The Reaction Engines Skylon/SABRE Master Thread (6)

[Jim]

Way too early to consider that.  This thread is good enough for now.

[Chris Bergin]

Would a  test vehicle qualify for a thread in
International Space Flight (ESA, Russia, China and others) > Other Launchers (Korean, Brazilian etc.) > BAE Valkyrie

or a part of a new sub-forum in
Commercial and US Government Launch Vehicles > BAE

While Jim doesn't speak for the site, I do. A new sub-forum requires at least 30-50 threads to be viable to be split into a standalone section and needs to show it will be creating numerous new threads as soon as that section is live. So this isn't a discussion for years.

No one will be happier if that actually does become a discussion we need to have, however!

[93143]

Wasn't the spill-ramjet dropped from the later designs?

Don't think so.  SABRE 4 wastes a lot less hydrogen than SABRE 3, but I'm pretty sure it still uses more than the core can burn.

In any case there is a real issue of a loss of ramjet expertise over the last couple of decades from all the people and organizations that actually worked on physical rather than lab or theory ramjets.

I was under the impression REL had old-school ramjet expertise on staff.  I know Mark Hempsell has talked up the UK's extensive history with ramjets and referred to the conservative spill ramjet specifications as one of their "hidden margins".

Doesn't negate your point of course.  I had a discussion once on Talk-Polywell with a GW Johnson, who noted with dismay that he was "one of America's last surviving full-capability ramjet engineers"...

[Ravenger]

I believe Alan Bond once suggested that Skylon could fly on bypass burners alone if for some reason the main engines failed during a flight and the spaceplane needed to abort back to a landing strip.

Like any ramjet that can only happen if it's travelling fast enough for the burners to work, but it would increase the chance of returning the spacecraft and payload intact if engine problems occur in the air-breathing phase at high speed.

[john smith 19]

Doesn't negate your point of course.  I had a discussion once on Talk-Polywell with a GW Johnson, who noted with dismay that he was "one of America's last surviving full-capability ramjet engineers"...

I think that's this fellow.



He's meant to be writing a book on ramjets. One of his blog entries mentions he feels the "dump combustor"  is poorly documented but has potential for more the the use rule-of-thumb range of 3 Mach numbers for a ramjet while remaining within the subsonic combustion regime.

I'd quite like to see his book as it sounds interesting, although I'd really like to see one from Doug Jones, XCOR's (and prior to that Rotary Rockets) key engine man.

AIUI the spill ramjet is more a way of countering thermodynamic losses due to air inlet flow exceeding the flow needed by the core and causing drag. I think Hempsell mentioned they are looking for it to contribute a few 100 m/s only. Again far enough inside the experience envelope (possibly now with GH2) that their design will do what they expect it to.

However this is fairly OT for SABRESkylon as  a whole. 

[Matthew Ak43]

Has anybody heard anything about the USAirforce doing a presentation at  (AIAA) Space conference, in Long Beach, 13-16 September showing plans for Two stage sabre engine vehicles? To be fair to them they said it would be this month or March.

[AnalogMan]

Has anybody heard anything about the USAirforce doing a presentation at  (AIAA) Space conference, in Long Beach, 13-16 September showing plans for Two stage sabre engine vehicles? To be fair to them they said it would be this month or March.

Session ST-02 "Resuable Launch Vehicles & Technology" Co-chairs: Adam Dissel  (Reaction Engines, Inc); Barry Hellman (Air Force Research Laboratory)

Tues 13 Sep 2016 4:00-4:30 PM

AIAA-2016-5320. Two Stage to Orbit Conceptual Vehicle Designs using the SABRE Engine B.M. Hellman; J.E. Bradford; B.D. St. Germain; K. Feld

[john smith 19]

Has anybody heard anything about the USAirforce doing a presentation at  (AIAA) Space conference, in Long Beach, 13-16 September showing plans for Two stage sabre engine vehicles? To be fair to them they said it would be this month or March.

Session ST-02 "Resuable Launch Vehicles & Technology" Co-chairs: Adam Dissel  (Reaction Engines, Inc); Barry Hellman (Air Force Research Laboratory)

Tues 13 Sep 2016 4:00-4:30 PM

AIAA-2016-5320. Two Stage to Orbit Conceptual Vehicle Designs using the SABRE Engine B.M. Hellman; J.E. Bradford; B.D. St. Germain; K. Feld

Oh dear. Spaceworks Engineering were hired to do consultancy.

So how big will the SCramjet be this time? 


