The company's infelicitously named president, Gwynne Shotwell, explained that the engine controller had spotted abnormally high pressure in one of the rocket's nine engines. The launch software spotted it, too, and did what it was supposed to do in such circumstances: abort engine five and then shut down the remaining eight. Ms Shotwell pointed out that once airborne, the rocket can run on just seven of its engines, "just not at lift-off".
This is not the first time the mission has been postponed. Dragon was originally meant to fly on February 7th, but has since been grounded for various reasons, including last-minute problems with its software.
Many people are growing anxious. NASA, America's space agency has already given SpaceX almost $400m to develop its rocket and capsule. America, which has done most to bankroll the $100 billion cost of the ISS (which this newspaper has always considered an orbital white elephant with an exorbitant price tag that does precious little useful science). Yet since it retired its space shuttle last year, the country has had to rely on Russians, Europeans and Japanese to fly cargo missions. The government would no doubt rather the hefty sums it pays for their services stayed at home.
Meanwhile, the firm's backers—led by Elon Musk, its founder, who made his fortune with PayPal, an internet-payments firm—are counting on a successful launch to begin recouping the hundreds of millions they have invested. Only then will SpaceX be in a position to begin a 12-flight commercial cargo contract to the ISS worth $1.6 billion.
