Second pair of new space station solar arrays set for launch on Dragon cargo ship

SpaceX’s Falcon 9 rocket and Cargo Dragon capsule on pad 39A at Kennedy Space Center. Credit: SpaceX

A second pair of new roll-out solar arrays to upgrade the International Space Station’s power system is set for launch as soon as Tuesday on a SpaceX Dragon cargo ship. Astronauts will help deploy the power-generating solar wings during a pair of spacewalks next week.

SpaceX plans to launch the company’s 26th Dragon resupply mission to the space station on a Falcon 9 rocket at 3:54 p.m. EST (2054 GMT) Tuesday, weather permitting. But there’s just a 10% probability of acceptable weather conditions for liftoff from pad 39A at NASA’s Kennedy Space Center, with rain showers and heavy cloud cover expected over Florida’s Space Coast.

If the mission doesn’t get off the ground Tuesday, the launch will be delayed to no earlier than Saturday at 2:20 p.m. EST (1920 GMT). SpaceX will not be able to launch the cargo mission around the Thanksgiving holiday, a period of busy travel in the United States, because the Federal Aviation Administration wants to ensure airspace is clear for commercial airline traffic.

Assuming the Dragon capsule takes off Tuesday, it will dock with the Harmony module on the International Space Station at 5:57 a.m. EST (1057 GMT) Wednesday. Astronauts on the space station will open hatches and begin unpacking cargo inside the pressurized compartment of the Dragon spacecraft.

The mission is SpaceX’s 26th Dragon cargo flight under a series of multibillion-dollar Commercial Resupply Services contracts with NASA. This mission is designated CRS-26, and will debut a brand new Dragon cargo capsule in SpaceX’s fleet of reusable Dragon spaceships. The CRS-26 mission will also use a new first stage booster on the Falcon 9 rocket.

It’s the sixth SpaceX cargo mission under the most recent CRS contract, which carries the Dragon cargo program through the CRS-35 mission slated for some time in 2026.

SpaceX says the new Dragon spacecraft launching on the CRS-26 mission will be the third and last cargo transportation spacecraft in the company’s latest-generation Dragon fleet. SpaceX has four human-rated Crew Dragon spacecraft in its inventory, and last week the company announced it will build one more Crew Dragon for astronaut missions beginning in 2024.

The CRS-26 mission is packed with about 7,700 pounds (3.5 metric tons) of hardware, supplies, and experiments for the space station and the seven-person crew living on-board the complex. The largest element of the cargo load is NASA’s second pair of new roll-out solar arrays to augment the space station’s power system.

Two ISS Roll-Out Solar Array units inside the Space Station Processing Facility last year at Kennedy Space Center. Credit: NASA/Frank Michaux

The cargo on the CRS-26 mission include clothing, food and sanitary items for for the space station crew, plus a slew of experiments, including a demonstration aimed at growing dwarf tomatoes on the orbiting laboratory. Previous plant growth experiments, part of the “Veggie” series of science investigations, have focused on growing leafy green vegetables to provide astronauts with a source of fresh food. The experiments also gather data for future expeditions into deep space, such as flights to the moon and Mars, where astronauts could grown their own food.

“We are testing tomatoes, looking at the impacts of light spectrum on how well the crop grows, how delicious and nutritious the tomatoes are, and the microbial activity on the fruit and plants,” says Gioia Massa, NASA life sciences project scientist and principal investigator for the tomato experiments, called Veg-05. “We also are examining the overall effect of growing, tending, and eating crops on crew behavioral health. All of this will provide valuable data for future space exploration.”

The CRS-26 mission will also deliver Moon Microscope, a kit that includes a portable hand-held microscope that can help astronauts collect medical-grade imagery of their own blood samples, then send the data to the ground for analysis by flight surgeons. The mission also carries a tech demo experiment called Extrusion that will test how liquid resin in microgravity can create shapes and forms impossible to make on Earth, due to the influence of gravity. “The capability for using these forms could enable in-space construction of structures such as space stations, solar arrays, and equipment,” NASA says.