The full program is here if nayone is interested.
http://www.aiaa-space.org/uploadedFiles/AIAA-Space_Site/Program/SPACE_2016_FINAL_PRINT_lowRes.pdf

[Asteroza]

Has anybody heard anything about the USAirforce doing a presentation at  (AIAA) Space conference, in Long Beach, 13-16 September showing plans for Two stage sabre engine vehicles? To be fair to them they said it would be this month or March.

Session ST-02 "Resuable Launch Vehicles & Technology" Co-chairs: Adam Dissel  (Reaction Engines, Inc); Barry Hellman (Air Force Research Laboratory)

Tues 13 Sep 2016 4:00-4:30 PM

AIAA-2016-5320. Two Stage to Orbit Conceptual Vehicle Designs using the SABRE Engine B.M. Hellman; J.E. Bradford; B.D. St. Germain; K. Feld

Oh dear. Spaceworks Engineering were hired to do consultancy.

So how big will the SCramjet be this time? 


The full program is here if nayone is interested.
http://www.aiaa-space.org/uploadedFiles/AIAA-Space_Site/Program/SPACE_2016_FINAL_PRINT_lowRes.pdf

Why the SEI haterade, aside from (generally well justified) generic scramjet dislike? Sure, their concept designs are typically a little big, but there seem to be a fair number of people who have Marquardt ramjets in their blood, which is usually a good thing.

SEI's SCAAT engine on a Skylon body strikes me as a reasonable comparison point to SABRE/Skylon.

[Star One]

Has anybody heard anything about the USAirforce doing a presentation at  (AIAA) Space conference, in Long Beach, 13-16 September showing plans for Two stage sabre engine vehicles? To be fair to them they said it would be this month or March.

Session ST-02 "Resuable Launch Vehicles & Technology" Co-chairs: Adam Dissel  (Reaction Engines, Inc); Barry Hellman (Air Force Research Laboratory)

Tues 13 Sep 2016 4:00-4:30 PM

AIAA-2016-5320. Two Stage to Orbit Conceptual Vehicle Designs using the SABRE Engine B.M. Hellman; J.E. Bradford; B.D. St. Germain; K. Feld

Oh dear. Spaceworks Engineering were hired to do consultancy.

So how big will the SCramjet be this time? 


The full program is here if nayone is interested.
http://www.aiaa-space.org/uploadedFiles/AIAA-Space_Site/Program/SPACE_2016_FINAL_PRINT_lowRes.pdf

Why the SEI haterade, aside from (generally well justified) generic scramjet dislike? Sure, their concept designs are typically a little big, but there seem to be a fair number of people who have Marquardt ramjets in their blood, which is usually a good thing.

SEI's SCAAT engine on a Skylon body strikes me as a reasonable comparison point to SABRE/Skylon.

Prepare to receive a lecture on the evil of Scramjets now.

[john smith 19]

Why the SEI haterade, aside from (generally well justified) generic scramjet dislike? Sure, their concept designs are typically a little big, but there seem to be a fair number of people who have Marquardt ramjets in their blood, which is usually a good thing.

SEI's SCAAT engine on a Skylon body strikes me as a reasonable comparison point to SABRE/Skylon.

I presume that would be this thing.

https://www.sbir.gov/sbirsearch/detail/313205

"The supporting secondary airflow from the inlet and the ramscoops increases the rockets Isp by an average of 15% - 30% when combusted. "

So that's an ISP of about 517-585secs for a LO2/LH2 Isp of 450secs then.

SEI have certainly written a lot of reports about stuff for people but I'm not quite clear what hardware they've built.

Can you point me toward anything they've made, rather than simulated being made in a computer?

[Asteroza]

Why the SEI haterade, aside from (generally well justified) generic scramjet dislike? Sure, their concept designs are typically a little big, but there seem to be a fair number of people who have Marquardt ramjets in their blood, which is usually a good thing.

SEI's SCAAT engine on a Skylon body strikes me as a reasonable comparison point to SABRE/Skylon.

I presume that would be this thing.

https://www.sbir.gov/sbirsearch/detail/313205

"The supporting secondary airflow from the inlet and the ramscoops increases the rockets Isp by an average of 15% - 30% when combusted. "

So that's an ISP of about 517-585secs for a LO2/LH2 Isp of 450secs then.

SEI have certainly written a lot of reports about stuff for people but I'm not quite clear what hardware they've built.

Can you point me toward anything they've made, rather than simulated being made in a computer?

From the the school of those that can't do, teach...

