Author Topic: The Reaction Engines Skylon/SABRE Master Thread (6)  (Read 437874 times)

Offline CameronD

  • Senior Member
  • *****
  • Posts: 2374
  • Melbourne, Australia
    • Norton Consultants
  • Liked: 868
  • Likes Given: 548
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #380 on: 11/22/2016 09:12 pm »
*=To put it mildly I am 'irked' significantly that in reality EVERYTHING about the SABRE concept has in fact been shown to be practical and hardware, (test if not flight weight) was tested to show this in the late 50s and early 60s but was dropped in the rush to accept that "Liquid Air Cycle," "Hypersonic Cruise" and "SCRamjets" were "required" for any air-breathing orbital concept. Coupled with the more recent, (and seemingly more pervasive) attitude that anything with 'wings' is the "Shuttle and therefor can never work as suggested" it makes it difficult to believe anyone can actually significantly lower the cost of space access when they refuse to actually examine all the possibilities rather than sticking to the 'usual' assumptions.

Randy, it comes down to money (physics too.. but mostly money) in the end.  REL have been working on SABRE for how long now? Decades? ..and exactly what do they have to show their backers apart from a long list of receipts?  At the time the Wright Brothers made history, both gliders and petrol engines were tested technologies - but they had to do a lot more than stick the two together to get airborne.

Examining multiple possibilities (your 'due diligence') costs money also, rushing off down an endless list of rabbit-holes.  One reason NACA/NASA was founded in the first place was to allow this 'research' to be carried out without impacting private companies' (American companies in particular) wallets.. and the aerospace world in general is a better place for that.  ..But REL are not NASA and neither is UKSpace.

IF REL can't make SABRE work, then who can?  What it tells me is that getting the SABRE concept to actually, practically, work is far, far, more difficult than REL are prepared to publically admit.
« Last Edit: 11/22/2016 09:25 pm by CameronD »
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline RanulfC

  • Senior Member
  • *****
  • Posts: 4595
  • Heus tu Omnis! Vigilate Hoc!
  • Liked: 900
  • Likes Given: 32
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #381 on: 11/22/2016 09:13 pm »
No one can 'break' a circle that in fact does NOT exist. Note that there IS a "demand" and a "market" in existence, the fact that it is not as large or extensive as some would like and that it does not in fact 'service' a market that does not exist but which some want to exist is totally beside the point.

But it does exist, which Skylon can service.

"Can" of course and the fact that Skylon is 'designed' to actually service that existing market puts it way ahead of MOST SSTO concepts which assume that orbit is "half-way-to-anywhere" is a truism rather than an observation :)

Quote
Quote
The fallacy here is "we" need to "make" destinations and markets for reusable SSTO, (and yes that's the main argument FOR SSTO by the way) by building an extensive LEO orbital infrastructure for them to service.

And it's one that REL is aware of and does not subscribe. Enable yes, require, no.

Again which is a plus for REL. But as I've noted before the same would apply to a SABRE powered TSTO design since actually "servicing" doesn't require an SSTO. SSTO is nice but it's not a 'make-or-break' proposition either. My point in this conversation is that NOT having SSTO isn't going to mean the market won't ever come but neither will having it ensure they come about either. It's much more about the 'economics' of space rather than getting there as a prime driver. At this point in time we could have free access every day and not be able to economically exploit having that capability. (VERY crude analogy so please treat it as such :) )

Quote
Quote
Not so obviously does this apply to SSTO vehicles mostly for the fact that MOST SSTO concepts have never managed to reach a comparable operational payload to an ELV or multistage reusable vehicle. Note I wrote "operational payload" rather than just 'payload' because in fact while Skylon is an SSTO it does in fact require a second stage to allow getting the 'payload' to the most in-demand destinations despite that fact. But at least REL was realistic about that and therefore designed the Skylon with more capacity than the average SSTO concept.

But note Skylon can support an "all electric" design by starting outside the Van Allan belts.

So can F9 and probably New Armstrong so that's not as much of a 'plus' as you might think. What sets Skylon apart from the other SSTO designs is REL at least admitted that "just" getting to orbit wasn't enough and started from the point of getting the payload AND a means to get it into the right 'place' from the start.

Quote
Quote
And lastly on which is the better 'strategy' of builder/operator or builder to owner/operator for the most part the differing sides seem bound and determined to ignore history and reality to make their point :)
The latter ALWAYS takes over from the former once a certain level of traffic is reached as the builders can no longer afford to do both they inevitably form partnerships/consortiums to "buy" the vehicles and then own and operate them while they then concentrate on design and manufacture of new and improved vehicles. REL is simply assuming that the traffic levels will hit the levels that both SpaceX and BO are PLANNING on reaching and planning accordingly while SpaceX and BO are currently not looking to that point. Yet.

Careful about "historical inevitability"   :)

No one has managed to find a historical example where it didn't happen eventually so I'm probably safe :)

Quote
While the market should transition to separate mfg and operators note that US market, where Boeing/TWA was probably broken up before this stage. IOW government intervention accelerated the split.

Actually the failure of Boeing to be able to provide the needed airframes for BOTH TWA and other airlines who demanded the 272 (IIRC) led to Douglas getting away from having to start its own airline to sell DC2's and the government only came along in pushing the process. It's not much different that Boeing and LM putting together ULA which initially was tasked with 'servicing' the Shuttle AND Boeing/LM commercial launch services. The "services" side gets to the point where it no longer makes economic or managerial sense to NOT have a more dedicated service organization. 

Quote
But any kind of VTO rocket is a potential ICBM so the odds on bet is govt intervention will be negative. I don't see ULA, SX or Blue setting up a Guianna branch any time soon, do you?

That has almost nothing to do with "ICBM" since (technically anyway) the Soyuz "R7" booster is STILL listed as an "ICBM" and there wasn't much issue when the French decided they wanted to allow them to launch from Guianna :) Point of fact you won't see ULA/SX/BO launching from there simply because the owners don't WANT to allow competition to use their facilities. Similarly even if the US/UK actually cooperate to build a Skylon based launcher it probably wont' launch from there unless they are specifically ESA 'owned' and operated.

