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#26 2012-07-18 17:29:43

orionblade
Member
From: Hampton Virginia
Registered: 2003-01-14
Posts: 60

Re: Reaction Engines

Der Germans can supply the CNC machines to cut all the parts that the other guys design. :-D

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#27 2014-01-19 14:28:32

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,706

Re: Reaction Engines

Bond’s Skylon to achieve dream of single-stage-to-orbit vehicle

http://newmars.com/forums/viewtopic.php … 13#p126513

SpaceNut wrote:

What we are talking about is a hybrid jet/rocket engine and Why BAE Could Lead the Next Commercial Space Launch Revolution with a SABRE engine.

Among the critical technology breakthroughs Reaction engineers claim is a heat exchanger that can cool incoming air as hot as 1,800 degrees Fahrenheit to subzero temperatures in a fraction of a second, allowing the engine to function at higher speeds than traditional air-breathing jet engines.

So condensing the airs oxygen to feed the rockets engine. About the same as turning on an onboard LOX supply when the scram jet engine doors are closed and turning it off so that the rocket engine can fire.

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#28 2014-01-19 16:01:16

Tom Kalbfus
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Registered: 2006-08-16
Posts: 4,401

Re: Reaction Engines

Interesting article. Just as an aside, maybe Mr Bond could name one of his ships "Moonraker" What do you think? wink

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#29 2014-01-19 17:49:37

louis
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From: UK
Registered: 2008-03-24
Posts: 5,868

Re: Reaction Engines

15 tonnes capacity to LEO?  That could be a lot of passengers - 50 maybe?


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#30 2015-01-28 21:53:38

SpaceNut
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From: New Hampshire
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Posts: 19,706

Re: Reaction Engines

UK spacecraft project completes major review

Reaction Engines has passed the first development milestone for a hybrid rocket engine designed to power its single-stage-to-orbit Skylon spacecraft.
Passing the preliminary requirements review has kept the programme on track to launch a demonstration of a full-scale Sabre test engine before 2020, Reaction Engines says.
The UK-based start-up calls Sabre potentially the “greatest advance in propulsion since the jet engine”.
Unlike two-stage-to-orbit designs, the Skylon is designed to take-off from a runway and launch into space without a booster stage. At high altitudes, the air-breathing engine uses a pre-cooler system to dramatically raise the pressure ratio of oxygen entering the ramjet inlet. This cooled, compressed air is then mixed with liquid fuel and combusted in a rocket engine.
The latest review of the full-scale engine comes about three years after Reaction Engines completed a series of component-level tests.

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#31 2015-01-29 15:05:17

Quaoar
Member
Registered: 2013-12-13
Posts: 489

Re: Reaction Engines

Here is a mars mission concept based o Skylon orbital transport:

https://www.youtube.com/watch?v=Uj45Au3KCRg

It uses a GW-like orbital assembly facility

http://exrocketman.blogspot.it/2014/02/ … ility.html

and an artificial gravity long axis spinning spaceship-

Last edited by Quaoar (2015-01-29 15:10:17)

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#32 2016-05-09 14:07:40

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Reaction Engines

Had an idea yesterday that probably belongs under reaction engines.

An arcjet basically works in the same way as a plasma torch.  The arc reaches temperatures of 10,000 - 20,000K, which is above the boiling point of any substance known to man.  With this in mind, could an arcjet use dust as a propellant?  By this I mean finely ground regolith from the lunar surface or a body like Phobos?  The basic idea would be to blow the dust through the arcjet using a diffuse gas.  The arc would vaporize the dust.  If it works, a Mars mission could be propelled by solar powered arcjet.  The outbound journey could use pulverised upper rocket stage as propellant.  The return journey would use Phobos surface regolith.

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#33 2016-05-09 22:24:53

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,150
Website

Re: Reaction Engines

General Dynamics MR-510 arcjet thruster uses hydrazine as propellant. Not UDMH or MMH, but pure hydrazine. So how does that work with regolith?

