SpaceX and Orbital Sciences Corporation will now have to deliver the majority of supplies needed to maintain the U.S. segment of the International Space Station (ISS) given ESA’s decision to retire its ATV freighter and JAXA limiting HTV cargo ship flights to one per year, NASA’s Aerospace Safety Advisory Panel (ASAP) said in a report this week.
The increased responsibilities come amid a 16-month gap in Orbital Science’s Cygnus flights to the space station that resulted from the explosion of the company’s Antares rocket on Oct. 28. The loss puts much more pressure on SpaceX, which has an aggressive schedule of five Dragon resupply flights to the space station this year.
ASAP noted in its 2014 Annual Report that both U.S. cargo delivery systems are “relatively immature from an operational perspective.” As the table below shows, Orbital and SpaceX also have fallen significantly behind schedule on launches.
“Even acknowledging the fact that some missions were put on contract prior to the completion of the system development, the schedule performance must significantly improve to enable consistent scientific research on the ISS,” ASAP said in its report. “There will be additional pressure on cargo logistics while Orbital works through its plan to resume cargo missions. NASA’s logistics planning and adjustments during this critical period will be a focus for the Panel in the coming months.”
SpaceX has five Dragon resupply missions to ISS scheduled in 2015. The first was successfully launched on Jan. 10. Additional flights are scheduled for April, June, September and December. Whether the company will meet that schedule is uncertain given continual slips in its manifest. Last year, SpaceX launched six Falcon 9 rockets out of a planned 10.
Orbital plans to launch a Cygnus cargo ship to ISS in late November aboard an United Launch Alliance Atlas V while it fits the Antares rocket’s first stage with a new type of engine. The company hopes to resume Cygnus flights aboard Antares in 2016; however, it is possible it will launch a second Cygnus aboard an Atlas V if it experiences delays with the modified booster.
Four Russian Progress freighters are set for launch in February, April, August and October. JAXA’s HTV cargo ship is scheduled for launch in August.
ASAP noted that both SpaceX and Orbital Sciences have experienced technical challenges during their Commercial Resupply Services (CRS) missions.
“Some of the early SpaceX missions under the CRS contract experienced water intrusion after landing and loss of power to returning science payloads. Additionally, SpaceX successfully overcame a Falcon 9 engine failure during ascent on SpX-1 and, with NASA’s help, a significant thruster issue on SpX-2,” the report stated.
Orbital Sciences did not suffer any serious anomalies during its first two commercial Cygnus missions to ISS. The third resupply ship was lost when Antares exploded. Cygnus is not designed to return cargo from space.
“Overall, the challenges faced by the commercial cargo providers are not unexpected,” ASAP said in the report. “Both Orbital and SpaceX are working to improve reliability and schedule performance. NASA oversight and certification of mission operations in the ISS ellipsoid have proven effective. With the CRS contract administered under the ISS Program, there has been transparency, the acknowledgement of challenges, and a positive safety culture. Additionally, the Panel noted that the recently released Request for Proposal for the next contract (CRS2) incorporated significant lessons learned by NASA.”
ASAP recommended that NASA undertake formal documentation of a risk mitigation strategy relating to commercial cargo.
“The ISS Program has an excellent track record for creatively solving problems, and logistics planners will need to continue emphasizing flexibility to accommodate delays or other possible mission failures,” the report states.
Because of the relative immaturity of SpaceX’s and Orbital’s cargo systems, the vehicles have been carrying only “non-critical” supplies to ISS. “NASA initially based its decision to certify only the mission operations occurring within the vicinity of the ISS (i.e., within the ISS ellipsoid) on the premise that the commercial providers would fly ‘non-critical’ cargo,” the report states.
However, NASA was planning to certify Cygnus vehicles to carry a critical cargo –water — to the space station in early 2015. The Antares explosion and resulting flight delays scrambled those plans. NASA began to develop a plan to certify SpaceX’s Dragon spacecraft for water delivery, negotiated with the Russians to transport water aboard their Progress cargo ships, and made efforts to return the station’s Sabatier recycling system to operational status.
“This response is viewed by the Panel as appropriate, and there is confidence that adequate water supplies will be maintained on the ISS,” ASAP wrote. “This particular example is meant to illustrate the importance of reliable cargo delivery services — regardless of cargo classification. In fact, the term ‘non-critical’ can mislead and cause inappropriate perceptions leading to the conclusion that the cargo is not important, which, as shown in the water example, may not be the case. The importance of a given piece of cargo depends on a number of factors, and using or not using the term ‘critical’ may lead to erroneous conclusions as to potential impact in the case of loss.”
The Japanese HTV mission in August is set to deliver water to ISS. However, the flight is scheduled for launch just over two weeks before ISS would run out of water on Sept. 2 if it wasn’t resupplied by other cargo ships. ASAP said the schedule provided little margin for delays.
ESA’s fifth and final ATV cargo ship, which was also certified to carry water, is currently docked with the International Space Station. It will be undocked from ISS in mid-February.