WASHINGTON — A Falcon 9 launched a cargo Dragon spacecraft to the International Space Station on a mission emphasizing station hardware and supplies over science.
The Falcon 9 lifted off from Kennedy Space Center’s Launch Complex 39A at 11:47 a.m. Eastern June 5. The Dragon spacecraft separated from the rocket’s upper stage 12 minutes after liftoff, a few minutes after the Falcon 9 first stage landed on a droneship in the Atlantic Ocean.
The launch of the mission, designated CRS-28 and part of SpaceX’s Commercial Resupply Services (CRS) contract with NASA, was scheduled for June 3 but postponed because of poor weather at the launch site and to provide more time to complete vehicle preparation. A June 4 launch opportunity was called off because of poor weather for the booster landing.
SpaceX continues to use droneship landings for cargo Dragon missions even as it shifts to landings back at Cape Canaveral for crewed launches, starting with the Ax-2 private astronaut mission May 21. SpaceX officials then that they had found sufficient additional performance in the Falcon 9 to enable landings back at the Cape for Crew Dragon launches.
“For every CRS mission we’ll evaluate the mission’s mass needs and performance needs and the performance of the vehicle against opportunities to return to the launch site,” said Sarah Walker, director of Dragon mission management at SpaceX, during a June 2 prelaunch briefing.
The CRS-28 mission is carrying about 3,300 kilograms of cargo to the station, and is scheduled to dock at about 5:50 a.m. Eastern June 6. Its biggest payload is a third pair of ISS Roll-Out Solar Arrays, or IROSA, that will augment the station’s ability to generate power. Those arrays will be installed during a pair of spacewalks currently scheduled for June 9 and 15.
Those arrays will join four IROSA arrays installed on other spacewalks, completing the planned upgrade of the station’s power system. At a June 1 briefing, Dina Contella, NASA ISS operations integration manager, said the agency is considering a fourth pair of IROSA arrays, but needed to identify funding for them.
Cygnus delays
In addition to the solar arrays, the Dragon is delivering nearly 1,110 kilograms of crew supplies, 490 kilograms of vehicle hardware and 266 kilograms of science. That is far less science that past cargo Dragon missions: the CRS-27 mission in March carried about 975 kilograms of science investigations, compared to 745 kilograms of supplies and 440 kilograms of vehicle hardware.
At a May 30 briefing about science on the mission, Kirt Costello, NASA ISS chief scientist, said that more supplies were flown on CRS-28 because of delays in the next Cygnus cargo mission, NG-19, by Northrop Grumman. “It’s also making up for the delays that we had in our NG Cygnus vehicle arriving at the station, so we’re sending up lots of extra logistics, crew supplies, for the crew to keep them going throughout the end of the year,” he said.
That Cygnus mission, once planned to launch in the spring, has slipped to later in the summer, although NASA officials have not announced a launch date yet for that spacecraft. “Our Northrop Grumman partners have been working to go determine when the vehicle is ready to fly,” said Phil Dempsey, NASA ISS transportation integration manager, at the June 2 briefing. “That one just wasn’t quite ready for the earlier opportunity.”
The previous Cygnus mission, NG-18, launched in November. It successfully arrived at the ISS and carried out its mission despite the failure of one of its two solar arrays to deploy after launch. Northrop said at the time that an acoustic blanket from its Antares launch vehicle lodged in the array mechanism and kept it from deploying, but neither NASA nor Northrop have disclosed additional information about the incident.
Asked if the readiness issue had to do with the Cygnus or the Antares, Dempsey said it was “a little bit of both.” The primary issue, he said, was understanding the “launch anomaly” on NG-18 and making sure it does not happen again on NG-19. “It’s really making sure that we have a completely healthy vehicle, from the launch vehicle and the Cygnus vehicle both.”
He added that there are “other things that the Northrop Grumman team is working and communicating with NASA on” for NG-19, but did not disclose those other issues.
NG-19 will be the last launch of the current version of Antares, which uses a Russian RD-181 engine in its Ukrainian-built first stage. Northrop announced last August a partnership with Firefly Aerospace to produce a new first stage, using engines under development by Firefly. Northrop will launch several Cygnus missions on SpaceX Falcon 9 rockets until the new version of Antares is ready.
CRS-28 science
Despite the limited room on the Dragon for science, Costello said at the May 30 briefing that there is still a “very good mix” of biological science, Earth science and technology demonstration payloads on the mission. Among them are experiments to study plant growth in space and observing upward-directed lightning in thunderstorms.
The spacecraft is also carrying five cubesats built by Canadian universities and sponsored by the Canadian Space Agency. Among them is ESSENCE, a cubesat that will monitor thawing permafrost in arctic regions, and Iris, which will expose a set of minerals to space and train a camera on them to monitor how they are affected by the space environment.
CRS-28 will remain docked to the ISS for about three weeks. There are no plans to extend the spacecraft’s stay at the ISS, officials said at the June 2 briefing, even though delays in the launch of Boeing’ CST-100 Starliner on a crewed test flight have eliminate the urgency of freeing up a docking port for that mission.
Costello said NASA is looking ahead to the CRS-29 cargo Dragon mission at the end of the summer along with the delayed NG-19 Cygnus. Those missions, he said, will be “bringing up a big collection of science that we’ve been accumulating on the ground, ready to go.”
