Quote from: RanulfC on 02/20/2015 06:57 pmThe two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated. The rest of your post was reasonable, but this I must inquire about:When was the rocket motor demonstrated? Did I miss that?
The two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated.
Quote from: Lars-J on 02/20/2015 08:15 pmQuote from: RanulfC on 02/20/2015 06:57 pmThe two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated. The rest of your post was reasonable, but this I must inquire about:When was the rocket motor demonstrated? Did I miss that?LOX apparently not air. So that's still a bit of question I suppose though to be honest the "Low-NOx" engine test would seem to indicate air use.http://www.reactionengines.co.uk/sabre_techdevel.html
Quote from: lkm on 02/20/2015 01:35 pmWhen are you proposing to stage this notional TSTO? Inside the atmosphere so you can use a simpler non rocket mode SABRE losing LOX tanks from the first stage or outside still using SABRE?Are you carrying the second stage internally or externally? If externally how are managing the damage that does to the aerodynamics and thermal protection? If internal how are making the vehicle trimable given the damage that does? What engine is powering the second stage? How does any of that make the development of SABRE cheaper? Either you're proposing using the SABRE design as is, or you're suggesting development of a second engine, on top of SABRE, without a pure rocket mode neither of which can be cheaper for REL as an engine developer than just building SABRE.Indeed. It's one of those ideas that sounds very sensible, until you look at it a bit more closely.
When are you proposing to stage this notional TSTO? Inside the atmosphere so you can use a simpler non rocket mode SABRE losing LOX tanks from the first stage or outside still using SABRE?Are you carrying the second stage internally or externally? If externally how are managing the damage that does to the aerodynamics and thermal protection? If internal how are making the vehicle trimable given the damage that does? What engine is powering the second stage? How does any of that make the development of SABRE cheaper? Either you're proposing using the SABRE design as is, or you're suggesting development of a second engine, on top of SABRE, without a pure rocket mode neither of which can be cheaper for REL as an engine developer than just building SABRE.
QuoteI can't help feel that rocketry (successfully putting things in orbit since 1957) is somewhat better understood that Scramjets ( someday soon we'll reach ten minutes cumulative flight time). Who is seriously researching scramjets for anything other than hypersonic cruise? Also please name these other people who think that the development challenges of NASP in 1984 are of comparable difficulty to the challenges of Skylon in 2015.That would be an interesting list.
I can't help feel that rocketry (successfully putting things in orbit since 1957) is somewhat better understood that Scramjets ( someday soon we'll reach ten minutes cumulative flight time). Who is seriously researching scramjets for anything other than hypersonic cruise? Also please name these other people who think that the development challenges of NASP in 1984 are of comparable difficulty to the challenges of Skylon in 2015.
QuoteMany people believe that VentureStar wasn't viable, but I don't think anybody believes the X-33 couldn't have flown and gathered useful data. The X-33 wasn't VentureStar, VentureStar was a powerpoint, X-33 was an active x-plane project with a similar budget and goals to the X-15. The X-15 wasn't a failure because it had no follow on project so why should the X-33? When the X-15 first flew it didn't have it's intended engine yet because it wasn't ready, so why should the X-33 not have been given the same leeway? Like I said, there was a change in administration, a desire to cancel and repudiate the projects of the previous one, people obliged.Actually the view amongst some people was that the X33 was extremely complex and risky for its stated purpose. I'd suggest VTOHL SSTO is the most difficult way to do it. It calls for both a T/W of at least 1.1:1 and a strong structure in two axes.
Many people believe that VentureStar wasn't viable, but I don't think anybody believes the X-33 couldn't have flown and gathered useful data. The X-33 wasn't VentureStar, VentureStar was a powerpoint, X-33 was an active x-plane project with a similar budget and goals to the X-15. The X-15 wasn't a failure because it had no follow on project so why should the X-33? When the X-15 first flew it didn't have it's intended engine yet because it wasn't ready, so why should the X-33 not have been given the same leeway? Like I said, there was a change in administration, a desire to cancel and repudiate the projects of the previous one, people obliged.
Quote from: Lars-J on 02/20/2015 08:15 pmQuote from: RanulfC on 02/20/2015 06:57 pmThe two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated. The rest of your post was reasonable, but this I must inquire about:When was the rocket motor demonstrated? Did I miss that?LOX apparently not air. So that's still a bit of question I suppose though to be honest the "Low-NOx" engine test would seem to indicate air use.http://www.reactionengines.co.uk/sabre_techdevel.htmlRandy
The X-33 wasn't VentureStar, VentureStar was a powerpoint, X-33 was an active x-plane project
What would people think of separating this thread into two threads: Skylon Updates and Skylon Discussion? There's been a lot of discussion in the Skylon threads, and not everyone who is interested in hearing about news from Skylon has the time or inclination to follow all the discussion.
when the space shuttle idea was proffered, did people say 'what's wrong with normal rockets?, we know how to do normal rockets' were there naysayers arguing for incremental steps?
Do I then assume that you deride the various "Fully-reusable TSTO is a done deal" SpaceX fans the same way?
And yes Skylon is the latest in a long line of "promising" SSTO vehicle but I'd point out that it in fact is much close to, and much easier to implement than most where and does not (at this point) really need as significant technologies as most of the previous concepts did.
