Claiming, no. Acting, yes. They are designing payloads and space stations and Mars missions around the size/capacity of the Skylon payload bay.
(Not to mention a hypersonic passenger plane.)
And Bond rejects out of hand any suggestions that Skylon may not be the optimal design (as John echoes, above). If you were an "airframer", would you get mixed up with an engine company which behaves like that? Or wait until they fail and just licence the engines from whoever buys the IP, and develop your own clean-sheet design?
To me, it's like some who wants to develop the world's first jet engine. So far they have one compressor fan. But they've not only designed the rest of the engine, and designed the entire airliner around that engine, and insisted it's the only possible design, but they are proposing new airport designs based around the door spacing on that proposed airliner for the proposed engine for which they have (after 20 years) only built a single compressor fan.
But you dare suggest they are being a bit premature...{sigh} Why is this idea so prevalent in aerospace?Two is more than one, so therefore it must cost twice as much to develop an aircraft to carry freight between cities and a truck to ferry between individual customers and the airfreight terminals than to develop a single vehicle which can fly between cities but land directly on the customers' driveways. Must. Because two is more than one.
Quoteand the testing around hypersonic separation.Only if they were stupid.When Chris is suggesting smaller stepping stones, when that's the entire premise of his argument, why would you assume he would be suggesting the hardest possible version of TSTO?
and the testing around hypersonic separation.
I'm not an expert on any of this so feel free to correct me, but wouldn't it make more sense to develop a TSTO Skylon in such a way that the skylon makes a suborbital hop and, once outside the brunt of the atmosphere, open the cargo bay and deploy an upper stage to which the payload is attached?In fact, hasn't something similar to this concept been proposed in this study by Mark Hempsell?It'd certainly be less complicated than staging inside the atmosphere at hypersonic velocities IMO.
Your line of reasoning leads to the logical conclusion that the simplest process is to not stage at all does it not?
I'm not sure where you're reading about sub orbital staging in the paper you cited.
IIRC no one they've been talking to said they really need this and further studies showed that the window between doors open, payload deployment and doors closed before re entry began was tight. With no one actually asking for it and little margin for error they deleted it as an option from the latest issue of the Skylon user manual.
Yet another new forum visitor. You really are coming out of the woodwork today. Welcome.
Not really. In the "suborbital + kick stage to orbit" TSTO method, your primary carrier doesn't need to have quite as thin a mass margin than in a fully SSTO vehicle. It gives you more room to work with.The only reason it goes above the atmosphere is to avoid the trouble with staging at hypersonic velocities while in the thick atmosphere.
Sorry, my bad. What I mostly meant with the study was that it contained the "fluyt" stage which could be scaled down from a GEO/Lunar transfer stage to a orbital circularization stage.Of course, the down side of all this kick stage mallarkey would be a smaller space for payload in the cargo bay, but given the larger mass fraction thus allowed, the cargo bay would have (probably) been expanded somewhat. I'm unsure on this.
Those were some issues that I have also considered, but given the fact that Skylon is a reusable system, in case of running the margin too close for comfort, the people launching could easily simply opt not to deploy the payload and simply return Skylon to the ground, with the payload intact, and try again after adressing any issues which might have cropped up. So, while the deployment window is short, I believe it is manageable.
Quote from: lkm on 10/17/2014 03:19 PM With regards to Skylon forming part of a military weapons platform, the Skylon user manual does detail the suborbital deployment of payloads of up to 30mt at Mach 20. Couldn't a module be designed to rack launch a load of HTV-2 like prompt global strike weapons using that mission mode?QuoteSorry; sub-orbital deployment is off the menu and is not in the latest issue of the Users' Manual. There were problems making the reentry work and, as there was no identified use for it, we gave up trying to find a solution. We found the very low orbit deployment worked better for maximising the payload. A further point is that the front payload mounting interface is now designed for a maximum of 17 tonnes so at the moment that is the biggest payload that can be carried regardless of where it is deployed.
The real issue with this TSTO concept I've outlined (at least from what I can tell) lies in getting the Skylon back to its launch site, as that would probably require prohibitive amounts of fuel so two facilities, one for launch and one for landing would most likely be required. Which would probably run the infrastructure maintenance bill through the roof.
