The third dedicated SpaceX Dragon mission to deliver 4,000+ pounds of cargo and supplies to the International Space Station under a $1.6 billion Commercial Resupply Services contract with NASA has been pushed back again, this time due to a helium leak discovered on the Falcon-9 rocket first stage earlier today.
The call to scrub today’s launch from Cape Canaveral Air Force Station came roughly 90 minutes before the scheduled liftoff time of 4:58 p.m. EDT. SpaceX teams are working to safe the vehicle on Space Launch Complex (SLC)-40 and will return it to a horizontal configuration in readiness for a second launch attempt later this week—assuming, of course, repairs can be made in the next day or two. The implications for the planned 22 April EVA-26 to replace a failed backup Multiplexer-Demultiplexer (MDM) on the ISS have yet to be determined.
Today’s launch attempt appeared to run smoothly. The countdown got underway about 15 hours ahead of the planned liftoff time, when the Dragon spacecraft was powered up and internal checks begun. Fueling of the Falcon 9 v1.1—which is flying its first Dragon mission and its fourth voyage in total—with liquid oxygen and a refined form of rocket-grade kerosene (known as “RP-1”) was completed by 2:00 p.m. EDT. During the latter stages of the countdown gases streamed from the vehicle, due to cryogenic oxygen boil-off, which was rapidly replenished to flight levels until close to launch time. However, at 3:39 p.m., “an anomaly was detected … and it is serious enough to halt the countdown and postpone the launch,” noted the AmericaSpace Launch Tracker. Spaceflight101 added that the helium leak was associated with systems to pressurize the Falcon 9 v1.1’s propellant tanks in flight, support the turbopumps of its Merlin-1D engines, and deploy the landing legs which it will use in an “experimental” attempt to accomplish a “soft” ocean touchdown.
As noted in our CRS-3 mission preview, in the immediate aftermath of the CRS-2 mission last March it was anticipated that CRS-3 would fly in the September-November timeframe, although this quickly became December as the schedule of U.S. visiting vehicles morphed to accommodate changing conditions. By August, both CRS-3 and the first dedicated Cygnus cargo flight by Orbital Sciences Corp. (ORB-1) were accommodated within the same December “launch window” and SpaceX accepted to postpone their mission until January 2014. By the end of the year, with ORB-1 itself delayed until January, this date had moved to no earlier than 22 February, which soon shifted to early March and finally settled on the 16th. A successful hot-fire test of the nine Merlin-1D first-stage engines on the Falcon 9 rocket was conducted at the Cape’s Space Launch Complex (SLC)-40 in the days preceding the opening launch attempt, but SpaceX notified NASA that it would postpone the mission for a further two weeks.
Citing its desire for “the highest possible level of mission assurance and allow additional time to resolve remaining open issues,” the Hawthorne, Calif.-based company, headed by entrepreneur Elon Musk, explained that it was now tracking 30 March as its next available launch date. In the aftermath of the delay, SpaceX President and Chief Operating Officer Gwynne Shotwell explained that the company was working up to four issues. “We were struggling on some buffering data-transfer with Houston,” Shotwell stated, as explained in an article by AmericaSpace’s Emily Carney. “We wanted a little more time to work with the range on trajectory. We are going to try to do some re-entry and landing burns on the first stage. My operations crew was in a time crunch for Dragon, which is a very new Dragon. Finally, we did notice stains on the impact shielding.” This staining was caused by “oil contamination from the manufacturing process,” which left “regular patterns” on beta-cloth shields within Dragon’s unpressurized Trunk. “It didn’t show up right away when the blankets were manufactured,” Shotwell continued. “Luckily, our pre-encapsulation checks caught it.” After assessments, it was decided that the level of contamination was acceptable.
A launch on 30 March also became untenable, when the Eastern Range—which monitors all missions originating from the East Coast—suffered an electrical short and a fire in a critical radar tracking asset which impacted the TEL-4 Telemetry Processing Facility, part of the Eastern Space and Missile Center (ESMC).
It is unknown at this time how long repairs to correct the helium leak might take, or how difficult such a task might be. The next available launch opportunity for SpaceX is Friday, April 18, at 3:25 p.m. EDT. The weather forecast for an April 18 launch is, however, rather poor, with only a 40-percent likelihood of acceptable conditions due to thick clouds and risk of precipitation.
Article written by both AmericaSpace writers Mike Killian and Ben Evans.Missions » ISS » COTS » CRS-3 »