Quote
Skylon does not look like an ICBM. It does not fly like an ICBM. It's very difficult to modify into an ICBM or an ICBM delivery vehicle and if you have the skills to do so you can probably make an ICBM yourself, so why bother?

Again "ICBM" has nothing to do with it as while it wouldn't make a very good weapons platform that in no way precludes it's USE as one. Commercial airliners* are not very "good' cruise missiles but that doesn't mean they can't be effective is used in that manner. And I'll point out that part of the whole IDEA of "selling" Skylons rather than operating them is to allow someone who does NOT have the ability to build an ICBM/LV to operate one.

*Point of fact we KNOW that they can make pretty good cruise missile busses and that's why sales are monitored

Quote
Only the REL business model (and something like it's architecture) have a chance of getting away, of unifying the market by giving the economies of scale of a large market IE every payload on the planet but giving individual countries (or even corporations) the security of delivery of their payload.

That would be a good thing but it's not very realistic. See most nations/corporations do not NEED better 'security' for payloads as they know that launch providers can already meet most of their needs if they can't already launch themselves. The nations that do not have launch capability for the most part can rely on those that do to orbit any assets they might need 'more' security on as it is unlikely those assets will be used against those that provide the launch services. Further most nations that are not currently capable of launch do not NEED much in the way of space assets as they can easily access security. surveillance, survey, and monitoring satellite services from a number of commercial operators. This does not change significantly with increased space access. Lastly if someone DOES purchase a "private" Skylon they then find themselves significantly 'under-the-microscope' of other nations BECAUSE they feel a need for un-monitored and more 'private' space launch capacity which begs the question of WHY they would think they need that?

This bears repeating; Anything that can place a payload into orbit can also be used to drop something nasty on a neighbor up to half the world away and space launch is never going to be as 'routine' as air travel because of that simple fact. It doesn't matter that someone from South American with a private Skylon didn't MEAN to drop a failed launch onto Moscow at the moment of very high tension between the US and Russia but the result effects everyone on Earth if it's not handled just right. And that doesn't even touch someone WANTING to do some damage if they can.

Quote
Telecos talk about the "last mile" of cable being the most expensive because there's so much of it to maintain and the individual payoff is so small but in space launch it's the first 100-200Km that's the major PITA. Skylon take that away in a way that no nation based rocket programme (and that includes Blue or SX) can ever do.

Now who needs to watch that 'historically inevitable' cliché? :)

Seriously, nothing shows that Skylon is going to be enough of a game changer to erase every other operational system when it's introduced. Honestly it's as complex as any other LV and while we can assume some operational simplicity by the time it flies systems by SX and BO could very well be much less operationally complex as well. And that assumes it doesn't fly as a TSTO itself which is probably more likely. Availability and flexibility are two of the more solid examples of what something like Skylon as a system could offer but as I pointed out above those are going to be tempered by outside factors and despite what Musk/Beezos want it's very much a question if they will get what they want. What REL wants is even more dependent on outside factors given the huge up-front requirements it needs to see operational use, and a bit LESS likely given their preferred operational mode.

Compromise very often doesn't let anyone get all of what they want but it's most often anyone gets any of what they want.

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline oddbodd

  • Member
  • Posts: 79
  • Liked: 32
  • Likes Given: 1
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #382 on: 11/22/2016 09:22 pm »
Just to nit-pick one thing. I did specify that the exploding thing was a hindrance to human presence, not cargo. Annual rocket failures seem to be bumping around in the 5% area, so 1 in 20 flights frequently has a fiery, premature end. Go to Heathrow and tell all those business and tourist travelers that every flight has a 1 in 20 chance of catastrophic failure, killing everyone aboard. Excluding the mentally ill, suicidal and people under extreme duress, I'll take a wild stab in the dark that zero people would choose to fly. Even if they were, there'd be no pilots or cabin staff willing to roll that D20-of-death every time they did their job. Hopefully the abort system in the SpaceX Dragon module will at least mean that it's just very expensive, instead of tragic.

Closer to 4% really (86 launches/5 failures in 2015, 72/1 this year) but the whole point was that humans ARE treated differently than cargo as in most transportation systems. Transport systems make a specific point to assure travelers that they have little chance of dying even in the worst case and given a "better than even" chance to survive an accident most people will willingly keep travelling. You would also be lying, (and liable :) ) if you told anyone that was their 'chances' in a launch accident since it's quite obvious that there are systems in place to keep the PEOPLE alive in the case of a failure. (None of the travelers at Heathrow have that option though and it does not seem to effect travel statistics)

OK, so 4%. I wasn't that far out, and you are using a very small sample size to argue the figure. I think the "1 in 20" is pretty widely accepted as a rule-of-thumb.

The reason Heathrow travel statistics aren't affected is because when people (often subconsciously) assess the risk of stepping onto a plane they conclude the risk is negligible. The US NTSB's preliminary stats for 2015 show no fatalities in all of their flights, and from the report http://www.usatoday.com/story/news/2016/02/15/2015-another-safe-year-airliners/80398194/ the worldwide equivalent is 1 in 3.1 million flights are lost.

According to many on this site if given the opportunity they would volunteer to ride a Dragon-1 WITHOUT an abort system come what may so I'd watch out throwing around the accusations of only the "mentally ill, suicidal and people under extreme duress" being willing to take their chances. If you've been over to the SpaceX ITS threads you'll note one discussing the lack of an abort system on the ITS which does in fact 'bother' some people but as noted it is in fact similar to current aircraft in that regard. If you are on an airplane that crashes you have no way of escaping and have to ride the plane to whatever the end point is, similarly if you were a passenger on Skylon you and the airframe are 'wedded' in fates. SSTO tends to assume a higher margin for 'safety' than a multistage design but in fact there is no basis for that assumption other than the "fact" that over their evolution most OTHER transport systems are 'technically' "single-stage" vehicles that have become much safer over time. Note that is OVER TIME during which they continually got safer and more efficient as they evolved.

