Whether he is sandbagging, or really just wanted to clarify, SpaceX founder Elon Musk used Twitter to correct media reports (including this one) that cited the odds of successful first stage landing at 75-80%. \
Odds of rocket landing successfully today are still less than 50%. The 80% figure by end of year is only bcs many launches ahead.
— Elon Musk (@elonmusk) April 13, 2015
Irrespective of what the odds actually are, and its not at all cleat that SpaceX can do anything but guess at this point, today they were zero, as the launch was scrubbed due to weather with less than four minutes remaining in the countdown.
And so it comes down to this.
At 4:33:15 PM EDT today, if weather and circumstance permits, a SpaceX Falcon 9 booster will lift off from Cape Canaveral’s SLC-40 on the 6th of what were originally scheduled to be 12 commercial supply runs to the International Space Station. For SpaceX, the program has been an unqualified success, one which helped pave the way for the Hawthorne, Ca. based company to win an even larger prize, one of two awards in NASA’s Commercial Crew Program and the opportunity to help the United States regain the ability to launch its own astronauts.
With the total number of cargo missions now apparently increased to 15, and a possible award in the follow-on CRS-2 contact which would take the series of cargo runs midway into the next decade, today’s flight no longer marks a symbolic halfway point in a history making program. Instead, all eyes will be on the bright white booster adorned with four carbon landing legs, an equal number of “hypersonic grid fins” and what SpaceX Vice President of Mission Assurance Hans Koenigsmann estimated at a pre-launch press conference as a 75-80% chance of a successful first stage recovery.
Somewhat ironically, if Koenigsmann is correct, the odds of a successful landing appear to be higher than those of a liftoff occurring in the first place. Launch weather officers of the 45th space wing are estimating a 60% chance of favorable conditions, as a strong frontal boundary to the north is allowing an influx of warm tropical winds and summertime weather pattern to emerge in what is ordinarily one of the driest months of the year.
If a launch occurs, the weather conditions in the landing zone will cooperate as well, with mild seas and acceptable winds. The only negative is reduced visibility from cloud cover, which is likely to impede photography. Upgraded with increased stablizer capacity following the rough weather which forced a cancellation of the most recent landing attempt, the Autonomous Spaceport Drone Ship bearing the nearly as cumbrous name “Just Read The Instructions” should have no difficulty being in the right place at the right time. And quite possibly, neither should the first stage. According to Koenigsmann, had the ship been in place during the DSCOVR launch, a landing would have taken place.
If the weather, or other factors force a scrub today, or on the backup slot on Tuesday, NASA and SpaceX will have to re-evaluate schedules and set a new launch date.
Whenever it does take place, the landing profile, as outlined in the SpaceX graphic below, is as follows:
Following stage separation and second stage ignition, the first stage will flip over 180 degrees and perform a boost back burn to prevent momentum from carrying it further down range. Thirty seconds later, it will deploy the hypersonic grid fins and coast to an altitude of 125 km. At that point, a second brief burn will be initiated to “tap the brake” and ease the stress of atmospheric re-entry. It is during this phase that the grid fins will perform their critical function of adjusting the stage’s angle of attack, controlling the lift generated by the fuselage itself. Finally, the landing legs will deploy and the single, center-mounted Merlin 1-D engine will bring the booster to a touchdown.
Much more to come..