SpaceX the Alan Notes

The latest SpaceX Dragon – and her crew of “Mousetronauts” – arrived at the International Space Station (ISS) on Tuesday. The orbital ballet between the giant orbital outpost and the commercial spacecraft resulted in the CRS-4 Dragon being captured by the Station’s “big arm” at 06:52 Eastern, ahead of berthing operations that were completed a few hours later.

Day of the CRS-4 Dragon:

The SpX-4/CRS-4 Dragon began her journey to the ISS atop of her Falcon 9 v1.1 partner on Sunday morning, a rocket that was launching just a fortnight after the previous SpaceX launch from SLC-40 at Cape Canaveral.

The “quick look” review of the duo’s performance during the ride uphill showed no major issues, with only inertial measurement problem on the Dragon noted as failed during ascent, per a NASA Mission Management Team (MMT) meeting.

With built-in redundancy, Dragon has merrily continued her orbital journey to catch up with the ISS, with the MMT praising the performance of the spacecraft.

The Dragon has been conducting numerous burns to position herself for Tuesday’s big day, with her propulsion system – a set of four “quads” of thrusters – successfully completing a priming phase, ahead of bringing the thruster systems up to operation via the pressurizing the fuel tanks and injection of gaseous helium.

The first burn completed was the coelliptic (CE) burn, with the 350 second firing resulting in a change of velocity of 96 mph.

An “Out Of Plane” burn was followed by the first Height Adjustment burn (HA1), with the 218 second firing resulting in a 34 mph change to the delta velocity.

Another coelliptic burn (CE1) was followed by two shorter burns, as Dragon chased down the ISS.

The arrival into the ISS’ back yard involved a whole series of thruster firings, each taking her closer to the station; holding at distances of 2, 500, 1, 200, 250, 30 and 10 meters, before finally being grappled by the Canadarm2 Remote Manipulator System, and attached to the nadir port of the Harmony module.

The initial series of finite maneuvers brought Dragon to just 2.5 km below ISS. A Go/No-Go was performed for the HA2/CE2 burn pair bringing Dragon to 1.2 km below ISS.

The HA3/CE3 burn pair, using RGPS and configured with the ISS’ own GPS system, was then conducted, followed by the HA4 (Ai) burn, taking Dragon inside the corridor where the crew began to monitor the spacecraft’s approach.

The approach was aided by Dragon’s LIDAR system, a key element of hardware that has a heritage of testing via the Space Shuttle Discovery during her STS-133 mission.