- Parabolic Arc
- September 27, 2023
Getting to Upmass: A Dragon’s Tale
A Station that Needs Everything
A Scrappy Startup Contracted to Ship 35.4 Metric Tons of It
Ought to be Easy Enough, Right?
By Douglas Messier
The International Space Station (ISS) is not exactly a self-sufficient outpost. The station’s occupants can’t jump into a Soyuz and pop over to an orbiting Wal-Mart when they run out of food, water or toothpaste. Everything the six astronauts need to survive — save for the random plastic wrench or replacement part they can now 3-D print — must be shipped up from the majestic blue planet 400 km below them.
Four supply ships from the United States, Russia and Japan service the station. Two American companies – Orbital ATK and SpaceX – provide resupply services under contract to NASA. The launch vehicles and spacecraft they use were developed under a public-private partnership with the space agency.
SpaceX’s Dragon supply ship speaks of the company’s ambition to fly astronauts to Earth orbit and, eventually, to Mars. To drive home the point, it even has a window — unsual for an automated cargo vessel.
The vehicle is composed of a capsule with a heat shield that can transport pressurized cargo to and from the space station — a capability no other supply ship possesses. Behind the capsule is the spacecraft’s trunk, a semi-enclosed area where unpressurized cargo is carried. This, too, is a unique capability among supply ships.
NASA awarded Commercial Resupply Services-1 (CRS-1) contracts to SpaceX and Orbital in December 2008. The space agency’s initial order from SpaceX was for 12 missions at a cost of $1.6 billion, or an averages of $133.3 million per flight.
Initially, NASA wanted the Dragons to carry 39.7 metric tons of cargo — known as upmass — to the space station. The total was later reduced to 35.4 metric tons – for an average of 2.95 metric tons per flight — in exchange for SpaceX returning cargo to Earth.
Following a successful Dragon demonstration flight to the space station in May 2012, SpaceX flew its first commercial mission in October of that year. A second resupply flight followed in March 2013.
Although both missions were successful, each one suffered a close call. On the inaugural flight, one of first stage engines on the Falcon 9 booster stopped, causing its faring coming apart. The other eight engines had sufficient reserve power to get Dragon into orbit.
However, a secondary payload, an Orbcomm OG-2 satellite, ended up in a lower than planned orbit. Due to mission rules designed to protect the space station, the satellite’s orbit could not be raised and re-entered the Earth atmosphere days later.
On the second flight in March, Dragon successfully entered orbit only to have its thrusters malfunction. Controllers managed to correct the problem with only a one-day delay in its berthing to the space station. Like vehicle splashed down in the Pacific Ocean after a successful flight.
Despite two missions in the books, SpaceX had a serious problem: the company was way behind on its upmass target. The SPX-1 and SPX-2 missions had carried only 450 kg and 865 kg of cargo, respectively. These totals were well short of the average of 2.95 metric tons per flight. Total cargo delivered was only 1.315 metric tons — a shortfall of 4.585 metric tons from what was required to keep the company on target.
The shortfall was primarily the responsibility of SpaceX, according to an audit released last month by the NASA Office of the Inspector General (OIG).
“The first two missions carried smaller loads because the empty cargo vehicles were heavier than expected and the Falcon 9 rocket did not meet its planned lift capability,” according to the OIG report. “SpaceX has since addressed both of these issues with an upgrade to its Falcon 9 rocket.”
Because the shortfall was a result of limitations on SpaceX’s side, the company “provided consideration for the reduced upmass on these flights,” the audit found.
Following the upgrades, the Dragon was able to carry significantly more cargo. For the SPX-3 through SPX-6 flights, upmass ranged from 2,024 kg to 2,338 kg. In all, the four resupply missions carried 8.872 metric tons of cargo, including 7.282 metric tons of pressurized cargo and 1.59 metric tons of unpressurized cargo.
Although a significant improvement on the first two flights, the loads carried were still below the 2.95 metric tons needed to fulfill the upmass requirement. The cargo weights were also well short of the projected 3.31 metric ton capacity of Dragon.
The shortfall was due to both physical and programmatic limitations. The Dragon capsule only had so much space, which was limited by the large volume of certain cargo. NASA and SpaceX were also on a learning curve in determining how to most efficiently pack the spacecraft.
