A kerosene-fueled X-33 as a single stage to orbit vehicle.

On 3/26/2010 4:54 AM, David Spain wrote:
I have serious issues with the drawing in Fig. 23 of this patent, which
purports to be a cross section of a proposed scramjet engine for the
'preferred second embodiment of vehicle 50'.

It says the drawing of the engine is simplified; I assume it's just to
show the basic idea and not the details on the engine's workings.


As drawn there is insufficient bypass to the supersonic flow.
If all intake air *must* pass through a shockwave to the injectors
and combuster, how is this any different from a traditional ramjet?
Which limits top speeds to around Mach 3?

Oh, you can get faster than that on a ramjet; when everyone was going on
about the scramjet-driven "Aurora" one of the scientists who worked on
the old Navy Triton missile project let drop the fact that they were
able to get speeds of Mach 5-6 out of the ramjets they were working on
for that without resorting to supersonic combustion, so he couldn't see
what all the fuss was about.
The drawing of the missile in Gunston's "Missiles and Rockets" shows it
with odd cylindrical ramjets on the wingtips that are fed by a cluster
of eleven venturis on the front, looking for all the world like
flat-fronted unguided rocket pods.

The cross section shown *might* have a chance to work, if what is
left out is the *huge* amount of bypass flow *around* (in front of
and behind) what is shown in the cross section.
The scramjet designs I've seen to-date that seem to have an inkling
of working only induce a shockwave in portions of the flow. Typically
shaping the shockwaves to allow combustion in the void, with the bulk
of the flow passing straight through the system unchanged. All designs
attempt to use a shaped void to pass combustion gasses through where
thrust is obtained by expansion between the engine casing and the flow
or directly expanding against the flow itself. In the first case the
engine casing and the flow act as a nozzle or nozzle ring, in the latter
case the supersonic flow itself acts as the nozzle.

One patent I already ran into in a cursory look at the related results
of patent 4,802,639 concerns a fuel injector for a hypersonic scramjet
that uses the fuel to cool it and keep it from melting as it sits in the
hot airflow, while simultaneously converting the fuel into a hot gaseous
form that will ignite on contact with oxygen:
http://www.google.com/patents/about?...J&dq=4,802,639


Pat