You are comparing two very different groups of people there at different stages in the industries evolution. The group at Heathrow are not at the vanguard of the industry, pushing the boundaries. These people are just getting from A to B to do a job, or get some sun, or visit family. The journey is expected to be routine and boring, at least in the sense of surviving it. The people in the forums are space fans (nuts?), who you could liken more to the Emilia Earhart's of the early aviation industry, and willing to take that extra risk to be the first, push further, helping make the remarkable routine. I'd also point out that people sitting behind a keyboard safe at home will say a lot of things they won't back up in real life. Stick them in a flight suit in the elevator up to the crew capsule with that 1 in 20 hanging over them, and I wonder how many would still actually go through with it.

My point is and was that the "chances" of dying being launched in a current rocket are no worse than most other transportation accidents SPECIFICALLY because passenger transport is currently considered and addressed as a safety issue.

Huh? I really cannot understand you here. Unless you're referring to a current transport system that has already gotten in an accident, and you're only talking about the survivability of the accident. But when we decide whether to get on board a rocket or plane (or train, or boat, or car, or motorbike) we have to account for the risk that that act bording will result in being in a catastrophic accident.
1 in 20
vs.
1 in 3,100,000

Sure, if you're on the one that does have the accident, chances of surviving either type are low.

This is only "different" in designs that assume, with no data to back that up, that the vehicle is much 'safer' because it emulates a CURRENTLY "more safe" evolved design of another form of transportation. AKA it's "safer" because it resembles and airplane which is rather silly because what it looks like has almost nothing to do with what it actually DOES over the majority of it's flight and over that flight conditions change radically from anything any "airplane" does except the very beginning and very end.

Skylon is still a LAUNCH VEHICLE with all that implies.
I don't think I said in this that Skylon specifically would be automatically safer. Simply that significant human presence would require better than what we have now. Current rockets don't have a lot of scope for craft survival of a big failure. They tend to explode, tumble and disintegrate, slam back down on the pad and explode, and so on. In the event of a problem, there is one option for the passengers to survive, which is to get the hell out of there with a Launch Escape System. One crew has been saved by these in the past.

Bringing the Skylon design into this, no, we can't say that it will be safer. We can only say that the design may allow more options. It's design allows for powered flight with the loss of half it's thrust (a complete single engine failure). It's design allows for gliding to an emergency abort site with no thrust (although it'd have to dump fuel and be close enough). I think it would probably still have to have an LES itself for anything that resembled the proposed SPLM carrying people.

The Space Shuttle is possibly a closer analogue to the Skylon design than a rocket. They did 25 to 39 missions each for those that weren't lost, with a total of 139. The two that were lost were:
1) Columbia, where foam insulation fell off the disposable tank and damaged the wing, causing disintegration during reentry. Skylon design is SSTO, so no external tanks to shed bits.
2) Challenger, where a known design flaw was not yet fixed, and the temperatures increased the risk from that flaw, resulting in an SRB failing. Again Skylon design is SSTO, so no SRB's.

Of course, the Skylon design will have it's own problems, but 400 unmanned test flights should find and fix many of these. I imagine that way in the future, if Skylon is ever realised, a unit would get built, have a number of non-passenger flights, then provide the option to carry people, up till some limit. Then it would go back to non-passenger till retirement or loss.

Offline RanulfC

  • Senior Member
  • *****
  • Posts: 4595
  • Heus tu Omnis! Vigilate Hoc!
  • Liked: 900
  • Likes Given: 32
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #383 on: 11/22/2016 10:08 pm »
Randy, it comes down to money (physics too.. but mostly money) in the end.  REL have been working on SABRE for how long now? Decades? ..and exactly what do they have to show their backers apart from a long list of receipts?  At the time the Wright Brothers made history, both gliders and petrol engines were tested technologies - but they had to do a lot more than stick the two together to make history.

Actually the money has always been the problem and it wasn't until REL began getting more that they managed to do more than component testing. And lets be honest they have a LOT to show investors as they DID test and prove those components which was the whole point. Much in the same way that in order to succeed the Wright's had to build their on engine, which many experts said was not possible mind you, in order to get the needed thrust. REL has to build it's engine to 'prove' what many say can't be done. Note that there is no physical (or physics) reason it should not in fact work as REL says it should it is simply that people don't believe it should work.

Quote
Examining multiple possibilities (your 'due diligence') costs money also, rushing off down an endless list of rabbit-holes.  One reason NACA/NASA was founded in the first place was to allow this 'research' to be carried out without impacting private companies' (Musk's and Bezo's in particular) wallets.. and the aerospace world is a better place for that.  ..But REL are not NASA and neither is UKSpace.

Ahm well that was a 'reason' NACA was founded but due to a lack of government support they had to depend on industry to allow for many of the programs they ran. This caused issues since as a government agency NACA could not guarantee that something one section of industry paid for wasn't available to all industry. It wasn't until just prior to WWII that NACA began to get any significant budget to run with. At which point industry as a whole gained significantly. NASA on the other hand was meant to 'fix' part of that problem by ensuring American aeronautical research was given more rounded and steady funding. Then JFK threw everything for a loop and if it wasn't directly related to getting men to the Moon and back it got dropped. Things still haven't significantly changed in that NASA is still only allowed to spend money on authorized research and projects of which most are directly related to a 'current' program or can be linked in some way. This means a lot of promising programs and research still lack funding or support simply because they don't 'relate' to what the current interest is.

(I should probably point out that one of the main reasons NACA was created was to prevent someone like the Wright's from locking up aeronautical research behind patent walls to the detriment of overall American aeronautical progress which was felt at the time to have been significantly held back due to such practices prior to WWI)

Musk and Bezos started with a certain premise and went forward in that direction. I'm not blaming them or saying that's wrong but it would be nice for people to understand they had no intention of every looking beyond what they had in mind which is very often the case. People think that IF they knew and considered SABRE and then went ahead with their designs anyway that MUST mean that SABRE doesn't work which is clearly false from the outset. As they never considered it or even knew of it assuming they somehow 'rejected' it due to technological or "physics" reasons is totally false, but that's an 'assumption' that's made because they 'obviously' considered every possible method for getting to orbit. They didn't, they didn't even try. I would very much like that to be clear which was my point.

