Seems accurate to me. Hybrids manage to have most of the downsides of
both solids and liquids, while adding new ones like complexity in
mixture ratio control and propellant depletion, unusual instability
modes, unfavorable CG and/or diameter mismatch, and--while not
required to be a hybrid, still quite common in hybrids--the complexity
of two phase flow. It's not a coincidence that none or near none of
the crop of new launch companies are using hybrids. Sierra Nevada,
which owns SpaceDev and a lot of hybrid building experience, abandoned
the idea of using hybrids on DreamChaser in favor of liquids.
Unrelated to hybrids, but related to you, Troy, I visited TU Wien in
Austria over the summer and they showed me their hardware. They have a
lot of very pretty stuff, like 3d printed metal fin cans for minimum
diameter rockets, but also built one or more of your balanced piston
pyroless deployment devices. It was neat to see the hardware "in the
wild" after seeing you post it here; I mentioned to them that they
should send you pictures if they hadn't.
On Sun, Mar 19, 2017 at 2:15 PM, Troy Prideaux
<troy@xxxxxxxxxxxxxxxxxxxxx> wrote:
As a generic blanket statement - that's absolute bullshit.
Troy
Hybrids combine the complication of solids with most of the complication of
liquids: you have to rebuild the "hot section" of the motor to put in more
fuel
for each firing, even though you have a feed system with tanks and valves to
deal with etc.
-dave w
