Speaking for us personally, We weren't sure yet that we could talk our
university into letting us build large solid motors, and we were thinking
that the Methane engine could eventually be used in high altitude flights.
We started the design about 8 months before FAR-MARS was announced. This
lead to an engine designed to fly a bigger rocket. When FAR-MARS was
initially announced we were excited to go and compete, and our plan was to
light-load propellants to fly to the competition altitude. When the Class 2
restriction was released a little later our entire architecture became
non-viable for the competition, our engine was too low thrust, our valves
were going to be too heavy, we needed more propellant to make altitude than
they'd let us use, etc.
We continued working on the dual-cryo test stand while we looked for a
methane supplier, of which LNG is fine. I seem to recall the problem at the
time was that we had run out of budget for the year to acquire a DOT rated
dewar, though maybe there were other problems. The engine was shelved at
the end of the 2016-2017 school year, mechanically complete, but pending
propellants and all testing (a single non-cryo cold flow complete). We
currently working on an Ethanol engine that will use the same test stand,
let us qualify the valves, and get us experience handling these things,
since it's been 3 years since our last liquid engine firing.
We won't be going to FAR-MARS anytime soon though, especially not since
we've re-focused on large solid motors.
On Wed, Jan 31, 2018 at 5:23 PM Ed Kelleher <Pres@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Yes, if ... :-)
Actually, at these small tank diameters, minimum gauge might let you have
high pressure relatively cheaply (Catalina tanks) and do a blow down cycle
to get your throttling ... if you really want it. I think the G loss and
Drag loss would be fairly close (longer burn means more G and less D). This
would be an interesting trade exercise.
Use a lot of film cooling to simplify the TC and you can get the overall
O/F down to where you get equal sized LOX/LNG tanks, which makes things
simpler and cheaper also.
Traditional high flow cryo ball valves with actuators are heavy. I don't
think burst disks play well with a blow down cycle, but single shot pyro
actuated valves (no throttling) would be just the thing. Use a normally
open set for cutoff to hit the altitude target if you have some weight
margin..
Definitely not trivial, but lots of room for innovation (fill and drain)
and fun. :-)
Sorry if I'm speaking out of school here.
Ed Kelleher
At 04:29 PM 01/31/2018, Zachary Martinez wrote:
If you can get an engine with throttle control the problem becomes much
easier. You can launch with a T/W of 5 until you are stable aerodynamically
and then throttle down to "cruise" up.Â
We were looking at possibly doing a 2 stage for the same reason because it
would allow a low throttle for most of the flight. Even with these
approaches, getting a biprop system to be light enough to make it work is
not trivial.
Zach
On Jan 31, 2018 3:15 PM, "Ed Kelleher" < Pres@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Thanks, I thought he meant the FAA Regs had changed and I didn't see
where. Ed Kelleher
At 12:14 PM 01/31/2018, Zachary Martinez wrote:
http://www.friendsofamateurrocketry.org/Launch_Contest_Rules.html  -
Must have a total-impulse of less than or equal to 9,208-lb-sec.
Zachary Martinez Chief Engineer Liquid Rocket Design Team Aerospace &
Mechanical Engineering Missouri S&T
On Wed, Jan 31, 2018 at 11:00 AM, Ed Kelleher < Pres@xxxxxxxxxxxxxxxxxxxxx>
wrote: > Changes to 14 CFR Part 101 regarding Class 2? > Do you have a
link to a description? > I didn't see anything new in eCFR other than
model aircraft. > > Thanks, > > Ed Kelleher > > > At 08:57 AM 01/31/2018,
Charlie Garcia wrote: >> >> Hi Eric, >> We were considering it, but last
year when they came out with the Class II >> restriction we pretty much
wrote it off, and then fully wrote it off when we >> couldn't find anyone
who'd sell us less than a train car of methane. >> Good luck! >>
Sincerely, >> Charlie > > >