And from what I saw over the last 25 years, that's part of the reason it's taken so long for Bond's ideas to receive backing. If you're an investor (or administrator) in aerospace/aviation and this comes across your desk; a report that's actually about some guy who thinks he's solved the pre-cooler icing problem, but if you saw a picture of Skylon and pages of detail on the vehicle, payloads and missions, would you even read the report? Would you wade through the rest to even get to the two paragraphs on Bond's actual pre-cooler design? Because Skylon hit the quadrella of aerospace "alarm bells": a tiny unknown company proposing a radical vehicle design, plus it's an SSTO, plus it uses air-breathing jet/rocket hybrid engines, plus it's all based (with no margins) around their own new unproven technology proposal. OTOH, you're in aerospace and a report crosses your desk about a small start-up that thinks it has solved the pre-cooler icing program. They point out that if their idea works, it could make high-speed turbojet engines more efficient and effective. Oh sure, they speculate - just as an aside, making it clear that they are just speculating - that the idea could even be useful for future space vehicles. And that's it, the report is about their pre-cooler idea, nothing else.
Out of curiosity, can you think of a single one of those previous designs whose advocates didn't say exactly the same thing about their design?
that's some back to front thinking you have going on there Paul451. REL need heavy investment. Investors need to be wooed. showing them what the ultimate goal of their investment is is logical.
about wooing investors with the promise of making high-speed turbojet engines more efficient and effective. why would they?
Paul451, I understand you haven't really been around
Quote from: banjo on 02/21/2015 09:42 amthat's some back to front thinking you have going on there Paul451. REL need heavy investment. Investors need to be wooed. showing them what the ultimate goal of their investment is is logical.And yet for over 20 years it didn't work. Only now are they picking up some actual revenue, and not for Skylon but for a hypersonic passenger plane study.
What your calling Science I would simply call 'real man's engineering' and looking something up from a book is 'engineering for dummies'. Iteration in engineering doesn't in my opinion make it a science because science is the creation and testing of theories, engineering is the creation and testing of devices.
make it a science because science is the creation and testing of theories,
I thought their money is from a 60 million pound government investment [...] Why are you leaving out the major sources?
Quote from: t43562 on 02/21/2015 10:41 amI thought their money is from a 60 million pound government investment [...] Why are you leaving out the major sources?Nothing sinister about it. It was an arbitrary decision to draw a distinction between the UK Govt giving them bare-minimum funding to keep REL viable, to keep from losing technology to someone else (even if they didn't believe in the technology enough to properly fund it), and someone completely independently saying "hey, you guys have mad skills, care to do some work for us?" The latter struck me as more significant, even if it garners fewer dollars pounds euros.
SpaceX's failure to deliver a fully reusable F9 strongly suggest that the current theories, and the models derived from them have flaws in them that mean going from their very public video to actual hardware was impossible. That's when you start doing Science.
Quote from: john smith 19 on 02/21/2015 10:44 amSpaceX's failure to deliver a fully reusable F9 strongly suggest that the current theories, and the models derived from them have flaws in them that mean going from their very public video to actual hardware was impossible. That's when you start doing Science.THIS is the kind of comment that destroys your credibility. As Lars-J said earlier is smacks of "Denigrating the hard work by done by people trying for the same goal but by different means." It has been pointed out repeatedly to you that SpaceX is not PURSUING full reusability for F9 because they have decided to focus on the followup vehicle which they DO intend to make fully-reusable. They have said this is a decision driven by market volume and development resource, NOT one forced on them by hitting technological barriers.But you have been repeatedly portraying this a technical failure on SpaceX's part and further more that this failure invalidates the vertical take-off, vertical landing paradigm, leaving your preferred Horizontal arrangement the 'only' viable solution. And you blatantly ignore that they are STILL WORKING on the goal, which puts them in the same race as REL, but miles ahead, while you try to treat them as if they have dropped out.And no this is not Science, it is ALL engineering. Science is creating the rocket-equation, Bernoulli's principle and all the other THEORIES that let us know how the world behaves. SpaceX nor any other Airo-space company dose science, they engineer vehicles using well established theories.
I kind of agree with what you said other than please do not just dismiss what REL has achieved so far by the glib sentence of saying that Space X is miles ahead.
Quote from: t43562 on 02/18/2015 09:49 pmQuote from: ChrisWilson68 on 02/18/2015 09:28 pmThat's fine, but this engine company is making projections about the performance and economic viability of the complete system, including engines and airframe.Don't they have to? Is it not necessary at all times to make such projections and keep updating them as new information is learned?There'd be no shame in their saying "we don't know yet".
Quote from: ChrisWilson68 on 02/18/2015 09:28 pmThat's fine, but this engine company is making projections about the performance and economic viability of the complete system, including engines and airframe.Don't they have to? Is it not necessary at all times to make such projections and keep updating them as new information is learned?
That's fine, but this engine company is making projections about the performance and economic viability of the complete system, including engines and airframe.
Personally I think the greatest threat to Skylon development will be a failure of an airframer to commit to it. I think REL may find that despite developing an engine that works well and engenders a lot of interest in the end there may be a general reticence to throw in with another companies grand scheme and disrupt their own planning among the likely consortium partners. I could see REL being bought by RR as a part of an attempt at forming a successful consortium only to end being used to get some lucrative US hypersonics research money.