Space Sunday: saving MAVEN, Tiangong readying to expand

An artist’s impression of MAVEN as it looks down on Mars’ Vallis Marineris. The NASA mission, which arrived in orbit in September 2014, is studying the Martian atmosphere

NASA’s MAVEN Mars orbiter has been in orbit around the planet since September 2014. For the majority of that time, and following science commissioning (Sept-November 2014), the spacecraft has been studying the Martian atmosphere, yielding valuable science. Except for the past three months, that is.

On February 22nd, 2022 – ironically the day Shannon Curry, appointed to take over the role of MAVEN’s Principal Investigator in August 2021, was making a three-hour presentation on the vehicle’s science findings at the conclusion of its latest 6-month mission extension – when Things Went Wrong.

We finally finished the presentation, I turn my ‘phone back on, and our project manager calls me immediately. I’m thinking, he’s calling me to be like, ‘Congratulations, you did it, you’re doing great!’ And he was, ‘Shannon, we’re in safe mode.’

– Shannon Curry

Shannon Curry was appointed to the role of Principal Investigator for NASA’s MAVEN mission in August 2021, and steered the project through its most serious issue between February and June 2022. Credit; via Wikipedia

Regulars to Space Sunday will know that “safe mode” is when a spacecraft has encountered a condition that exceeds its programmed parameters / expectations, causing it to shut down most of its non-essential systems and services and ‘phone home with a call of “I’m in a spot of trouble, folks!”

Safe modes are rarely easy to diagnose and resolve remotely, with MAVEN (Mars Atmosphere and Volatile EvolutioN mission), the issue would prove to be almost catastrophic.

In order to both study Mars and communicate with Earth, MAVEN must periodically re-orient itself. Up until 2017, it did so by using one of two Inertial Measurement Units (IMUs) to calculate its position, attitude and rotation. However, from 2017 through until the end of 2021, MAVEN has been reliant on just one unit – IMU-2 – after IMU-1 experienced data issues.

By the start of 2022, IMU-2 was starting to show issues of its own, so a project was started to write new software to enable MAVEN to orient itself using the stars in what the mission team called “stellar mode”, a project that would take until late 2022 to complete. In the meantime, the vehicle was instructed to switch back to using IMU-1, with the power to the unit being periodically recycled to help with keeping it operating smoothly.

However, on February 22nd, 2022, with MAVEN oriented to communicate with Earth, a power recycle was started and IMU-1 crashed, and when IMU-2 automatically started, it had absolutely no idea of where it was, and MAVEN went into a loop of trying to restart IMU-1 after shutting down all science operations.

When it was clear IMU-2 was “lost”, and IMU-1 was not going to recover, risking MAVEN drifting out of communications alignment, the mission team took a desperate step: heartbeat termination.

That term is not just for dramatic effect: basically, it’s like ripping the cord out of the wall. We ordered the vehicle to shutdown and reboot its primary computer without switching to the back-up. When that failed, we had no choice but to then swap to the back-up and we’ve never been on that before.

– Shannon Curry.

Whilst the switch to the never-used back-up computer was a risk, it nevertheless allowed position data to be given to  IMU-2 to ensure communications could be maintained with Earth. This allowed the mission team to accelerate the work on developing the “stellar mode” software.

On April 19th, the first version of the software was uplinked to MAVEN five months ahead of its due date. However, it could only be tested by shutting-down IMU-2. If the software failed, there was no guarantee either IMU would reboot, leaving MAVEN to drift out of its communications orientation within hours. Fortunately, the software demonstrated it could keep the vehicle correctly oriented, and the mission team were able to continue to refine the software and add the tasks required for MAVEN to use stellar mode for both communications and science operations.

In May, work had reached a point where the science instruments could each be brought out of safe mode and tested to ensure they had suffered no long-term damage. Then on May 28th, the order was given for MAVEN to fully transition all operations to use the stellar mode for navigation / orientation, allowing science operations to resume.

There will still be periods in MAVEN’s operations when it will have to rely on an IMU, but for now the mission team has brought the mission back from the brink of disaster, and are now focusing on ways in which the craft can better deal with possible data hiccups from the IMU systems.

