Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 421695 times)

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1480 on: 04/06/2016 07:17 PM »
What IS new is that rather than carrying pre-processed oxidizer in a heavy tank, they are collecting and processing oxygen as they go up

They're not. SABRE is not a LACE
SABRE is an evolutional development of LACE. The principal responsible for SABRE was co-creator of LACE, and all the work on SABRE was a continuation of the lessons learnt from LACE research. The essential difference between the two is that LACE liquified the oxygen, whereas SABRE keeps the oxygen above the condensation point, which I have already alluded to. There is also a difference in the intended structural design of the host craft (Skylon vs HOTOL) in that the engines are moved forward to correct for a cascade of problems resulting from the original engine placement causing the CG to be moved too far back.

Note on the historical "evolution" of the SABRE cycle and LACE in general;

Alan Bond created a series of LACE and LACE-like engines but LACE itself was researched and developed in the United States in the mid-50s for the "Aerospaceplane" project. LACE, (Liquid Air Cycle Engines) have always suffered from a high "wastage" of hydrogen required in order to liquefy air to feed into the rocket engine. The air was turned to liquid because of a basic assumption that it HAD to be liquid to allow it to be compressed by a high-speed turbo pump to reach a high enough pressure to feed into a rocket combustion chamber. (Secondarily to allow it to be stored in on-board tanks to feed afore mentioned rocket engines later in flight)

Around the same time the first actual liquid hydrogen rocket engines were being developed and tested and several things were noted. First of all "liquid" hydrogen engines actually performed better if the hydrogen was injected as a high pressure "gas" rather than a liquid and second that the previously assumed "required" pressures in the combustion chamber had been over-estimated by a large factor. Lastly that if both the oxygen and hydrogen were injected as gasses mixing and combustion was much more efficient.

Unfortunately the people who were developing the rockets were not talking to those developing LACE and vice-versa in any significant way. So many of the basic assumptions that were directing the design of LACE development were in fact wrong.

During this time a sub-contractor on the Aerospaceplane LACE system discovered that highly cooled air, (very cold but NOT liquefied) could be compressed and pumped by modified turbo-pumps that were compatible with use in a rocket engine BUT did not reach the pressures that the teams developing LACE were assuming were required so deep-cooling as it was know was not pursued and eventually both LACE and Aerospaceplane were dropped. (Of course another down-side is "deep-cooled" air wasn't as efficient to store as LOX but that was actually "minor" since it was a "silly" idea to use "deep-cooled" air in a rocket engine when you needed LIQUID oxygen... Yep, dropped the ball there guys :) )

Several improvements on the basic concept of LACE came along over the years but pretty much all of them ended up using more liquid hydrogen than they actually needed to run the engine cycle because of the delta-t needed to go from "deep-cooled" to "liquid" so most work concentrated on methods of "using" that excess hydrogen.  LH2 turbofans, turbojets, and ramjets all burning the "excess" hydrogen were considered, researched and eventually discarded over and over again until Bond re-/discovered the idea of a deep-cooling rocket engine.

The situation is very much one of those historical "Doh!" moments when the answer was sitting right in front of everyone but missed because the "right" answer everyone knew was in fact not as "right" as was assumed.

And probably even MORE annoying than the history of the subject is the fact that after HOTOL was proposed but was having other issues, several OTHER people re-discovered the previous deep-cooled cycle work AND the fact that there had been tests running an RL10 on "deep-cooled-but-not-liquid" oxygen/air done in the late-60s/early-70s! Worse, "officially" everyone was assuming the reason HOTOL 'failed' was because the engines didn't work!

There are none so blind....