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#34 2016-05-10 06:11:09

Antius
Member
From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Reaction Engines

Not sure.  Hydrazine can be stored as liquid and decomposes into low molecular mass components, hence a better ISP.  Most dusts would have higher molecular mass and high heat of vapourisation so would be inferior on an ISP basis.  But dust is free in most cases.  The question is, would it work?

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#35 2019-10-27 12:46:26

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,706

Re: Reaction Engines

I think I did post about this type of engine before where the intake scoups up oxygen on its way up from launch to reduce mass.

Air-breathing engine precooler achieves record-breaking Mach 5 performance  ESA-supported development of the air-breathing SABRE engine, paving the way for a revolution in space access and hypersonic flight.

The Synergetic Air-Breathing Rocket Engine (SABRE) is uniquely designed to scoop up atmospheric air during the initial part of its ascent to space at up to five times the speed of sound. At about 25 km it would then switch to pure rocket mode for its final climb to orbit. This ground-based test achieved the highest temperature objective of the company's 'HTX' hot heat exchanger test programme: it successfully quenched airflow temperatures in excess of 1000 C in less than 1/20th of a second.

The tests demonstrated the precooler's ability to cool airflow at speeds significantly in excess of the operational limit of any jet-engine powered aircraft in history. Mach 5 is more than twice as fast as the cruising speed of Concorde and over 50% faster than the SR-71 Blackbird aircraft - the world's fastest jet-engine powered aircraft.

This most recent test builds upon the success of previous HTX hot tests undertaken in April which saw the precooler successfully operate at temperatures of 420C - matching the thermal conditions corresponding to Mach 3.3 flight.

This speed is where the magic of continual increase that this become significant as we need to go faster to get to orbit.

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#36 2020-04-02 14:23:20

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,706

Re: Reaction Engines

repost

elderflower wrote:

Sabre engine, {if it can be made to work!} will solve many of the SSTO problems.
https://www.reactionengines.co.uk/news/ … conditions

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#37 2020-04-02 17:28:52

tahanson43206
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Registered: 2018-04-27
Posts: 3,531

Re: Reaction Engines

Could someone please investigate to see if this type of vehicle would be a suitable candidate for matching with the ElectroMagnetic Launcher concept under discussion in kbd512's topic by that name.

The NASA proposal from 2009 (as listed in kbd512's topic in Post #5) offered a ramjet vehicle as the air breathing stage.  The Sabre engine vehicle would (presumably) be able to fly all the way to orbit, and having a nice boost before it ignites its engines would surely add to its appeal.

(th)

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#38 2020-04-02 19:07:56

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,078
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Re: Reaction Engines

SABRE does not operate as an airbreather above Mach 5.  It is just a hydrogen-fueled rocket running with stored oxygen or air they scooped up on the way to the Mach 5 point.  I hope they are separating the oxygen from the nitrogen in the air they liquify,  because otherwise,  the thrust and Isp potential is much lower. 

It's not a direct airbreather.  Captured air is liquified,  then (hopefully) the oxygen and hydrogen fuel fed to a more-or-less conventional rocket engine.  Because it is a rocket engine,  the frontal thrust density of a SABRE nacelle is proportional to a chamber pressure measured in thousands,  not dozens of psi. 

Ramjet chamber pressures are typically about 4-5 times higher than local atmospheric.  Turbine is heavier,  but higher frontal thrust density because its chamber pressures are typically 12-18 times higher than atmospheric.  Frontal thrust density is what limits your climb angle or acceleration capability with an airbreather. 

Thrust and drag decrease in the thin air up high,  but weight does not.  That is where "service ceiling" comes from.  That is fundamentally why the scramjet powered X-30 of about 1990 could not have worked even if its scramjet propulsion had been ready to apply (which it still is not today).