Starship + Crew Dragon Update

Starship

The FAA report on the SpaceX starship facilities at Boca Chica, Texas, will now not be published until June 13th. In the meantime, it has been confirmed that the first orbital launch attempt will be undertaken by Ship 24 and Booster 7.

At the time of my last Starship update, Booster 7 had suffered a failure with a downcomer pipe, resulting in the booster being returned to the production facilities for examination, together with speculation that Booster 8 might replace it for the orbital launch attempt. However, repairs were made to Booster 7, enabling its return to the launch area.

Starship 24 undergoing liquid nitrogen cryogenic tests. A similar test at the end of May 2022 resulted in a header tank feed pipe failing, ejecting heat shield tiles from the underside of the vehicle. Credit: NASASpaceflight.com

At the end of Mays, Ship 24 was been rolled out to the test stands where cryogenic tests using liquid nitrogen commenced – only for a feed pipe connected to its LOX header tank to fail, throwing heat shield tiles off of the vehicle as the hull flexed. As a result, the pipe in question went through a rapid pipe redesign whilst on the test stand, with additional expansion joints being fitted to prevent any over-pressurisation.

With engines now being fitted to both ship and booster, and deliveries of liquid oxygen, liquid methane and liquid nitrogen being made to the tank farm, SpaceX appear confident the FAA report will give the green light for the orbital launch test – a test that will include a test deployment of Starlink satellites through the small payload slot.

This view exemplifies one of the issues SpaceX may still have with the Boca Chica launch facility. The orbital launch tower can be seen centre top; to the bottom left and in close proximity to the launch facilities, is the propellant and consumables tank farm, well within the blast radius should a starship / super heavy combination to explode at launch, the earth berm between tanks and launch stand notwithstanding. The horizontal tanks to the right of the upright tanks were installed after-the-fact in part to pre-empt concerns from the FAA on this matter. Credit: RGV Aerial photography

Even if this first flight test is a success (which is unlikely), it is perhaps important to note it is not a prototype test flight per se, but is rather an initial proof of concept. This is because the starship vehicle is far from its final configuration (Musk has announced first possible changes to the design). Nor is Ship 24 reflective of an “operational” starship: it has no means to carry the volume of payload promised (100-150 tonnes), the mechanism(s) required to support such a mass during launch, or the means to deploy it payload bay doors and their mechanisms. As such, there is a long way to go before starship reaches an actual prototype flight, with a lot more to prove. Even then, the realities of its promise are still highly questionable – something I hope to be looking at in a future Space Sunday.

Crew Dragon

NASA has announced it plans to purchase 5 more SpaceX Crew Dragon flights to the ISS – for a fee that has not been publicly disclosed. The move comes on top of the purchase of three flights – Crew 7 through 9 – in February 2022 in a contract extension that saw the cost to NASA rise by $20 million per seat on what is supposedly a fixed-price contract.

NASA has stated the move is to relieve Boeing of pressure as it prepares its Starliner vehicle. However, in the same week, NASA indicated it believes Boeing is on course to complete flight tests of Starliner in 2022 and to commence operational flights in 2023. In all, NASA has purchased 6 flights of Starliner at $90 million a seat. This has also been critiqued, as has the development cost of Starliner when compared to Crew Dragon. However, the latter comparison tends to miss the fact that Drew Dragon was an iteration of an existing vehicle design, whilst Starliner had to be designed from scratch.

ISS / Artemis Commercial Space Suit

NASA has also indicated it has turned to commercial assistance for the development of the space suits intended for use as a part of the return to the Moon under Project Artemis.

Initial contracts have been awarded to Axiom Space – who are already engaged in space station activities, and Collins Aerospace + ILC Dover – a team that has decades of experience with the current EVA suits used by NASA – to come up with designs for a new space suit that can be used both for EVAs on the International Space Station and to be used as a part of the return to the Moon.

