The USC rocket propulsion lab (USCRPL) is now announcing they intend to make their attempt to suborbital space in April this year:
https://www.uscrpl.com/traveler-iii/
Advancing from a flight of 100k feet, to a flight of 100k meters in one year will be an impressive accomplishment if they succeed.
Ad Astra, USCRPL!
The efforts of the USC team reminds me of the efforts by the Maverick Civilian Space Foundation team. They are a group of professional engineers who instruct high school and university students in building and launching two-stage APCP rockets to reach 100,000 feet. Their rocket uses three clustered motors for the first stage and one motor for the second stage. The total propellant load is about 200 kg, like the SpaceLoft and GoFast suborbital rockets.
Each of the four Maverick motors composing their rocket have a ca. 50 kg propellant load. However, their rocket uses aluminum casings as indicated in this video:
California Academy of Math & Science Explorers Program - The Rocket Project.
[video=youtube;MutkJ0HKyA8]https://www.youtube.com/watch?v=MutkJ0HKyA8[/video]
This reduces the mass ratio and therefore the delta-v possible. BUT suppose the Mavericks used also carbon fiber casings for the 3-cluster first stage? Then the first stage alone might have sufficient delta-v for a suborbital space flight, as it would be larger than the USC rocket at a ca. 150 kg propellant load. You might want to use a fiberglass or carbon fiber cylindrical aeroshell to cover the 3-clusters though for aerodynamics reasons, as it would be traveling faster than the Mavericks original version not having to carry the heavy upper stage.
You would have to get the carbon fiber casings however. The USC team built their own carbon fiber winder. And you can find on the net examples of other amateurs who have built their own carbon fiber or filament winders. But one can be purchased for ca. $3,000 from the X-winder company.
It maybe though you want to use all four of the Maverick's motors clustered together. This would give a rocket of the same propellant size as the GoFast and SpaceLoft suborbital rockets. You would still need to give the motors carbon fiber casings to get the needed mass ratio and delta-v.
The 50 kg motors making up the Maverick's rockets are Q-class motors. Then actually two of them stacked one on top another would make up an R-class rocket, same as the USCRPL rocket. Then switching to carbon fiber casings may allow just two of the Maverick's motors to be used to reach suborbital space.
There are only a few Q-class motors that have been launched by amateur high power rocketeers. But if the USCRPL team succeeds, this suggests other high power rocketeers by using carbon fiber casings for their Q-class motors and stacking one on top of another making an R-class motor, they also could succeed at reaching suborbital space.
One other Q-class motor was the Qu8k motor that reached 100k feet:
https://ddeville.com/derek/Qu8k.html
The Qu8k motor had a 70 kg propellant load. Then two stacked would have a 140 kg propellant load, actually larger than the USCRPL rocket. Then it also given carbon fiber casing and stacked one on top of the other could reach suborbital space.
Bob Clark