The second Orbital Flight Test (OFT-2) of Boeing’s CST-100 Starliner spacecraft must wait a little longer, following a scrubbed launch attempt on Tuesday. According to Boeing, “unexpected valve position indications” in the spacecraft’s propulsion system were observed during checkouts after electrical storms passed over the Kennedy Space Center (KSC), earlier this week, and that the team would stand down to achieve a better understanding of the anomaly. Perched atop its 172-foot-tall (52.4-meter) Atlas V booster, the Starliner will be returned to the protective cover of the Vertical Integration Facility (VIF) at Space Launch Complex (SLC)-41 at Cape Canaveral Space Force Station, Fla., where the spacecraft is more readily accessible for analysis.
“Engineering teams have now cycled the Service Module propulsion system valves with the Starliner and Atlas V on the launch pad and have ruled out a number of potential causes, including software,” Boeing explained in a statement. “Additional time is needed to complete the assessment and, as a result, NASA and Boeing are not proceeding with tomorrow’s launch opportunity.”
“Starliner has a valve issue,” tweeted ULA CEO Tory Bruno after Tuesday’s scrub. “Atlas and the pad are fine. We will protect for a recycle tomorrow if NASA and Boeing are able to resolve.” But as circumstances transpired, the backup launch opportunity at 12:57 p.m. EDT on Wednesday, 4 August, would also be missed.
It is yet another unfortunate blow for this beleaguered mission, which represents an uncrewed reflight of the Starliner, more than 19 months after the troubled OFT-1. Originally targeting a launch of OFT-2 last 29 March, this date was initially moved forward to the 25th, then back to no sooner than 2 April, due to a need for additional hardware processing.
But with a packed manifest of ISS visitors through the summer months—including Russian and U.S. crew exchanges and coming-and-going science-loaded cargo missions—a further push of the beleaguered mission to 30 July proved inevitable.
Last Friday’s opening launch attempt was scrubbed following the troubled rendezvous and docking of Russia’s Nauka (“Science”) lab at the station and due to classified Eastern Range activities the next available opportunity for OFT-2 to fly was 1:20 p.m. EDT on Tuesday, 3 August.
Yesterday’s attempt proceeded without incident, deep into the countdown, as ULA teams fueled the Atlas V Common Core Booster (CCB) and its Dual-Engine Centaur (DEC) upper stage with cryogenic liquid oxygen and hydrogen.
All told, about 4,150 gallons (18,870 liters) of liquid oxygen and 12,300 gallons (55,900 liters) of liquid hydrogen were loaded aboard the Centaur, whose dual RL10A-4-2 engines will execute a seven-minute-long “burn” to push the Starliner towards low-Earth orbit.
And about 48,800 gallons (221,800 liters) of liquid oxygen were pumped into the Atlas V. An additional 25,000 gallons (113,600 liters) of highly refined kerosene (known as “RP-1”) had been previously loaded aboard the Atlas V on Monday.
Throughout yesterday’s countdown, it seemed that Mother Nature would have the definitive “final say” on whether OFT-2 would fly. According to the 45th Weather Squadron at Patrick Space Force Base, an iffy 60-percent likelihood of acceptable conditions at T-0 deteriorated slightly to 50-50 as it was feared the presence of “ample moisture” might “encourage scattered to numerous afternoon showers and thunderstorms”.
In the pre-dawn darkness of Tuesday morning, brewing storms over the eastern Gulf of Mexico generated “considerable cloudiness” over the northern half of the Florida Peninsula.
Other than Mother Nature’s threatened depradations, however, it seemed a good day to fly. “Bird looks good,” Mr. Bruno tweeted of the status of the Atlas V. “Pretty windy. Think calm thoughts.”
But ultimately the weather proved a moot issue, when the launch was stood down due to the issue aboard the Starliner. The stack was due to be rolled back under cover inside the 300-foot-tall (90-meter) VIF on Wednesday.
“We’re going to let the data lead our work,” said John Vollmer, vice president and program manager of Boeing’s Commercial Crew Program. “Our team has worked diligently to ensure the safety and success of this mission and we will not launch until our vehicle is performing nominally and our teams are confident it is ready to fly.”
To put it mildly, it has been a long and convoluted road to space for the Starliner. The spacecraft first launched on the OFT-1 mission at 6:36 a.m. EST on 20 December 2019.
However, shortly after attaining orbit, an automated timing issue obliged flight controllers to call off its rendezvous and docking and the spacecraft returned to Earth two days later, becoming the first U.S. human-rated capsule to touch down on solid ground when it landed via parachutes and air bags at White Sands, N.M., early on 22 December.
Despite the disappointment of an incomplete mission, OFT-1 successfully demonstrated Starliner’s propulsion systems, communications systems, Guidance, Navigation and Control (GNC), the Environmental Control and Life Support System (ECLSS) and—via a series of in-flight extension/retraction tests—its NASA Docking System (NDS).
Although NASA later noted that an actual ISS docking was not a mandatory requirement to “crew-certify” Starliner, and pointed out that had astronauts been physically aboard OFT-1 they could have taken manual control and likely overcome the automated timing problem, it became increasingly likely as 2020 dawned that a reflight would take place.
That reflight has already fallen foul to multiple delays, which pushed its No Earlier Than (NET) launch date from last fall into early 2021, then late spring and ultimately midsummer.
And with Northrop Grumman Corp.’s NG-16 Cygnus cargo mission—named in honor of Challenger hero Ellison Onizuka—scheduled to launch atop an Antares 230+ booster from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va., on 10 August, there remains the real possibility that OFT-2 might slip yet further into the late summer.
When the Atlas V does eventually take flight, it will mark the 100th rocket launch from SLC-41, which—in its original incarnation as “Launch Complex 41” (LC-41)—first saw service on 21 December 1965 on the third test flight of the Titan IIIC booster.
Although the launch itself was successful, the rocket’s final stage suffered a leaky valve in its attitude-control system and the payload was released much later than intended. All told, the pad saw ten Titan IIIC launches through May 1969, followed by seven Titan IIIE missions from February 1974 through September 1977.
These delivered a mixture of satellites for military communications, nuclear detonation and surveillance, as well as civilian technology, magnetospheric research and solar science, plus the twin Viking orbiters/landers, bound for Mars, and the two Voyager deep-space probes. The pad was then deactivated for more than a decade, before launching ten missions in support of the Titan IV program between June 1989 and April 1999.
SLC-41 was again deactivated for modifications, ahead of its emergence back into operational service for ULA Atlas V missions from August 2002. Since then, the pad has logged 72 Atlas V flights with payloads which ran the gamut from national security and defense to science and planetary exploration.
They included Solar Orbiter, the Jupiter-circling Juno probe, five exploratory forays to Mars, the Pluto-bound New Horizons and the OSIRIS-REx sample-gathering voyage to asteroid Bennu. Most recently, SLC-41 saw off the fifth geostationary-orbiting element of the Space-Based Infrared System (SBIRS GEO-5) in May 2021.