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 john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1481 on: 04/06/2016 07:31 PM »
Huh? Maybe it's a language thing, but co-creator? It reads a bit like you are saying the same person who came up with LACE also came up with SABRE, which is not true. I think it is a lost-in-translation thing though. Yes, the SABRE learnt from the lessons of LACE, but they are substantially different. AIUI LACE is a single mode engine that collects and uses/stores liquid oxygen (discarding the 80% nitrogen) before powering out of the atmosphere meaning it has to cruise in atmosphere for some period of time to collect sufficient oxygen. SABRE is a dual-mode engine that uses atmospheric gaseous oxygen/nitrogen while in-atmosphere and ground loaded on-board liquid oxygen for the exit from the atmosphere, which means it does not need to cruise along collecting oxygen. I'd call SABRE a cousin rather than progeny of LACE.

LACE was never an option for HOTOL, so not sure why you bring up the difference between HOTOL and Skylon here. The RB545 was designed for HOTOL, and is still classified top secret. I'd love to know what the big deal was with that engine.
"William Escher" of NASA is often mentioned relevant to LACE. He came up with a way of describing most (all ?) air breathing space launch systems, which is why SABRE can be described as a "Deeply pre-cooled turbo rocket." Wheather he can be described as the inventor of LACE, as I suspect several companies had this idea around the same time.

I don't think there's any evidence he was in contact with any of the REL team.
« Last Edit: 04/06/2016 08:36 PM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1482 on: 04/06/2016 08:33 PM »
Except what LM is looking into longer term for its air breathing vehicle isn't a pure scramjet.

Quote
Hewson also showed an image of a third hypersonic concept, similar to the HAWC but with a recoverable “turbine-based combined cycle” engine, Weiss explained. The HAWC’s booster is designed for a single use, he stressed. There is not yet a DARPA project for this capability, and Lockheed still needs to mature the propulsion technology, he said.

http://www.defensenews.com/story/defense/air-space/2016/03/16/lockheeds-marilyn-hewson-touts-breakthroughs-hypersonic-weapons/81836070/

Actually no, LM is NOT looking into "long-term" and the concepts ARE in fact "pure" SCramjets... As we've been saying over and over again SCramjets need another engine system to reach operational speed. That's quite clear from the article. Note also that it clearly states LM needs to "mature" the propulsion technology, (ie: getting a SCramjet to actually work on a consistent basis) and that there are currently NO DARPA requirements for the concept vehicles.

Fun facts from the cited article;
- Lockheed is NOT working on any of the propulsion systems, that's Aerojet-Rocketdyne if they don't go out of business first.

- Both primary and secondary projects are in fact for "one-shot" weapons system with no "long-term" use. It is only when you get to a third "concept" vehicle they even mention a "reusable" turbine-based-combined-cycle BOOSTER for the one-shot SCramjet weapon.

- The article keeps pointing out that Lockheed (and the military) are aiming for speeds "up-to" Mach-5 which is barely hypersonic AND where we already know SCramjets have a hard time operating. (The speed is actually LOW for a supersonic internal engine flow, point-of-fact SUBSONIC combustion ramjet engines were lab-tested to speeds as high as Mach-7+ with "positive thrust-to-weight" factors HIGHER than tested SCramjets. Engineers who actually designed and built subsonic combustion ramjets stated they saw no problems other than materials in one going as fast as Mach-10. So one probably SHOULD question why everyone seems to think you need a SCramjet to do the job being described)

- Love the quote: “We are now producing a controllable, low-drag, aerodynamic configuration capable of stable operations from takeoff to subsonic, transonic, supersonic and hypersonic, to Mach 6.” Which sounds great until you realize the hypersonic flight portion has to take place at altitudes above 75,000ft or the airframe burns up.

