HP-18J Twin Turbine Self-Launch Sailplane

On Wednesday, July 27, 2016 at 7:24:53 PM UTC+12, wrote:
Congratulations! Nicely done. If you email me I'll send you my jet performance spreadsheet (not for widespread dissemination at this time). It seems to be validated by reports of performance of various jet projects.

My own jet is closing in on being finished. Just need to check out electrics and software in the extend/retract controllers. All automated with just a master switch for each engine and a retract/extend/run 3 position switch for each. Single throttle rotary pot.

Some observations:

Performance depends quite sensitively on the deployed engine/mount/airframe doors and hole drag. Minimising this is a REALLY good idea as jets like to fly fast. Power delivered to glider = thrust x true airspeed

A simple ejector nozzle as used on early Learjets as an add on for noise reduction can reduce noise by 3 to 5dB. That is one half to one third the noise level. If done right you should get a few percent thrust increase too. See some early turbojet powered DC-8 aircraft.
I've been to a few jet R/C model meets and the jets really don't seem all that noisy until they are moving away from you and you can see the exhaust pipe. Even then not so bad. Small turbines produce most of their noise in the ultrasonic range.

It's quite noticeable with offroad motorcycles that 2 stroke bikes sound louder close up, but it's the thumpers you can hear from 5 km or a couple of valleys away.