Quote from: john smith 19 on 02/19/2015 12:07 pmYet another new forum visitor. You really are coming out of the woodwork today. Welcome.Thanks. I've been registered here a while, but I mostly prefer to lurk as I often feel like I don't really have anything to add to the conversation.
Quote from: t43562 on 02/18/2015 07:13 pmQuote from: ChrisWilson68 on 02/18/2015 06:06 pmThe people working on Skylon have been working on the idea for decades. They are certainly dedicated and well-meaning, and they have some competence. But they have been working on theory and small components. They don't have experience in system integration. They haven't built real flight hardware. They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.I don't have a biography to hand of each one of them but I suggest that it's a sweeping statement to say that they have no experience in system integration. At the very least some of them are veterans of Blue Streak and others of the aerospace industry.But that goes for almost any aerospace start-up. Among its employees you would expect to see some veterans from other aerospace firms - but that does not mean that the "organizational experience" as a whole translates to this new organization.
Quote from: ChrisWilson68 on 02/18/2015 06:06 pmThe people working on Skylon have been working on the idea for decades. They are certainly dedicated and well-meaning, and they have some competence. But they have been working on theory and small components. They don't have experience in system integration. They haven't built real flight hardware. They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.I don't have a biography to hand of each one of them but I suggest that it's a sweeping statement to say that they have no experience in system integration. At the very least some of them are veterans of Blue Streak and others of the aerospace industry.
The people working on Skylon have been working on the idea for decades. They are certainly dedicated and well-meaning, and they have some competence. But they have been working on theory and small components. They don't have experience in system integration. They haven't built real flight hardware. They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.
Quote from: t43562 on 02/18/2015 09:25 pmThey are an engine company not an airframe company. Let the airframe company use its great institutional experience for its part of the work.That's fine, but this engine company is making projections about the performance and economic viability of the complete system, including engines and airframe.
They are an engine company not an airframe company. Let the airframe company use its great institutional experience for its part of the work.
There'd be no shame in their saying "we don't know yet".
Actually, that demonstrates my point quite well. DC-X never progressed to an operational vehicle. It was never more than a sub-scale technology demonstrator. Working on DC-X wouldn't give any experience with the very difficult transition from technology demonstration to a system that is economically successful as an operational system.And "worked on" isn't the same as being in charge.
REL is the one who chose to design it for an SSTO vehicle. They chose to optimize it for that role rather than as part of a reusable first stage of a two-stage launch system, which would be the more conservative choice and give them more margin and require much less in the way of pushing the edge of what technology can do.And everything gets cheaper when things are smaller.
Getting to Mach 5.5 isn't the challenge. They still have to get to Mach 25 to make orbit. True, in some ways it's easier if they're only air breathing to Mach 5.5. But in other ways it's harder. They have to carry much more oxidizer, and their engine has to work well in both air-breathing and rocket mode. Going from Mach 5.5 to Mach 25 in rocket mode (with some of that rocket mode in the dense part of the atmosphere at Mach 5.5) means they need a very good mass fraction.
Like I said, they don't have exactly the same challenges NASP had, but they have very great challenges, and I think they're at a comparable level of difficulty. Apparently, others think they are too, which is why others are continuing SCRAMJet research and development.
In other words SpaceX was "unproven" until they actually flew something successfully. (That would be the F9 btw )
5) To be a valid comparison for Skylon any competitor has to be a) Fully reusable b) Able to deliver at least 15 tonnes to LEO c) Able to deliver at least 6 tonnes to GTO. If a candidate vehicle cannot manage this then it's not a valid comparison.
4) SpaceX have built a very fine ELV
6)The arguments that "It's never been done before" or "Others have tried and failed" are in fact the reason why startups are started. Their founders believe something can be done which has either not been done before or where previous attempts have failed.
And REL have built a heat exchanger.They have not built SABRE and are nowhere near ready to build even a test version of SABRE. They have not built and are not building Skylon. They have built a heat exchanger. Can we agree on that? I think that would move any discussion on much more.
Whereas insisting...Quote5) To be a valid comparison for Skylon any competitor has to be a) Fully reusable b) Able to deliver at least 15 tonnes to LEO c) Able to deliver at least 6 tonnes to GTO. If a candidate vehicle cannot manage this then it's not a valid comparison....seems to be the very thing that prevents any progress in the discussion.
