Getting to love logistics on the space station
by Jeff Foust
|“I can breathe kind of a sigh of relief with this flight. There were definitely some food and some other things that the crew needed,” said Gerstenmaier.|
NASA and the private sector are getting to love logistics as well. With the Space Shuttle long since retired, the International Space Station (ISS) partners now rely on a fleet of robotic spacecraft to deliver cargo of all kinds—including food, water, propellant, equipment, and experiments—to the station, and to take out the trash or bring items back to the Earth. With an increased emphasis on utilization of the station, timely delivery of supplies becomes ever more important, something the two companies with commercial cargo contracts from NASA are still getting a handle on.
The challenges in space station logistics could be seen in the latest resupply mission. At 12:52 pm Eastern time Sunday, an Antares rocket lifted off from the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Virginia. The rocket, built by Orbital Sciences Corporation, successfully placed into orbit a Cygnus spacecraft, also built by Orbital. The spacecraft, on a mission designated Orbital-2 or Orb-2, is on track to arrive at the ISS early Wednesday morning, to be grappled by the station’s robotic arm and berthed to the station’s Harmony node.
While the launch went off flawlessly, it also took place more than two months later than originally planned. An early May launch of the mission was postponed because of delays in another ISS resupply mission by SpaceX, which slipped until mid-April because of both technical difficulties as well as problems with a tracking radar at Cape Canaveral. That delay pushed the launch back to early June, after the SpaceX Dragon spacecraft returned to Earth.
In late May, though, an AJ26 engine undergoing an acceptance test at NASA’s Stennis Space Center in Mississippi suffered an unspecified failure. The Antares first stage is powered by two such engines, originally manufactured decades ago in the former Soviet Union by the Kuznetsov Design Bureau as the NK-33 and refurbished and rebranded by Aerojet Rocketdyne. While the investigation was ongoing, Orbital postponed the launch, waiting until the completion of inspections of the engines early this month to set a new launch date.
In pre-launch briefings, Orbital officials declined to go into detail about the issue with the AJ26 engine, but said they were confident that whatever issue caused the May failure would not be a problem for this launch. “One of the outcomes of that process was a desire to go back and conduct specific inspections of the engines” on this Antares, said Mike Pinkston, Antares program manager at Orbital, in a pre-launch briefing Saturday, referring to the investigation of the May failure. That inspection, he said, was designed “to confirm the presence and proper configuration of some critical features within the engine that were areas of interest relative to the failure.”
Pinkston didn’t discuss what those specific “areas of interest” were, but said that the inspections confirmed the engines were in proper condition. “We saw what we needed to see,” he said. “We have a lot of confidence that the two engines on Orb-2 are ready to go.”
Weather conditions provided one last obstacle for the mission: stormy weather in the days leading up to the launch delayed the rollout of the rocket to the launch pad, and then launch preparations, pushing the launch back from Friday to Saturday, and then to Sunday. Fortunately, it all came together Sunday for the launch, with the Antares lifting off at the beginning of a five-minute launch window, disappearing into some clouds a couple minutes later.
|“We saw what we needed to see,” Orbital’s Pinkston said of inspections of the two AJ26 first-stage engines on Antares.|
After the launch, a top NASA official said he was relieved that the Cygnus and its nearly 1,500 kilograms of cargo were en route to the ISS. “I can breathe kind of a sigh of relief with this flight. There were definitely some food and some other things that the crew needed,” said William Gerstenmaier, NASA associate administrator for human exploration and operations. “We had some margin, but it was getting to be where it was a little tense.”
A little later in the briefing, though, Gerstenmaier toned down those concerns. “We had time until the fall,” he said, noting that later this month both a Russian Progress and a European ATV cargo spacecraft were slated to launch to the station. However, he said from a “pragmatic, worrier’s standpoint” he could foresee potential delays to those missions and thus “you could see that margin evaporate pretty quick.”
“We really didn’t have any problem until the fall, so I probably overstepped a little bit by saying I was concerned,” he said, but added he was still relieved Cygnus got off the ground Sunday.
Employees of Planet Labs, including co-founder Robbie Schingler (second from left) pose with a full-sized engineering model of the company’s Dove series of small remote sensing satellites after a pre-launch briefing Friday. Twenty-eight of those satellites are included in the cargo launched Sunday on the Cygnus. (credit: J. Foust)
NASA and Orbital are, understandably, happy with the successful launch, but another company is as well. Inside the Cygnus are 32 small satellites that will later be deployed from the ISS, one of the applications of the space station that was not widely expected until the last couple of years. Of those 32, 28 are satellites for commercial remote sensing company Planet Labs.
That set of satellites, collectively known as Flock-1b, will be deployed from the airlock on the Japanese module Kibo at some point after arrival. Orbital vice president Carl Walz said at a briefing Friday that the timing of the deployment would depend on other ISS activities, including the arrival of the Progress and ATV cargo spacecraft in the coming weeks.
Planet Labs has flown satellites on all four Antares launches to date, noted company co-founder Robbie Schingler in a pre-launch briefing Friday. The previous Antares launch, of a Cygnus on the Orb-1 mission in January, brought to the station the company’s Flock-1 fleet of 28 satellites, later deployed from the station. “With Flock-1, we learned how to operate these spacecraft, commission these spacecraft, and get them going,” he said.
|“This is agile aerospace,” Schingler said. “It’s about more launches and more satellites, but it’s really about getting rich data.”|
Most of the Flock-1 spacecraft have since reentered, but in addition to the Flock-1b satellites on this Cygnus, a Dnepr launch from Russia last month placed 11 Dove spacecraft, collectively called Flock-1c, into orbit. Unlike the ISS-launched spacecraft, the Flock-1c spacecraft are in higher, sun-synchronous orbits. The company plans to start releasing imagery from those satellites in the coming weeks, he said.