What I find really funny is in fact both NACA and NASA were aware of the general concept behind the SABRE cycle and specifically noted that the ONLY issue at the time it was studied was the lack of a viable heat-exchanger system AND the fact that their work required using "Liquid Air" as it was not clear that a rocket engine could be run on 'deep-cooled' air even though a subcontractor had indicated that it WAS possible. So if you want to think of it this way NASA in fact DOES know that SABRE is not only NOT a "rabbit hole" but that their own public records show they are well aware that no matter what else REL has solved the ONE problem they did have with the technology in the first place!

Quote
IF REL can't make SABRE work, then who can?  What it tells me is that getting the SABRE concept to actually, practically, work is far more difficult than REL are prepared to publically admit.

Expensive does not equal difficult though to be honest the fact that REL is in a corner due to the requirements of the design is annoying. But NASA had issues with working with and exploiting liquid hydrogen which took billions of dollars and years of effort to get operational so it would only make sense with REL having a fraction of the budget and manpower available to NASA, (let alone NACA before it) it may take them longer to achieve.

I very much suspect I understand why REL hasn't made the connection to NASA's earlier work more clear but the fact that I among others have pointed out that connection and the relevant background but been ignored because NASA clearly isn't 'interested now' in the technology is annoying to say the least.

Money and access to it is the ONLY real problem facing REL, much as it has been from the beginning. Given their bias and obvious intent, (with some obvious issues both political and practical granted for a non-US company) neither Musk or Bezos would have invested in REL but the fact that have not should in no way reflect on the viability of the SABRE engine since they did not WANT to even consider that type of propulsion.

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline lkm

  • Full Member
  • ****
  • Posts: 541
  • Liked: 117
  • Likes Given: 1
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #384 on: 11/22/2016 11:00 pm »
So I was having a crazy thought about whether you could retrofit one of these ground development engines into an English Electric Lightning and how fast it would get before it melted/fell apart and it occurred to me that the thing on top of the 'D-21' could be a second engine, a small turbojet to allow powered flight once the cryogenic tanks are empty.
If the thing has wet wings then the extra fuel wouldn't get in the way of the cryogenic tanks and it would provide a measure of security that they wouldn't loose an expensive drone if the test engine failed.
Alternatively there are plenty of lightnings around the south of England and Alan Bond's into Spitfire restoration so he probably knows a guy.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10351
  • Everyplaceelse
  • Liked: 2431
  • Likes Given: 13606
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #385 on: 11/23/2016 07:00 am »
Actually the money has always been the problem and it wasn't until REL began getting more that they managed to do more than component testing. And lets be honest they have a LOT to show investors as they DID test and prove those components which was the whole point. Much in the same way that in order to succeed the Wright's had to build their on engine, which many experts said was not possible mind you, in order to get the needed thrust. REL has to build it's engine to 'prove' what many say can't be done. Note that there is no physical (or physics) reason it should not in fact work as REL says it should it is simply that people don't believe it should work.
Funny how people won't believe the fairly pedestrian thermodynamics of SABRE but one investor (the USG) will pour Billions into SCramjets when the detailed flow around the engine is still active research problem.
Quote
Musk and Bezos started with a certain premise and went forward in that direction. I'm not blaming them or saying that's wrong but it would be nice for people to understand they had no intention of every looking beyond what they had in mind which is very often the case. People think that IF they knew and considered SABRE and then went ahead with their designs anyway that MUST mean that SABRE doesn't work which is clearly false from the outset. As they never considered it or even knew of it assuming they somehow 'rejected' it due to technological or "physics" reasons is totally false, but that's an 'assumption' that's made because they 'obviously' considered every possible method for getting to orbit. They didn't, they didn't even try. I would very much like that to be clear which was my point.
A point worth repeating.
Quote
What I find really funny is in fact both NACA and NASA were aware of the general concept behind the SABRE cycle and specifically noted that the ONLY issue at the time it was studied was the lack of a viable heat-exchanger system AND the fact that their work required using "Liquid Air" as it was not clear that a rocket engine could be run on 'deep-cooled' air even though a subcontractor had indicated that it WAS possible. So if you want to think of it this way NASA in fact DOES know that SABRE is not only NOT a "rabbit hole" but that their own public records show they are well aware that no matter what else REL has solved the ONE problem they did have with the technology in the first place!
Mind you that problem is very far from non trivial. You can call it an "implementation detail" but it's a biggie.  Something I hope REL guard very carefully.
Quote
Expensive does not equal difficult though to be honest the fact that REL is in a corner due to the requirements of the design is annoying. But NASA had issues with working with and exploiting liquid hydrogen which took billions of dollars and years of effort to get operational so it would only make sense with REL having a fraction of the budget and manpower available to NASA, (let alone NACA before it) it may take them longer to achieve.

I very much suspect I understand why REL hasn't made the connection to NASA's earlier work more clear but the fact that I among others have pointed out that connection and the relevant background but been ignored because NASA clearly isn't 'interested now' in the technology is annoying to say the least.
Don't forget that in the late 60's Rolls Royce did a development LH2/LO2 engine called the RZ20. This was a GG cycle with a LH2 turbopump, so the UK was not without LH2 experience. Access to NTRS does certainly help.  Personally I've always been baffled by NASA's insistence on solid shafts between turbopump turbines and impellers, give the substantial thermal expansion and compression forces involved. There are any number of couplings that could transmit force and simply absorb the longitudinal forces.
Quote
Money and access to it is the ONLY real problem facing REL, much as it has been from the beginning.
Indeed. Their business model has made seeing a direct path from investing in them to seeing a return from the final product, but as a small company with limited resources that was the only way real way to go.
Quote
Given their bias and obvious intent, (with some obvious issues both political and practical granted for a non-US company) neither Musk or Bezos would have invested in REL but the fact that have not should in no way reflect on the viability of the SABRE engine since they did not WANT to even consider that type of propulsion.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10351
  • Everyplaceelse
  • Liked: 2431
  • Likes Given: 13606
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #386 on: 11/23/2016 07:29 am »
OK, so 4%. I wasn't that far out, and you are using a very small sample size to argue the figure. I think the "1 in 20" is pretty widely accepted as a rule-of-thumb.