As far as I am aware, SEI is mostly a paper study consulting outfit that has never built a partial or complete ramjet or scramjet, though they dabble in some hardware, like their GoLauncher air launch system

http://generationorbit.com/

Currently static flight testing their version 1 rocket (which fits on a learjet wing pylon, did you know that was a purchasable option for a bizjet?!?)

and TVA, an ISS small cargo return capsule venture

http://terminalvelocityaero.com/


They are quite literally working the small end of NewSpace activities, though small things are somewhat easier to fund...

[john smith 19]

As far as I am aware, SEI is mostly a paper study consulting outfit that has never built a partial or complete ramjet or scramjet, though they dabble in some hardware, like their GoLauncher air launch system

http://generationorbit.com/

Currently static flight testing their version 1 rocket (which fits on a learjet wing pylon, did you know that was a purchasable option for a bizjet?!?)

Amazing what you can find in a catalogue, isn't it?  I'm curious what they will be using for the engine. going liquid helps with the Isp of course. Logically that's LOX or HTP.

and TVA, an ISS small cargo return capsule venture

http://terminalvelocityaero.com/

They are quite literally working the small end of NewSpace activities, though small things are somewhat easier to fund...

I believe the provision of down mass is substantially under appreciated as an enabling tool for refining components, on orbit mfg systems etc.

I'm curious if these divisions are "home grown" or did SEI buy them up, but that's right OT for this thread.

[RanulfC]

SEI and SCramjets; Give the customer what they ask for, and occasionally what they actually want rather than what they THINK they want SEI does studies for which the customer, (NASA, AF, whoever) tends to set the requirements and assumptions. Size-wise that means you do the work around the amount of payload the customer gives you. Given the amount of money tied up in assuming SCramjets work, when the customer specifies to include them that is what you do. Have to wait till the presentation is available but I'd be surprised if anything REL is involved with includes them.

GW Johnson; Someone needs to sit that man down and record his brain or something. I'm terrified he's going to forget something important, or something and not get stuff written down!

GO and TV; SEI helped fund them and has an interest in them. How much control that translates into...

Down-mass is only an issue when you have more of it than you do up-mass which is not really the case currently. Nice to have if you don't put up a lot of mass often though which IS the current case, especially for some proposed automated experimental/production facilities. Nice to see someone thinking about it ahead of the game

Plumbing on Learjets; Yep it's an option. It is with any biz-jet that gets sold in a "military" version and can be plumbed before or after it's built. Pretty generic and usually plumbed for multiple uses.

Couple notes, anyone catch the design of the TV capsules? Interesting. The GO-Future stuff is interesting as well.

Back on-topic (ish?): As I understood it the spill-ramjet was something to use left over GH2 is a way to reduce the drag losses, but I was under the impression that there wasn't that much 'waste' GH2 in the system and that the latest version didn't have enough to bother with having a spill-ramjet at all.

Everything I've read on "deep-cooling" versus "liquefying" the air pointed to liquefying needing so much LH2 that you pretty much HAD to come up with ways to either re-liquefy it or specialized propulsion systems to use it because you had to carry far more than you needed. While deep-cooling used so much less LH2 the GH2 'excess' could be used in a spill-ramjet to reduce drag losses, dumped into the existing rocket or ramjet, or just plain dumped and therefore had to carry much less LH2 initially.

The thing is the design and working of such a "spill-ramjet" is tricky, (I recall discussing it with GW Johnson at one point) and it's an open question if the effort is worth it for the performance over a wide operating range. That's part of the reason I understood REL was seeking to reduce the 'waste' GH2 in the first place because your possible 'recovery' is all over the place depending on atmosphere, speed, and AoA.

In something with an adjustable inlet flow like SABRE, especially as you get into speeds over Mach-2/3 where adjustments are constantly happening, it would seem questionable to incorporate unless you have a lot of GH2 to deal with. Adding a few "100k/s" isn't really helpful unless it is consistent enough to effect the average ISP over the whole flight which is doubtful, and again the whole point is that deep-cooling means you have a lot less waste GH2 in the first place. Part of this is because unlike most "combined cycle" engine types the SABRE actually and air-breathing rocket engine so there isn't any convenient place to dump the excess GH2 into the flow path so you can't dump it in the afterburner or duct-burn it as is done in most CC engine designs. So burning it in a bypass, or spill-ramjet to make up some loss during portions of the flight makes sense, especially if you have an intake air imbalance. But on the other hand with a constantly adjusting intake system you shouldn't have that much of an imbalance and it shouldn't be significant enough over the air-breathing flight envelope to justify a specifically designed spill-ramjet.

Nice if you can get it cheap and easy but nothing I've seen says that's the case if you don't have a LOT of GH2 to burn off.

