Full story at the link.
In World War II, the OSS wanted the National Defense Research Committee (NRDC), a gathering of eggheads led by Harvard’s former head James Conant, to address the question of projectile launching, starting at first principles, with the objective of producing silent weapons. Stanley P. Lovell, a former NRDC guy who’d been transferred to OSS to help the nascent spy and sabotage agency develop the specialty equipment such missions required, drafted the initial requirement, complete with an innocuous cover name:
No. 1 – Impact Testing Machine
You are directed to study, and if possible produce, a gun having the approximate following military characteristics:
Silent
Flashless
Muzzle velocity of 1000 ft./s.
Maximum calibre bullet compatible with a, B, and C, preferably 50-calibre.
Minimum reloading time, preferably under 30 seconds.
The project may conceivably eventuate as two weapons, one for relatively long-range sentry assault, the other as a personal short-range weapon. The US Armed Forces prefer the former and there are indications that our Allies wish both types of arms.
WildBill. But I'm wondering what advantage the slingshot side of the weapon has over the crossbow, unless it can hurl a hand grenade a really, really long ways. 
