Sodramjet: the Mach 16 chinese scramjet

Quaoar · 2021-03-31 03:39:44

I have found this article

https://www.sciencedirect.com/science/a … 6120305227

about a new chinese scramjet able to reach Mach 16 (almost 5.5 km/s).
If it works it will be very useful to build a SSTO.

tahanson43206 · 2021-03-31 07:15:25

For Quaoar re #1

Best wishes for success with this promising new topic!

The British appear to be on a similar track with their technology to dramatically cool air as it arrives in the intake, using liquid Hydrogen as the cooling agent.

I'm looking forward to reading the article when I move to a modern computer later in the day.

Edit#1: Thanks again to Quaoar for providing the link to this very interesting paper.

The paper is on the longish side, as befits a subject of this complexity and importance. The illustration of the "oblique" concept later on is quite helpful (to me for sure). I'd been forming an incorrect mental image, so appreciate seeing the actual wind tunnel test apparatus.

A detail that may intrigue some (a few?) NewMars readers is that (if I understood the paper correctly) this design begins to become useful at Mach 5, and it (appears to) extend all the way to Mach 9.

I'd appreciate someone else having a look to see if my impressions are close to the mark (or not).

I came away thinking that a vehicle using this kind of engine might need more than one engine, to accelerate to Mach 5 and then to hand over responsibility to this engine design.

Another detail I found interesting is the offer to drop the term "supersonic combustion" and to substitute "combustion in supersonic conditions".

(th)

SpaceNut · 2021-03-31 17:17:05

It still starts with some oxygen since you need to push oxygen into the unit only to have just 21% of it to use with the fuel.

GW Johnson · 2021-03-31 21:40:54

Let's just say I am skeptical. The conditions they tested at allow the compressible flow models they used. Conditions in real flight at their Mach 6-16 conditions do not allow the use of their model.

That being said, the notion of a standing detonation may in the end prove useful. Just bear in mind that is is a play-toy tested in a shock tunnel, which is an extreme transient. I remember when scramjets were similar play-toys tested in similar shock tunnels. It took 50 years to get from there to the X-43A.

And bear in mind that ANY airbreathing engine of ANY type will operate at a chamber pressure somewhere about 3 to 15 times local ambient. At super high altitudes where the air is so thin that it is kissing cousin to the vacuum of space, then 3 to 15 times nothing is still nothing, for chamber pressure. Nothing for chamber pressure is nothing for thrust.

Which is why ALL airbreathers have no frontal thrust density when flown too high. It's very fundamental physics, and it is the very definition of "service ceiling". Often ignored by marketeers (as it was for X-30) but there it is! No one is ever really going to power a spacecraft to orbit with an airbreather.

I say that with great confidence, despite the possible future ascent success of the UK Skylon to be powered by SABRE engines. Those engines breathe air to Mach 5. Then they operate as rockets. Period.

BTW, Skylon as envisioned will not survive descent from orbit. The bow shocks off the engine nacelle compression spikes will cut the wings off. There is a very good (and totally compelling) reason that no spacecraft ever flown has had nacelles on pylons. It's called shock-impingement heating.

GW

Last edited by GW Johnson (2021-03-31 21:42:37)

Quaoar · 2021-04-01 09:41:12

GW Johnson wrote:

Let's just say I am skeptical. The conditions they tested at allow the compressible flow models they used. Conditions in real flight at their Mach 6-16 conditions do not allow the use of their model.
That being said, the notion of a standing detonation may in the end prove useful. Just bear in mind that is is a play-toy tested in a shock tunnel, which is an extreme transient. I remember when scramjets were similar play-toys tested in similar shock tunnels. It took 50 years to get from there to the X-43A.
And bear in mind that ANY airbreathing engine of ANY type will operate at a chamber pressure somewhere about 3 to 15 times local ambient. At super high altitudes where the air is so thin that it is kissing cousin to the vacuum of space, then 3 to 15 times nothing is still nothing, for chamber pressure. Nothing for chamber pressure is nothing for thrust.
Which is why ALL airbreathers have no frontal thrust density when flown too high. It's very fundamental physics, and it is the very definition of "service ceiling". Often ignored by marketeers (as it was for X-30) but there it is! No one is ever really going to power a spacecraft to orbit with an airbreather.
I say that with great confidence, despite the possible future ascent success of the UK Skylon to be powered by SABRE engines. Those engines breathe air to Mach 5. Then they operate as rockets. Period.
BTW, Skylon as envisioned will not survive descent from orbit. The bow shocks off the engine nacelle compression spikes will cut the wings off. There is a very good (and totally compelling) reason that no spacecraft ever flown has had nacelles on pylons. It's called shock-impingement heating.
GW

Thanks GW.

GW Johnson · 2021-04-03 09:07:41

Quaoar:

Like I said, the standing detonation wave may ultimately prove useful. Just don't hold your breath waiting for it. It is likely about half a century away.

GW

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#1 2021-03-31 03:39:44

Sodramjet: the Mach 16 chinese scramjet

#2 2021-03-31 07:15:25

Re: Sodramjet: the Mach 16 chinese scramjet

#3 2021-03-31 17:17:05

Re: Sodramjet: the Mach 16 chinese scramjet

#4 2021-03-31 21:40:54

Re: Sodramjet: the Mach 16 chinese scramjet

#5 2021-04-01 09:41:12

Re: Sodramjet: the Mach 16 chinese scramjet

#6 2021-04-03 09:07:41

Re: Sodramjet: the Mach 16 chinese scramjet

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