The way around that is not combined-cycle engines,  but parallel-burn dual propulsion.  Combined-cycle compromises the performance of each component trying to make incompatible geometries "go together" as a single unit,  and ends up killing the performance.  That is why you still cannot buy one off-the-shelf from any manufacturer.  But you can buy rockets,  ramjets,  and gas turbines off-the-shelf. 

Lower down in the atmosphere,  if you burn rocket and ramjet engines simultaneously,  you can climb vertically while accelerating,  but have majority airbreather in your thrust mix.  High up in the thin air,  you can still do that,  but your mix is mostly rocket.  Much over 30 km/100 kft you'll have to shut the airbreather down,  they cannot work at internal pressures that low. 

There is no panacea there.

As for EM launch,  anything capable of generating thrust could be powering the vehicle flung into the air by such a device.  But your trajectory is inherently afflicted by drag,  because it is not vertical.  Vertical leaves the air faster,  getting rid of drag losses sooner.  A trajectory that stays low at too high a speed will eat up your potential gains in drag losses. 

Even the vertical launch guys are only doing about Mach 2 to 3 as they leave sensible air at 30+ km more or less vertically.  And staging is only about 2.5-ish km/s at about 45 km or so,  which is pretty much essentially exoatmospheric,  and almost horizontal. 

I am intrigued by the SABRE engine concept,  and hope they succeed.  It is the Skylon airframe shape that I don't think can work.  It leaves the sensible air at only Mach 5 and about 45 km,  so it won't suffer fatally from shock impingement heating on ascent.  But during entry,  speeds are a whole lot higher coming down to 45 km,  and the shocks shed from the nacelle inlet spikes are going to cut the wings off.  Every single time they try to enter with that shape.

You cannot fly above about Mach 5 at any altitude where there is even thin air with any sort of parallel-nacelle shape.  The shock impingement heating will always cut your vehicle apart. 

GW

Last edited by GW Johnson (2020-04-02 19:20:52)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#39 2020-04-03 04:30:47

tahanson43206
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Registered: 2018-04-27
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Re: Reaction Engines

For GW Johnson re #39

Thanks for taking a look at the potential benefit of EML for SABRE.

The low G force achievable by the proven catapult technology would appear to point toward an application for passenger vehicle acceleration, with a blended solution of air breathing engines and rocket powered ones. 

Your cautions regarding the vehicle shape for return from orbit imply (to me at least) that the designers will address the issue if they are successful in building the ascent capability at all.  The achievements to date seem impressive, but they are just promising hints of potential at this point.

(th)

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#40 2020-04-03 08:03:42

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,706

Re: Reaction Engines

While the mach 5 speed is impressive and I am sure that we are near space (24 mi) when we achieve it. The question is how much oxygen is onboard to feed the rocket engines for the remaining part of the trip to orbit as we will need to accelerate to above mach 10...

Of course for the eml launch we would be using it as the carrier to the rocket that would finish the trip with the reaction engines returning to earth.
GW is correct with the need to seperate the nitrogen for the oxygen to be of any use for the oxidizer for the remaining portion of the rockets efforts to achieve orbit.

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#41 2020-04-05 06:03:41

elderflower
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Registered: 2016-06-19
Posts: 1,260

Re: Reaction Engines

The vehicle design carries LOX for the rocket stage of the flight, and for deorbiting. I don't think the engine separates air for these purposes. It can run as a turbojet to an extremely high altitude by virtue of its cooler, but beyond that it runs basically as a normal rocket.
The previous design vehicle, of which the present one is a development, was called HOTOL and it didn't have the engines in separate nacelles, it was mounted in the back of the vehicle.

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#42 2020-04-05 06:54:19

tahanson43206
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Registered: 2018-04-27
Posts: 3,531

Re: Reaction Engines

For elderflower re #42

In your post, you included a section that I am wondering about, and hope you would be willing to develop further.

The vehicle design carries LOX for the rocket stage of the flight, and for deorbiting.