The reason Heathrow travel statistics aren't affected is because when people (often subconsciously) assess the risk of stepping onto a plane they conclude the risk is negligible. The US NTSB's preliminary stats for 2015 show no fatalities in all of their flights, and from the report http://www.usatoday.com/story/news/2016/02/15/2015-another-safe-year-airliners/80398194/ the worldwide equivalent is 1 in 3.1 million flights are lost.
With numbers of flights as small as those in spaceflight that 1% is quite a difference. Note also Shuttle has loss statistics IRL not much better than an expendable. But also note it was semi-reusable at best.


SSTO tends to assume a higher margin for 'safety' than a multistage design but in fact there is no basis for that assumption other than the "fact" that over their evolution most OTHER transport systems are 'technically' "single-stage" vehicles that have become much safer over time. Note that is OVER TIME during which they continually got safer and more efficient as they evolved.
What makes them safer is the elimination of staging and engine ignition events, both of which are complex and have  to work. This is called "intact abort." AFAIK it may be possible to add that to a TSTO if both stages run the same propellants, which after the retirement of Titan had not been the case in Western practice (with the exception of some Ariane upper stages). Historical (Bono style VTOL) expected to do limited engine restart of a segmented engine.

But the wings let you glide in a way that does not exist for any VTOL concept moving below about M5. That gives you time and control. BTW REL's goal has always been to accumulate flight hours and once they are high enough (and it's high by ELV standards but not by aircraft) get it certified safe for passengers.
Quote
You are comparing two very different groups of people there at different stages in the industries evolution. The group at Heathrow are not at the vanguard of the industry, pushing the boundaries. These people are just getting from A to B to do a job, or get some sun, or visit family. The journey is expected to be routine and boring, at least in the sense of surviving it. The people in the forums are space fans (nuts?), who you could liken more to the Emilia Earhart's of the early aviation industry, and willing to take that extra risk to be the first, push further, helping make the remarkable routine. I'd also point out that people sitting behind a keyboard safe at home will say a lot of things they won't back up in real life. Stick them in a flight suit in the elevator up to the crew capsule with that 1 in 20 hanging over them, and I wonder how many would still actually go through with it.
Very true. Although I think 2 LV explosions is likely to put a dampener on such thoughts till an LES  arrives.  :(
Quote

Huh? I really cannot understand you here. Unless you're referring to a current transport system that has already gotten in an accident, and you're only talking about the survivability of the accident. But when we decide whether to get on board a rocket or plane (or train, or boat, or car, or motorbike) we have to account for the risk that that act bording will result in being in a catastrophic accident.
1 in 20
vs.
1 in 3,100,000

Sure, if you're on the one that does have the accident, chances of surviving either type are low.
I don't think I said in this that Skylon specifically would be automatically safer. Simply that significant human presence would require better than what we have now. Current rockets don't have a lot of scope for craft survival of a big failure. They tend to explode, tumble and disintegrate, slam back down on the pad and explode, and so on. In the event of a problem, there is one option for the passengers to survive, which is to get the hell out of there with a Launch Escape System. One crew has been saved by these in the past.
And that's the real issue for anyone looking to massively raise the number of people in space.  :(

While you're using an ICBM architecture you will always need an artillery range in case  of a launch mishap.  Musk plans to side step this by putting a lot of people up at a time and (AFAIK) making the whole 2nd stage an LES.
Quote
I think it would probably still have to have an LES itself for anything that resembled the proposed SPLM carrying people.
Dumping fuel (well actually the LO2 and most of the LH2 depending on wheather the engines still needed) alone reduces the explosion risk radically. Note again REL don't expect to get human certified without a lot of safely completed missions first. The goal is to let any Skylon be a passenger carrier. That means a passenger module inside the standard payload bay doors.
Quote
The Space Shuttle is possibly a closer analogue to the Skylon design than a rocket. They did 25 to 39 missions each for those that weren't lost, with a total of 139. The two that were lost were:
1) Columbia, where foam insulation fell off the disposable tank and damaged the wing, causing disintegration during reentry. Skylon design is SSTO, so no external tanks to shed bits.
2) Challenger, where a known design flaw was not yet fixed, and the temperatures increased the risk from that flaw, resulting in an SRB failing. Again Skylon design is SSTO, so no SRB's.

Of course, the Skylon design will have it's own problems, but 400 unmanned test flights should find and fix many of these. I imagine that way in the future, if Skylon is ever realised, a unit would get built, have a number of non-passenger flights, then provide the option to carry people, up till some limit. Then it would go back to non-passenger till retirement or loss.
Actually the goal is once enough Skylons accumulate enough hours any of them can carry passengers.
« Last Edit: 11/23/2016 03:30 pm by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Mutley

  • Member
  • Posts: 69
  • Liked: 24
  • Likes Given: 1
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #387 on: 11/23/2016 08:00 am »
Quote
Don't forget that in the late 60's Rolls Royce did a development LH2/LO2 engine called the RZ20. This was a GG cycle with a LH2 turbopump, so the UK was not without LH2 experience.]Don't forget that in the late 60's Rolls Royce did a development LH2/LO2 engine called the RZ20. This was a GG cycle with a LH2 turbopump, so the UK was not without LH2 experience.



and erm.. one of the people involved in the design of the RZ20 engine was a Rolls Royce engineer by the name of Mr Alan Bond!
« Last Edit: 11/23/2016 12:00 pm by Mutley »

Offline t43562

  • Full Member
  • **
  • Posts: 298
  • UK
  • Liked: 164
  • Likes Given: 101
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #388 on: 11/23/2016 09:05 am »

Quote
I think you might be under the illusion that state support is bad...

No.  I just like to keep the lines clear on what is state aid and what is payment for services rendered.

I think you mean keeping the line unclear.  However you weasel around it, the state is helping an industrial sector to compete against foreigners - for whatever reasons and with whatever justification. Whether or not they have a right to is completely beside the point - I don't care about that and I can't see anyone else here who does.  It only matters in as much as it seems improbable at this time that one might survive without such arrangements.

