The Reaction Engines Skylon/SABRE Master Thread (6)

[john smith 19]

From this simple diagram it looks like SABRE 4 should be able to work with different types of fuel such as LCH4, is that so?

That depends. A compressor that can tolerate 127c inlet temp obviously needs less cooling. The question would be will you retain this in an operational vehicle? If not better to bite the bullet and go with LH2 from day one. The downside would be if you still want to go with SSTO you take a big hit on Isp. Air breathing is up to Mach 5.5. Orbital is more like M23. Air breathing can deliver several 1000 secs of Isp but I doubt it can make up for the loss in payload mass fraction that the lower Isp of LCH4. How important that is only REL know, although I'm sure they can (and have) modeled it.

Drop tanks for takeoff->subsonic climb seems not unreasonable, after examining the zero start takeoff test envelope.

AFAIK the only drop tank for cryogens was the Shuttle ET. Unless they were very low cost I think REL would prefer to get all the test flights done with a straight vehicle and avoid the complexity and expense, since they would be the only customer for this.

Don't forget there are carrier planes available, such as StratoLaunch's Roc, and perhaps the Virgin Galactic SS2 carrier plane, which could do an air launch to reach other test envelopes.

Is the Roc complete yet? AFAIK it's still being built, let alone had its first test flight.  White Knight 2 is flying but the problem with either is that they get  REL even further into the US ITAR rules minefield. 

[hkultala]

From this simple diagram it looks like SABRE 4 should be able to work with different types of fuel such as LCH4, is that so?

1) It still needs quite cool fuel to be able to cool the air
2) All the pipe and pump sizes are calculated for H2.

[lkm]

There are some interesting renders on the Reaction Engines Twitter feed (attached).
The first one shows the 'D21' test vehicle, a Skylon, and another twin-engined vehicle.  This vehicle is also shown in the second render.  It doesn't look like the AFRL TSTO concept - could it be an intermediate test vehicle?  Apologies if you've already covered this upthread and I missed it.
I note that one render shows it with straight engine nacelles, and the other with Skylon's curved nacelles.

This is originally from some university research paper. They were studying an alternative aerodynamic configuration for skylon, and doing some CFD modeling  and comparing this to the official skylon configuration.

The paper was released something like one year ago.

I'm not so sure about that. They're similar to cfastt but not the same. Cfastt hasn't got winglets, and has a flat nose and curved trailing edges on the wings and the rear isn't totally flat on top.
To wild mass guess for a moment, to me it looks  like images from their projected test program and that along with the 'D21' they're thinking about a sub scale x-plane with 2 Ground Development to test the technology of the full scale Skylon and that the other image is perhaps the mythical Skylon E, the result of BAE aerodynamicists performing the same optimisations that resulted in cfastt and thus resulting in an aircraft that looks very similar, which would explain why the x plane resembles it.

[john smith 19]

I'm not so sure about that. They're similar to cfastt but not the same. Cfastt hasn't got winglets, and has a flat nose and curved trailing edges on the wings and the rear isn't totally flat on top.
To wild mass guess for a moment, to me it looks  like images from their projected test program and that along with the 'D21' they're thinking about a sub scale x-plane with 2 Ground Development to test the technology of the full scale Skylon and that the other image is perhaps the mythical Skylon E, the result of BAE aerodynamicists performing the same optimisations that resulted in cfastt and thus resulting in an aircraft that looks very similar, which would explain why the x plane resembles it.

The "D21 like vehicle would be about the simplest configuration you could use if you only had one engine available. If you can afford a pair then you could go for something more Skylon like. The other fairly obvious option would be something resembling the V1

Moving engines to mid wing lowers the mass at the end of the cantilevers but probably complicates the airflow quite a lot. The SR71 essentially attached them to the upper portion of the engine housing, so servicing the engine meant you needed a building capable of holding the whole length of the wing and the engine cowling in the up position.

My feeling is that structural analysis is on firmer ground than airflow analysis so engines on wing tips is more structurally risky but less aerodynamically risky, and airflow is the one that's much less predictable.

[knowles2]

May be we will be lucky and Reaction Engines new site will give us details of their plans and they plan to proceed over the next 5 years or so.

[adrianwyard]

I just noticed the temporary home page on REL's site includes a small graphic of a test vehicle, although what's depicted is different from the other D21-like ones elsewhere. It has wing-tip vertical stabilizers as opposed to one on the fuselage, and what could be an additional square inlet on top...

[john smith 19]

I just noticed the temporary home page on REL's site includes a small graphic of a test vehicle, although what's depicted is different from the other D21-like ones elsewhere. It has wing-tip vertical stabilizers as opposed to one on the fuselage, and what could be an additional square inlet on top...

You're right. the winglets are a departure from the D21 design although the wing layout looks pretty similar. Depending on the angle of the design that could be an additional inlet of some kind or an opening in the top surface. The classic reason for something like that would for an in flight refueling receptacle, which makes no sense. 

