the airframe at least 10 times...RandyExpressing the life expectancy of an air frame in years may be odd but it is normal to express the shelf life of silicon chips in years. 10 years is about the maximum shelf life of a Flash Memory.Ref: http://www.wdc.com/WDProducts/SSD/whitepapers/en/NAND_Evolution_0812.pdfWhether the entire Skylon needs replacing after 10 years or only its electronics would need investigating. Things like the hydraulics and seals may also need replacing.To be clear the exact quote I'm referencing is :QuoteMark said they were aiming for 10 year lifespan for Skylon and rapid reuse
I did a little data extracting from <https://imgur.com/a/F87pA> and came back with thefollowing pictures, comparing Isp and T/W from several iterations of the SABRE engine.I call it SABRE 1/2/3 and SABRE 4A (older data) / SABRE 4B (most recent taken from the link above).There is clearly a dramatic improvement from the first to second group.Also there is a marked difference between Isp and T/W from SABRE 4A to 4B.
Quote from: tatarana on 03/24/2016 10:04 pmI did a little data extracting from <https://imgur.com/a/F87pA> and came back with thefollowing pictures, comparing Isp and T/W from several iterations of the SABRE engine.I call it SABRE 1/2/3 and SABRE 4A (older data) / SABRE 4B (most recent taken from the link above).There is clearly a dramatic improvement from the first to second group.Also there is a marked difference between Isp and T/W from SABRE 4A to 4B.Where is your older data from? Aside from Varvill & Bond (2003) and the C1 trajectory spreadsheet, I know of no sources that give (or can be analyzed to give) Isp curves for SABRE.
New Skylon article with some details on the test program at the end.http://epizodsspace.no-ip.org/bibl/inostr-yazyki/aerospace-america/2016/3/8-11.pdf
A scramjet can go up to Mach 10.
Mach 5 you can do with a turboramjet, to my knowledge.Both have very bad thrust-to-weight ratios, but that's not a showstopper for atmospheric flight. Space launch is hardly a relevant market at this point.
Quote from: lkm on 03/27/2016 10:30 pmNew Skylon article with some details on the test program at the end.http://epizodsspace.no-ip.org/bibl/inostr-yazyki/aerospace-america/2016/3/8-11.pdf Looks like they are planning a single engine suborbital test vehicle. Props to AM_Swallow for predicting this.EN: "The first flight test vehicle, with its single engine, would look more like a missile than a space plane, [Richard] Varvill [REL chief designer] says. It would be built to test the initial stage of a flight to space — taking off from the ground and accelerating to about Mach 5 with air-breathing engines — and then the engine would shut off and the air-craft would glide back to the ground."As I said before, the company is clearly more flexible than people trying to "defend" the company.
As I said before, the company is clearly more flexible than people trying to "defend" the company.
That is according to Skunk Works head Rob Weiss, who confirmed that it would be an unmanned vehicle, at least at first. Hewson says the company’s long-term ambition is to “enable hypersonic passenger flights and easier access to space”.
Hewson, while displaying an artist’s rendering of the SR-72, said it would cost “less than $1 billion” to develop and fly a demonstrator aircraft the size of a the company's F-22 Raptor.
[In] 2016 [there] will be a decision on winners; more than one, likely, on one or both programmes,” says Weiss, adding that flight tests are planned for 2018.