A Northrop Grumman Antares rocket lifts off from Wallops Island, Virginia, November 2 carrying a Cygnus cargo spacecraft on the first mission under the company’s CRS-2 contract with NASA. (credit: J. Foust)
by Jeff Foust
Monday, November 11, 2019
On a Saturday morning a little more than a week ago, a Northrop Grumman Antares rocket lifted off from the Mid-Atlantic Regional Spaceport on Wallops Island, Virginia, carrying a Cygnus cargo spacecraft bound for the International Space Station. Less than 48 hours later, that Cygnus was grappled by the station’s robotic arm and attached to a port on the station. Neither the launch of the Cygnus nor its arrival looked out of the ordinary, much like many other missions over the last several years.
|“CRS-2 I would describe as more of a step-function change in the capability” of the overall Antares/Cygnus system, said DeMauro.|
That routine aspect of the mission is a testament of how far commercial cargo has come. A decade ago the program was still something of an experiment with an uncertain outcome, one that had already had setbacks (Rocketplanet Kistler, which received one of two original awards, lost its funded Space Act Agreement when it failed to meet financial milestones.) There were delays, technical problems, and even launch failures along the way that raised questions about whether commercial vehicles could keep the station adequately supplied. Today, though, both Northrop and SpaceX regularly haul supplies and experiments to the station, and the emphasis is now less on the missions and more on what unusual investigations are bound for the ISS on each mission.
But this Cygnus launch, while looking familiar, was in fact a milestone in the commercial cargo program. The mission was the first for a new round of commercial cargo contracts, called Commercial Resupply Services 2 (CRS-2), that NASA awarded in 2016. By the end of 2021, two other companies, SpaceX and Sierra Nevada Corporation (SNC), will start their own missions under CRS-2, maintaining a regular stream of cargo deliveries to and from the station while offering new capabilities.
A “step function” upgrade
Northrop’s CRS-2 contract continues the use of the Antares rocket and the Cygnus spacecraft from its original CRS contract. Both underwent upgrades and other changes during the original CRS contract, notably the replacement of the AJ26 engine of the original Antares with the new RD-181 engine after the spectacular Antares launch failure in October 2014. Other changes focused on the improvements to the Cygnus spacecraft.
The CRS-2 contract introduces improvements to both the rocket and spacecraft. “CRS-2 I would describe as more of a step-function change in the capability” of the overall system, said Frank DeMauro, vice president and general manager of Space Systems at Northrop Grumman, at a press conference the day before the launch of that first CRS-2 mission, designated NG-12.
The biggest change for this particular mission was the ability to carry more cargo. The Cygnus launched with more than 3,700 kilograms of cargo on board, several hundred kilograms more than previous missions. That includes the ability to carry more middeck lockers filled with experiments: ten, six of which have power, compared to six lockers, of which four were powered, on previous missions. New telemetry capabilities allow researchers to monitor those experiments, and send commands as needed, from launch through berthing.
Another new capability, introduced on the previous Cygnus mission, NG-11, in April, is the ability to do “late loads” of time-sensitive cargo, like biological experiments. After being rolled out to the pad and raised for fit checks, the Antares is lowered back to the horizontal position and a mobile clean room moved into place around the top of the rocket. A new “pop top” payload fairing allows the top to be removed, giving technicians access to the spacecraft inside for loading cargo within 24 hours of launch.
The Cygnus also has the capability to perform long-duration missions after departing the ISS. Previously, Cygnus spacecraft reentered no more than a few weeks after leaving the station, its holds now filled with garbage for disposal. The Cygnus can now spend months in orbit, using a control moment gyro to minimize the use of propellant needed for attitude control.
The NG-11 Cygnus, which left the station in early August, is still in orbit, performing tests of its long-duration capabilities. “We haven’t set a deadline for when we’ll bring it back,” DeMauro said before the launch of the NG-12 Cygnus. “I don’t expect it to be that much after NG-12 on orbit.”
|Using Crew Dragon for future cargo missions will provide 30 percent more pressurized volume, said SpaceX’s Reed, along with the ability to dock autonomously and stay at the ISS longer.|
That capability meant that Northrop Grumman had to modify its mission control center in Virginia to be able to monitor two Cygnus spacecraft at once. DeMauro said Northrop tested that new setup extensively to make sure that, when spacecraft controllers send a command, they do so to the right spacecraft.
The improvements to the Cygnus, which both increase the spacecraft’s cargo capability and its dry mass, required changes to the Antares. The launch was debut of the Antares 230+, with the “+” signifying changes to improve its performance. Among them were changes to increase the structural strength of the first stage so that its RD-181 engines can operate at full thrust throughout their entire burn. That eliminates what Kurt Eberly, Antares vice president at Northrop Grumman, called the “throttle notch” where the engines had to throttle down at maximum dynamic pressure before going back to full thrust for the rest of their burn.
Other changes included modifications to lower the overall mass of the two stages, such as consolidating composite structures in the upper stage. Those changes, along with a change that placed the Cygnus in a slightly lower initial orbit than past missions, increased the overall payload capacity of the Antares by about 800 kilograms, Eberly said.
DeMauro called the improvements to Antares and Cygnus a “step function” in part because, after gradual improvements during the original CRS contract, Northrop doesn’t plan to make similar upgrades to the vehicles during the life of the CRS-2 contract, which covers a minimum of six missions through 2024, but won’t rule them out if something arises.
“Our current plan is to keep the capabilities we currently have throughout the first part of CRS-2,” he said. “However, as we go through these missions and NASA identifies additional needs that they have, or we identify good ideas to increase those capabilities, we’ll work those with NASA and potentially add more upgrades.”
