The reasons launch startups have tended to develop their own propulsion
would make, well, at least a chapter in a book. (Though the
metaphysically minimal answer is "AJR".) Yes, I was implicitly taking
that as a given in my advice, and at some point it needs to change.
I thoroughly approve of companies aiming to become specialized
propulsion suppliers. The industry does need that, yes. (There was a
missed opportunity ten years ago...)
How close are these two to having engines ready to go? How wise would a
launch startup be to, right now, tie its fortunes to either of theirs?
Henry
On 12/13/2018 10:46 PM, Bill Bruner wrote:
My contribution to 20-20 hindsight is - if you're a rocket company with $500K, buy printed engines from Ursa Major <https://www.ursamajortechnologies.com/> or ARC <http://arc-engines.com/>.
Airplane makers don't make their own engines - that went out with the Wright brothers.
On Thu, Dec 13, 2018 at 4:33 PM Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx <mailto:hvanderbilt@xxxxxxxxxxxxxx>> wrote:
On 12/13/2018 5:18 PM, Henry Spencer wrote:
> On Thu, 13 Dec 2018, Henry Vanderbilt wrote:
>> Looked like a middlin' hard start instantly removed the nozzle and
>> most of
>> the thrust chamber, but the injector and feed plumbing did
survive and
>> completed the run.
>>
>> Insta-diagnosis, the combination may not have been as reliably
>> hypergolic as
>> hoped, if enough could mix in the chamber before igniting to
produce the
>> observed results.
>
> A quick Googling for past work on this combination reveals an
> all-too-common refrain: while ignition of ethanolamine plus a
bit of
> copper-chloride catalyst with peroxide might look pretty quick,
when
> it was actually measured, an unpleasantly large amount of
catalyst was
> needed to get marginally tolerable ignition delays even with a
bit of
> fudging (injecting the fuel hot). Now, throw in the fact that
> ethanolamine is miscible with water, which is to say that it'll
almost
> certainly be miscible with peroxide too. Result: a combination
that's
> just looking for a chance to pool and form an explosive mixture
when
> overoptimistic people try to reduce the catalyst content to
something
> practical.
>
> At least they apparently were suitably cautious about it, since
nobody
> was hurt by their Rapid Unscheduled Disassembly Event. Takes a
certain
> amount of chutzpah to claim this as a successful test, though!
Well, if you've spent your seed money and this is what you have to
show
for it, you're more or less obliged to show it, think positive REALLY
HARD, talk fast, and hope for the best. Because if you didn't believe
the problems could be profitably solved you shouldn't have been
trying
that in the first place.
My contribution to 20-20 hindsight here is, if you're working on a
shoestring with an untried propellant combination, you should
probably
scale the initial tests WAY down - 50lbf chamber? - so the shoestring
has a better chance of paying for enough test iterations to achieve
reliable clean ignitions and burns. _Then_ you have a plausible
story
to tell second-round investors about scaling it up to an operational
size engine. Going straight for the operation engine size saves
time,
sure - IF everything goes right the first time.
Words for new entrants to heed and live by: Everything _never_ goes
right the first time. Plan accordingly.
Henry