February 23, 2017 by Chris Gebhardt

After lifting off from historic LC-39A at the Kennedy Space Center, FL, on Sunday morning, SpaceXs Dragon capsule for the SpX-10/CRS-10 mission is making a second approach to the International Space Station during rendezvous and berthing operations following an abort on Wednesday. The mission is delivering thousands of pounds of supplies, hardware, food, and experiments to the ISS.

Launch and quick-look pad 39A condition:

Since launch on Sunday morning from the Kennedy Space Center, Dragon had enjoyed an issue-free ride to the International Space Station (ISS) ahead of an abort just hours prior to capture, blamed on a relative GPS hardware issue, on Wednesday. The issue was fixed to allow for a second arrival attempt on Thursday.

Cruising to orbit on her Falcon 9 first and second stages, the SpX-10 Dragon spacecraft had slipped into her preliminary orbit without issue.

Meanwhile, the Falcon 9 first stage successfully flew itself backto the Cape Canaveral Air Force Stations Landing Zone 1 (LZ-1) for the third landing of a SpaceX rocket on land.

In the immediate hours after liftoff, teams performed a quick assessment of Launch Complex 39A, starting the process of documentation of all elements of the pad damaged during Sundays launch.

Damage to the launch pad is always expected following the liftoff of a rocket generating over a million pounds of thrust.

However, the Falcon 9s ~1.71 million pounds of thrust is relatively nothing compared to the ~7 million pounds of thrust LC-39A endured during its days with the Space Shuttle program, and SpaceX officials in the post-launch news conference were confident that only cosmetic damage would be present at LC-39A.

Accordingly, the quick look condition of the pad on Sunday afternoon noted that the launch complex appeared to be in excellent condition.

With the U.S. federal holiday on Monday, teams began a more thorough and extensive inspection on Tuesday of the launch pads systems and support services an inspection that will reveal just how much work and time it will take to refurbish the historic pad ahead of the currently planned albeit unlikely for the 28 February launch of the Echostar XXIII mission.

Rendezvous and berthing:

Following orbit insertion, Dragon performed a series of trajectory adjustment burns over the capsules three-day chase with the orbital outpost to properly align itself 6 km from the Station on Wednesday morning for final approach operations.

Following approval from NASA, SpaceX controllers commanded Dragon to begin its final approach sequence with the HA4 Approach Initiation burn at 03:16:00 EST at which time the ISS crew began actively monitoring the spacecraft.

Notably, this was deemed to have occurred 15 minutes ahead of schedule.

This was a potential sign of a problem, as Dragon then opted to abort her approach as a bad value in an ISS State Vector and a relative GPS error was noted by her flight computer.

The ability for Dragon to maintain proper alignment with the ISS is provided by the Relative Navigation System which was developed by SpaceX and debuted on CRS-3 on 20 April 2014.

The spacecraft was 1.2 km from the Station when the abort was called.

Dragons abort corridor saw her move into a racetrack around the Station, allowing for a second attempt to take place in 24 hours.

With the Thursday attempt going to plan, a series of maneuvers started with the 7-second HA4 burn that changed Dragons relative velocity to the ISS by 0.3 m/s.

This was followed by the HA4-MC1 and the HA4-MC2 burns designed to keep Dragon properly aligned with her targeted 350 m hold point.

Once Dragon arrived at the 350 m hold point she fired her thrusters to hold relative position with the Station at which time controllers at SpaceXs Mission Control Center (MCC-X) in Hawthorne, CA, commanded Dragon to perform a 180 degree Yaw maneuver to place the craft into the proper orientation for grapple at the end of the approach sequence.

After the yaw maneuver, MCC-X and MCC Houston (MCC-H) controllers confirmed the health of Dragons systems, after which the spacecraft departed the 350 m hold point.

The next hold point for Dragon was at 250 m below the ISS, where controllers once again confirmed the health of Dragons systems as well as the crafts orientation before giving a go to press ahead toward capture.

At any point during this phase of the approach sequence at a hold point or otherwise ground controllers, as well as the Station crew, also had the ability to manually abort Dragons approach through the Commercial Orbital Transportation Services Ultra High-Frequency Communication Unit (CUCU) if an off-nominal condition presents itself.

For the rendezvous, once a go to proceed is given, Dragon left the 250 m hold point and arrived at the 30 m hold point.

Once here, teams will perform final assessments of Dragons readiness to close to the capture point 10 m below the ISS.

Under the ideal plan, Dragon will depart the 30 m hold point and arrive atthe 10 m Capture Point (CP).

Once Dragon arrives at the CP, ISS Commander Shame Kimbrough and Flight Engineer Thomas Pesquet working in the Robotic Work Station in the Cupola lab will extend the Space Station Remote Manipulator System (SSRMS) arm toward Dragons grapple fixture.

After receiving a Go for Capture from Houston, Kimbrough and Pesquet will use the SSRMSs camera on the Latching End Effector (as overviewed in a detailed presentation available in L2) to precisely move the SSRMS to grapple posture.

At this point, Kimbrough and Pesquet will inhibit the Stations thrusters and Dragon will be commanded to free drift mode.

Kimbrough and Pesquet will then move the SSRMS over the Dragons grapple fixture pin and trigger the capture sequence.

Assuming a nominal, prime timeline, capture is expected at 06:00EST (11:00 UTC).

The backup capture window, should something preclude capture in the prime window, opens at 07:03:22 EST and closes at 08:20:08 EST.

After capture, a series of initial post-grapple checkouts will occur before Kimbrough and Pesquet carefully translates Dragon to its pre-install position 3.5 m away from Node-2 Harmonys nadir port.

Once at the pre-install position, Station crewmembers will take camcorder and photographic footage of Dragon for post-launch and rendezvous engineering evaluation.

Kimbrough and Pesquet will then move Dragon to 1.5 m from Node-2, at which point the ISS crew will wait for the final go for berthing call to move Dragon the rest of the way into the Common Berthing Module interface to begin securing the spacecraft to the Station.

Under the current plan, the CRS-10 Dragon will remain berthed to the ISS until late March, at which point it will reenter Earths atmosphere and splashdown for recovery in the Pacific Ocean.

The next cargo resupply mission set to dock to the ISS is the Progress MS-05 spacecraft which launched just hours ago from the Baikonur Cosmodrome in Kazakhstan and is scheduled to dock on Friday morning at 08:34 UTC (03:34 EST).

The next U.S.-launching resupply mission to the Station is Orbital ATKs OA-7 Cygnus mission on 20 March.

(Images: SpaceX; NASA)

The rest is here:

CRS-10 Dragon making second rendezvous and berthing attempt with Station - NASASpaceflight.com