- The "perspective" of a jet flying at Mach 5 "could cross the continental United States in about half an hour" is deceptive because said hypersonic jet is above 70,000ft where as the weapon needs to survive flying at that speed long enough to hit the target which will be well below 20,000ft! TPS requirements are going to make orbital reentry look like a campfire in "perspective" and the weapon has to survive that for probably a couple of minutes at least. (@Mach-5=3,600mph=60mpm=6mps. Hint: Russia is set to deploy an "long-range" AAA missile with a range of up to around 25 miles. To reach if from beyond effective range, say 30 miles to be generous the weapon has to survive for over 30 seconds at very low altitude and very high speed assuming the target is stationary mind you. CEP for a good kill on an armored target will be less than 100' and probably closer to 50' with a "standard' warhead including the weapon velocity)

Oh and I should mention the article is wrong, the X-15 went to Mach-6, (Mach-6.7 in fact which is faster than the SCramjet has gone) in the 1960s, not Mach-5 as stated.

Take away? LM is still trying to sell the idea of the "SR-72" in some fashion and are willing to turn it into a single use "prototype" weapon for the government if said government will fund them to the tune of a couple of billions dollars for ONE copy. Ignore the facts they have no engine, no aerodynamics, thermal or control systems since we're using the "Skunk-works" to propose this you should simply believe us when we say we can do what we haven't managed to do yet with the money you gave us already.

Oh and about nothing to do with the Skylon I should point out :)

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 RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1483 on: 04/06/2016 08:48 PM »
Huh? Maybe it's a language thing, but co-creator? It reads a bit like you are saying the same person who came up with LACE also came up with SABRE, which is not true. I think it is a lost-in-translation thing though. Yes, the SABRE learnt from the lessons of LACE, but they are substantially different. AIUI LACE is a single mode engine that collects and uses/stores liquid oxygen (discarding the 80% nitrogen) before powering out of the atmosphere meaning it has to cruise in atmosphere for some period of time to collect sufficient oxygen. SABRE is a dual-mode engine that uses atmospheric gaseous oxygen/nitrogen while in-atmosphere and ground loaded on-board liquid oxygen for the exit from the atmosphere, which means it does not need to cruise along collecting oxygen. I'd call SABRE a cousin rather than progeny of LACE.

LACE was never an option for HOTOL, so not sure why you bring up the difference between HOTOL and Skylon here. The RB545 was designed for HOTOL, and is still classified top secret. I'd love to know what the big deal was with that engine.
"William Escher" of NASA is often mentioned relevant to LACE. He came up with a way of describing most (all ?) air breathing space launch systems, which is why SABRE can be described as a "Deeply pre-cooled turbo rocket." Wheather he can be described as the

I don't think there's any evidence he was in contact with any of the REL team. I'm not sure he can be described as the inventor of LACE, as I suspect several companies had this idea around the same time.

Escher was working for Mardquart at the time and they were one of the companies doing the development of LACE, (as well as initial SCramjet research and advanced ramjet work) and he was interested in the "deep-cooling" effect. But only in the context of increasing the density of intake air for T/W purposes. He was still advocating LACE for the rockets, (and moved to SCram-LACE as a 'standard' later on) and only briefly mentioned using the "excess" hydrogen from the LACE process injected in the after-burner portion of the SES/RJ (Supercharged-Ejector-SCram/Ramjet) engine as part of the bypass system during LACE operations. Most of his "Spaceliner" engine systems used LACE collection up to speeds in excess of Mach-10 so you can guess why he found a 'significant excess' of hydrogen being produced :)

To address the cycle question, and so we're all on the same page, LACE uses liquid hydrogen to turn incoming air liquid. The air is separated into oxygen and nitrogen using a variety of methods, (usually the least complex and lighters are preferred but there are trade offs) with the nitrogen dumped and the now liquid oxygen being stored and/or used in a rocket engine to continue acceleration. Dozens of variations exist from "simply" collecting the lox while in subsonic flight to the afore mentioned supersonic/hypersonic collection and liquefying idea and everything in between.