No, Ron is right, there's a very clear line between payment for goods and services and payment that is not in exchange for goods and services, or above the price the government would have to pay for those goods and services from another source.  There's no weaselling involved.  It's the distinction that makes the most sense to make.

It's the difference between business and charity.

All you have to do is invent some reasons for the business and you're away, you can also choose a mechanism for doing it that spreads more money or less money around.  The whole set of reasons around it may be "nice-to-have" rather than critical to national survival which is true of some big infrastructure projects too.  Then you limit the competition to your own companies and hey presto - competitive advantage through state funding.   Without this kind of thing, SpaceX would be far behind at best or on powerpoint at worst and probably a lot of other industries in other countries too.


Offline ChrisWilson68

  • Senior Member
  • *****
  • Posts: 5266
  • Sunnyvale, CA
  • Liked: 4992
  • Likes Given: 6459
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #389 on: 11/23/2016 10:21 am »

Quote
I think you might be under the illusion that state support is bad...

No.  I just like to keep the lines clear on what is state aid and what is payment for services rendered.

I think you mean keeping the line unclear.  However you weasel around it, the state is helping an industrial sector to compete against foreigners - for whatever reasons and with whatever justification. Whether or not they have a right to is completely beside the point - I don't care about that and I can't see anyone else here who does.  It only matters in as much as it seems improbable at this time that one might survive without such arrangements.

No, Ron is right, there's a very clear line between payment for goods and services and payment that is not in exchange for goods and services, or above the price the government would have to pay for those goods and services from another source.  There's no weaselling involved.  It's the distinction that makes the most sense to make.

It's the difference between business and charity.

All you have to do is invent some reasons for the business and you're away, you can also choose a mechanism for doing it that spreads more money or less money around.  The whole set of reasons around it may be "nice-to-have" rather than critical to national survival which is true of some big infrastructure projects too.  Then you limit the competition to your own companies and hey presto - competitive advantage through state funding.   Without this kind of thing, SpaceX would be far behind at best or on powerpoint at worst and probably a lot of other industries in other countries too.

So you're claiming that somehow the ability to send cargo and crew to LEO is a "nice-to-have" but not necessary for NASA?  That they don't really need to resupply ISS, they're just doing it to keep SpaceX afloat?  I guess if there are people who believe the Apollo moon landings were a hoax, you'll find people who will believe anything.

Offline ChrisWilson68

  • Senior Member
  • *****
  • Posts: 5266
  • Sunnyvale, CA
  • Liked: 4992
  • Likes Given: 6459
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #390 on: 11/23/2016 10:35 am »
Something I'd like people to keep in mind.  Let's just repeat that for people who think either of them looked at Skylon:

neither Musk or Beezos did much 'due-diligence' work on anything OTHER than the concepts they went forward with.

 ::)  Repeating such an assertion does not make it any more true.

Repeating the truth no matter how much some people may not like it does not make the statement false either :)

Both projects started with clear bias which were stated and quite visible up-front.

That's utter nonsense.  If you think that's true, cite a reference that shows that bias.

No concepts beyond those already in mind were considered or 'traded' and this has been stated by both SX and BO.

If you're going to claim SpaceX and Blue Origin said something, you'd better be prepared to cite a reference to prove it.

Neither considers Skylon as a viable concept,

Finally, you said something that is true.  But you've apparently misunderstood it.

To consider Skylon not to be a viable concept is to have a judgement about it.  To have a judgement about it means it was considered.

more to the point neither has any consideration that an air-breathing rocket engine capable of operation from zero-to-Mach 20 has any 'use' in their plans.

Of course they don't have it in their plans -- they considered it and rejected it early on.  That's not evidence of a bias.

Both Musk and Beezos started with an idea of what they wanted in the end to have, it is no surprise that they ended up with pretty much what they wanted in the first place.

Nonsense.  What they started with was a dissatisfaction with the current state of the launch industry and a desire to find some way to revolutionize it to lower costs and expand access.  They looked into how to revolutionize the launch industry and both independently came to the same conclusion: vertical launch and landing of chemical two-stage reusable rockets.

Neither one of them had any background in rockets.  The idea that they would start out with vertical take-off and landing reusable rockets as a preconceived idea makes no sense whatsoever.

There is no evidence that they seriously considered any concepts or ideas that did not fit their already pre-conceived ideas on what they would end up with, (which oddly enough is something REL is accused of doing as if it were a "bad" thing) and there IS evidence that the only 'trades' done were within the already defined parameters rather than anything more general and inclusive.

If you're going to claim there is evidence, present that evidence.

Offline Coastal Ron

  • Senior Member
  • *****
  • Posts: 8862
  • I live... along the coast
  • Liked: 10199
  • Likes Given: 11934
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #391 on: 11/23/2016 03:19 pm »
I think you mean keeping the line unclear.

No, I meant what I said, and I like to use clearly defined and accepted definitions for words.

Quote
However you weasel around it, the state is helping an industrial sector to compete against foreigners - for whatever reasons and with whatever justification.

Regarding the Falcon 9, if you look into the contracts that SpaceX has won from NASA, no money was designated for building the Falcon 9.  The only contracts SpaceX has won are related to ensuring that their Dragon spacecraft is able to carry and deliver cargo to the ISS (i.e. COTS & CRS), and that they can safely carry and deliver humans to the ISS (i.e. CCDev 1&2, CCiCap, & CCtCap), and for all the contracts SpaceX has had to deliver or accomplish specific goals in order to be compensated.

In contrast, a subsidy would be a payment to a company with no expectation of a product or service in return.  That is typically what "state aid" is, but as I've described, that is not the case with SpaceX and NASA.

Quote
Whether or not they have a right to is completely beside the point - I don't care about that and I can't see anyone else here who does.  It only matters in as much as it seems improbable at this time that one might survive without such arrangements.

This regards U.S. companies having access to taxpayer funded NASA research.  I don't know, but I would imagine this happens in every democracy, and likely in the UK.  Have you researched it?

