Hi Ben,
what thrust class / chamber pressure the engine you helped to test was in ?
Do you have any idea where to get more powerfull motors than the ones
described in my first email ?
Very interesting idea to recharge the battery during free flight phases.
However wouldn't this require quite long recharging times ?
Best,
Peter
Am 04.12.2016 um 22:27 schrieb Ben Brockert:
I've helped test fire an electric pump fed rocket. There's definitely
a payload size range where they beat the performance of pressure fed
and are easier to develop than gas generator. I'm interested to see if
anyone gets around to attempting to stage batteries, which would
increase the performance even more.
But the killer app I've seen is for in-space propulsion on missions
that require multiple burns. Using solar panels to recharge your
batteries cuts down the battery mass hugely, which is the main
downside of electric pump fed. If you're doing an orbital mission that
requires large delta-v in multiple burns, like multiple plane changes
(space tug, deorbiting debris, multi-plane cubesat deployment) or a
rideshare planetary mission (GTO to TLI burn, TLI to high lunar orbit,
high orbit to low orbit) you can have a much lower tank and engine
mass than a pressure-fed vehicle, the current standard.
Ben
On Sun, Dec 4, 2016 at 5:33 AM, <cnc-engineering@xxxxxx> wrote:
Dear all,
electric driven turbopumps did gain quite a lot of attention lately.
For sure all of you are aware of a famous example – NewZealand Rocket Lab !
http://cdn.satellitetoday.com/wp-content/uploads/2016/04/Stage-Two-Image-B.jpg
While personally I am more convinced to use classic turbine driven turbo
pumps when total power demand is larger than ~ 70 kW, below that value
electric driven pumps might become quite interesting. (For sure this is not
a fixed value and it will depend on a lot of boundary conditions as well as
personal preferences.)
When it comes to restartable engines to be used for example in upper stages,
electric propulsion to my understanding has a significant advantage over
turbine driven systems. This should be even more valid, in case engine
throttling would be involved.
Our present study in the field of upper stage propulsion shows requirements
as listed (planning stage):
- Power demand: ~ 55 kW
- RPM pf pump: 25,000 – 50,000 (pump characteristics are acceptable
within this envelope. Exact RPM number will be adapted depending on the
characteristics of available motors, electronics and batteries. )
- Total energy demand: ~ 1 kWh (= ~ 60 s operation @ 55 kW)
My questions:
- What recommendations do you have when it comes selecting electric
motors, electronics and batteries ? Any specific recommendation with respect
to the requirements mentioned above ?
(Quite interesting seems to be this motor, even though it is limited to
about 30 kW @ 50,000 rpm .
http://www.lehner-shop.com/Inrunner/Series-30/3080::48.html ;;
http://www.lehner-motoren.com/doc/man_30_series_en_11_2013.pdf
- Is anyone involved in electric driven turbo pump activities ?
- What are your general thoughts about the use of these kind of turbo
pumps ?
(BTW: eventually this paper might be interesting for you ('Electric feed
systems for liquid propellant rockets' :
http://www.dima.uniroma1.it:8080/STAFF2/jpp12r3.pdf ;)
Have a great weekend,
Peter