A great number of people still get confused with the difference between LACE and SABRE since they see an air-intake at one end and rocket motors at the other. There's still a lot of people who think that if you have rocket engines then obviously you have to feed them LIQUID oxygen. On the other hand there are still a lot of EXPERTS that think the same thing so I think the confusion can be forgiven :)

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 john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1484 on: 04/06/2016 08:49 PM »
Take away? LM is still trying to sell the idea of the "SR-72" in some fashion and are willing to turn it into a single use "prototype" weapon for the government if said government will fund them to the tune of a couple of billions dollars for ONE copy. Ignore the facts they have no engine, no aerodynamics, thermal or control systems since we're using the "Skunk-works" to propose this you should simply believe us when we say we can do what we haven't managed to do yet with the money you gave us already.
That sounds less like the X30 (NASP) and reather more like the X33 for NASA.

That was for an SSTO (with the demo vehicle pitched to M15), cost $1.1Bn and delivered no flight vehicle.  :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1485 on: 04/06/2016 09:07 PM »
If you follow the thread back I was the original person criticizing the article - that was only about Skylon - for quoting the opinions of scramjet researchers. The article (http://forum.nasaspaceflight.com/index.php?topic=36826.msg1508669#msg1508669) had nothing to do with LM except for referencing the LM X-33 program that never flew and was canceled some 15 years ago. No-one else mentioned LM, so I don't understand the relevance of your point/response to Randy, which I guess relates to the proposals for their new SR-72 program engines.

It was supposed to show that "someone" working on SCramjets, (which LM actually isn't but a proposed weapon that would USE a SCramjet) is looking towards "long-term" use. Which is supposed to be connected to the use of "long-duration" in the article. The problem is that it is obvious that the article and LM were talking about a WEAPON system so "long-duration" is only enough time to go from launch to the target. (Which at Mach-5 you are talking seconds probably and less than a minute at best)

This IS a key point because what nobody mentions is that while a SCramjet has flown at hypersonic speed, (Mach-5.1 to be exact) it was at 60,000ft and what they military wants is something that can fly at Mach-5 from 20,000ft to ZERO feet! (It's a weapon after all) The SR-71 operated at speeds of Mach-3+ BUT only over 45,000ft, (closer to 65-70Kft actually) because it would fall apart at lower altitude from the heating.

What the military wants is something that can be launched from around 20,000ft to Mach-5 and then REMAIN at Mach-5 all the way to impact and zero feet. That's a key factor to keep in mind. What is required is a combined propulsion system as everyone keeps pointing out. What I find interesting is that LM and everyone else seem to be missing the point though. Yes a SCramjet can keep a vehicle at hypersonic speed (barely it seems) once its brought there by another propulsion system, but SCramjets, and ramjets actually work LESS efficiently as you decrease the altitude at higher speeds, (specifically hypersonic) because your aero-heating goes up significantly fast.

In essence what is being suggested by the requirements is a weapon that can be launched from beyond engagement range of the target defenses, accelerates to Mach-5 then SUSTAINS that speed until it "engages" the target and keeps that speed all the way to impact.

Nobody asks me but it's pretty clear that what you need is NOT a SCramjet but a boosted ramjet (expendable solid booster, dropped once the ramjet comes online) to Mach-5 at 20,000+ft, "cruise" to engagement range of the target, (the faster the better which is where a Mach-6-8 ramjet would come in handy, point is you need to keep a significant T/W which we already know the SCramjet can't do), lock on to target and expend the ramjet and light up another solid rocket to boost till target impact. Rather simpler and probably cheaper than a "billion dollars" since we've already built and flown integral rocket/ramjet missiles to over Mach-5 (albeit because of a stuck fuel valve but that's kind of makes my point) and all you're adding is another short-duration, high thrust rocket motor.

I'm going to leave this link here (http://www.designation-systems.net/dusrm/app4/asalm.html) and simply say this weapon was designed to fly at Mach-4.5 with a fixed inlet ramjet to a range of 300 miles (480km) with inertial and duel mode active guidance, (ok we'd lose the thermonuclear warhead but I'm not seeing that as a real "down-side" given the mission) in 1980... Explain to me again why LM (and everyone else) seems to think there's an urgent need for the SCramjet engine to meet the requirements?

