Northrup Grumman’s Cygnus cargo spacecraft conducted a successful reboost of
the International Space Station over the past weekend, on Saturday, June 25,
2022. The Cygnus NG-17 “Piers Sellers” is the first US-based spacecraft to
provide a substantial orbital adjustment to the ISS since the space shuttles
retired in 2011. Russia’s Progress cargo spacecraft has been the primary
source for station reboosts, attitude control, and debris avoidance
maneuvers.
“This reboost of the ISS using Cygnus adds a critical capability to help
maintain and support the space station,” said Steve Krein, vice president,
civil and commercial space, tactical space systems, Northrop Grumman, in a
press release. “It also demonstrates the enormous capability Cygnus offers
the ISS and future space exploration efforts.”
Cygnus fired its gimbaled delta velocity engine for a total of 301 seconds,
raising the station’s perigee by about 0.8 kilometers (1/2 mile) and its
apogee by nearly 0.2 kilometers (.1 mile) for a test of “this enhanced
capability for a standard service for NASA,” Northrup Grumman said.
“This Cygnus mission is the first to feature this enhanced capability as a
standard service for NASA.”
Cygnus had been docked to the ISS since February and now has departed,
leaving on June 28. Back in 2018, the ninth Cygnus resupply mission
conducted a test of the reboost capability by conducting a short 50 second
burn of its main engine, raising the Station’s altitude by 90 meters (295
feet). The thruster firing on June 25 was actually the second attempt to
raise the station’s orbit with the Cygnus NG-17, as on June 20, the maneuver
was aborted after just five seconds. Northrup Grumman said the abort was
triggered automatically and came as a “precautionary measure.” An
investigation by engineers showed that the observed parameters were as
expected and acceptable.
Having US capabilities to provide propulsion to the ISS came to the fore as
an issue following Russia’s invasion of Ukraine in late February 2022. After
sanctions imposed on Russia by the US and other countries who are part of
the space station consortium, thinly-veiled threats by Dmitry Rogozin, the
Director-General of the Russian State Space Corporation (Roscosmos)
indicated that Russia might be terminating its cooperation in space; he also
suggested the country might use the ISS as a weapon. The Russian news agency
RIA Novosti also showed a CGI video depicting the Russian modules detaching
from the ISS. Other volleys on social media from Rogozin and others made for
a tense few months, but tempers seemed to have cooled lately.
NASA says that normally, all International Space Station propulsion is
provided by the Russian segments and Russian cargo spacecraft. A set of
thrusters on the Zvezda module can be used, however, they are mainly
reserved for when the Soyuz can’t conduct the task, as propellant on board
the station is limited. The U.S. gyroscopes provide day-to-day attitude
control or controlling the orientation of the station. “Russian thrusters
are used for attitude control during dynamic events like spacecraft dockings
and provide attitude control recovery when the gyroscopes reach their
control limit,” NASA said.
Of course, since Cygnus has now departed, the space station remains reliant
on the Russian sources for any needed maneuvers. While the head of SpaceX
has intimated Dragon capsules could help maneuver the station, they
currently do not hold that capability.
Northrup Grumman said providing reboosts and thruster capabilities is the
latest in a series of improvements made to the spacecraft since its first
mission to the station in 2013. The company has increased the amount of
cargo it can carry to the station with a larger cargo module, added lighter
and more powerful solar arrays and fuel tanks, and upgraded many of its
systems to make reboost possible.
So far, Cygnus spacecraft have delivered more than 5,000 kg 112,000 pounds
of equipment and supplies to the astronaut crews aboard the ISS. The Cygnus
vehicle was packed with garbage before undocking, and it conducted
controlled reentry over the Pacific Ocean on June 29.
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