Space Sunday: of Soyuz aborts and telescopes

Cosmonaut Alexey Ovchinin (l) and astronaut Nick Hague (r) prior to their flight aboard Soyuz MS-10 – a flight that was a lot shorter and a little more exciting than either man anticipated. Credit: Roscosmos

On Thursday, October 11th, 2018, the Soyuz MS-10 spacecraft carrying two crew – American astronaut Nick Hague and Russian cosmonaut Alexey Ovchinin to the International Space Station (ISS) suffered a core second stage failure, triggering an emergency launch abort. Both Hague and Ovchinin survived the ordeal – although the way some of the media were reporting things, one might have thought they were hoping otherwise.

Soyuz utilises a R7 booster family of launch vehicle. This comprises a single-engined core element (confusingly called the 2nd stage, surrounded by 4 liquid-fuelled strap-on boosters referred to as the first stage. Each of these also has a single motor with, like the core stage, four combustion chambers. At launch, all five elements are fired, with the four strap-on boosters running for around 2 minutes. Then, with their fuel expended, they are jettisoned.

The view from the ground as Soyuz MS-10 starts its flight, October 11th, 2018. Credit: NASA TV

It is at this point – 2 minutes into the vehicle’s ascent from the Baikonaur Cosmodrome, Kazakhstan, that things went awry,  and gave observers watching from the ground the first indication of trouble – telemetry being relaid to mission control in Star City, near Moscow give little indication of a problem, causing commentators there to keep to their prepared scripts even as the drama unfolded.

Due to the way they fall clear of the core stage, the four strap-on boosters perform a controlled tumble with their exhaust plumes still visible. Seen from the ground, this forms distinctive and almost symmetrical pattern around the core stage called the “Korolev Cross” in honour of the father of modern Soviet / Russian space flight, Sergei Korolev, who also designed the original R7 rockets.

On this occasion, however, following separation, a decidedly asymmetrical Korolev Cross briefly formed, before the sky around the rocket became spotted with debris as if something had broken up.  At the same time, video of the cabin in the Soyuz vehicle’s decent module, where the crew sit during both ascent to orbit and their return to earth, showed Ovchinin  and Hague suddenly experiencing a brief period of weightlessness, almost as if thrust from the vehicle’s second stage had ceased, before they were pushed back into their seats and the plush toy suspended in front of the camera (used as a very rough-and ready G-force indicator) suggested a rapid acceleration.

This sudden acceleration was the result of the launch escape system kicking-in, separating the payload shroud containing the upper two modules of the Soyuz from the failing rocket. The manoeuvre recorded a 6.7 G acceleration right when the crew would have been expecting a 1.5G climb up to orbit as a result of jettisoning the spent strap-on boosters.

Once clear of the rocket, the fairing deployed a set of aerodynamic breaking flaps, slowing it to allow the Soyuz descent module to detach. The normal parachute and retro rockets where then used to bring the capsule back to Earth and execute a safe landing.

The distinctive “Korolev Cross” of booster separation see with R7 launches (l), and how it looked with Soyuz MS-10 (r). The first visual indications from the ground that something had gone wrong. Credits: NASA TV

Precisely what caused the failure has yet to be determined. As well as recovering the two crew safely and returning them to Baikonour unharmed, teams have also been busy recovering parts of the failure rocket, and Roscosmos believe they’ll be in a position to use the parts so far recovered together with telemetry from the vehicle’s ascent to provide a preliminary report on the failure within a week.

In the meantime, space experts have been examining video footage of the launch, and it would appear some form of malfunction during the separation of one of the four strap-on boosters may have caused it to actually collide with the core rocket. In his analysis of the flight, Scott Manley points to both the asymmetrical pattern of debris from the booster separation and what appears to be a radical slewing in the exhaust plume of the core stage as evidence there was some form of collision.

A remarkable shot of Soyuz MS-10 captured by ESA astronaut Alexander Gerst from the ISS. Credit: A. Gerst / ESA / NASA

Some confusion also exists over what actually happened during the abort sequence. Like Apollo crewed rockets, Soyuz has a tower-like escape system at its top. In an emergency, rockets mounted in the tower fire, pulling the crew module clear with a brief acceleration of about 14 G. As the reported acceleration with MS-10 was less than this, there was speculation the escape system hadn’t been used.

However, the Russian escape system, called the Sistema Avariynogo Spaseniya (SAS), unlike American systems, has two sets of motors: those in the tower, and a set of lower-thrust motors mounted directly on the payload fairing, and capable of around 7 G acceleration – the reported speed of the Soyuz on separation. It’s theorised it was these motors that pulled the Soyuz clear, the vehicle not having reached a velocity warranting the use of the tower rockets in order to pull the Soyuz clear.

Left: the Soyuz escape system (SAS) and how it works. The system uses two sets of motors which can be used together or independently of one another to pull the upper section of the payload fairing and the Soyuz clear of a malfunctioning rocket. The Soyuz descent module can then jettison, using its parachute and landing motors to return to Earth. Right: The SAS motor tower (boxed) with four rockets, and the second set of 4 RDG rockets mounted on the payload fairing (ringed). Credits: assorted.

Following separation, the descent module landed some 500 km (312 mi) down range of the launch site, and rescue teams were quickly able to recover the crew, who were flown back to Baikonour for medical check-ups and to be reunited with their wives.