The ISS-deployed spacecraft, while having lifetimes on the order of six months, still allow for technology demonstration and development: lessons learned from the Flock-1 spacecraft have been incorporated into the Flock-1b spacecraft, even though Schingler said the company only had weeks between the time the Flock-1 satellites were deployed and when the Flock-1b satellites had to be delivered for loading into the Orb-2 Cygnus spacecraft. “This is agile aerospace,” he said. “It’s about more launches and more satellites, but it’s really about getting rich data.”
When the Flock-1b satellites are deployed, Planet Labs will have launched a total of 71 satellites since April of last year. “Every two to three months, we learn from building spacecraft, putting them in space, and testing them in the laboratory in space,” Schingler said. By coincidence, he noted that at the beginning of the week, the company hired three more employees, bringing the company headcount to… 71.
The first (right) and second stages of the next Antares rocket, slated for launch in October, in Orbital’s Horizontal Integration Facility at MARS. This will be the first Antares to use the Castor 30XL second stage motor. (credit: J. Foust)
With Cygnus in orbit and the AJ26 engine problems presumably behind it, Orbital is hoping to resume a regular cadence of supply missions. Executive vice president Frank Culbertson said prior to the launch that they hoped to launch the next Cygnus on the Orb-3 mission in October; hardware for the Antares rocket that will launch it is already at Wallops. Three more Cygnus missions are planned for 2015, he said.
The timing of Orb-3 and future missions will depend on the overall schedule of various cargo and crew missions to the ISS, though. Dan Hartman, deputy ISS program manager, said in Saturday’s pre-launch briefing that the International Space Station Control Board would meet this week to review the upcoming manifest of ISS missions. He added that SpaceX’s next cargo mission, SpX-4, is now tentatively scheduled for September 12; it was previously planned for launch in August. (One obstacle had been delays in the launch of six ORBCOMM satellites on a Falcon 9, which took place as this article was being prepared for publication Monday morning after two months of delays.)
Orbital, meanwhile, is making both near-term and long-term plans for both Antares and Cygnus. The next Antares launch will use a new second stage, the Castor 30XL, that will generate more thrust and increase the payload capacity of the rocket. That will allow Orbital, starting with the Orb-4 mission next year, to move to an “enhanced” version of the Cygnus with a pressurized module a meter longer than the current version, as well as a number of other upgraded components, “all adding up to increased performance and higher cargo capability,” Culbertson said.
Orbital is also looking at other ways to use the Cygnus. Culbertson said the company is studying new reentry profiles for the vehicle that minimize propellant, allowing the spacecraft to remain in orbit for extended periods after unberthing from the station. That would allow Cygnus to perform experiments not possible on the station.
|“We’re still in the process of negotiating with the proposers on the next block of engines for Antares,” Culbertson said. “We’ll probably announce that some time this summer.”|
“Because Cygnus does destructively reenter, there are some examples of fire investigations that make a good fit for the Cygnus vehicle,” said Kirt Costello, assistant ISS program scientist. He added experiments dealing with spacecraft breakup and reentry also could be tested on Cygnus at the end of its mission.
Orbital is also investigating how Cygnus could be used for missions other than ISS resupply. “We’ve talked to different NASA groups about the possibility of using Cygnus as a habitat, potentially, in cislunar space, in addition to providing cargo out beyond low Earth orbit,” Walz said. “It could operate in conjunction with the Asteroid Redirect Mission, providing additional space for astronauts.”
Antares, meanwhile, could get an upgrade to its first stage. Orbital has been in discussions with several companies about either procuring a new batch of AJ26 engines or replacing the AJ26 with a new engine of some kind. The company hasn’t said what alternatives it is considering, but much of the speculation has focused on a solid motor from ATK (which is in the process of merging with Orbital) or an RD-180 or a derivative of that engine from Russia’s NPO Energomash.
“There are a number of options available to us,” said Orbital senior program manager John Steinmeyer on Friday. There are additional AJ26 engines in Aerojet Rocketdyne’s inventory in Sacramento, California, he said, beyond what Orbital has contracted to acquire for its existing manifest of commercial resupply missions. Another option would be to restart production of those engines in Russia. “There are also other suppliers that could provide engines for us.”
“We’re still in the process of negotiating with the proposers on the next block of engines for Antares,” Culbertson said Sunday. “We’ll probably announce that some time this summer.”
That upgraded Antares likely wouldn’t be used until after Orbital completes its current Commercial Resupply Services (CRS) contract with NASA, for which Sunday’s launch was the second of eight such missions. “We’re looking forward to the next six missions and the next contract,” Culbertson said.
The competition for that contract, called CRS-2, is still in development. Gerstenmaier said a draft request for proposals (RFP) was issued earlier this summer, with a final RFP planned for the fall. The goal, he said, “is to select some time towards December or January.” While the two current CRS contract awardees, Orbital and SpaceX, are expected to compete for CRS-2, they may face competition from Boeing and Sierra Nevada Corporation, who are developing vehicles under the Commercial Crew Program that could also be used for cargo resupply.
For now, though, NASA and its commercial partners are still getting up to speed on CRS, creating a regular schedule of cargo deliveries to avoid getting “a little tense” about station logistics. “We planned that it might take a little while to get some of these cargo vehicles established. It’s not easy launching a vehicle to space,” Gerstenmaier said. “To get into kind of a cadence or a routine of launching regularly, that doesn’t happen quite as easily as you think.”
As the ISS matures into a full-fledged orbital laboratory, though, that cadence of regular resupply missions will be critical to keep the station’s supplies topped off and its experiments updated. To make that happen, you have to love logistics.