Because it makes no sense to the taxpayer to NOT make it available to domestic industry to increase the overall GDP.  Right?  So this is not just a NASA issue, but what many government do.  Otherwise you're just wasting taxpayer money, and that would not be in the best interests of anyone...
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline t43562

  • Full Member
  • **
  • Posts: 298
  • UK
  • Liked: 164
  • Likes Given: 101
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #392 on: 11/23/2016 03:59 pm »
I think you mean keeping the line unclear.
...
Because it makes no sense to the taxpayer to NOT make it available to domestic industry to increase the overall GDP.  Right?  So this is not just a NASA issue, but what many government do.  Otherwise you're just wasting taxpayer money, and that would not be in the best interests of anyone...

I think you're arguing about something different - like you're making some defensive WTO presentation about protectionism. That is not relevant to Skylon or this thread.

I'm trying to point out something quite different which is that without a similar arrangement I think it is going to be difficult to see Skylon and SABRE take off.  I think some government needs to make up some random goal (e.g. "provide sovereign access to space" or some other nonsense) and put it out to contract in such a way that Reaction Engines and possibly several other smaller developers are highly likely to get a big chunk of money and can demonstrate whatever :-).  It could be the same as an air ministry specification for a new aircraft.

Essentially providing money for a goal that isn't commercial is what I mean.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10351
  • Everyplaceelse
  • Liked: 2431
  • Likes Given: 13606
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #393 on: 11/23/2016 04:09 pm »
Coupled with the more recent, (and seemingly more pervasive) attitude that anything with 'wings' is the "Shuttle and therefor can never work as suggested" it makes it difficult to believe anyone can actually significantly lower the cost of space access when they refuse to actually examine all the possibilities rather than sticking to the 'usual' assumptions.
Not quite.

In the UK, anything winged, big and fast was viewed like Concorde, which British civil servants had a horror of repeating.  :(

It has literally taken the retirement or death of a generation of senior civil servants, to get the UKG to consider helping (slightly) a UK company do a winged vehicle and a launch vehicle.   :(

Something I'd like people to keep in mind.  Let's just repeat that for people who think either of them looked at Skylon:

neither Musk or Beezos did much 'due-diligence' work on anything OTHER than the concepts they went forward with.

 ::)  Repeating such an assertion does not make it any more true.
OK then where have they mentioned when either of them said they looked at HTOL and concluded it was unworkable?

Given Musk's goal has always been Mars I doubt he spent a second on the idea. As anyone with a cursory knowledge of spaceflight and general engineering would expect. REL don't want to build a Skylon that can land on Mars. They'd be happy to enable a greatly cheaper Mars mission based on Skylon flights to LEO however.

So where did Bezos mention this? Interview? Media event? Tweets?

You seem so very sure he's wrong. Do you have facts or just your simple faith to guide you?
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline lkm

  • Full Member
  • ****
  • Posts: 541
  • Liked: 117
  • Likes Given: 1
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #394 on: 11/23/2016 04:27 pm »
I think you mean keeping the line unclear.

No, I meant what I said, and I like to use clearly defined and accepted definitions for words.

Quote
However you weasel around it, the state is helping an industrial sector to compete against foreigners - for whatever reasons and with whatever justification.

Regarding the Falcon 9, if you look into the contracts that SpaceX has won from NASA, no money was designated for building the Falcon 9.  The only contracts SpaceX has won are related to ensuring that their Dragon spacecraft is able to carry and deliver cargo to the ISS (i.e. COTS & CRS), and that they can safely carry and deliver humans to the ISS (i.e. CCDev 1&2, CCiCap, & CCtCap), and for all the contracts SpaceX has had to deliver or accomplish specific goals in order to be compensated.

In contrast, a subsidy would be a payment to a company with no expectation of a product or service in return.  That is typically what "state aid" is, but as I've described, that is not the case with SpaceX and NASA.

Quote
Whether or not they have a right to is completely beside the point - I don't care about that and I can't see anyone else here who does.  It only matters in as much as it seems improbable at this time that one might survive without such arrangements.

This regards U.S. companies having access to taxpayer funded NASA research.  I don't know, but I would imagine this happens in every democracy, and likely in the UK.  Have you researched it?

Because it makes no sense to the taxpayer to NOT make it available to domestic industry to increase the overall GDP.  Right?  So this is not just a NASA issue, but what many government do.  Otherwise you're just wasting taxpayer money, and that would not be in the best interests of anyone...
Absolutely it's not state aid. It's state support of an industry. Which is what we're talking about.
A decade ago the U.K. Government paid BAE to build Taranis a UCAV  stealth x-plane because BAE didn't have anything for their designers to work on and wanted to develop some competency in stealth and UAV's. That wasn't state aid but was absolutely state support of the industry and there's no reason they couldn't  follow up Taranis with paying  BAE to build a hypersonic test vehicle.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10351
  • Everyplaceelse
  • Liked: 2431
  • Likes Given: 13606
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #395 on: 11/23/2016 04:34 pm »
Finally, you said something that is true.  But you've apparently misunderstood it.
To consider Skylon not to be a viable concept is to have a judgement about it.  To have a judgement about it means it was considered.
Wow, what an amazingly twisted piece of logic.

Seriously you're going to claim Musk looked at Skylon and thought "How can I land this on Mars?"

When you a) know your end goal is another planet b)Have limited resources c)have no requirement to carry out any kind of "competition" for proposals.

Only governments have to put up with nonsense. It's the reason no Shuttle proposal could have a plug nozzle, because that would mean only Rocketdyne could supply the engine and that would not be "fair."  :(

And the rest is now history.
Quote
Of course they don't have it in their plans -- they considered it and rejected it early on.  That's not evidence of a bias.
Ahhhh,I see. So if they spent 5 seconds or 5 months looking at an option it's still "considered." Is that about right?

