Compare the size of the A/C in comparison with the towing unit.
That is not a very big A/C at all... but since it doesn't need a crewman, and tech things can be made a lot smaller in today's world vs in the 60s when the SR 71 Came out...
no wonder that bird has the speed capability it does...
What interests me is what have they used for the skin on the SR 72 to withstand the air friction. If you've ever seen videos of some of the first flights of the B 70 back in the 1970s... they were painted white, with some special additives to keep the A/C cool from the air friction, The B 70 could obtain speeds in testing capabilities, that eventually would peal the paint off the skin, and it burst into flames from air resistance/ friction.
I also know the SR 71s, would leak fuel like crazy until they got airborn and opened up their throttle, air friction would heat up the skin, and that would shrink and seal the fuel leaks.
Would like to see the technology being used, to allow the SR 72 to be able to reach the speeds it can, without dealing with air resistance & friction. on the other hand, maybe it flies faster than the air resistance /Friction, so is therefore limited by that for top speed.
Hypersonic sled travels at 6,599 mph (Mach 8.6) at Holloman Air Force Base Air Force Test Center May 20, 2019
Holloman Air Force Base is home to the High-Speed Test Track. This was a hypersonic test that traveled Mach 8.6, which is 6,599 mph which is over one mile a second.