Space Sunday: the ISS, SLS, brown dwarfs and other bits

The ISS as of September 2021, showing the newly-arrived SpaceX CRS 23 resupply vehicle docked alongside the Crew Dragon Endeavour. At the far end of the station are the Russian modules: the recently-arrived Nuaka, Zvezda and Zarya, which has been found to have small fissures in its outer skin. Credit: NASA

Some sections of the tabloid media became excited this week about “cracks” being discovered “on the International Space Station”, with one or two predicting the end of the ISS is now nigh.

The cause of the reports was the announcement by Energia NPO, the company responsible for fabricating the Russian-built elements of the ISS, that “superficial fissures” have been found in the outer skin of the Zarya module.

The Zarya module imaged from the space shuttle Endeavour in December 1998, as the shuttle approach the module in preparation to attach the US Unity module. Credit: NASA

Zarya – also called the Functional Cargo Block (FCB) – was the first module of the ISS to be launched (November 1998), and was initially responsible for providing electrical power, storage, propulsion, and guidance to the ISS during the early years of assembly. However, as more specialised units, notably the Russian Zvezda module (attached to the aft end of Zarya), were launched, the role of the Zarya module has been gradually downgraded to the point where today it is primarily used for internal and external storage space.

Thus far, neither NASA nor Roscosmos have indicated whether or not the fissures have caused any internal pressurisation issues for the station. However, similar fissures – likely the result of exposure to extremes of temperature as the ISS passes between direct sunlight and the cold shadow of Earth and back every 45 minutes – were discovered on the Zvezda Module in 2019, and despite repairs in 2020 and 2021, they continue to be an annoyance.

Whether the Zarya fissures will become a similar issue can only be determined in time – but they are a reminder that while the ISS is not in imminent risk of a major failure, it is genuinely showing its age, particularly the three original modules – Zvezda, Zarya and Unity – all of which are at least 25 years old (including fabrication / construction time), and are potentially becoming increasingly vulnerable to fatigue. Such issues might also cause Russia to make further noises about withdrawing from the ISS after 2024, this time of the grounds of the station’s increasing age, so they can start work on their own space station.

The Accident – the Strangest Brown Dwarf

Brown Dwarfs are sometimes called “failed stars”, in that they have a mass that sits above the most massive gas giant planets we have so far discovered, but below that of the smallest stars. This leaves them incapable of achieving hydrogen fusion, hence the idea they have “failed” as stars. However, they are massive enough to give off considerable infra-red radiation, which tends to point to them being extremely old.

In reviewing data returned by the Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE), citizen scientist Dan Caselden has discovered the strangest brown dwarf to so far be discovered – so strange it has been given the nickname “The Accident”.

Located around 50 light years from Earth, it is officially called WISEA J153429.75-104303.3 and classified a Class Y substellar object – the oldest and coolest classification of such brown dwarfs. All of which is really not that interesting; astronomers have discovered many brown dwarfs in local space around our solar system over the last 30 years.

A comparison between a “typical” brown dwarf and other stellar and planetary objects. Credit: NASA

What is strange about The Accident is firstly, it is spinning about its axis at a speed of 200 kilometres a second (that’s 720,000 km/h)- 25% faster than the next fastest stellar object of its kind.

The second – and more intriguing – thing is that The Accident has the oddest brightness pattern of any brown dwarf. Due to their nature, these objects only give off light in the infra-red wavelengths, and The Accident’s output is – at least in part – at the end of that part of the spectrum that points to it being really old: perhaps 13 billion years old – almost as old as the galaxy itself (13.6 billion years. This extreme age is also supported by The Accident’s rotational speed, something that could only be achieved via  thousands of encounters with massive stellar objects down the aeons.

But there’s a twist: The Accident is not consistent in its infra-red brightness, as it also “shines” in parts of the infra-red that indicate that it is a lot, lot, younger than the other data suggest, making the object an anomaly – and accident of nature, so to speak, hence its nickname. This difference in brightness has puzzled scientists, and has led to The Accident starting to get a lot of attention to determine what might be going on inside it.