Chris's post (which started the discussion that so far dominates Part 5) was asking if Skylon might not the best development path for REL's proposed technology. They are trying to jump too many steps ahead of themselves. Hence 20 years and all they have is a heat exchanger. Surely after all this time, we're allowed to ask, "Is this the best path?"
Is that question so offensive to you?
REL is trying to develop a fundamentally new type of engine. A radical air-breathing jet engine/rocket hybrid.
When you are doing something so untried, so deep in unexplored territory, you don't try to lock down the end design of a vehicle that might use that engine. Simply because you can't.
That's all people are saying. That's what you can't seem to move beyond.
REL doesn't and can't know the actual performance of any eventual engine. None exist, and the very concept is so new and untried that there's no reasonable extrapolation from prior technology. Therefore, without that, they cannot possibly design a vehicle yet. So the idea that this early in the process they are designing end-user missions around the size of the payload bay of that vehicle is bonkers.
Quote from: john smith 19 on 02/20/2015 08:06 am4) SpaceX have built a very fine ELVAnd REL have built a heat exchanger.They have not built SABRE and are nowhere near ready to build even a test version of SABRE. They have not built and are not building Skylon. They have built a heat exchanger. Can we agree on that? I think that would move any discussion on much more.
Quote from: lkm on 02/18/2015 11:50 pmQuote from: ChrisWilson68 on 02/18/2015 06:06 pmTo start off the new thread, here's a summary of my own reasons for being skeptical about Skylon. Some of these views are probably shared by other skeptics. Feel free to reply with opposing views; hopefully, this will help clarify exactly where opinions differ and help undecided readers of these forums see both sides and make up their own minds.First off, I don't think there's a known flaw in Skylon that definitely makes it impossible. It's not like a perpetual motion machine that violates known laws of physics. My issue with Skylon is that there are too many unknowns and the proponents of Skylon assume those unknowns will work out, while history shows this is seldom the case. There are enough unknowns and enough projections that seem very optimistic to me that the odds of Skylon actually achieving its goals seem remote to me.The people working on Skylon have been working on the idea for decades. They are certainly dedicated and well-meaning, and they have some competence. But they have been working on theory and small components. They don't have experience in system integration. They haven't built real flight hardware. They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.I don't think you are fully aware of the background the REL team. Mark Hempsell for example worked on the DCX.http://forum.nasaspaceflight.com/index.php?topic=19127.msg493088#msg493088Actually, that demonstrates my point quite well. DC-X never progressed to an operational vehicle. It was never more than a sub-scale technology demonstrator. Working on DC-X wouldn't give any experience with the very difficult transition from technology demonstration to a system that is economically successful as an operational system.And "worked on" isn't the same as being in charge.
Quote from: ChrisWilson68 on 02/18/2015 06:06 pmTo start off the new thread, here's a summary of my own reasons for being skeptical about Skylon. Some of these views are probably shared by other skeptics. Feel free to reply with opposing views; hopefully, this will help clarify exactly where opinions differ and help undecided readers of these forums see both sides and make up their own minds.First off, I don't think there's a known flaw in Skylon that definitely makes it impossible. It's not like a perpetual motion machine that violates known laws of physics. My issue with Skylon is that there are too many unknowns and the proponents of Skylon assume those unknowns will work out, while history shows this is seldom the case. There are enough unknowns and enough projections that seem very optimistic to me that the odds of Skylon actually achieving its goals seem remote to me.The people working on Skylon have been working on the idea for decades. They are certainly dedicated and well-meaning, and they have some competence. But they have been working on theory and small components. They don't have experience in system integration. They haven't built real flight hardware. They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.I don't think you are fully aware of the background the REL team. Mark Hempsell for example worked on the DCX.http://forum.nasaspaceflight.com/index.php?topic=19127.msg493088#msg493088
To start off the new thread, here's a summary of my own reasons for being skeptical about Skylon. Some of these views are probably shared by other skeptics. Feel free to reply with opposing views; hopefully, this will help clarify exactly where opinions differ and help undecided readers of these forums see both sides and make up their own minds.First off, I don't think there's a known flaw in Skylon that definitely makes it impossible. It's not like a perpetual motion machine that violates known laws of physics. My issue with Skylon is that there are too many unknowns and the proponents of Skylon assume those unknowns will work out, while history shows this is seldom the case. There are enough unknowns and enough projections that seem very optimistic to me that the odds of Skylon actually achieving its goals seem remote to me.The people working on Skylon have been working on the idea for decades. They are certainly dedicated and well-meaning, and they have some competence. But they have been working on theory and small components. They don't have experience in system integration. They haven't built real flight hardware. They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.