I note the full graphic shows Skylon on the left and the A2 design for the LAPCAT M5 hypersonic transport project on the right.

[lkm]

If we accept for the sake of argument that it is a sub scale x plane design using two GDE's then by simple scaling it should be able to put a couple of mt in orbit, and there does seem to be a small payload bay area on the render. So is there any utility to that beyond testing? Is anyone going to come along and say we'd like the small one please?

[Rocket Science]

I just noticed the temporary home page on REL's site includes a small graphic of a test vehicle, although what's depicted is different from the other D21-like ones elsewhere. It has wing-tip vertical stabilizers as opposed to one on the fuselage, and what could be an additional square inlet on top...

I wonder if it is a ram intake to cool the outside of the engine bell and to use the hot expanded air to contribute to overall thrust...

[Ravenger]

It's a very interesting picture. The thing that confuses me is that the rectangular 'intake' feature doesn't make much sense given the streamlining of the vehicle.

I was wondering if what we're looking at is actually a wind tunnel or test model  (for air dropping or a rocket sled) and the strange feature on top is some sort of mount. 

[dror]

If we accept for the sake of argument that it is a sub scale x plane design using two GDE's then by simple scaling it should be able to put a couple of mt in orbit, and there does seem to be a small payload bay area on the render. So is there any utility to that beyond testing? Is anyone going to come along and say we'd like the small one please?

I realy hope so.
Smaller payloads can use the advantages of a SSTO more intuitively than bigger ones.
A small skylon can take care of ISS ferry and resupply and deliver most of the LEO payloads. With on orbit refueling it can also deliver most of the SSO payloads.
But I remember reading here that they weren't interested in developing multiple vehicles, and that the guiding parameter was payload diameter, rather than mass.

[john smith 19]

It's a very interesting picture. The thing that confuses me is that the rectangular 'intake' feature doesn't make much sense given the streamlining of the vehicle.

I was wondering if what we're looking at is actually a wind tunnel or test model  (for air dropping or a rocket sled) and the strange feature on top is some sort of mount. 

The mount is usually called a "stinger."  That's possible. It would depend what part of the model you specifically wanted information about as for aircraft they usually have the mount at that extreme rear.

If we accept for the sake of argument that it is a sub scale x plane design using two GDE's

GDE's?

Most speculation seems to have been around it being a launch bay for a 2nd or 2 stage LV to take small payloads (110Kg) to LEO.

Once you get away from full reusability operating costs rise considerably and you're in danger of being the maker/operator business model.

[lkm]

If we accept for the sake of argument that it is a sub scale x plane design using two GDE's

GDE's?

Most speculation seems to have been around it being a launch bay for a 2nd or 2 stage LV to take small payloads (110Kg) to LEO.

Once you get away from full reusability operating costs rise considerably and you're in danger of being the maker/operator business model.

GDE: Ground Development Engine which from the slide seems to be what they're calling a single propulsive unit SABRE, although given SABRE now seems to be able to consist of an arbitrary number of units behind an appropriately sized precooler and compressor I think they need a new naming scheme.

To my eyes the launch bay isn't really that big on the 'x plane', maybe a couple of metres long, is that big enough for any sort of existing  second stage and a payload ?

[oddbodd]

Looks like the new website is live... and it's... underwhelming.

A fairly generic site with pretty pictures, and most of the older interesting info gone so far as I can tell. More a brochure than an information site.

Also seems to me that focus has shifted toward hypersonic flight, with space access almost feeling like an "oh yeah, that too". It gets mentioned, but always secondary to hypersonic flight or mentions of how quickly you could fly from X to Y.

Is it just me, or is this picture (from the careers page) a little telling:
https://www.reactionengines.co.uk/wpcms/wp-content/uploads/2016/05/1607-REL-FIA2016-012_B-1-e1471338140911.jpg

Varville seemingly being pushed into the background, and no sign of Alan Bond. It's such a shame that we don't have a Brit version of Elon Musk. A bit of vision, some balls, and a honking big bag of cash. I'd love to be proved wrong, but it looks like the original vision is as dead as the proverbial parrot. Splattered over the windscreen by the relentless drive to justify ones existence on a per-quarterly clock.

[a_langwich]

Looks like the new website is live... and it's... underwhelming.

Isn't the lower vehicle in the header on this page
https://www.reactionengines.co.uk/vehicles/

a side view of the D-21-like vehicle mentioned above?  Or was that already known?

[Star One]

Looks like the new website is live... and it's... underwhelming.

A fairly generic site with pretty pictures, and most of the older interesting info gone so far as I can tell. More a brochure than an information site.

Also seems to me that focus has shifted toward hypersonic flight, with space access almost feeling like an "oh yeah, that too". It gets mentioned, but always secondary to hypersonic flight or mentions of how quickly you could fly from X to Y.