Another experiment on the CRS-26 mission will study how yogurt, fermented milk, and a yeast-based beverage could be used to produce nutrients to maintain crew health on long-duration space missions.

Eight small CubeSats are stowed inside the Dragon spacecraft for NASA, the Canadian Space Agency, and companies in Italy and Taiwan. The CubeSats will be transferred by the space station crew to the Japanese airlock for release into low Earth orbit with a Nanoracks deployer.

The Dragon spacecraft’s rear cargo bay holds the two roll-out solar arrays to be installed outside the space station.

“Of critical importance to us is the two new solar arrays that we’ll be doing spacewalks at the end of November and early December to install and deploy on-board the International Space Station,” said Joel Montalbano, NASA’s ISS program manager. “In addition to the two solar arrays that are to be delivered on SpaceX-26, we have some life support equipment being delivered, some GPS hardware, some exercise hardware, and some medical equipment. This mission will say docked to the International Space Station about 45 days … All in all, we’re looking forward to an exciting mission.”

While crew members inside the space station unpack cargo from the Dragon’s internal cabin, the station’s Canadian robotic arm will reach into the cargo ship’s trunk to remove the two new solar array units. The arrays are rolled up on spools, and together weigh more than a ton. Two astronauts will venture outside the space station for a pair of spacewalks to assist in the deployment of the new solar arrays.

Astronauts Thomas Pesquet and Shane Kimbrough, at left, work with the ISS Roll-Out Solar Array during a spacewalk last year. Credit: Oleg Novitskiy/Roscosmos

The first two ISS Roll-Out Solar Arrays, or iROSA units, launched in June 2021 on SpaceX’s CRS-22 resupply mission. They were unfurled during a pair of spacewalks later that month on the P6 segment on the port side, or far left end, of the station’s solar power truss. One of the iROSA arrays launching on CRS-26 will go on the port-side P4 truss segment just inboard of the P6 section, while the other solar array will be mounted on the starboard-side S4 truss area.

The iROSA arrays are being extended over six of the the station’s eight existing solar array wings, canted at angles to partially cover the older solar panels. Fully deployed, the roll-out solar arrays stretch 63 feet long and 20 feet wide (19-by-6 meters), about half the length and half the width of the station’s current solar arrays. Despite their smaller size, each of the new arrays will generate about the same amount of electricity as each of the original solar panels.

A mounting bracket plugs the new arrays into the station’s power channels and rotary joints, which keep the solar wings pointed at the sun as the spacecraft races around Earth at more than 17,000 mph. Ahead of the CRS-26 mission, astronauts completed spacewalks to install the mounting brackets to receive the new solar arrays.

The International Space Station has eight power channels, each fed with electrical power generated from one solar array wing extending from the station’s truss backbone. The original solar panels launched on four space shuttle missions from 2000 to 2009. As expected, the solar panel efficiency has degraded over time.

When all six iROSA units are deployed on the station, the power system will be capable of generating 215 kilowatts of electricity to support at least another decade of science operations. The enhancement will also accommodate new commercial modules planned to launch to the space station.

The new roll-out solar arrays were developed by Deployable Space Systems in Goleta, California, under contract with Boeing, which oversees space station engineering and maintenance work under a separate contract with NASA. Deployable Space Systems was acquired last year by Redwire, a space infrastructure company based in Jacksonville, Florida.

The solar arrays give the space station one of its most significant mid-life upgrades since NASA and its international partners completed large-scale assembly of the complex in 2011. The six new solar array wings, coupled with 24 new lithium-ion batteries launched to the station on a series of Japanese resupply missions, will help ensure the lab’s power system, can support continued operations through 2030.

The final pair of roll-out solar arrays are scheduled to launch on SpaceX’s CRS-28 cargo mission next year.

At the end of the CRS-26 mission, the reusable Dragon capsule will undock from the station and head for a parachute-assisted splashdown off the coast of Florida in early January with several tons of cargo.

This email address is being protected from spambots. You need JavaScript enabled to view it. the author.

Follow Stephen Clark on Twitter: @StephenClark1.