We’re flying this afternoon, and will be back in a week, but I’ll have computers there.
[Update on September 8th]
OK, I decided to just take a break, other than a couple posts. We went up into Rocky Mountain National Park, and did a lot of chores at the place in Golden.
[Bumped]
Some aero thoughts.
A hybrid-fan for a shoulder-fired tactical missile
Normally everybody uses a regular solid rocket motor for ATGMs, with all sorts of different thrust profiles. For cruise and strike envelopes like we see with the Javelin, a hybrid would offer better performance and some ability to throttle. For larger longer range cruise missiles everybody opts for a turbojet or turbofan, due to the vastly higher ISP.
But what if you took a solid or hybrid engine and ran the exhaust over a free turbine that drove a fan? That eliminates the entire compressor section of a jet engine, plummeting the cost. Relatively inert fillers could be added to the solid or hybrid fuel grain to bring down combustion temperatures, and thus turbine inlet temperatures. Two-thirds of a jet engine turbine’s power output goes to compress the incoming air, and that gets eliminated, so all the power can go to the fan, helping offset the weight penalty of carrying the oxidizer.
Maybe there’s some reason they don’t do this, but it seems like something a model-jet hobbyist could experiment with.
Conventionally hinged flapperons
Starhip moves the entire flaperon, but if they were made as a conventional control surface, but one whose elevator or aileron component could bend upwards by 90 degrees, then during a belly-flop the control surface would be able to alter their area perpendicular to the airstream. I think it would accomplish the same control as the existing method while eliminating the thermal problems at the joint of the rocket body and the flaperon.
But SpaceX surely modeled this and found a flaw in the idea.
Do a search on air-turborocket.
That is very close to what I was thinking! But I wasn’t looking to compress the air and light an afterburner, just run a high-bypass style fan or even a propeller, but do it cheaply and expendably, and in a small package that infantry could carry.
So I’m wondering if a small solid or hybrid rocket motor running a turbine could replace the electric motor and battery in something akin to a ducted-fan RC jet model, providing far more power for a short flight to the target, while providing longer range or endurance than an ordinary solid rocket motor, hopefully without a horrifying jump in cost.