A few posts ago, GW Johnson expressed (what I took to be) doubt that the Skylon design could return safely from orbit, if the plan were to return at orbital speeds.  As I understood his comments, the vehicle structure would not be able to withstand the heating and stress of re-entry at that velocity.

However, the word "deorbiting" could mean more than just dropping  velocity enough to fall into a region where drag would pull the vehicle down.

It ** could ** mean reducing the velocity to the point the vehicle could return safely.

However, ** that ** would imply the vehicle had enough LOX (and H2) on board to not only reach orbit in the first place, but then to reduce velocity enough to be able to return safely.

(th)

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#43 2020-04-05 09:07:53

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,706

Re: Reaction Engines

Planes only need to glide to earth profile as they use a runway to land not using any fuel other than to deorbit burn to slow the vehicle and all that is needed then is a heatshield to protect the craft on re-entry. The question for that is the engines being tempered to withstand that heat of the re-entry.
There are other topics that may have more details of the vehicle..

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#44 2020-04-05 11:27:34

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,078
Website

Re: Reaction Engines

In air at temperatures where the sound speed is around 300 m/s = 0.3 km/s,  a Mach 5 speed corresponds to 1.5 km/s.  Compare that to orbit speed at 7.9 km/s.  The usual deorbit burn is around 100/s velocity change,  or maybe a bit more,  but not a whole lot more. 

For a parallel-nacelle configuration to survive shock impingement heating,  your entry interface speed has to be under 2 km/s,  most likely nearer 1.5 km/s,  depending upon what you are made of.  That's a deorbit burn on the order of 6.4 km/s vs 0.1 km/s.  That's a whole 'nother very large rocket stage!

Why not just eliminate the parallel nacelles and let aerobraking do the job without any shock impingement risk,  instead of carrying all that ridiculous extra deorbit propellant?

As for shock impingement heating,  that very nearly downed an X-15 at Mach 6.7 with an Inconel-X skin covered in ceramic paint,  back in 1969.  Pete Knight flew that one.  I put an article up on "exrocketman" about that,  with photos of the damage.  A few more seconds,  and the shock wave would have cut the tail off the bird and killed him. That article is "Shock Impingement Heating Is Very Dangerous",  dated 12 June,  2017.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#45 2020-04-05 11:49:09

tahanson43206
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Registered: 2018-04-27
Posts: 3,531

Re: Reaction Engines

For GW Johnson re #45

Thank you for considering the question.

The plane hasn't flown yet, so there is plenty of time to address the challenge of re-entry.

It seems to me that no one knows how effective the design team will be in saving oxidizer by using atmospheric oxygen.

It might be possible to estimate the savings, and I have to believe the investors to date have had faith that projections of a win at the end of this process are reasonable, but only actual tests will reveal the answer.

I think this is probably a quote from GW Johnson, somewhere along the line.

(th)

Last edited by tahanson43206 (2020-04-05 11:50:43)

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#46 2020-04-05 13:36:39

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,706

Re: Reaction Engines

GW Johnson wrote:

Louis:

No,  the real problem is one of making heat transfer occur as fast as the other propulsion processes,  when it truly and fundamentally does not want to be that fast.  Skylon's engine is basically a liquid air cycle engine.  No one else has ever made liquid air that fast,  ever.  But,  Reaction Engines just might.  I'm rootin' for 'em. 

GW

edit to add in content
ttp://newmars.com/forums/viewtopic.php?pid=126514#p126514

GW Johnson wrote:

SABRE isn't an airbreathing engine in the same sense as a ramjet,  scramjet or gas turbine.  It's a sort of a combined-cycle device,  except that it is not really one of those either.  It's really a variant on the 1960's idea of the liquid air cycle engine (LACE),  which is really a rocket engine with machinery for scooping up and liquifying air added to it.  It's fundamentally always a rocket,  and not thrust-limited by altitude low density.  Only the air scoop/liquifaction rate suffers the low density problem at altitude. 