Randy

[Asteroza]

SEI and SCramjets; Give the customer what they ask for, and occasionally what they actually want rather than what they THINK they want SEI does studies for which the customer, (NASA, AF, whoever) tends to set the requirements and assumptions. Size-wise that means you do the work around the amount of payload the customer gives you. Given the amount of money tied up in assuming SCramjets work, when the customer specifies to include them that is what you do. Have to wait till the presentation is available but I'd be surprised if anything REL is involved with includes them.

GW Johnson; Someone needs to sit that man down and record his brain or something. I'm terrified he's going to forget something important, or something and not get stuff written down!

GO and TV; SEI helped fund them and has an interest in them. How much control that translates into...

Down-mass is only an issue when you have more of it than you do up-mass which is not really the case currently. Nice to have if you don't put up a lot of mass often though which IS the current case, especially for some proposed automated experimental/production facilities. Nice to see someone thinking about it ahead of the game

Plumbing on Learjets; Yep it's an option. It is with any biz-jet that gets sold in a "military" version and can be plumbed before or after it's built. Pretty generic and usually plumbed for multiple uses.

Couple notes, anyone catch the design of the TV capsules? Interesting. The GO-Future stuff is interesting as well.

Back on-topic (ish?): As I understood it the spill-ramjet was something to use left over GH2 is a way to reduce the drag losses, but I was under the impression that there wasn't that much 'waste' GH2 in the system and that the latest version didn't have enough to bother with having a spill-ramjet at all.

Everything I've read on "deep-cooling" versus "liquefying" the air pointed to liquefying needing so much LH2 that you pretty much HAD to come up with ways to either re-liquefy it or specialized propulsion systems to use it because you had to carry far more than you needed. While deep-cooling used so much less LH2 the GH2 'excess' could be used in a spill-ramjet to reduce drag losses, dumped into the existing rocket or ramjet, or just plain dumped and therefore had to carry much less LH2 initially.

The thing is the design and working of such a "spill-ramjet" is tricky, (I recall discussing it with GW Johnson at one point) and it's an open question if the effort is worth it for the performance over a wide operating range. That's part of the reason I understood REL was seeking to reduce the 'waste' GH2 in the first place because your possible 'recovery' is all over the place depending on atmosphere, speed, and AoA.

In something with an adjustable inlet flow like SABRE, especially as you get into speeds over Mach-2/3 where adjustments are constantly happening, it would seem questionable to incorporate unless you have a lot of GH2 to deal with. Adding a few "100k/s" isn't really helpful unless it is consistent enough to effect the average ISP over the whole flight which is doubtful, and again the whole point is that deep-cooling means you have a lot less waste GH2 in the first place. Part of this is because unlike most "combined cycle" engine types the SABRE actually and air-breathing rocket engine so there isn't any convenient place to dump the excess GH2 into the flow path so you can't dump it in the afterburner or duct-burn it as is done in most CC engine designs. So burning it in a bypass, or spill-ramjet to make up some loss during portions of the flight makes sense, especially if you have an intake air imbalance. But on the other hand with a constantly adjusting intake system you shouldn't have that much of an imbalance and it shouldn't be significant enough over the air-breathing flight envelope to justify a specifically designed spill-ramjet.

Nice if you can get it cheap and easy but nothing I've seen says that's the case if you don't have a LOT of GH2 to burn off.

Randy

Does that imply that eliminating spill ramjets would lead to running fuel rich out the rocket nozzles then? Is the simplicity worth the direct losses there, compared to either a spill ramjet, or some sort of mixing aerospike nozzle (as E-D nozzle wouldn't provide an usable opportunity to burn external air)

[Archibald]

In something with an adjustable inlet flow like SABRE, especially as you get into speeds over Mach-2/3 where adjustments are constantly happening, it would seem questionable to incorporate unless you have a lot of GH2 to deal with. Adding a few "100k/s" isn't really helpful unless it is consistent enough to effect the average ISP over the whole flight which is doubtful, and again the whole point is that deep-cooling means you have a lot less waste GH2 in the first place. Part of this is because unlike most "combined cycle" engine types the SABRE actually and air-breathing rocket engine so there isn't any convenient place to dump the excess GH2 into the flow path so you can't dump it in the afterburner or duct-burn it as is done in most CC engine designs. So burning it in a bypass, or spill-ramjet to make up some loss during portions of the flight makes sense, especially if you have an intake air imbalance. But on the other hand with a constantly adjusting intake system you shouldn't have that much of an imbalance and it shouldn't be significant enough over the air-breathing flight envelope to justify a specifically designed spill-ramjet.

Nice if you can get it cheap and easy but nothing I've seen says that's the case if you don't have a LOT of GH2 to burn off.

