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Reaction engines Flight Test Vehicle speculation


I’d guess REL would want it to run in rocket mode long enough for any plausible transient behavior to have died away. My instinct is maybe 10-20 secs

For STERN, “Each firing was restricted to less than a second [… which] provided sufficient time for the flow to stabilise, and all the required data to be obtained” but these are bigger and more complicated than STERN.
The STS was launched six seconds after the SSMEs were started, which was long enough for transients to have gone and the required data to be collected.
It’s likely to be somewhere between the two. Of course, after the engine has started and is stable, the air-breathing core needs to shut down, which affects the exit plane. At some point in the rocket flight the nozzle extension will be …err… extended – but it’s not entirely clear when that would be, and so it’s difficult to predict if that’s in the flight envelope of HTB.

That makes no sense.  :( If you’re going to test the AB/rocket transition then the nozzle extension is a critical part of that process. You don’t have a complete test without it. There are multiple possible options for how to do it. Some of them may be eliminated through ground test and simulation but a flight test of at least one of them is crucial.

No, that’s testing deploying the nozzle extension. The air-breathing shutdown has to be complete before moving the nozzle, so it can’t happen during air-breathing to lox transition

The sequence is most likely to be hydrolox start -> air breathing shutdown -> nozzle extension,
but could be air-breathing shutdown -> nozzle extension -> hydrolox start

Quote from: john smith 19

or the rocket is already in idle.
Those question will set the operating parameters for whatever actuators are chosen to produce that motion, and the environment they will have to operate in.

It’ll be ballscrews as previously discussed elsewhere.

Quote from: john smith 19

data acquisition systems have improved enormously since then, 30 Hz x 1024 channels fits in 4x20x45 cm,  and 128kHz x 32 channels are smaller. Pair those with 1 GB SSD and you can gather hours of flight data. Buy as many of each as you need for your requirements.

(1024)^3 / (128 000 *32) –> 262.144 secs of recording time, assuming the data and storage are byte wide. 
The first example gives something like 19hrs at byte wide data

OK, you got me, I only calculated for the slow recorder, eyeballing the other as roughly the same ballpark.
The smallest SSDs around tend to be 128GB, so there should be plenty of space for recording the portions of the flight of interest.

Quote from: john smith 19

As always the jokers in the pack are flight duration, resolution and sample rate.

Welcome to the 21st century, where a TB of storage weighs around a gram.

I’d suggest 4 bytes for values, two at a pinch, and 8 bytes per row for TAI64 timestamps. That should gives you over a minute of storage on 128GB for the fast recorder.

In general data can be striped across multiple disks (better for write bandwidth), but failing that SSDs up to 100TB are available, but NVMe (which I’d recommend for weight and performance) is topping out at around 16TB, but that should still give two hours of storage at the high data rate.

Quote from: John Smith 19

The HTB study was being performed by Cranfield Aerospace, an offshoot of Cranfield University – who operate their own airport, are a registered airline and operate their own “airborne laboratory”
An example of their research:

High speed intake aerodynamics and flow distortion
Applications are invited for fully-funded PhD studentship in the area of aero-engine intake aerodynamics within the Propulsion Engineering Centre at Cranfield University. The research will focus on propulsion system – supersonic intake integration and dynamic distortions for novel aircraft configurations

These guys probably know a thing or two about monitoring.

True, but they are  usually done in a lab on the ground with instruments that are not flight weight. Very little work seems to have been done in this area for vehicle mounted sensing.

OK, it’s only Mach 2, but…. they instrumented a Typhoon for temperature

They have people who do this for a living, and if scramjet research has done nothing else it has developed hypersonic instrumentation which will be in the literature/conferences, so they would probably know more about it than armchair enthusiasts like me. I probably know more about strorage than they do though.



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