
Blue Origin just sent a jolt through the aerospace industry - rbanffy
https://arstechnica.com/science/2017/10/blue-origin-has-successfully-tested-its-powerful-be-4-rocket-engine/
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indubitable
I am certainly excited about the possibility of a new competitor in the
aerospace industry, but it is absolutely stupefying how much press Blue Origin
manages to... obtain... in spite of having done absolutely 0. Literally - they
have yet to even put a single thing into orbit. They've done some "landings"
but these are suborbital launches, which in other words means you go straight
up and then come back down, like a model rocket. Orbital launches involve
accelerating along the x axis to incredibly high velocities. As Douglas Adams
said the trick to flying, or staying in orbit, is to simply keep missing the
ground as you fall.

To say a 3 second half power static fire is "sending jolts through the
aerospace industry" is plainly ridiculous. Yet, of course, I clicked on it --
something I never would have done if the title actually represented the
contents of the article. Ahhhhhhhh....

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ChuckMcM
The title is a bit misleading but that is sort of par for the course. Blue
Origin did the first "hot fire" test of the BE-4.

What that means is that everything on the engine was turned on and the fuel
ignited. This is the one of the final steps in engine development where you
run it for a short period, collect data about as much stuff as possible, try
to predict trends from that data to insure that the motor wasn't destroying
itself. That sets up the next hot fire test which, I've read, are between 2
and 10x longer. Then you get durability tests (you run it at a variety of
external temperatures, and conditions) and longevity tests (you run it for the
entire mission life) then you take it completely apart and retest the
metallurgy on bits that got hot (to insure they didn't get changed into
something that would be out of spec for the engine) and check for erosion in
the combustion chamber etc etc. Its a long and detailed process to go from a
rocket engine 'design' to a rocket engine 'data sheet'.

It is a very large engine. With 50% more thrust than the SpaceX Raptor.
Historically, engine thrust has been significant because the overall
"efficiency" of rockets has been the fraction of the overall mass of the
complete rocket they can get into orbit (or where ever they are going). So for
a given engine what is important is what does the engine and its components
weigh, versus the thrust it delivers. According to NASA this was the reasoning
behind the F1 engines in the Saturn V, they had only 5 engines but they were
huge, which gave them the thrust they needed but only 5 turbo pumps, 5 sets of
propellant valves, 5 nozzles, etc.

It is also less complex to operate fewer engines.

On the flip side an engine out is a bigger loss of capability (and one of the
advantages touted by the F9's 9 engines, the ability to achieve orbit with one
engine out). And if you're re-landing these things, the ability to finely tune
the throttle is very challenging on a larger engine. Look at the F9 which
lands with exactly 1 engine firing. It has been reported that the landing
weight of the F9 booster stage is such that even at its lowest throttle
setting the booster would accelerate if the engine was left on. That means no
'hover' ability, just trying to intercept the ground before the rocket starts
going up again :-).

Blue Origin still 'feels' about 3 years behind SpaceX though, and I continue
to think the challenge here will be whether or not Falcon Heavy is successful
in its first flights. SpaceX has the booster recovery aspects working
smoothly, and Heavy has enough extra capacity to lift all the 'common'
payloads, so it could monopolize a lot of the launches (and money that goes
with them). That will make it much more difficult for New Shepard, because
there will be little if any margin of error, and unlike SpaceX which can now
lower prices given their understanding of recoverability, New Shepard will
need to be able to compete from the first flight forward.