A mock-up of the Exploration Extravehicular Mobility Unit (xEMU) lunar spacesuit being revealed in 2019, the last in a line of not-happening EVA suit designs from NASA stretching back to work that started in 2007. Credit: NASA/Joel Kowsky

The move is somewhat embarrassing for the agency, which has been attempting to develop new, multi-purpose space suits since 2007, initially for use on the ISS (those currently used on the ISS owe their design to the original Apollo missions to the Moon), and then more specialised suits for use on the Moon.  The latter was unveiled to huge fanfare in 2019 (see: Space Sunday: Mars, Starliner woes, accusations & spacesuits) – only for NASA’s own Office of Inspector General (OIG) indicating that much needed redesigns to the suit and other issues meant it would not be ready in time for the first Artemis crewed lunar landing, then due in 2025.

The new current contracts are only for suit design – but both teams have the opportunity to receive initial orders for suits that can be demonstrated on the ISS by 2025, and the first Artemis lunar landing, now likely to take place in 2026 (or 2027) – with a total of $3.4 billion to cover NASA’s suit need through until 2034 up for grabs. Even so, the idea that suits can be ready to start tests in 2025 is highly ambitious. So, to help move things along, NASA propose certifying each design on a step-bay-step basis as each is developed and tested, rather than assessing and certifying either suit on delivery of initial prototypes.

Whilst new to space suit design, Axiom has a vested interest in developing the capability: the company intends to effectively take over ISS operations with their own privately-financed space station, with modules initially attached to the ISS. As a part of the financing for this new station, they plan to offer space tourism opportunities to the ISS which include space walks.

Tiangong: Shenzhou 14 Arrives, Wentian Prepares

China’s nascent Tiangong space station (which confusingly for some has the same name as two prior (and now de-orbited) space laboratory modules) has entered a very busy  period that will see it rapidly grow to full size before the end of 2022.

At 02:44 UTC on June 5th, 2022 the Shenzhou 14 mission lifted-off from the Jiuquan Satellite Launch Centre in the Gobi Desert, carrying aloft Tiakonauts Chen Dong (mission commander), Liu Yang and Cai Xuzhe on a “fast track” 7-hour flight to rendezvous with the Tinahe 1 core module of the space station, which currently has the Tianzhou 4 automated re-supply vehicle docked with it.

Docking occurred at 09:42 UTC, marking the start of the second 6-month crewed mission aboard the station and the third crew mission to Tiangong overall. During the initial phase of the mission, the crew will be engaged both in off-loading supplies and equipment from Tianzhou 14 – which will also provide the station with manoeuvring power for upcoming rendezvous operations.

The Shenzhou 14 crew of (l to r) Chen Dong (mission commander), Liu Yang and Cai Xuzhe, during a pre-launch media briefing. Credit: CCTV

The first of those operations is expected to occur in late July when a Long March 5B booster will loft the Wentian module into orbit.

Massing some 22 tonnes, the 17.9 metre long module is the first of two science facilities that will be attached to the forward docking node on Tianhe-1, aligned along the core module’s longitudinal axis. The Shenzhou 14 crew will then use the station’s main robotic arm to detach and move the module to one of the radial ports on the docking node, prior to engaging on set-up and commissioning work with the module.

Wentian is due to be followed in October by the second science module, Mengtian. Of similar dimensions and mass as Wentian, the second module will perform a similar initial rendezvous and docking, prior to being moved to a second radial port on Tinahe 1’s docking node to give the completed station a T-shaped appearance, leaving the forward port on the node and the aft port on Tinahe 1 both free for Shenzhou crewed flights and Tianzhou re-supply missions.

The core elements of a Long March 5B laid out at the Tianjin vehicle assembly facility ahead of being shipped to the Wenchang Launch Centre, Hainan, for stacking and integration. In the foreground are the fairings that will enclose the Wentian science module, centre rear is the core booster stage and flaking that are two pairs of the four solid rocket boosters that form the “first stage”. Credit: CMSA.

The Shenzhou 14 crew is expected to remain on the station through until December 2022, when they will hand over to the Shenzhou 15 crew, marking the first on-orbit crew rotation for the station, and the start of its planned continuous occupation.

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