Some of this attention is also devoted to studying it on the basis of its age – if it really is 13 billion years old, then it formed at a time when the galaxy was a very different place in terms of chemistry, a time when many elements we take for granted (carbon and methane being just two) simply could not exist. Thus, understanding its nature and composition could reveal more about the galaxy’s formation and birth. What’s more, that so strange an object should be found so relatively close to Earth suggests there could be many of these unusual brown dwarfs awaiting discovery.

Virgin Group Ups and Downs

Sir Richard Branson is having some ups and downs in his space endeavours.

The ups are with Virgin Orbit, the smallsat launching service that uses the LauncherOne rocket, lifted to altitude by a modified 747 before being launched, to place payloads of up to 300 KG to a Sun-synchronous orbit or 500 KG to low Earth orbit.

Following the first successful launch of a commercial payload to orbit at the end of June, the company has now passed a critical Federal Aviation Administration (FAA) environmental review that could allow it to use Andersen Air Force Base, on the island of Guam in the western Pacific Ocean, as a base for launch operations.

Virgin Orbit has passed an FAA environmental review that could pave the way for the company to offer payload launchers out of the US territory of Guam in the western Pacific Ocean. Credit: Virgin Orbit

If final approval is granted – and the FAA do have reservations about Virgin Orbit being able to operate from such a remote location – the company plan to use Guam to make up to 25 air launches over a period of 5 years, possibly commencing before the end of 2021.

Following the success of the June launch, Branson noted that Virgin Orbit is to be capable of highly responsive launches from almost any point in the world. To this end, the company has already signed an agreement with Spaceport Cornwall (Newquay Airport) in the UK, and the Brazilian government has selected the company to provide launch services out of that country’s Alcântara Space Centre. These, together with Guam and their existing facilities at the Mojave Air and Space Port mean that Virgin Galactic may soon have four launch locations around the world from which it can reach a variety of orbital inclinations as required by customers.

VSS Unity drops clear of its air launcher, MSS Eve during the Unity 22 mission, ahead of engine ignition. Credit: Virgin Galactic

The down is with Virgin Galactic, the sub-orbital, tourist-focused service. Following its first successful passenger-carrying flight in July (see: Space Sunday: Unity 22 Flies), the FAA announced on September 2nd that the the sub-orbital VSS Unity is grounded, following a review of that flight, forcing a halt to the company’s operations.

The review has been triggered following an article appearing in The New Yorker magazine stating the pilots on VSS Unity ignored a warning triggered during the vehicle’s powered ascent that should have caused them to abort the flight and return the the ground. The warning indicated the vehicle was not climbing at a sufficiently steep angle to remain within it’s “entry glide cone” – the volume of space in which it can make a safe unpowered glide back to a successful runway landing at the end of the flight – during its return to Earth, and so could miss the runway entirely.

While the company has defined The New Yorker’s report as “inaccurate”, telemetry from the Unity 22 mission shows that the vehicle did exceed the limits of FAA-defined “protected airspace” for one minute and 41 seconds during the descent to landing, further justifying the FAA’s decision to order the grounding, preventing any further operations by Virgin Galactic for the next few weeks.

Virgin Galactic had been gearing-up for its next crewed flight for VSS Unity, a dedicated research flight for the Italian Air Force that would carry aloft Colonel Walter Villadei, Lt. Colonel Angelo Landolfi and aerospace engineer Pantaleone Carlucci, alongside Virgin Galactic’s chief astronaut instructor Beth Moses and pilots Michael Masucci and C.J. Sturckow when the ground of the spacecraft was announced. The mission will now not fly until the FAA concludes their review of the Unity 22 flight.

NASA’s SLS – Unlikely to Fly Before Spring 2022

NASA’s Space Launch System (SLS), the new heavy lift launch vehicle central to the agency’s goals for crewed and uncrewed deep space missions – notably the return to the Moon with Project Artemis – now seems unlikely to launch before the spring of 2022 after a further critical deadline slipped.

As I noted in June 2021, having arrived at Kennedy Space Centre, Florida, the core stage of the rocket was successfully mated with its two huge solid rocket boosters (SRBs). Then in July, the launcher’s upper stage, called the Interim Cryogenic Propulsion Stage (ICPS), was also positioned and stacked above the core stage. The mounting of the ICPS was followed by the mounting of a mass simulator matching the bulk and weight of the Orion and its service module to the top of the rocket.