The bugaboo with that concept all these decades was totally-inadequate heat transfer technology for rapid liquifaction.  If the Brits have really solved that difficulty (and I do hope they have!!!!),  then this will be a significant advancement.  I'd really like to see it fly. 

I am worried about their airframe shape for HOTOL with its tip-mounted SABRE engines,  though.  The strong shock waves off the compression spikes are going to cut into the wing leading edges very severely above Mach 4 or 5.  This may well be a fatal problem for reentry at Mach 25;  so I wonder how hard they have really looked at their airframe concept relative to these problems. 

Things like Avcoat and PICA will be inadequate under shock-wave impingement,  that's why no reentry vehicle has ever had adjacent connected nacelles.  They'll likely need several inches of silica-phenolic in the shock impingement zones,  heavy as it is,  and they'll likely need to replace it every flight. 

GW


http://newmars.com/forums/viewtopic.php … 22#p126522

Antius wrote:

I don't see how this could possibly work.  The engine has to physically stop an airstream moving at kilometres per second, cool it from +1000C to -200C and overcome latent heat of boiling, only to inject it into a rocket engine where it can burn to produce thrust.  Where is the heat sink for cooling the incoming air?  Even if the fuel is cryogenic it won't help very much with cooling.  The airstream outweighs the fuel 20-1 at stoichiometric ratios.  The drag imposed by the air on the intake would rival the thrust produced by the engine long before orbital speed were reached (exhaust velocity would be at least 40% lower in air fed mode as the combustion products weigh 3 times more).


http://newmars.com/forums/viewtopic.php … 23#p126523

GW Johnson wrote:

Essentially stopping a supersonic or hypersonic airflow is exactly what the inlets of ramjets and gas turbine engines do.  And yes,  the inlet ram drag is on the order of at least half the nozzle thrust force.  A Mach 3 gas turbine is doing this with air at about 0.9 km/sec,  and a Mach 5 ramjet does it with air at 1.5 km/sec.

The only real problem arises above about Mach 4 or 5,  when the captured decelerated air starts approaching flame temperatures.  I show inlet total temperatures near 3000 F (near 1650 C) at Mach 6 100,000 foot conditions,  for example.  There's certainly no such thing as cooling air for vehicles trying to fly at these speeds. 

The SABRE engine is liquid hydrogen fueled.  I do not know how they separate the nitrogen or what they do with it,  but they claim a breakthrough in heat exchanger technology that allows them to liquify the air as fast as they scoop it up,  using the hydrogen as the heat sink.  In rocket mode,  it burns hydrogen and (largely) air-derived oxygen that it stored in tanks.  The chamber pressure is typical rocket:  fairly high. 

The high heat exchange rate and heat exchanger icing risk are the two historical show-stoppers with that,  but they claim to have solved those problems.  What little ground test data I have seen points in the direction of verifying their claims,  but they have a long way yet to go before they fly. 

And no,  they do not operate the air scoops above Mach 5 on ascent,  or at all during descent.  I think the HOTOL launch trajectory says they are climbing and accelerating at Mach 5 at somewhere around 100,000 ft when they cease scooping air and go plain rocket on the propellants they have on-board.  Above that flight point there just isn't enough air to do anything with it that is useful.  They leave the sensible atmosphere long before reaching anything approaching orbital speeds. 

The idea is not to take off with a full load of LOX,  but to scoop up a major portion of it as they ascend. 

As I said in the other posting,  the real dangers occur during reentry.  How they protect their air scoop and machinery I have no idea,  although a static gas column is the best heat shield by far.  Perhaps they simply allow no flow through the inlet by closing it off,  I don't know.  But the inlet compression spike sticks out and is at risk,  at least. 

And as I said in the other post,  the real vulnerability here is the wing leading edges,  hit by shock impingement coming off those spikes.  That is an inherent risk they face for deciding to use wingtip-mounted engines.  It's far worse on reentry,  but has become significant on ascent by about Mach 4-ish. 

GW

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