SpaceX ship carrying two tons of cargo to ISS delayed
Electrically active anvil clouds approaching the Cape Canaveral Air Force Station Monday forced SpaceX to order a 24-hour delay for launch of a Falcon 9 rocket carrying a Dragon cargo ship loaded with nearly 4,400 pounds of scientific equipment, spare parts, food and other crew supplies -- including an espresso machine -- to the International Space Station.
Liftoff from complex 41, originally planned for 4:33 p.m. EDT (GMT-4), was tentatively reset for 4:10 p.m. Tuesday. But forecasters expect more of the same summer weather, giving SpaceX just a 50-50 chance of acceptable conditions.
Because the propellant demands of a station flight are slightly less than for a commercial satellite launching, SpaceX will make another attempt to land the rocket's first stage on a remotely controlled barge-like platform stationed a few hundred miles east of Jacksonville, Fla.
Earlier landing attempts were only partially successful due to stormy weather and problems with stabilizing fins needed to help control the descent.
But this time around, SpaceX managers are hoping for better results, thanks to improvements in the rocket's descent system and upgrades to the landing ship, named "Just Read The Instructions." A senior SpaceX manager put the odds of success at up to 80 percent, but company founder Elon Musk said that's the expectation by the end of the year.
"Odds of rocket landing successfully today are still less than 50 percent," Musk tweeted Monday. "The 80 percent figure by end of year is only bcs (because) many launches ahead."
Whenever it takes off, the flight plan calls for the Falcon's first stage engines to burn for a little under three minutes to boost the rocket out of the dense lower atmosphere. At that point, the Falcon's single-engine second stage will take over the push to orbit, putting the Dragon cargo capsule into an initially elliptical orbit to set up a three-day rendezvous with the space station.
While the second stage continues the climb to orbit, the first stage will flip around and re-enter the atmosphere, using three rocket firings to reduce its velocity and bring the booster down on the landing barge.If all goes well, the Dragon will reach the space station early Friday, pulling up to within about 30 feet and then standing by while Italian astronaut Samantha Cristoforetti, representing the European Space Agency, locks on with the station's robot arm. Ground controllers then will remotely operate the arm to pull the capsule in for berthing at the Earth-facing port of the forward Harmony module.
For SpaceX's sixth operational resupply flight, the Dragon is loaded with 1,142 pounds of station hardware, 1,860 pounds of science gear, 1,102 pounds of crew supplies -- including a month's supply of food -- and another 86 pounds of computer gear and spacewalk equipment. Also on board: 20 mice serving as test subjects in research to learn more about the effects of weightlessness.
The Dragon will remain attached to the station for 35 days, a record duration for SpaceX that was driven in part by the rodent experiment to learn more about the effects of microgravity on bone and muscle loss. When it departs May 21, the capsule will be loaded with more than 3,000 pounds of research samples, no-longer-needed equipment and trash. The Dragon is the only cargo ship currently flying to the station that is capable of bringing material back to Earth.
SpaceX holds a $1.6 billion contract for 12 resupply missions to deliver some 44,000 pounds of cargo to the station. NASA recently ordered three additional flights to help offset a resupply shortfall triggered by the failure of an Orbital Sciences Antares rocket last October. Contract details have not been announced.
Recovering the first stage of the Falcon 9 rocket is not part of the NASA contract and is considered a strictly secondary objective. But it is a key element in the company's ongoing drive to lower costs by recovering, refurbishing and relaunching booster stages.