Quote from: lkm on 02/18/2015 11:50 pmQuote from: ChrisWilson68 on 02/18/2015 06:06 pmThe team at REL has consistently proposed building a large-scale single-stage-to-orbit system. That shows poor judgement, in my opinion. SpaceX started with Falcon 1. Then then moved to a full-expendable Falcon 9. Now they are working on perfecting reuse of only the first stage. Along the way, they have learned many lessons and constantly changed their plans, all while retaining their goal of greatly reducing the cost of launch. I believe that kind of incremental, flexible approach is very effective. It is the opposite of the REL approach. With REL going directly for a huge, single-stage-to-orbit system, there is little room to learn operational lessons and change plans. And Skylon is so much different from existing systems it is very likely to need far more flexibility for lessons learned than Falcon.SABRE is a SSTO engine, I'm not sure what intermediate stage there can be for engine explicitly designed to take a single stage into orbit. I can't imagine designs cost get significantly smaller by making a smaller version.REL is the one who chose to design it for an SSTO vehicle. They chose to optimize it for that role rather than as part of a reusable first stage of a two-stage launch system, which would be the more conservative choice and give them more margin and require much less in the way of pushing the edge of what technology can do.And everything gets cheaper when things are smaller.
Quote from: ChrisWilson68 on 02/18/2015 06:06 pmThe team at REL has consistently proposed building a large-scale single-stage-to-orbit system. That shows poor judgement, in my opinion. SpaceX started with Falcon 1. Then then moved to a full-expendable Falcon 9. Now they are working on perfecting reuse of only the first stage. Along the way, they have learned many lessons and constantly changed their plans, all while retaining their goal of greatly reducing the cost of launch. I believe that kind of incremental, flexible approach is very effective. It is the opposite of the REL approach. With REL going directly for a huge, single-stage-to-orbit system, there is little room to learn operational lessons and change plans. And Skylon is so much different from existing systems it is very likely to need far more flexibility for lessons learned than Falcon.SABRE is a SSTO engine, I'm not sure what intermediate stage there can be for engine explicitly designed to take a single stage into orbit. I can't imagine designs cost get significantly smaller by making a smaller version.
The team at REL has consistently proposed building a large-scale single-stage-to-orbit system. That shows poor judgement, in my opinion. SpaceX started with Falcon 1. Then then moved to a full-expendable Falcon 9. Now they are working on perfecting reuse of only the first stage. Along the way, they have learned many lessons and constantly changed their plans, all while retaining their goal of greatly reducing the cost of launch. I believe that kind of incremental, flexible approach is very effective. It is the opposite of the REL approach. With REL going directly for a huge, single-stage-to-orbit system, there is little room to learn operational lessons and change plans. And Skylon is so much different from existing systems it is very likely to need far more flexibility for lessons learned than Falcon.
Quote from: lkm on 02/18/2015 11:50 pmQuote from: ChrisWilson68 on 02/18/2015 06:06 pmThere have been many programs with similar or lesser optimistic goals that have failed. The U.S. National Aerospace Plane had far more resources available and a similar level of technological challenge, and it failed. Note that I'm not saying the details of the technological challenge are similar -- they are not. But the programs are similar in having a goal that required many unknowns to be overcome and having people with some competence in specific areas convinced they could overcome them.The technical challenge of airbreathing to Mach 18 is clearly of a vastly higher level than airbreathing to Mach 5.5 and the number of unknowns in geting to Mach 18 in 1984 far greater than achieving Mach 5 thirty years later.Getting to Mach 5.5 isn't the challenge. They still have to get to Mach 25 to make orbit. True, in some ways it's easier if they're only air breathing to Mach 5.5. But in other ways it's harder. They have to carry much more oxidizer, and their engine has to work well in both air-breathing and rocket mode. Going from Mach 5.5 to Mach 25 in rocket mode (with some of that rocket mode in the dense part of the atmosphere at Mach 5.5) means they need a very good mass fraction.Like I said, they don't have exactly the same challenges NASP had, but they have very great challenges, and I think they're at a comparable level of difficulty. Apparently, others think they are too, which is why others are continuing SCRAMJet research and development.
