Couldn't they have a smaller parasite hypersonic vehicle for access to orbit carried on the back of a larger slower carrier craft.
Quote from: Mutley on 04/15/2015 03:02 pmhttp://www.reactionengines.co.uk/press_release.htmlNew press release from Reaction EnginesLooks like the USAF agrees with ESA with regards the feasability of the SABRE conceptFrom the press release:Quote"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."Given the huge projected development cost of the SSTO version, I kind of agree with that.
http://www.reactionengines.co.uk/press_release.htmlNew press release from Reaction EnginesLooks like the USAF agrees with ESA with regards the feasability of the SABRE concept
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."
Agreed that USAF is probably not looking to SABRE for just orbital launch, but in the press release, Barry Hellman (USAF Program Manager) weighs in on the SSTO/TSTO topic by saying:Quote"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."That's what people are responding to.
Quote from: Oli on 04/15/2015 03:53 pmQuote from: Mutley on 04/15/2015 03:02 pmhttp://www.reactionengines.co.uk/press_release.htmlNew press release from Reaction EnginesLooks like the USAF agrees with ESA with regards the feasability of the SABRE conceptFrom the press release:Quote"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."Given the huge projected development cost of the SSTO version, I kind of agree with that.Many of us has argued that from the start. But some staunch Skylon supporters (like John Smith 19) think it has to be SSTO or nothing. The logic of that escapes me, but then again they also seem to find smaller versions of Skylon (to test technology) to be a waste of time. Skylon needs to be a massive SSTO, apparently. Boeing didn't start out by building 747's. The 747 wasn't even their first jet aircraft.
Given the huge projected development cost of the SSTO version, I kind of agree with that.They could, for example, leave the atmosphere at lower speed, in order to reduce aerodynamic pressure, and reenter at Mach 15 or so instead of orbital speed. The vehicle would then land downrange similar to the Hopper concept and could be towed back to Kourou.An upper stage with Vinci could do the rest. It would probably fit into the vehicle (with a longer bay obviously).Any other ideas?
To seriously address a TSTO vehicle with SABRE engines what it amounts to is pretty much exactly the same flight profile as proposed for the Skylon; Take off and acceleration under air-breathing SABRE power to Mach-5+ then switching to pure rocket SABRE to Mach-10 to Mach-15+ outside the effective atmosphere with the release of the upper stage from that point. (For you imagination, take the twin-vertical version of the Skylon and recess a second stage just behind the point where the fuselage is maximum diameter and that's what it would look like)And then ask yourself if, using the structural mass and propellant mass from the "second stage" you couldn't get the "carrier" aircraft up to around Mach-20 and orbit with about the same payload margin that's projected for the SSTO version of Skylon... And all your getting for the cost of two vehicle development programs, (please don't anyone think for a moment you can use an "off-the-shelf" rocket for a second stage) is a small increase in payload to orbit.As an operational note, the Hopper as far as I understand it is CARRIED back to the launch site not towed and any operational SABRE powered vehicle will be fully capable of self-ferry by its nature. Unlike a rocket powered vehicle
Quote from: adrianwyard on 04/15/2015 07:05 pmAgreed that USAF is probably not looking to SABRE for just orbital launch, but in the press release, Barry Hellman (USAF Program Manager) weighs in on the SSTO/TSTO topic by saying:Quote"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."That's what people are responding to.Since we think that SABRE might not scale down all that well, what are the options for vehicles with only one SABRE engine, full size?
Many of us has argued that from the start.
But some staunch Skylon supporters (like John Smith 19) think it has to be SSTO or nothing.
The logic of that escapes me, but then again they also seem to find smaller versions of Skylon (to test technology) to be a waste of time. Skylon needs to be a massive SSTO, apparently.
- If the upper stage has a propellant mass fraction of 0.9 staging at Mach 15 gives me ~2.5x the payload (Skylon C1).
Richard Varvill's talk has now been uploaded at:https://player.vimeo.com/video/124910371
No structural penalty on the first stage for shoehorning a big second stage into the existing design?Also keep in mind that Skylon's payload is already large enough to capture the bulk of the market, and you can't scale the vehicle down because the combination of payload diameter requirements and aerodynamic considerations pretty much dictate its current size (believe it or not it has nothing to do with using LH2).
Well the "first stage" doesn't reenter from orbit anymore and has less tank volume, could go both ways IMO.
Maybe, but REL says the Mach 5+ atmospheric flight is driving the TPS design just as much as the orbital reentry. And as I said the tank volume isn't driving the shape - well, it is, in the sense that they had to make the fuselage shorter at the cost of increased drag to avoid wasting structural mass on empty space...
Richard Varvill's talk has now been uploaded at:https://player.vimeo.com/video/124910371Everyone should watch it, it's quite a good viewing. Although I have to say that watching it online where I can pause and have a think about what is being said makes for a much more informative lecture than live at the venue, where I felt like I couldn't possibly remember everything he was saying!!
Define "driving just as much", doesn't mean they have the same requirements. At least the active cooling won't be required anymore. And why not go only to Mach 3 or so in the atmosphere? Well, that will lower the payload but might make other things easier.
Regarding the tank, I thought the tank doesn't support the structure, so they could just make it smaller if there's less propellant without changing the shape.
Quote from: topsphere on 04/15/2015 09:25 pmRichard Varvill's talk has now been uploaded at:https://player.vimeo.com/video/124910371Everyone should watch it, it's quite a good viewing. Although I have to say that watching it online where I can pause and have a think about what is being said makes for a much more informative lecture than live at the venue, where I felt like I couldn't possibly remember everything he was saying!!you know, the subject was most interesting and I enjoyed the talk content, but either Varvill's is not a good speaker or it was a bad time for him. I found it somewhat of a snoozefest and Varvill's sounded like he wanted to be somewhere else, or that he was pessimistic about the future.I hope Varvill's is not in charge of selling Skylon...