A Northrop Grumman Cygnus spacecraft, carrying a record 11,000 pounds of supplies for the International Space Station (ISS), has encountered an engine problem that will prevent its scheduled arrival. NASA confirmed on Tuesday that the spacecraft's main engine shut down earlier than planned during a critical orbital maneuver, placing the mission's timeline under review.
Key Takeaways
- Northrop Grumman's Cygnus XL spacecraft experienced a main engine shutdown during orbital burns.
- The mission, carrying a record 11,000 pounds of cargo, will not arrive at the ISS on its scheduled Wednesday date.
- This is the first flight of the larger Cygnus XL model, designed to carry 33% more cargo.
- Engineers are evaluating backup options, but the loss of the entire payload is a possibility if the spacecraft cannot reach the station.
Engine Malfunction Halts ISS Approach
The problem occurred early Tuesday following the spacecraft's successful launch on Sunday. The Cygnus XL was performing a series of engine burns designed to raise its orbit to match that of the International Space Station.
According to a statement from NASA, the main engine shut down prematurely during two of these scheduled burns. While all other systems on the spacecraft are reported to be functioning correctly, the failure of the primary propulsion system has interrupted its planned trajectory.
Ground teams are now analyzing the situation to determine the cause of the malfunction and explore potential solutions. A new arrival date for the space station is currently being reviewed, with no immediate timeline provided.
Mission Background
Designated NG-23, this mission is Northrop Grumman's 22nd commercial resupply flight for NASA. The Cygnus XL spacecraft launched aboard a SpaceX Falcon 9 rocket from Cape Canaveral Space Force Station in Florida on Sunday at 6:11 p.m. ET.
A Mission of Increased Importance
This particular cargo delivery carries greater significance than a typical resupply run. The mission's importance was elevated after a different Cygnus spacecraft, scheduled for an earlier launch this year, sustained damage during shipment from its manufacturing facility in Italy.
While efforts are underway to repair the damaged module, officials decided to proceed with the next available spacecraft to maintain the supply chain to the ISS. This decision placed additional pressure on the NG-23 mission to succeed.
First Flight for Cygnus XL
This mission marks the debut of the Cygnus XL, an upgraded and larger version of the cargo vehicle. It is 5.2 feet (1.6 meters) longer than its predecessor, enabling it to carry 33% more cargo. The 11,000-pound payload on this flight is the heaviest ever sent to the ISS on a commercial cargo vehicle.
Technical Challenges and Potential Solutions
The main engine on the Cygnus spacecraft uses a hypergolic propellant mixture of hydrazine and nitrogen tetroxide. This type of system is generally considered highly reliable because the propellants ignite on contact, simplifying the engine design.
In addition to its main engine, the spacecraft is equipped with a set of smaller reaction control system (RCS) thrusters. These are typically used for fine-tuned maneuvers and maintaining the spacecraft's orientation.
One potential backup plan may involve using these smaller thrusters to perform a series of gradual orbital adjustments to guide Cygnus to the space station. However, it was not immediately clear if this is a feasible option or if the RCS thrusters have enough capability for such a large orbital change.
"Ground teams are evaluating backup plans that might still allow the Cygnus spacecraft to reach the space station, just not on schedule," NASA stated in a press release on Tuesday.
Record-Breaking Cargo at Risk
The 11,000-pound (approximately 5,000 kg) payload is crucial for the station's crew and ongoing scientific research. The manifest includes a variety of critical items:
- Fresh food for the astronauts
- Hardware for biological science and technology demonstration experiments
- Spare parts to replenish dwindling supplies for the station's life support systems
- Components for the urine processor and station toilet
Unlike SpaceX's Dragon capsule, the Cygnus spacecraft is not designed for atmospheric reentry. After its stay at the station, it is typically filled with trash and intentionally burned up over a remote area of the Pacific Ocean.
This design means that if Cygnus cannot reach the ISS, there is no way to recover the vehicle or its valuable cargo. The entire payload would be lost, representing a significant setback for station logistics and research.
The Cygnus Capture Process
The Cygnus vehicle follows a different docking procedure than some other spacecraft visiting the ISS. Instead of an automated docking, it requires a capture by the station's robotic arm.
The spacecraft was planned to fly to a position within 30 feet of the orbiting laboratory. At that point, NASA astronaut Jonny Kim was scheduled to use the Canadian-built Canadarm2 to grapple the vehicle.
Once captured, the robotic arm would guide the Cygnus to an attachment port on the station's Unity module. The mission plan called for the spacecraft to remain attached for up to six months before its disposal. This entire sequence is now on hold as engineers work to resolve the engine issue.