Both Musk and Beezos started with an idea of what they wanted in the end to have, it is no surprise that they ended up with pretty much what they wanted in the first place.
Quote
Nonsense.  What they started with was a dissatisfaction with the current state of the launch industry and a desire to find some way to revolutionize it to lower costs and expand access.  They looked into how to revolutionize the launch industry and both independently came to the same conclusion: vertical launch and landing of chemical two-stage reusable rockets.
I notice you miss out the time factor in this and the knowledgebase (IE risk)) element in this. Once you factor that in VTOL rockets always come to the top of the list because if you want to do what you've already done you use what's already been done.

And in fact Bezos and Musk did not  choose the identical path. Musk went the start fast/Get to the competition level/Hope something turns up Silcon Valley startup route and Bezos has been a bit more measured but not started generating revenue.
Quote
Neither one of them had any background in rockets.  The idea that they would start out with vertical take-off and landing reusable rockets as a preconceived idea makes no sense whatsoever.
And the fact that 90%+ of the literature on RLV's would be for VTOL and that all of the practicing rocket engineers they spoke to were AFAIK VTO rocket engineers and the only US example of a HTO rocket was the Pegasus didn't bias their thinking?

Really?
Quote
If you're going to claim there is evidence, present that evidence.
Here's the question I can't figure out the answer to. Why is it so important to you that you claim Bezos and Musk looked at SABRESkylon and rejected it?

It's not a good fit for Musk's end game and it's too big and risky for Bezos.

Which we already knew.

Neither is going to use it for their goals.

So  what's your point? Tell us what you think this "proves," because as you said, neither has a background in rockets and AFAIK Bezos has no involvement other than signing the checks (which is important and noble work and no doubt greatly under appreciated by the people who spend the money  :) )
« Last Edit: 11/23/2016 04:42 pm by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Lars-J

  • Senior Member
  • *****
  • Posts: 6809
  • California
  • Liked: 8485
  • Likes Given: 5384
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #396 on: 11/23/2016 05:33 pm »
Something I'd like people to keep in mind.  Let's just repeat that for people who think either of them looked at Skylon:

neither Musk or Beezos did much 'due-diligence' work on anything OTHER than the concepts they went forward with.

 ::)  Repeating such an assertion does not make it any more true.
OK then where have they mentioned when either of them said they looked at HTOL and concluded it was unworkable?

Given Musk's goal has always been Mars I doubt he spent a second on the idea. As anyone with a cursory knowledge of spaceflight and general engineering would expect. REL don't want to build a Skylon that can land on Mars. They'd be happy to enable a greatly cheaper Mars mission based on Skylon flights to LEO however.

So where did Bezos mention this? Interview? Media event? Tweets?

I don't think you understand how this works. YOU made the claim, with no evidence to back it up. I challenged it.

But since you asked, here is what Musk has said about air breathing launch vehicles: http://shitelonsays.com/transcript/elon-musk-lecture-at-the-royal-aeronautical-society-2012-11-16   (search in page for 'reaction engines')

You seem so very sure he's wrong. Do you have facts or just your simple faith to guide you?

Pot, kettle, black? You are so convinced that Skylon is the way forward, that anyone who did 'due diligence' on it must have selected it, and the only way one could explain them not selecting that path is by not doing 'due diligence'.  ::)

I know we are in a post-facts society, but at least TRY to step out of your bubble.

Offline Khadgars

  • Full Member
  • ****
  • Posts: 1750
  • Orange County, California
  • Liked: 1132
  • Likes Given: 3156
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #397 on: 11/23/2016 05:58 pm »
Something I'd like people to keep in mind.  Let's just repeat that for people who think either of them looked at Skylon:

neither Musk or Beezos did much 'due-diligence' work on anything OTHER than the concepts they went forward with.

 ::)  Repeating such an assertion does not make it any more true.
OK then where have they mentioned when either of them said they looked at HTOL and concluded it was unworkable?

Given Musk's goal has always been Mars I doubt he spent a second on the idea. As anyone with a cursory knowledge of spaceflight and general engineering would expect. REL don't want to build a Skylon that can land on Mars. They'd be happy to enable a greatly cheaper Mars mission based on Skylon flights to LEO however.

So where did Bezos mention this? Interview? Media event? Tweets?

I don't think you understand how this works. YOU made the claim, with no evidence to back it up. I challenged it.

But since you asked, here is what Musk has said about air breathing launch vehicles: http://shitelonsays.com/transcript/elon-musk-lecture-at-the-royal-aeronautical-society-2012-11-16   (search in page for 'reaction engines')

You seem so very sure he's wrong. Do you have facts or just your simple faith to guide you?

Pot, kettle, black? You are so convinced that Skylon is the way forward, that anyone who did 'due diligence' on it must have selected it, and the only way one could explain them not selecting that path is by not doing 'due diligence'.  ::)

I know we are in a post-facts society, but at least TRY to step out of your bubble.

To make it easier, I've listed Elon's response to Reaction Engines from your link.

Quote
[Question about Reaction Engines.] This is using an air breathing engine? When I looked at the numbers it didn't seem too compelling compared to having a slight increase in the size of the first stage. So if you're going to add a whole bunch of complexity, it needs to really pay off and, at least using the numbers I've seen, I have a hard time seeing how it does pay off - but I could be wrong about that. If there is really a big advantage then it would be worth investigating, but it would have to be a big advantage. I would be reluctant to add essentially some sort of jet engine on top of the rocket engine problem.
Evil triumphs when good men do nothing - Thomas Jefferson

Offline Alpha_Centauri

  • Full Member
  • ****
  • Posts: 759
  • England
  • Liked: 336
  • Likes Given: 158
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #398 on: 11/23/2016 06:05 pm »
So in other words he hasn't seriously investigated it.

Offline Khadgars

  • Full Member
  • ****
  • Posts: 1750
  • Orange County, California
  • Liked: 1132
  • Likes Given: 3156
Re: The Reaction Engines Skylon Master Thread (6)
« Reply #399 on: 11/23/2016 06:12 pm »
So in other words he hasn't seriously investigated it.

He's looked at the numbers and it didn't make sense to him.  The payoff had to be too large to make it worth while, though he leaves the door open to being wrong.
« Last Edit: 11/23/2016 06:12 pm by Khadgars »
Evil triumphs when good men do nothing - Thomas Jefferson

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1