Randy

HOTOL actually cooled air by dumping large amounts of liquid hydrogen that then went to waste. Skylon is trying not to bleed liquid hydrogen, hence the helium loop (AFAIK !)

[RanulfC]

Does that imply that eliminating spill ramjets would lead to running fuel rich out the rocket nozzles then? Is the simplicity worth the direct losses there, compared to either a spill ramjet, or some sort of mixing aerospike nozzle (as E-D nozzle wouldn't provide an usable opportunity to burn external air)

I thought the engines were already "fuel-rich" which is why I wasn't thinking they could 'dump' into the them

HOTOL actually cooled air by dumping large amounts of liquid hydrogen that then went to waste. Skylon is trying not to bleed liquid hydrogen, hence the helium loop (AFAIK !)

The engine design was similar to SABRE as far as anyone can tell so I doubt it dumped "large amounts" so the same issue applied. Looking at various versions of the HOTOL design you'll note that all the way to the last iterations the air intake system was capable of incorporating some type of by-pass or spill burner because the rockets engines weren't directly in the  flow-path as they are with SABRE. This made the HOTOL engine much more complex and heavy but did away with the "dump" issues as you can see in some engine illustrations, and descriptions since it used the some of the 'waste' to power the compressor turbine and some to power a pre-burner. Incorporating a spill-ramjet would have been pretty straight forward especially when they were using the vertical ramp intake system similar to the XB-70 which had a pretty straight forward intake-spill system.
http://www.aerospaceweb.org/question/spacecraft/q0202.shtml
https://en.wikipedia.org/wiki/HOTOL#/media/File:HOTOL.JPG
http://www.astronautix.com/r/rb545.html

And yes that's why SABRE is using the helium loop instead of direct LH2 cooling but again that was pretty much the point in that you had much more GH2 to deal with in the RB545 than in SABRE and improvements continue to reduce the 'waste' but dealing with what there is seems to be a minor issue that continues to crop up.

Which is to be expected of course, issues always crop up

Randy

[93143]

According to my calculations, SABRE 2/3 as represented in the C1 spreadsheet used roughly 2.7 times as much hydrogen as the core could burn (stoichiometric - if you're airbreathing and have got spill ramjets, I'm not sure running the core fuel-rich does you any good) over the whole airbreathing trajectory.  The ratio varied from about 2.4 to about 2.9 with increasing airspeed.

If one assumes that (a) Skylon D1 goes through exactly the same delta-V before transition as C1, and (b) my calculation of said delta-V (3657 m/s) from the C1 spreadsheet is correct, SABRE 4's average Isp can be calculated from the data in the NISSIG presentation as approximately 4889 s.  The value I got for SABRE 2/3 was 2274 s.  This yields an equivalence ratio for SABRE 4 of about 1.25.

Not bad...  of course that's not constant during the trajectory...

[FutureSpaceTourist]

Session ST-02 "Resuable Launch Vehicles & Technology" Co-chairs: Adam Dissel  (Reaction Engines, Inc); Barry Hellman (Air Force Research Laboratory)

Tues 13 Sep 2016 4:00-4:30 PM

AIAA-2016-5320. Two Stage to Orbit Conceptual Vehicle Designs using the SABRE Engine B.M. Hellman; J.E. Bradford; B.D. St. Germain; K. Feld

Couple of quotes from this talk:

Jeff Foust ‏@jeff_foust 1h1 hour ago

Barry Hellman, AFRL: SABRE engine technology very fascinating, but it alone doesn’t solve vehicle issues of SSTO Skylon. #AIAASpace

https://twitter.com/jeff_foust/status/775834301082406912

Jeff Foust ‏@jeff_foust 1h1 hour ago

Hellman: instead studied using SABRE on TSTO vehicle concepts, including partially reusable design with 5000 lb payload. #AIAASpace

https://twitter.com/jeff_foust/status/775834522097115138

[john smith 19]

Couple of quotes from this talk:

Jeff Foust ‏@jeff_foust 1h1 hour ago
Barry Hellman, AFRL: SABRE engine technology very fascinating, but it alone doesn’t solve vehicle issues of SSTO Skylon. #AIAASpace

https://twitter.com/jeff_foust/status/775834301082406912

Was anything going to do that if they decided something cannot be done?

Jeff Foust ‏@jeff_foust 1h1 hour ago

Hellman: instead studied using SABRE on TSTO vehicle concepts, including partially reusable design with 5000 lb payload. #AIAASpace

https://twitter.com/jeff_foust/status/775834522097115138

Looks like I will finally have to get a twitter account.