Quote
I only seek enlightenment btw, not trying to start a flame fest.

Oh sure, you're an enabler and you know it ;)
Hope I helped explain things somewhat.

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 RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1486 on: 04/06/2016 09:26 PM »
Take away? LM is still trying to sell the idea of the "SR-72" in some fashion and are willing to turn it into a single use "prototype" weapon for the government if said government will fund them to the tune of a couple of billions dollars for ONE copy. Ignore the facts they have no engine, no aerodynamics, thermal or control systems since we're using the "Skunk-works" to propose this you should simply believe us when we say we can do what we haven't managed to do yet with the money you gave us already.
That sounds less like the X30 (NASP) and reather more like the X33 for NASA.

That was for an SSTO (with the demo vehicle pitched to M15), cost $1.1Bn and delivered no flight vehicle.  :(

Actually the demo was not supposed to initially go faster than Mach-12, but very soon after LM got the contract this was reduced to Mach-10, Mach-8, Mach-7, I think you get the picture :)

If you read the article can I ask if you were as amused by the statement by LM that “Lockheed Martin has a legacy of making fast aircraft,” with no hint of irony in that they are only know for doing so, what, twice? (F-104 and SR-71) Both of which were expensive to operate and maintain? The Skunk works isn't anything like what it was when those were designed and built and nothing gives me confidence that LM can actually accomplish what they say they can despite trying to build on a legacy they no longer follow.

And again I specifically have to question why they wouldn't consider actually using technology and systems they already HAVE to fill this supposed "urgent" need? Asking for a billion dollars for a single prototype when they could probably deliver an operational system for the same amount makes me wonder if we shouldn't see if we can run some copper wiring around Kelly Johnsons body and take advantage of all that spinning he's doing for the greater good...
(Sorry that was tacky but true:( )

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 john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1487 on: 04/06/2016 10:05 PM »
Actually the demo was not supposed to initially go faster than Mach-12, but very soon after LM got the contract this was reduced to Mach-10, Mach-8, Mach-7, I think you get the picture :)
I didn't recall the exact starter Mach number.

I certainly recall the gradually dropping Mach numbers where it got to (IIRC) "Single Stage to Colorado" at the end.
Quote
If you read the article can I ask if you were as amused by the statement by LM that “Lockheed Martin has a legacy of making fast aircraft,” with no hint of irony in that they are only know for doing so, what, twice? (F-104 and SR-71) Both of which were expensive to operate and maintain?
Somehow I thought they'd made more M2+ aircraft.

The F104 seemed to need a blown flaps system like the BAC Buccaneer (with a few more operating issues) to handle takeoff and landing.

Not to mention their aggressive marketing campaign for F104.
Quote
The Skunk works isn't anything like what it was when those were designed and built and nothing gives me confidence that LM can actually accomplish what they say they can despite trying to build on a legacy they no longer follow.
They played that card with the X33. Worked with NASA, but the DoD would have better access to the actual results
Quote
And again I specifically have to question why they wouldn't consider actually using technology and systems they already HAVE to fill this supposed "urgent" need? Asking for a billion dollars for a single prototype when they could probably deliver an operational system for the same amount
I think you hit the nail when you pointed out the Skunkworks of today is not the outfit Kelly Johnson ran through the 40s,50s and 60s. It's goal is not to keep Lockheed design ahead of the field, it's to get a cashflow from who'll ever pay them regardless of wheather there are cheaper ways to solve the problem.  :(
Quote
makes me wonder if we shouldn't see if we can run some copper wiring around Kelly Johnsons body and take advantage of all that spinning he's doing for the greater good...
(Sorry that was tacky but true:( )
I'm quite a fan of novel clean energy concepts myself.  :)

I'd love to see what would happen if people just said "We'll give the SCramjet a break and just see what the best conventional ramjet we can build using the latest CFD and diagnostics to build a really good fixed geometry system." The rule of thumb has been 3 Mach numbers and maybe slowing the airstream to M0.3. Make it 5 Mach numbers (possibly by slowing air to say M0.9) and if the rocket can get them to M2 that's well into the hypersonic range already.

