Engine problems delay delivery of record cargo shipment to ISS
Kyiv • UNN
Northrop Grumman's Cygnus XL spacecraft's main engine shut down earlier than expected during two burns needed to raise the spacecraft's orbit. This will prevent it from delivering approximately 5,000 kg of cargo and experimental materials to the International Space Station as planned.
A problem with the main engine of Northrop Grumman's Cygnus XL spacecraft will prevent it from delivering approximately 5,000 kg of cargo and experimental materials to the International Space Station as planned on Wednesday, Ars Technica reports, writes UNN.
Details
In a statement released Tuesday afternoon, NASA said ground teams were evaluating backup plans that might allow the Cygnus spacecraft to reach the space station, but not on schedule. According to NASA, the problem occurred early Tuesday morning when the spacecraft's main engine shut down earlier than expected during two burns needed to raise the spacecraft's orbit for rendezvous with the ISS.
Officials did not release other details about the engine problem, but all other Cygnus XL spacecraft systems are operating normally, NASA said. The agency said a new arrival date and time at the space station are "under consideration."
The Cygnus XL spacecraft launched on Sunday at 6:11 PM ET (01:11 AM on September 17 in Kyiv) aboard a SpaceX Falcon 9 rocket from Cape Canaveral Space Force Station in Florida, USA. A series of main engine firings was supposed to move the spacecraft from the orbit it was placed in by the Falcon 9 to an orbit matching the ISS altitude.
The mission was scheduled to arrive at the station on Wednesday morning. Unlike SpaceX's crewed and cargo Dragon spacecraft, which dock autonomously at the station, Cygnus was to be captured by the Canadian laboratory's robotic arm. NASA astronaut Jonny Kim was to use the manipulator to capture the Cygnus spacecraft as it flew 9 meters from the complex. The robotic arm would then install the spacecraft on the Unity module's docking port, where it could remain for up to six months.
This is Northrop Grumman's 22nd cargo mission to the space station under a multi-billion dollar commercial cargo contract with NASA. All but one have successfully reached the station. This mission took on greater significance than a typical cargo flight after engineers discovered damage to a Cygnus spacecraft that was scheduled to launch earlier this year.
The damage occurred during the shipment of the spacecraft's pressurized cargo module from its manufacturer in Italy. While Northrop Grumman hopes to repair the module and launch it on a future flight, officials decided it would be quicker to move forward with the next spacecraft in line for launch this month.
This is the first flight of a larger Cygnus spacecraft model, known as Cygnus XL. The spacecraft is 1.6 meters longer and capable of carrying 33% more cargo than the previous Cygnus variant. With this upgrade, this mission is carrying the largest cargo ever delivered to the ISS by a commercial cargo spacecraft.
The Cygnus spacecraft's main engine runs on a mixture of hydrazine and nitrogen tetroxide. This mixture is hypergolic, meaning the fuel components ignite on contact with each other, which is a key design feature. The spacecraft is equipped with a separate set of less powerful reaction control system engines, which are typically used for small maneuvers and to orient the spacecraft in the correct direction on its way to the ISS.
If the main engine is deemed inoperable, one possible solution to the main engine problem could be to use the less powerful engines to make smoother orbital adjustments for the Cygnus spacecraft to align it with the ISS in the final trajectory segment. However, it is not yet clear how viable this option is.
Unlike SpaceX's Cargo Dragon spacecraft, Cygnus is not designed to return to Earth intact. Astronauts fill it with trash before it departs the ISS, after which the spacecraft heads for a destructive re-entry into the atmosphere over the remote Pacific Ocean. Thus, a problem preventing the spacecraft from reaching the ISS would result in the loss of all cargo on board.
The cargo for this mission, designated NG-23, includes fresh food, equipment for numerous biological and technological demonstration experiments, and spare parts for devices such as the urine processor and space station toilet, to replenish their dwindling supplies on the space station, the publication writes.