The booster failure means that Soyuz launches are now grounded until such time as the precise cause of the accident can be established, and any required remedial actions identified and taken. In the meantime, the three remaining crew aboard the ISS – US commander Serena Auñón-Chancellor, European Space Agency astronaut Alexander Gerst and cosmonaut Sergey Prokopyev – are in no danger. They have a Soyuz vehicle docked at the station which can be used as an evacuation craft in a major emergency, and resupply missions can still be flown out of the United States using the Cygnus and Dragon resupply vehicles.

Ovchinin (centre, left) and Hague (centre, right) are greeted by their wives on their return to Baikonur following the aborted launch. During the emergency, an unruffled Ovchinin was heard to comment, “An accident with the booster, 2 minutes, 45 seconds. That was a quick flight,” as the Soyuz descended back to Earth. Credit: NASA / Bill Ingalls

That said, the reduction in crew will mean activities aboard the station will inevitably be scaled back to match the available number of crew. One area likely to be hit is that of commercial research aboard the ISS. The US company NanoRacks had so far flown over 700 experiments on the ISS from 32 nations. Speaking shortly after the MS-10 incident, the company’s CTO, Mike Lewis, acknowledged experiments the company currently have aboard the station will likely be impacted.

How long Soyuz will remain grounded is currently open to debate. Currently, NASA expects flights are unlikely to resume before December 2018 at the earliest – although if a substantial  defect / issue is discovered, Soyuz could be out of commission for a lot longer.

Telescope Woes and Joys

It’s a little up and down for space telescopes of late.

On Monday, October 8th, 2018, NASA confirmed that following a failure with one of its gyroscopes over the weekend, the Hubble Space Telescope had entered a “safe” mode.

In all, the 28-year-old orbital telescope has 6 gyroscopes, three of which are generally used at any one time to keep it both pointing in the right direction within its 540 km (340 mi) high orbit and hold it steady while making observations. However, since 2009, the last time the gyroscopes could be replaced, two have completely failed, while a third was taken off-line after exhibiting what NASA referred to at the time as “funny behaviour”.

The Hubble Space Telescope (HST) as seen from the departing space shuttle Atlantis, flying STS-125, the final HST Servicing Mission, in 2009. This mission completely overhauled the space telescope, including replacing the gyroscopes for the last time. Credit: NASA

A failure with one of the three remaining operational gyros had been anticipated, and NASA had been planning to swap it for the last remaining back-up, the gyroscope that had been exhibiting “funny behaviour”. Only operations didn’t switch to it when the suspect gyroscope did fail, and it was this failure that actually triggered the “safe” mode.

While the telescope can function with just two operational gyros, three is the preferred minimum. It’s not clear what happened with the back-up gyro  – telemetry appears to be reporting it has rotation rates “orders of magnitude higher than they actually are,” according to the agency, and engineers are trying to ascertain the cause. Contingency plans are also being drawn up in case the issue cannot be rectified. While  Hubble can operate with only two gyros, Engineers believe Hubble can function with just one without impacting its science capability, allowing the other remaining gyroscope to be powered down and held in reserve.

Even so, there is a high confidence level that the faulty back-up gyro can be made to behave itself.

I think Hubble’s in good hands right now, I really do. The fact that we’re having some gyro problems, that’s kind of a long tradition with the observatory. Obviously, we don’t want to make things worse, [but] we’ll be fine. I’m sure Hubble has many years of good science ahead of it.

– Kenneth Sembach, director of the Space Telescope Science Institute.

An artist’s impression of the Chandra X-Ray Telescope. Credit: NASA

Coincidentally, 48 hours after the announcement of the situation with Hubble, another of NASA’s Great Observatories, the Chandra X-ray Observatory (CXO), also placed itself in a safe mode, suspending science operations.

Launched in July 1999, Chandra has been observing the cosmos around us in the x-ray wavelengths, and while less well-know than Hubble, has been responsible for some remarkable discoveries. Precisely why it entered safe mode has yet to be determined confirmed, but like Hubble, it is believed a gyroscope on the observatory may have failed. Following the status change, NASA were able to confirm the observatory had shut down all critical systems successfully, and there is high confidence it can be returned to normal operations once the issue has been diagnosed and rectified.

It is not all bad news, however, as the Kepler Space Telescope once again called home.

As I’ve reported several times in these pages, the planet hunter responsible for finding mote than 2,600 exoplanets is running out of the fuel it needs to orient itself and hold itself steady when making observations. The 19th of the 80-days periods of observation had been due to start on August 6th, 2018, but with the observatory dropping in and out of safe modes due in part to the critical fuel situation, it didn’t actually start until August 29th, 2018 – only to shut down again lass that a month later.

But on October 11th, and almost in line with Hubble and Chandra taking themselves off-line from observations, Kepler woke up for one of its scheduled transmissions with Earth – it occupies a solar orbit similar to our own, but trailing Earth by about 137 million kilometres, and so is programmed to periodically re-orient itself so it can communicate with NASA’s Deep Space Network to both download data gathered during its observations and receive commands and updates to it operations.

It’s not clear whether the observatory will attempt to remain awake and resume observations, or whether it will drop back into safe mode again. The reason it initially failed to start the campaign on August 6th, 2018 was due to a faulty thruster. While that issue was overcome, it also meant Kepler would likely use its remain dregs of fuel a lot faster – potentially causing it to put itself back to sleep until the next scheduled communications period.