The Interim Cryogenic Propulsion Stage is moved in position over the top of SLS in preparation for stacking, July 2021. Credit: NASA

This was to allow the entire stack to undergo a series of vibration tests without risking any damage to the Orion vehicle. Data from these test will allow engineers to better understand the difference between the natural vibrations of the full stack versus those caused by external forces, and the results will be added to the flight control software to help it better identify and respond to anomalous vibrations during flight. These test should have been completed by the end of July – but as of the start of September, are still in progress, and may remain that way through the rest of the week.

All of which leaves very little time in the schedule to complete the necessary final operations in preparation for the Artemis 1 launch. These operations include removing the mass simulator, stacking the Orion vehicle to the top of the rocket, connecting power and other systems between the Orion vehicle and the rocket, and running a battery of tests referred to as modal tests on both the rocket’s and the capsule’s electrical and data systems. Only after these have been completed will the vehicle stack be cleared for roll-out to the launch pad, where further pre-flight tests will take place.

While NASA is still pointing to an end-of-year launch as still being on the cards, the US East Coast is in the midst of its hurricane season, making weather an uncertainty through until the end of November, after which colder winter weather may further disrupt plans through until the new year – and there are also holiday periods to contend with as well. This had led some involved in the project to privately suggest early spring 2022 is a more realistic time frame for the first flight.

Firefly Alpha Blows Up

Firefly Aerospace, another private US space launch provider, attempted to make the first flight of its two stage Firefly Alpha rocket on September 3rd (September 2nd, US time), 2021, from facilities at Vandenberg Space Force Base in California, and things didn’t go well for the 29 metre tall rocket.

The first Firefly Alpha rocket to fly seen at Vandenberg Space Force Base being raised to a vertical position ahead of its September 2nd/3rd launch. Credit: Firefly Aerospace

An expendable launch system, Firefly Alpha is intended to deliver payloads of up to one metric tonne to low Earth orbit or 630 kg to a Sun-synchronous orbit (SSO), and this first launch was very much a test for the vehicle, although it was carry a 92 kg payload that included several cubesats, technology demonstrations of a plasma thruster and drag deorbit sail, and “non-technical” payloads like photos and memorabilia.

Lifting-off from Space Launch Complex 2 at Vandenberg at 02:59 UTC on September 3rd, 59 minutes after a technical issue had forced an initial launch attempt abort. All appeared to go well first the first 2.5 minutes of ascent before the rocket started to tumble, prompting the launch range safety officer at Vandenberg to trigger the vehicle’s self-destruct in order to avoid it breaking up in an uncontrolled manner and striking populated areas. Even so, there were reports of debris from the rocket falling in the town of Orcutt, California, just north of Vandenberg.

The company is now reviewing data from the flight along with the FAA to determine their next steps with the vehicle.

COVID’s Other Impact on the US Space Industry

Away from its direct health implications, we’re all familiar with the impact the SARS-CoV-2 situation has had on things like working practices, the use of traditional workspaces, etc., and the space industry hasn’t been immune to these. However, it is also suffering the effects of the pandemic in two unusual, but related, ways.

Thanks to the surge in hospitalisations in the US, there has been a massive increase in demand for oxygen. As this must be shipped in its liquid state – LOX – the priority for shipping has been given to the needs of hospitals and medical centres, leaving a severe shortage of drivers trained to handle super-cold and super-combustible liquids, causing supplies of LOX for launch operators two dwindle. So much so that SpaceX has already warned it may not be able to meet its Falcon 9 launch schedule for the rest of the year.

The Firefly Alpha rocket is destroyed by the Range Safety Officer at Vandenberg after the rocket started an uncontrolled tumble, 2.5 minutes into is ascent. Credit: USSF

A further knock-on effect of this is that skilled drivers and the tankers that would normally transport super-cold liquid nitrogen on America’s road have also been diverted to the job of keeping the LOX supplies rolling. As liquid nitrogen is used in a variety of roles in launchers and satellites, the lack of deliveries is also starting to impact launch operations. NASA, for example, has announced its next Landsat satellite, originally set for launch on September 16th, has been postponed for a minimum of a week due to the liquid nitrogen shortage, with other launch operators also eying their launch schedules carefully.

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