Rather than re-engineer the cart to use a different block? I mean, I guess when a part reaches end-of-life, your first move is to buy as many as you can, before you try to re-engineer things so it isn't needed, but... horsepower is horsepower. Torque is torque. It shouldn't be that hard to replace...
> The original design was conceived by two Lockheed Skunk Works engineers who had prior race car engine knowledge. In the mid-1970's, the engines of the start carts was changed to Chevrolet LS-7 454's. The Chevrolet big block engines developed 465 horsepower each. Even so, for many years they were still referred to as the Buick's.
And eventually the start carts themselves got replaced.
> In the '80's the AG-330 Start Carts were mothballed and in there place came a Pneumatic Air starting system for the SR-71's. It is true that the start carts were hard to maneuver around. Logistically, a recovery of a Blackbird at another base could be done easier with Pneumatic Air.
Yeah, big car engines is actually not that impressive, rather surprisingly primitive. Modern jets have external APUs for starting, usually via compressed air, that have compact yet powerful gas turbines inside.
Sure, less impressive than a contraption with a bunch of car engines but much more powerful.
It could have, sure. That would have been easy. But it would have added weight and complexity. That would have reduced speeds and/or altitude and/or range between in-flight refuelings.
We fixed it the other easy way: In the event that an SR-71 makes an unscheduled stop somewhere that wasn't prepared for it, then we send out a bunch of dudes with a cargo plane and some starter carts. That just takes money, which even easier.
It also takes time, but time was not a big deal: The plane was going to be there for awhile anyway. It could go over 15,000 miles between takeoff and landing; it wouldn't have landed where it did if it weren't broken somehow to begin with.
It'd need repaired by the crews who actually knew how to work on it -- who would also need flown in.
It would also need fuel before it could leave. That's problematic since the JP-7 it required was shared by ~nothing else in the sky, so: More deliveries.
Waiting for some Buick V8 starter carts to be delivered from the other side of the world wasn't really a roadblock at all.
They would have to make the plane bigger. The SR71 is already an enlarged version of the A-12, made bigger to support more fuel, a heavy camera, and an extra pilot. It needed something like 900lb-ft torque per engine; even modern electric motors would add enough weight that it would be problematic.
There's a bit in the Skunkworks book that talks about added weight costing significant altitude. I don't have my copy in front of me but it's quite a severe tradeoff: some fairly small amount (100kg perhaps, might even have been less) reduces ceiling by 1,000'.
For military planes, every bit of weight you can shed up front increases some operational capability of the plane. In this case, not carrying an extra 200-300kg of weight for starters meant 200-300kg more spy equipment /could/ be carried along on the mission.