I'll note the key reason REL switch to rocket at about M5.5 is that (as they've pointed out numerous times) at that point the energy you loose in slowing down the airflow inside the duct you have to put back burning fuel. That may be pessimistic based on a conservative ramjet design rules used in the spill ramjet buners, but I doubt it's that conservative. 
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Archibald

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1488 on: 04/07/2016 12:14 PM »
Quote
I didn't recall the exact starter Mach number

Initially it was to be mach 15, but then it dropped to mach 12. Did they dropped further before cancellation ?

Offline Star One

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The Reaction Engines Skylon Master Thread (5)
« Reply #1489 on: 04/12/2016 03:25 PM »
Reading this article may answer why REL has yet to see the investment promised by the UK government. It seems since the General Election the industry now faces a more sceptical government when it comes to space related activities.

http://spacenews.com/is-britains-5-year-space-investment-locomotive-running-out-of-steam/
« Last Edit: 04/12/2016 03:25 PM by Star One »

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1490 on: 04/12/2016 05:06 PM »
Actually the demo was not supposed to initially go faster than Mach-12, but very soon after LM got the contract this was reduced to Mach-10, Mach-8, Mach-7, I think you get the picture :)
I didn't recall the exact starter Mach number.

I certainly recall the gradually dropping Mach numbers where it got to (IIRC) "Single Stage to Colorado" at the end.

Actually it was always "Single-Stage-To-New Mexico" from Utah which was the Air Force proposed (and accepted) flight profile. With some "reverse" trips included. It was funny because the site in Utah is ALSO called "White Sands" and it was very clear that the Air Force lost interest pretty much as soon as the contract was signed because they canceled all work on repairs and upgrades to the launch site around that same time.

Quote
I didn't recall the exact starter Mach number

Initially it was to be mach 15, but then it dropped to mach 12. Did they dropped further before cancellation ?

The program goal was given as initially to Mach-15 and was dropped to Mach-12 when the contract was signed. LM kept dropping the goal all the way to cancelation which was Mach-6, maybe, by the time of cancelation.


I'll note the key reason REL switch to rocket at about M5.5 is that (as they've pointed out numerous times) at that point the energy you loose in slowing down the airflow inside the duct you have to put back burning fuel. That may be pessimistic based on a conservative ramjet design rules used in the spill ramjet burners, but I doubt it's that conservative.

Key note: REL is talking about air slowed for use in a compressor/fan, not the bypass/ram air which you need to keep in mind. While the air in a subsonic ramjet has to be slowed to use the combustor actual engineers who designed, built and tested standard ramjets were confident that a subsonic combustion ramjet could be designed to work from Mach-2 to Mach-10 with ease. I'll also note the "rule-of-thumb" that is being cited for the "3 Mach Numbers" is normally for a FIXED inlet ramjet where as an adjustable intake/exhaust system is pretty much insensitive to such issues. Around Mach-7 you have to inject more fuel to keep accelerating but the actual amount is not as significant as it's made out to be by SCramjet advocates. From what I understand after Mach-10 the amount of shocks needed to keep the flow sub-sonic is mechanically difficult and generally not thought to be worth the effort. (Not for anything that one wants to reuse that is :) )

I though the temperature of the intake air also became a problem above this speed?

Above Mach-5 intake air just keeps getting hotter as it's shocked to subsonic speeds and compressed. SABRE helps a lot since it's still cooling the air with the HE system where as a standard subsonic ramjet doesn't have such a system but once you've got an airframe and engine system that can stand up to higher speeds your intake air temperature is less of a problem. Again, engineers who worked on ramjets were confident they could be used up to Mach-10... But they were honest that there wasn't an airframe out there that could do the same :)

Really there isn't much of a requirement for sustained travel at hypersonic speeds. Almost every 'cited' use is for niche uses that for the most part are single-use missions OR ones that are just "passing through" speeds over Mach-5.