“With the exception of SpaceX’s first two missions (SPX-1 and SPX-2), which delivered 450 kg and 865 kg to the ISS, respectively, NASA has generally loaded Dragon 1’s pressurized module to its volumetric limit,” the OIG report said. “However, the amount of upmass stored in the module and trunk has varied by mission based on NASA’s needs and the volume and density of particular cargo.”
NASA and SpaceX gradually got better at packing supplies into the capsule. The OIG report noted that packing efficiencies and greater payload mass allowed the SPX-5 and SPX-6 vehicles to carry larger loads.
Another problem was that NASA was unable to fully use Dragon’s trunk for unpressurized cargo. The space agency placed no cargo in the trunk for the first and sixth missions. For the other four missions, the amount of cargo carried there was below the maximum possible amount.
“The ISS Program acknowledged it struggled to utilize the Dragon 1’s trunk on the early CRS-1 missions, noting that after the Space Shuttle retired a gap in procurement and planning for this type of payload existed while the commercial partners were developing transportation capabilities,” the audit found. “As a result, appropriate payloads were not ready at the time the SpaceX missions flew.”
NASA officials said they are working to fully utilize the trunk on future flights. The OIG report recommended that the space agency “consider preparing alternative unpressurized upmass payloads in the event scheduled payloads cannot be launched.
However, the space agency rejected the proposal as unreasonable.
“There is a significant amount of flight specific analysis to certify the cargo vehicle to fly with the unpressurized cargo,” NASA wrote in response. “Typically this analysis takes months to perform at considerable cost to the service provider. Costs for unpressurized payloads are in the tens to hundreds of millions of dollars and once a sponsoring organization has committed this level of funding, it is not reasonable to put the payload on a ‘reserve’ flight list awaiting a launch opportunity only when another payload misses its scheduled delivery date.”
Under the CRS-1 contract, NASA is responsible for manifesting the cargo for each flight. Thus, the space agency must pay the negotiated price for each mission whether it fills spacecraft to capacity or not. It is not due any of the “consideration” on pricing it had received for the SPX-1 and SPX-2 missions, where upmass shortfalls were primarily due to the limitations of SpaceX’s delivery system.
When SPX-6 splashed down in the Pacific Ocean on May 21, 2015, SpaceX was offically halfway through its initial order for 12 flights. The company had transported only 10.187 tons of cargo to the station — less than a third of the contracted amount of 35.4 metric tons. Even with NASA’s plans to maximize use of the truck section, the company was going to be about 7 metric tons short of that goal with 12 flights – the better part of three supply flights.
However, NASA and SpaceX already had that shortfall covered.
“In September 2014, NASA modified the SpaceX CRS-1 contract to extend the period of performance through December 2016, added mission pricing for calendar years 2017 and 2018, and ordered SPX-13 and SPX-14,” according to the OIG report. “NASA ordered SPX-15 in December 2014.”
At the time, SpaceX President Gwynne Shotwell put the value of the flight at approximately $150 million apiece for a total of $450 million. The additional orders raised the total of the CRS-1 contract to $2.05 billion for 15 flights.
By the summer of 2015, everything was looking pretty good. Resupply flights were running more smoothly, NASA and SpaceX were finding efficiencies in loading cargo into the Dragon, and the upmass shortfall had been addressed with additional flights.
But, then came June 28, 2015. A sunny Sunday in Florida. Another picture perfect launch for Falcon 9 into Florida’s blue skies. Then, two minutes 19 seconds into the flight–
Boom! Falcon 9’s upper stage suddenly disintegrated. A Dragon resupply ship stripped of its trunk tumbled out of control in a large white cloud. The spacecraft and 2.478 metric tons of cargo worth $118 million ended up at the bottom of the Atlantic Ocean. Months of work would be required before the rocket could fly again.
The pressurized cargo lost in the flight included:
- 690 kg of food, oxygen and other consumables;
- 573 kg of science experiments and supporting equipment for NASA, the Canadian Space Agency, European Space Agency, and Japan Aerospace Exploration Agency (JAXA);
- 462 kg of vehicle hardware, including tanks and filter inserts for the Station’s Environmental Control and Life Support System;
162 kg of extravehicular activity (EVA) equipment, including a spacesuit; and,
36 kg of computer resources, including a projection screen, laptop, and power modules.
