in OTL in 1960 there were Only 4 unmanned test
Mercury-Atlas 1 unmanned suborbital test, the booster explode 59 sec after lift off
Little Joe 5 a unmanned Launch Escape System test, First flight of a production Mercury spacecraft.
Mercury-Redstone 1 unmanned suborbital test, the most insane test in rocket history!
http://en.wikipedia.org/wiki/Mercury-Redstone_1
Mercury-Redstone 1A unmanned suborbital test,
If even Mercury-Redstone 1 was a sucess
Mercury-Redstone 2 (1A) Carried Ham the Chimpanzee on suborbital flight.
so how can we chance Mercury project ?
chance the Redstone by Jupiter missiles (wat was planed, but chanceld by due to budget constraints.)
http://en.wikipedia.org/wiki/Mercury-Jupiter
with Mercury-Jupiter as Biological suborbital test, Carried Chimpanzees and Monkeys on board
the Mercury-Redstone are Free for Astronauts
with unmanned Mercury-Redstone 1 a succes
first manned Mercury-Redstone 2 (1A) launch is in 19 december 1960
this is most early date for Astronaut flight in Mercury Program.