Quote from: ChrisWilson68 on 02/18/2015 06:06 pmThere have been many programs with similar or lesser optimistic goals that have failed. The U.S. National Aerospace Plane had far more resources available and a similar level of technological challenge, and it failed. Note that I'm not saying the details of the technological challenge are similar -- they are not. But the programs are similar in having a goal that required many unknowns to be overcome and having people with some competence in specific areas convinced they could overcome them.The technical challenge of airbreathing to Mach 18 is clearly of a vastly higher level than airbreathing to Mach 5.5 and the number of unknowns in geting to Mach 18 in 1984 far greater than achieving Mach 5 thirty years later.
There have been many programs with similar or lesser optimistic goals that have failed. The U.S. National Aerospace Plane had far more resources available and a similar level of technological challenge, and it failed. Note that I'm not saying the details of the technological challenge are similar -- they are not. But the programs are similar in having a goal that required many unknowns to be overcome and having people with some competence in specific areas convinced they could overcome them.
Quote from: lkm on 02/18/2015 11:50 pmQuote from: ChrisWilson68 on 02/18/2015 06:06 pmThe X-33/VentureStar is another launch program that had optimistic goals and failed. I think that X-33/VentureStar looked far more realistic at its outset, with less of a techonological leap required, than Skylon today. And yet it failed because of the engineering details in turning the theory into reality.X-33 didn't fail, it was cancelled due to a change in administration, just as many Clinton era space programs were cancelled by the Bush administration. What many people forget is that the X-33 was just a rocket powered x-plane like the X-15, like the X-15 it had a ton of not flown before technology some of which had teething problems, and like the X-55 if it had flown it would have provided invaluable hypersonic flight data. Getting into the details of X-33 is off topic, but lets just say that opinions differ about X-33 -- many people believe it was cancelled because the progress up to that point indicated it was not able to meet its projections and wouldn't have been viable.
Quote from: ChrisWilson68 on 02/18/2015 06:06 pmThe X-33/VentureStar is another launch program that had optimistic goals and failed. I think that X-33/VentureStar looked far more realistic at its outset, with less of a techonological leap required, than Skylon today. And yet it failed because of the engineering details in turning the theory into reality.X-33 didn't fail, it was cancelled due to a change in administration, just as many Clinton era space programs were cancelled by the Bush administration. What many people forget is that the X-33 was just a rocket powered x-plane like the X-15, like the X-15 it had a ton of not flown before technology some of which had teething problems, and like the X-55 if it had flown it would have provided invaluable hypersonic flight data.
The X-33/VentureStar is another launch program that had optimistic goals and failed. I think that X-33/VentureStar looked far more realistic at its outset, with less of a techonological leap required, than Skylon today. And yet it failed because of the engineering details in turning the theory into reality.
There's a difference between Science and Engineering. REL have done Science to do Engineering. Spacex have done Engineering, now they are doing Science. And Science is not predictable
Quote from: RanulfC on 02/19/2015 03:48 pmIn other words SpaceX was "unproven" until they actually flew something successfully. (That would be the F9 btw ) Actually it'd be the F1.SpaceX actually did the whole incremental development thing. Are still doing it. And I think it explains a lot about their success. Imagine they had tried to jump directly to MCT/Raptor. (Even then, I think they are still skipping necessary stepping stones.)
I'm confused.It has been posted that all that REL has built is a heat exchanger. My understanding is the heat exchanger is the linchpin. The rest of the engine is based on existing technology.Is that incorrect?If the heat exchanger is the linchpin idea is correct, then REL is suffering from NBNBR (No Bucks, No Buck Rogers - Bucks meaning money not dollars). Things will be slow due to money issues, not technology issues.To recap, REL's heat exchanger is the show stopper and REL has accomplished that, the engine is based on known technology working with the heat exchanger (not easy but not necessarily ground breaking), and REL could work faster is they has more money.That my understanding.
i don't understand the animosity toward REL. what have they done to offend so? to me REL brings to mind two things - the sentiment behind the quote “We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard." and Concorde.REL are working really hard on a disruptive idea that they had; one that they think can achieve the same as elon musk's goal of cheap rapid access to space for the benefit of mankind. good for them. that should inspire, not generate a load of naysaying. what's wrong with you people?