SNC expects to launch its first Dream Chaser mission to the ISS in late 2021. (credit: SNC)
Dragons and Dream Chasers
Northrop is one of two companies that had original CRS awards, dating back to the original Orbital Sciences Corporation (Orbital merged with ATK to become Orbital ATK in 2014, which was then acquired by Northrop Grumman in 2018.) SpaceX, the other CRS awardee, still has two more mission under that contract: SpX-19 (called CRS-19 by SpaceX) next month, and SpX-20 in early 2020.
Later in 2020 SpaceX will shift to the CRS-2 contract, and in the process change spacecraft. The original cargo Dragon used on its CRS missions will be replaced by a version of the Crew Dragon the company has been developing for NASA’s commercial crew program. Flying both cargo and crew missions on the same spacecraft will eliminate the need for SpaceX to maintain two separate Dragon production lines.
Switching to the Crew Dragon offers other improvements. “It has 30 percent more pressurized volume,” said Benji Reed, director of commercial crew mission management at SpaceX, during a presentation last month at the International Symposium for Personal and Commercial Spaceflight in New Mexico. It will be able to dock autonomously with the station, like the Crew Dragon vehicle did on its Demo-1 test flight in March, rather than be berthed by the station’s robotic arm. Reed said the Dragon will now be able to remain docked to the station for up to 75 days per mission, rather than the month-long stays of the existing cargo Dragon.
Other tweaks address the cargo inside. The new Dragon will support eight powered lockers up to the station and four for the return trip, Reed said. An “accelerated” return option will have experiments in the hands of researchers within three hours of splashdown, compared to the day or more it takes on cargo Dragon missions today.
When NASA made the CRS-2 awards in early 2016, it decided to add a third company to the mix. SNC will start flights to the station in late 2021 using a cargo version of its Dream Chaser vehicle, a runner-up to Boeing and SpaceX in the commercial crew competition in 2014.
SNC marked a milestone in the construction of Dream Chaser last month, when the composite structure for that vehicle arrived at a company facility in the Denver suburbs. That structure was built by Lockheed Martin at a factory in Ft. Worth, Texas, which makes composite structures for the F-35 aircraft.
With that structure in its possession, SNC plans to start full-scale assembly of the vehicle. “Now we have something to hang things on,” said John Curry, SNC’s Dream Chaser program director for its CRS-2 contract, at an event marking the arrival of the structure.
|“We’re really looking forward to having this capability,” Shireman said of Dream Chaser’s larger cargo capacity and ability to land on a runway.|
Over the next year and a half, the Dream Chaser will take shape, both with the upcoming arrival in the next few months of its wings and a cargo module and the outfitting of spacecraft. By the spring of 2021, the vehicle will be ready for shipment by C-5 cargo plane to NASA’s Plum Brook Station in Ohio for environmental testing, and from there to Florida for launch preparations.
That first launch could take place as soon as September (at the SNC factory, one cubicle had a countdown to that date) on what will likely be the second flight of United Launch Alliance’s new Vulcan rocket. SNC announced a contract with ULA in August for six Vulcan launches of Dream Chaser, covering the minimum number of CRS-2 missions under its contract.
“ULA had a pretty significant advantage because we have been working with ULA from day one,” Eren Ozmen, president of SNC, said at an August press conference announcing the ULA launch contract. SNC had originally planned to launch the crewed Dream Chaser on an Atlas 5. Ozmen added that her company considered proposals from SpaceX and Blue Origin, as well as European and Japanese vehicles, but picked ULA because of that relationship and a “really good competitive price” that the companies declined to disclose.
A single Dream Chaser should be sufficient for all CRS-2 missions, since the vehicle is designed to fly at least 15 missions in its lifetime. (A new cargo module will be needed for each mission since that component is used to dispose of trash, separating from the Dream Chaser after departing the station to burn up in the atmosphere.) SNC will build at least one more Dream Chaser as a backup, and to support any additional missions, but hasn’t said when that vehicle will be ready.
If the space station’s cargo needs are currently being met by Cygnus and Dragon (along with Japan’s HTV and Russia’s Progress), why add another vehicle to the mix? Kirk Shireman, NASA’s ISS program manager, said at the SNC event last month that Dream Chaser offers “unique capabilities,” among them the ability to send up to 5,500 kilograms of cargo to the ISS, more than even the upgraded Cygnus and Dragon.
Another advantage is that the Dream Chaser will return to a runway landing at the Shuttle Landing Facility runway at the Kennedy Space Center, allowing almost immediate access to its cargo of up to 1,850 kilograms of experiments and equipment returned to the station. “We’re really looking forward to having this capability,” Shireman said.
|SNC hopes that, once people see the cargo version of Dream Chaser flying, they’ll be interested in a crewed version, Curry argued. “I think we’ll be flying crew soon enough.”|
At the event, Steve Lindsey, SNC senior vice president of space exploration systems, disclosed that the company had spent “over a billion dollars of our own money” on Dream Chaser. With an investment like that, the company is looking for returns beyond cargo missions. SNC has touted the ability of Dream Chaser to do free-flyer missions not associated with the ISS for microgravity research or other applications.
The company also hasn’t closed the door on a crewed version of the spacecraft. Lindsey said the cargo version of Dream Chaser has about 85 percent in common with the crewed version, making it easy for the company to create a crewed version if there’s demand from NASA or others, such as operators of proposed private ISS modules or space stations.
SNC hopes that, once people see the cargo version of Dream Chaser flying, they’ll be interested in a crewed version. “So I think one of these days, once we fly our missions to the space station, it’ll be like ‘Field of Dreams’: build it and they will come,” Curry argued. “I think we’ll be flying crew soon enough.”
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