
Skylon’s SABRE Engine Passes a Big Test - sohkamyung
https://www.universetoday.com/143810/skylons-sabre-engine-passes-a-big-test/
======
nickpinkston
In case anyone was confused by the article's description, here's the
Wikipedia:

"SABRE (Synergetic Air Breathing Rocket Engine) is a concept under development
by Reaction Engines Limited for a hypersonic precooled hybrid air-breathing
rocket engine. The engine is being designed to achieve single-stage-to-orbit
capability, propelling the proposed Skylon spaceplane to low Earth orbit.
SABRE is an evolution of Alan Bond's series of liquid air cycle engine (LACE)
and LACE-like designs that started in the early/mid-1980s for the HOTOL
project.

The design comprises a single combined cycle rocket engine with two modes of
operation. The air-breathing mode combines a turbo-compressor with a
lightweight air precooler positioned just behind the inlet cone. At high
speeds this precooler cools the hot, ram-compressed air, which would otherwise
reach a temperature that the engine could not withstand, leading to a very
high pressure ratio within the engine. The compressed air is subsequently fed
into the rocket combustion chamber where it is ignited along with stored
liquid hydrogen. The high pressure ratio allows the engine to provide high
thrust at very high speeds and altitudes. The low temperature of the air
permits light alloy construction to be employed and allow a very lightweight
engine—essential for reaching orbit. In addition, unlike the LACE concept,
SABRE's precooler does not liquefy the air, letting it run more efficiently.

After shutting the inlet cone off at Mach 5.14, and at an altitude of 28.5 km,
the system continues as a closed-cycle high-performance rocket engine burning
liquid oxygen and liquid hydrogen from on-board fuel tanks, potentially
allowing a hybrid spaceplane concept like Skylon to reach orbital velocity
after leaving the atmosphere on a steep climb."

[https://en.wikipedia.org/wiki/SABRE_(rocket_engine)](https://en.wikipedia.org/wiki/SABRE_\(rocket_engine\))

~~~
trhway
>After shutting the inlet cone off at Mach 5.14, and at an altitude of 28.5
km, the system continues as a closed-cycle high-performance rocket engine
burning liquid oxygen and liquid hydrogen from on-board fuel tanks

the benchmark of today - SpaceX - separates the first stage at Mach6-8 at
65-80km height. Thus, the SpaceX second stage has less delta-v to add and
don't have to carry all that weight - the SABRE would naturally be bigger than
the 2nd stage for the same payload. The economical space related case of
HOTOL/SABRE single-stage-to-orbit pretty much disappeared for a foreseeable
future when SpaceX started to recover the 1st stage. That not to say about
suborbital flights SF-Shanghai though. Or even "just" hypersonic as SABRE tech
seems to successfully deal with one of the major/key obstacles for it (and
that is huge, i'm in no way trying to dismiss their work). And one can see how
SABRE can be used in some cases as a convenient 1st stage, i.e. by being able
to launch from any big airport instead of only specially designed spaceports
(such a 1st stage would probably be better than that
[https://en.wikipedia.org/wiki/Pegasus_(rocket)#Carrier_aircr...](https://en.wikipedia.org/wiki/Pegasus_\(rocket\)#Carrier_aircraft)).

~~~
SECProto
Imagine putting SABRE on the first stage though - the engines would be
heavier, but using air instead of carrying oxygen, for the full burn of the
first stage. The payload mass fraction would be dramatically higher without
carrying the oxidizer mass on board.

~~~
trhway
It is possible though cost&complexity seems high - we theoretically can even
today bundle a bunch of SR-71 engines and probably stretch them beyond
designed Mach 3.3 for the short time. Having low thrust-to-weight (SABRE
promises up to 14, SR-71 had 6) we'd need either a lot of them for VTOL which
leads to high cost, or we're limited by the size of maximum realistically
possible hypersonic capable plane, plus the plane body being the additional
weight. For example VTOL calculation - say engine weights 1 ton, we can lift
off 13 ton of fuel and payload. It will use 40 ton of O2 from the air. For
rocket engine - 1 ton engine can lift off 100+ ton, and if we just take the 13
ton fuel plus 40 ton O2 we'd have 45 ton budget for the rest (body plus
payload). In reality you'd need higher fuel ratio, and this is why VTOL for
atmospheric breathing engine pretty much isn't an option .

Going beyond pure rocket engine for the 1st stage i think air-augmented rocket
([http://astronautix.com/g/gnom.html](http://astronautix.com/g/gnom.html))
being simpler (thus cheaper) would be the next step that would get us closer
(specific impulse wise) to what SABRE is targeting.

------
privateSFacct
These guys don't disappear - they have been around forever with their Skylon
plane.

Just a heads up, it's a long way from testing one component of an engine on
the ground to getting a full engine demo going to then testing it in the air
to then build the plane then integrating engine - then getting orbital trips
working with reentry!

I am curious how much private capital they have been able to attract (outside
of govt contract players). Obviously if this is really revolutionary then they
will but this always felt like a long term / govt kinda of cool - tech forward
but pork barrel project for the UK.

More of their background from a somewhat more balanced source - at least the
headline put revolutionary in quotes.

[https://www.bbc.com/news/science-
environment-36773074](https://www.bbc.com/news/science-environment-36773074)

They do claim to have the "best engineers" in the industry - so beating out
big players like rolls royce, PW, CFM, spacex, blue origin, ariane aerospace -
so that is a positive they have.