Is it just me, or is this picture (from the careers page) a little telling:
https://www.reactionengines.co.uk/wpcms/wp-content/uploads/2016/05/1607-REL-FIA2016-012_B-1-e1471338140911.jpg

Varville seemingly being pushed into the background, and no sign of Alan Bond. It's such a shame that we don't have a Brit version of Elon Musk. A bit of vision, some balls, and a honking big bag of cash. I'd love to be proved wrong, but it looks like the original vision is as dead as the proverbial parrot. Splattered over the windscreen by the relentless drive to justify ones existence on a per-quarterly clock.

Or you empathise what you have at least a half realistic chance of getting financed and built in the short to medium term. Rather than complaining about the loss of something that probably didn't have a chance of becoming reality until at least the technology had actually proved itself in practical use.

There is also nothing in the new site that says that they've abandoned their longer term goals. Especially given on the vehicles page the first thing that's mentioned is space access, which hardly tallies with a downgrading of the importance of space.

I personally think the new site looks far more presentable and modern.

[Mutley]

The part i found most interesting was on this page:
https://www.reactionengines.co.uk/sabre/#6

"There are three core building blocks to the SABRE engine, the pre-cooler, the engine core and the rocket system. We plan to demonstrate each of these independently at flight scale in 2017, 2018 and 2019 respectively.

We’re about to start building a significant new UK test site to test critical subsystems and aim to test a fully integrated engine in 2020."

[Alpha_Centauri]

Looks like the new website is live... and it's... underwhelming.

Isn't the lower vehicle in the header on this page
https://www.reactionengines.co.uk/vehicles/

a side view of the D-21-like vehicle mentioned above?  Or was that already known?

Yes that's new. Hard to tell but it looks like the possible intake mentioned previously is some kind of auxiliary jet. Can't fathom why though.

[john smith 19]

This is the 3rd generation of the REL website. It's certainly the most polished and about the least informative, if you're aware of the previous versions in terms of what their background work has been.  All the PDF's are gone AFAIK.

Pulled up the SABRE page, tried to scroll down.Needed to allow "typekit" before it would let me. I'm wondering if the site was tested by someone on the laptop they wrote it on instead from another browser outside their network. 

I think the most interesting thing about this page is their plan to test the precooler, engine core and rocket system in 2017/18/19 at flight scale, with the goal of a flight vehicle in 2020.

Note they did not say full trajectory, IE to LEO, so I doubt this will be an SSTO, but even a few seconds past the rocket transition (in a flight vehicle) would retire a lot of risk.

Possibly the most interesting stuff was a couple of press releases. In July this year they were part of a consortium headed by "Orbital Access Ltd" looking at small space launchers for the UK. Interestingly this was specifically in regard to HTO and included SSTL and both Strathclyde and Glasgow universities. They are based at Prestwick airport.

That said their website shows something quite a lot like an Orbital-ATK Pegasus.

Another item dates from 2015 when REL announced they had been working with the Defense Science Technology Laboratory of the MoD since 2013 on military applications of SABRE.

IIRC that pre dates their work with the USAFRL.

The new website is a bit more outward looking and REL looking to be trying to capitalize on the skills and IP they've generated over the last thirty years to be more self funding in pursuing their goals.

[john smith 19]

Looks like the new website is live... and it's... underwhelming.

Isn't the lower vehicle in the header on this page
https://www.reactionengines.co.uk/vehicles/

a side view of the D-21-like vehicle mentioned above?  Or was that already known?

You're right. It is new. On the "placeholder" page you appeared to be looking down from the front onto the vehicle. I thought it could be in flight refueling receptacle, but that made no sense. There are no known LH2 flight refueling tankers anywhere in the world.

From the side it's obviously a separate fairing. It's possible it could be housing an auxiliary engine for return to base when it finishes its test flight but this is not as sensible as it seems. If this will be a sub scale SABRE presumably it will have close to SABRE 4 T/W IE 14:1. No jet is that good. It would make more sense to glide back with the main intake closed (to limit LH2 use) to a low enough speed then restart the SABRE briefly. Remember SABRE in air breathing has the Isp of a jet, not a rocket.  The features that made this a good idea for Shuttle don't really apply.

So what is it. Some sort of payload bay? Maybe. What it reminds me quite strongly of is the XCOR plan for the Lynx spaceplane.  While part of their business plan was near space joy rides for wealthy tourists they were also looking at the small sat launch market. Their plan was the pilot would fly solo, with a small rocket in a dorsal pod, to protect it from the worst of the reentry heating. Once high and fast enough they would put the Lynx into an appropriate attitude, open it and fire the rocket. Since this was in place of a passenger the whole package was planned as a separate unit to be mounted, and de-mounted as needed.

We know REL were looking to do a liquid fueled sounding rocket to simulate air breathing performance using IIRC LOX/Ammonia/GN2 to get the right gas properties. How big a payload would depend on what the flight vehicles performance was. SSTL satellites are in the 70cm cube, 100Kg range IE well above cubesats.

It's also interesting the head of their US office came from the LM branch that deals with "Responsive Space." That's the US military term for short notice, fast turnaround launches to increase, or replace space assets to carry out a particular task.