The most significant loss was located in the trunk. Lost in the accident was the first of two International Docking Adapters (IDA). The $32.4 million adapter was part of an upgrade of the space station’s docking system in preparation for commercial crew vehicles being developed by SpaceX and Boeing. The first of four flight tests of the spacecraft is scheduled for May 2017.
A Dragon is scheduled to carry the second IDA to the station later this month. However, a replacement adapter will not be launched until February 2018 – most likely after four tests flights by SpaceX and Boeing will be completed. The lack of a second IDA raises the risk of a failed mission if a vehicle has difficulty using the lone adapter on the station.
The accident came at the worst time for NASA and the space station program. Eight months earlier, an Orbital Sciences Antares rocket exploded, destroying a Cygnus resupply ship carrying $51 million worth of supplies to ISS. Now both of NASA’s commercial cargo suppliers were off line.
Two months before Falcon 9 crashed, a Russian Progress supply ship tumbled out of control in orbit after being launched from the Baikonur Cosmodrome. Controllers were unable to save the ship, so the mission was a complete loss.
The Falcon 9 would stay grounded for six months while SpaceX addressed the cause of the accident. In the meantime, NASA sent some of the most crucial supplies aboard JAXA’s HTV-5 cargo ship, which launched in August 2015, and Russian Soyuz and Progress spacecraft headed for the station. Progress resupply flights resumed in July, five days after Falcon 9 crashed.
Dragon made a successful return to flight on April 8, 2016, carrying its heaviest load yet – 3,259 kg — to the space station. The spacecraft’s trunk was volumetrically full with Bigelow Aerospace’s BEAM module, which was attached to the station to test inflatable habitat technology. The flight brought total upmass to just under 13.5 metric tons.
Despite the loss of nearly 2.5 metric tons of cargo on the seventh resupply flight, SpaceX believes it can still meet its 35.4 metric ton upmass requirement using the extra three Dragon flights added in 2014. NASA is more skeptical.
“SpaceX officials expect SPX-11 through SPX-15 to each carry a full load of 3,310 kg,” the OIG report reads. “However, ISS Program officials noted because the Dragon’s pressurized cargo module is volume-limited and has yet to transport more than 2,024 kg on a mission, this may not be attainable.”
“In the aftermath of the SPX-7 failure, NASA and SpaceX negotiated an equitable adjustment to compensate NASA for launch delays resulting from the failure,” the OIG audit found. “Most notably, SpaceX agreed to provide at no additional cost significant enhancements to the Agency’s science and operational capabilities.”
One key improvement SpaceX has made is to upgrade the power available to experiments flying aboard Dragon capsules.
“By increasing powered capability, SpaceX tripled the number of powered payloads that could be accommodated, which provides a significant enhancement to ISS science capability,” the OIG audit said. “A by-product of this redesign is the ability to reallocate spacecraft power between internal and external payloads on a flight by flight basis, adding more flexibility to accommodate various types of payloads.”
NASA officials said that although the power upgrades and other improvements could not be quantified in monetary terms, they are “just as important to the Agency and the science and research community, or in some cases, more important than dollars saved.”
While SpaceX and NASA were investigating and addressing the cause of the SPX-7 failure, they were also negotiating a further extension of the company’s supply contract through 2018.
The extension was primarily due to delays in awarding the follow-on CRS-2 contracts. The date of the contract awards was repeatedly pushed back throughout 2015, delaying the start of CRS-2 flights until 2019.
In December, NASA and SpaceX reached an agreement for an additional five missions. Industry sources estimated the value of the contract at about $700 million, or $140 million per flight. The additional orders increased the value of SpaceX’s CRS-1 contract to approximately $2.7 billion for 20 missions.
The OIG reported that in light of the SPX-7 failure, NASA was able to negotiate “significant consideration in the form of adapter hardware, integration services, manifest flexibility, and discounted mission prices for the SPX-16 through SPX-20 resupply missions.”
In January 2016, NASA split the CRS-2 contract three ways. SpaceX, Orbital ATK and Sierra Nevada each received contracts for a minimum of six flights apiece to carry cargo to ISS between 2019 and 2024, with additional orders at NASA’s discretion.