~~~
walkingolof
These things take time, but it's not the complete story, Virgin Galactic has
been around since 2004, so the same year GMail launched, without producing a
single passenger flight.

Blue Origin has been around for almost 20 years, and they have a few
suborbital flights to their credit, and an engine that has yet to fly.

SpaceX, on the other hand, has been around since 2002 and achieved orbit in
2008, and have completed a lot of milestones since then.

I suspect the biggest difference between these companies is not talent or
vision, but sens of urgency

~~~
heisenbit
Sense of urgency lets one leverage the best current technologies and take the
best compromises within the time and monetary budget. But this is incremental
innovation. It fails at tackling novel concepts where the paths forward are
not so clear. You can't incrementally tunnel through a wall.

At one point maybe SABRE is ready and the next SpaceX comes along and will
build a spaceship with it. The spoils of innovation seldom accrue with the
inventors.

~~~
growlist
> The spoils of innovation seldom accrue with the inventors.

We are British, why change the habit of a lifetime ;)

That said, critical aspects of the design are protected and the private
investors (big scary defense contractors etc) would no doubt sic the lawyers
on anyone that attempted to rip it off.

------
jcims
Skyon's SABRE Engine _Component_ Passes a Big Test.

Still very cool progress and quite the test setup.

------
joshmn
How do you pronounce it? Sah-brey or say-ber?

~~~
cryptozeus
Haha if this was office reference

~~~
joshmn
It is.

------
credit_guy
Everyone over here on HN seems to be quite negative about the SABRE engine.
While there's very little evidence for this engine being useful for orbital
applications, it is instead a very compelling idea for a Concorde and/or SR-71
replacement. Scramjet engines don't seem to be happening anytime soon (I just
listened to a Queensland University researcher saying that their research may
yield an actual engine in 4-5 decades). This idea of pre-cooling the incoming
air seems closer to reality.

------
travisporter
Here’s to a single stage to orbit craft a la Kerbal space program’s RAPIER
engine (although it’s probably still not realistic to expect better than two
stage due to the rocket equation)

~~~
btbuilder
Pretty sure KSP RAPIER is a fictional copy of the described SABRE engine.

~~~
riffraff
The names seem to indicate that, both being similar kind of weapons.

~~~
travisporter
Absolutely.
[https://wiki.kerbalspaceprogram.com/wiki/CR-7_R.A.P.I.E.R._E...](https://wiki.kerbalspaceprogram.com/wiki/CR-7_R.A.P.I.E.R._Engine)

------
jacquesm
Looking forward to the integration test, if they get this to work it will be
quite the engine.

------
zer0sugar
Isn't it inevitable the SpaceX will (and already does) dominate the entire
space industry?

Won't it be cheaper to launch on starship than anythign else even for very
small payloads? Yes, I know about RocketLab but I wonder if they will be able
to survive once starship is up and running.

~~~
ggm
European governments will continue to back Ariane because strategically it
makes sense. Russia will bankroll energyia likewise. Dominance is not static
and private capital will not entirely replace state actions.

~~~
avmich
A nitpick, Energiya doesn't make rockets this days, rather Soyuzes,
Progresses, satellites, upper stages (Block D)... Launchers are made mostly by
Khrunichev (Proton) and Progress (Soyuz-2).

Russia tries to develop new rockets, but so far it's really slow and quite
expensive. It's possible that when NASA will stop paying for Soyuz transport
to ISS, it will become even slower. It's not a particularly good time in
Russia for new rockets paid by the state.

~~~
ggm
All true, but do you seriously think Putin will renounce a domestic space
industry? They might pick jv partnerships like ariane to stay afloat. Or sell
engines or something but i dont see them giving up. To your side of this, the
cash flow to a russian space sector will end when a man rated launcher from
the U.S. starts making regular trips to the ISS, I guess.

~~~
avmich
> do you seriously think Putin will renounce a domestic space industry?

Probably not. It's possible to bring the space industry to the state of
aviation industry, but 1) some resources are still available to maintain some
level (as you mentioned) 2) to keep the same level, one needn't spend too much
effort and 3) there are some interested parties in Russia which wouldn't want
too deep degradation of space industry (e.g. periodically some hints to that
come from Samara).

So a likely outcome could be maintenance of some expertise, at least for
military purposes, and possibly attempts to cooperation with foreign partners
- China, Europe etc. No total destruction; "just" \- potentially - another
deep crisis.

