[AR] Re: Spartan: Hovering hybrid
- From: Jonathan Goff <jongoff@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Fri, 17 Oct 2014 08:16:36 -0600
Korey,
The four engine design was abandoned because the engines were crap and
highly inconsistent from engine to engine. I can say that because they were
my design and I was soooo glad when we finally killed those and went to the
new engine design. We tried to move too fast from single engine sort of
working on the test stand in a fixed configuration to four flight engines.
We were also outsourcing our GN&C at the time, and there were issues with
how that was handled. By the time I left in 2010, I think we had the GN&C
and engines to a point where we could've done a 4 engine vehicle had we
wanted to... we were just still at a point where a single engine vehicle
was a lot easier to work with.
Multi-engine liquid VTOLs probably only start making sense when:
1- Your engines have enough development on them that they are reliable and
consistent from vehicle to vehicle
2- You are getting near a "step function" in the engine size versus
development cost curve, where doing multiple copies of a smaller engine
would be a lot cheaper than developing a big new engine.
3- You're getting the rest of your vehicle to flight reliability levels
where engine-out actually makes a difference reliability-wise.
Masten will get there if it keeps plugging along. And it could go there
today, it just doesn't make sense for them at the moment. It probably makes
sense at XS-1 scale though.
Anyhow, all that is conjecture since I left there over four years ago. If
they let Dave Masten respond, I'd love to see how his thinking compares to
mine.
~Jon
On Fri, Oct 17, 2014 at 8:07 AM, Korey Kline <k2@xxxxxxxxxxx> wrote:
> Did Masten ever get the four engine version to hover? Has anybody?
>
> On Fri, Oct 17, 2014 at 9:50 AM, <joesmith@xxxxxxxxx> wrote:
>
>> Even Armadillo was able to hover. Masten as well.
>>
>>
>> On Fri, 17 Oct 2014 00:38:03 -0700, George Herbert <
>> george.herbert@xxxxxxxxx> wrote:
>>
>> For some reason I jump straight to a single centerline hybrid with cold
>> nitrous gas attitude control, but each to their own...
>>
>> George William Herbert
>> Sent from my iPhone
>>
>> On Oct 16, 2014, at 2:44 PM, "Troy Prideaux" <GEORDI@xxxxxxxxxxxxxxxx>
>> wrote:
>>
>>
>> Jon,
>>
>>
>> You’re thinking in liquid mode ie. LOX. You need to think monoprop
>> oxidizers eg. Nitrous or Peroxide. If you look at Nitrous:PE for
>> example, the performance for O:F ratios between 5:1 to 10:1 is pretty much
>> the same. The internal bond energy of the oxidizer provides a significant
>> portion of the propulsion energy.
>>
>>
>> Saying that, I generally agree that typical hybrids aren’t suited for
>> this application although if your expertise is in hybrids and you’re really
>> comfortable with them…
>>
>>
>>
>> Troy
>>
>>
>>
>> ...Because once you've done all the work to figure out how to do fire
>> and throttle valves, building another set with slightly different
>> characteristics is just too hard. Much easier to deal with a chamber that
>> changes geometry throughout the burn, and where you have no real control
>> over mixing efficiency.
>>
>>
>> I mean, cool if they can pull it off, but I've got to scratch my head
>> on why they'd do it that way. There *are* places where hybrids might make
>> sense, but I have a hard time believing a hovering vehicle is one of them.
>> Unless bobbing around like crazy in a semi-controlled fashion is good
>> enough.
>>
>>
>> Sorry if that came off overly negative, I just wonder about people's
>> design choices sometimes.
>>
>>
>>
>> ~Jon
>>
>>
>>
>> On Thu, Oct 16, 2014 at 8:12 AM, Mark C Spiegl <mark.spiegl@xxxxxxxxx>
>> wrote:
>>
>>
>> I have no connection with these guys.
>>
>> They're building an LLC type vehicle using hybrid rocket motors instead
>> of biprop.
>>
>> http://www.spartanproject.eu
>>
>> --MCS
>>
>> .
>>
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>
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