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 RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1491 on: 04/12/2016 05:14 PM »
Reading this article may answer why REL has yet to see the investment promised by the UK government. It seems since the General Election the industry now faces a more sceptical government when it comes to space related activities.

http://spacenews.com/is-britains-5-year-space-investment-locomotive-running-out-of-steam/

Interesting and not actually unexpected. Governments have a tendency to make decisions based on bias' upon which they are elected, no matter how short-sighted those bias' are.

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 Archibald

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1492 on: 04/12/2016 05:29 PM »
Quote
LM kept dropping the goal all the way to cancelation which was Mach-6

Oh damn, was it THAT worse ?  >:(

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1493 on: 04/12/2016 07:03 PM »
Reading this article may answer why REL has yet to see the investment promised by the UK government. It seems since the General Election the industry now faces a more sceptical government when it comes to space related activities.

http://spacenews.com/is-britains-5-year-space-investment-locomotive-running-out-of-steam/

Interesting and not actually unexpected. Governments have a tendency to make decisions based on bias' upon which they are elected, no matter how short-sighted those bias' are.

Randy

My heart sunk on reading as it seems like the UK might return to the old status que when it comes to the industry. Which wouldn't bode well for any more flights involving Tim Peake.

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1494 on: 04/12/2016 08:46 PM »
Quote
LM kept dropping the goal all the way to cancelation which was Mach-6

Oh damn, was it THAT worse ?  >:(

Well, you can think of them being ahead of the curve for DARPA's XS-1 project, sorta :)

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 lk555

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1495 on: 04/14/2016 05:58 PM »
Has anyone got a record of where I can find the STERN results? There was definitely a paper published and I had it from somewhere on open access, but I have no idea where it has saved.

Any help would be fantastic.

Offline t43562

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1496 on: 04/19/2016 03:04 PM »
Has anyone got a record of where I can find the STERN results? There was definitely a paper published and I had it from somewhere on open access, but I have no idea where it has saved.

Any help would be fantastic.
this? http://enu.kz/repository/2011/AIAA-2011-5688.pdf

Editted to add:
or this http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30547.0;attach=534797

Those were quite interesting to read.  The conclusions don't seem to be absolutely definitively in favour of E/D nozzles and they do mention a follow on STRICT programme to see what might be done to cope with the issue they found.   It would be rather interesting to know what came out of that but I havenot been able to find anything so far.

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1497 on: 04/22/2016 03:24 PM »
from the other thread:

Why are you dodging the point?  Skylon's tanks are very low pressure and are not load-bearing; it's the truss that matters.

Just out of curiosity; are Skylon tanks rated at 1 atm gauge pressure all the way to the orbit (absolute pressure inside tanks reduced as the ambient pressure drops on the way up) or do they cope with 2 atm absolute?
Tank pressure falls with altitude. After MECO the main tanks are vented as a safety precaution OMS/RCS/APU are driven off a separate set of tanks.

When ambient pressure drops to near vacuum do Skylon tank pressures drop to 1 atm absolute, during powered flight??
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Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1498 on: 04/22/2016 07:52 PM »
When ambient pressure drops to near vacuum do Skylon tank pressures drop to 1 atm absolute, during powered flight??

According to the ESA report, yes.

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1499 on: 04/23/2016 06:23 AM »
Read elsewhere that the hydrogen is subcooled to 16K. If the tank pressure is reduced to 1 atm during flight then NPSH drops to about 0.7atm minus all the losses on the way to the pump inlet. The turbopump guy is not going to be very happy about this.
« Last Edit: 04/23/2016 06:23 AM by R7 »
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