In my opinion, a test stand is for your version 0.1 development on your
engine; or for one-off tests and investigations. So where you will possibly
want to iterate through design modifications quickly, or do some sort of
testing that only needs to be done a few times or only on the ground. So a
good test stand has lots of space to easily mount things to, so you can
quickly mount hardware without extra effort. As well as a blast plate to
protect your expensive equipment. As test stand tests often are higher
risk, or are pushing the limits. So not having to replace a bunch of
hardware in addition to your test article is a nice thing. If you already
have a working engine design, or a high confidence that the design will
work, a test stand is not as necessary.
A chain-down test bed, isn't just making things light. It's also packaging.
It can take a lot of effort to cram everything you need into an airframe.
So it is a bit wasteful to do this when you might not entirely be sure that
the components you have, are actually the ones you want to use in the end.
So in my opinion chaindown tests are best for version 0.8-0.9 of your
rocket. Where you are doing flight readiness testing, or making sure your
new configuration isn't going to cause unexpected problems. It is a great
place to figure out if the vibration and acoustics of the engine are going
to cause havoc with your electronics. Startup sequencing is also a great
thing to test out on a chain down test. Basically, It's testing to do to
increase your level of confidence in your flight article before you risk
the whole thing on a flight.
The main case that I feel would be best to do your (v0.1) development on a
chaindown test stand, would be if you only have enough resources to do just
one thing. If that is the case, then it's better to just build something as
close to flight as you can, and hope you don't burn it up.
If you can afford to do many tests and a hardware revision or two. Getting
tests done on a test stand will probably save you money/time in the long
run.
On Fri, Jun 7, 2019 at 10:57 AM Carl Tedesco <ctedesco@xxxxxxxxxxxxxx>
wrote:
As far as I can tell, Starship is very early hardware and massive
marketing. I had not heard of a flight yet. Can you point me to a video of
this Starship prototype flight?
--- Carl Tedesco
*From:* arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> *On
Behalf Of *Craig Fink
*Sent:* Friday, June 7, 2019 11:47 AM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Embry-Riddle Prescott Liquid Rocket Engine Hot-fire
Yeah, I always tend to take things to the limits, to see what that looks
like. A rocket spread out all over the place is much easier to work with,
which is what a test stand is. Taking things to there limits is usually too
far.
SpaceX went from starting to build the Starship prototype to first flight
in under 5 months, including first burn of the new Raptor motor at a test
stand, integration into the vehicle, and first flight at a new space port.
They are extremely high on the learning curve and accelerating fast, soon
to be out of sight of any competitors.
On Fri, Jun 7, 2019 at 9:06 AM Stephen Daniel <swd@xxxxxxxxx> wrote:
In my very limited experience a test stand is much easier to work with
than the inside of a rocket.
Our current motor development project is to build a motor that will
eventually fit inside a 6" diameter rocket. However the motor today is
various bits of plumbing, tanks, chamber, valves, etc all bolted to a
uni-strut frame that is about 2' wide and 4' tall.
This makes everything easy to access for modifications, rebuilding, etc.
Some of the plumbing is simple flex-hoses. When we had some issues with
contamination clogging our filters and valves we could easily take them out
and clean them. Building all the plumbing to fit within a 6" airframe is
going to be a significant challenge, one we will not take on until this
version of the motor is reliably working to spec.
Our test stand is a 16' length of antenna tower, strapped down to large
stakes. We mount the motor frame onto the tower with some bolts.
The motor is instrumented with pressure sensors, but we have no strain
gauges or load cells. We compute thrust knowing the chamber pressure and
the nozzle geometry.
In short, I believe motor design is much simplified by using a test stand.
On Fri, Jun 7, 2019 at 11:39 AM Craig Fink <webegood@xxxxxxxxx> wrote:
On Thu, Jun 6, 2019 at 10:51 AM Daniel Dyck <daniel.dyck.379ba@xxxxxxxxx>
wrote:
Jake, not really. I have started writing some stuff here:
https://danieldyck.com/portfolio/test-cell-3/, but its far from complete.
I'm happy to answer any questions about the facility, as that is what I led.
Craig, all the same points that Henry made, as well as the fact we plan on
testing engines that won't be used in flight: heat sink engines,
demonstrator engines, etc.
Daniel, nothing wrong testing engines in a test stand if your not building
a rocket, even if you are building a rocket.
I just find SpaceX campaign to build their next rocket interesting, it
should be much shorter than traditional approaches. SpaceX campaign to land
the Falcon 9 was anything but traditional, getting customers to pay most of
the development, testing and destroyed vehicles along the way.
I suspect Blue Origin is using a more traditional approach, so when they
crash their first beautifully designed, fully tested, stylish and expensive
New Glenn during development, it will be a big set back in both time and
money.
If you want to be successful in the future, you can emulate NASA like Blue
Origins, or you can emulate SpaceX. The SpaceX approach for a 4 year
undergraduate degree where the student learns more about rockets, less
about test stands and gets to fly more would also be more fun.
--
Craig Fink
WeBeGood@xxxxxxxxx
--
Craig Fink
WeBeGood@xxxxxxxxx
