Agreed the articles leaves technical information to be desired.
On the point of 3,000 MPH. One of the comments on the TechCrunch article maybe provides some insight on why they aren't targeting 17,500 MPH.
"even if they need to supplement with rocket propulsion (after exiting the rotational acceleration phase), the amount of rocket energy needed will be way less. could see a huge increase in payload mass fraction as a result. maybe closer to 20 or 30% instead of 1 or 2%"
IF they are flying beyond Mach 1, drag coefficient will actually drop as Mach number increases. [1] Gravity loss will play an interesting roll as well for a system launching with a high initial velocity. There will be a balance between aerodynamic drag and gravity drag losses. The lower the angle launched, the higher the aerodynamic drag but the low the gravity drag loss. [2] Typically launch vehicles actually need more than 9.5 km/s of delta-v even though the orbital velocity for low earth orbit is only 7.8 km/s. This is due to predominantly to account for the large drag forces the velocity experiences during the vertical portion of ascent at sub, trans, and lower super sonic speeds prior to exiting the atmosphere. Some allocation will need to be made for drag loss, but I suspect it is less than a traditional launch vehicle. I would also suspect there is a balance between launch speed, fuel fraction reduction, and difficulty of implementation. The sweet spot between those three things will be important to hone in on.
At its face it does sound pretty crazy but I found some analogs of previous and ongoing projects that provide some reason to suspend disbelief.
Here's what I can find on high G launch vehicle's and payloads:
Breakthrough Starshot: Backed by physicist and VC Yuri Milner and lead by former director of NASA Ames, Peter Worden. 10,000 G's. Project Ongoing. [1]
Hiller Hornet: US Army helicopter, powered by jet turbines located at the tips of the helicopter blades. The turbines operated under 14,000 Gs. Project Completed [2]
HARP Project: Joint US Army & Canadian effort. Successfully launched electronics (radios, control systems, etc) and solid fueled rockets. 10,000+ Shock G's. Project Completed. [3]
A variety of documents come up while researching g-hardening electronics. The US Army Research Lab a a few papers. Linked one of them. 30,000 + Shock G's. Various Projects Completed and Ongoing[4]
The Hiller Hornet is likely the most applicable given it is a propulsion system operating at over 10,000 G's. I wonder how they designed the Hornet's turbine given Finite Element Analysis wasn't really a thing in 1950.
I have a bit of background on rotor systems. That TsF-18 is puny compared to other rotational systems. See below.
Largest Centrifuge:
Regarding the largest centrifuge in the world, perhaps the TsF-18 in Russia has a large diameter but the JET Tokamak [1] flywheel spun a 775 TON rotor at a speed nearly 6 times what is cited for the TsF-18. The Tokamak's centrifuge's provided over 3.8 gigajoules of energy. To provide a more intuitive sense of that energy, 3GJ is equivalent to a 100kg mass traveling at 7.7km/s [2].
Fast Flywheels:
OakRidge National Laboratory [3] achieved over a 1.4 km/s tip speed and that was back in 1985.
Large Vacuum Chambers:
The Large Hadron Collider[4] is a vacuum system over 5 miles in diameter although toroidal in nature.
I don't think they are targeting 17,500mph. Guessing they are trying to do something sub Mach 10 for aero reasons to reduce fuel and increase structural margins that are held tight by the rocket equation. Reduced delta v = improved margins.
On the point of 3,000 MPH. One of the comments on the TechCrunch article maybe provides some insight on why they aren't targeting 17,500 MPH.
"even if they need to supplement with rocket propulsion (after exiting the rotational acceleration phase), the amount of rocket energy needed will be way less. could see a huge increase in payload mass fraction as a result. maybe closer to 20 or 30% instead of 1 or 2%"
IF they are flying beyond Mach 1, drag coefficient will actually drop as Mach number increases. [1] Gravity loss will play an interesting roll as well for a system launching with a high initial velocity. There will be a balance between aerodynamic drag and gravity drag losses. The lower the angle launched, the higher the aerodynamic drag but the low the gravity drag loss. [2] Typically launch vehicles actually need more than 9.5 km/s of delta-v even though the orbital velocity for low earth orbit is only 7.8 km/s. This is due to predominantly to account for the large drag forces the velocity experiences during the vertical portion of ascent at sub, trans, and lower super sonic speeds prior to exiting the atmosphere. Some allocation will need to be made for drag loss, but I suspect it is less than a traditional launch vehicle. I would also suspect there is a balance between launch speed, fuel fraction reduction, and difficulty of implementation. The sweet spot between those three things will be important to hone in on.
[1] https://en.wikipedia.org/wiki/Drag_(physics)#/media/File:Qua... [2] https://en.wikipedia.org/wiki/Gravity_drag