Space Sunday: saving Oppy, ISS leaks, and humans to Mars

NASA’s MER rover, Opportunity (MER-B) arrived on Mars in January 2004. It has been in a “sleep” mode since the start of June 2018, as a result of a globe-spanning dust storm on Mars. Credit: NASA/JPL

NASA has announced it will undertake a 45-day campaign to try to re-establish contact with its long-lived Mars Exploration Rover (MER) Opportunity. in the wake of contact being lost was a globe-spanning dust storm started to grip Mars in June 2018.

After running its course for almost three months, the storm is now abating, and whilst not the biggest storm seen on Mars since “Oppy” arrived there it the start of 2004, it is one of the most intense in terms of the amount of dust thrown up into the Martian atmosphere.

Contact with the rover was lost in early June 2018. With sunlight barely able to penetrate the dust in the air, it is thought the rover went into hibernation to conserve battery power – terminating contact with Earth in the process.

The attempt to re-establish communications will commence once the tau in the region where “Oppy” is located has dropped below 1.5. Tau is the term used to measure the opaqueness of the dust in the Martian atmosphere, and it is usually around 0.5. Opportunity requires a tau of below 2.0 to avoid triggering its sleep mode, and by early June the value had reached 10.8 – making this dust storm the densest the rover has ever encountered during its fourteen years on Mars.

As a solar-powered vehicle, there are a number of risks Opportunity faces during a long duration dust storm. The first is that as the batteries cannot be charged, they could run out of sufficient power required to keep the rover’s sensitive electronics warm – although this is partially mitigated by the fact that during a storm like this, the heat normally radiated away by the planet gets trapped in the dusty atmosphere, raising the ambient temperature and thus offsetting the amount of power the rover needs to use to keep itself warm.

How the dust storm progressed. Taken 15 days apart through the same telescope and viewing the same face of Mars. On the left, taken on June 8th and the storm started to rise, features such as Syrtis Major ( the dark India-shaped marking below centre) are visible. On the right, taken on June 23rd, they are almost totally obscured by dust. Note that south is top the top of both images. Credits: Damian Peach (left) / Christopher Go (right)

To other points of concern with the rover are the potential for a clock failure, or what is called an “uploss” recovery being triggered. Opportunity’s on-board clock allows the rover to track when an orbiting satellite – vital for relaying signals from the rover to Earth – is above the local horizon, allowing Opportunity to make contact with Mission Control. If it has failed or now has an incorrect reading as a result of power fluctuations, “Oppy” might not be easily able to establish contact with Earth by itself. An “uploss” recovery is triggered when the rover has failed to establish contact with Earth for an extended period. There is a concern that if the rover didn’t enter its hibernation state correctly, the lack of any communications might have triggered this mode, forcing the rover to continuously re-try different methods to receive a signal from Earth, using up its power reserves.

The 45-day campaign will be a pro-active attempt to re-establish contact with “Oppy” from Earth by sending commands out to it. However, if there is no response from the rover, a grim warning was given in the announcement:

If we do not hear back after 45 days, the team will be forced to conclude that the Sun-blocking dust and the Martian cold have conspired to cause some type of fault from which the rover will more than likely not recover. At that point, our active phase of reaching out to Opportunity will be at an end.

– John Callas, Opportunity project manager, NASA Jet Propulsion Laboratory

This has drawn some sharp criticism from former members of the MER team, particularly those who worked with Opportunity. They point out that when communications were lost with the other MER vehicle, Spirit, in 2010, NASA spent 10 months trying to re-establish contact. In response to the criticism, NASA state that the 45-day period has been dictated by the decreasing amount of sunlight the rover is receiving as winter approaches, requiring the rover to start conserving power once more, but they will continue to listen for any attempts by the rover to re-establish communications after 45 day campaign has come to an end – they just won’t continue to try to make the connection pro-actively.

Even if communications are re-established, it doesn’t necessarily mean “Oppy” is out of danger; there is a chance that the storm has caused the rover to use its batteries for so long without charge, then may not longer have the capacity to charge correctly or to efficiently retaining their charge – either of which could severely impact further operations for the rover, and require careful assessment.

Soyuz Pressure Leak at the ISS

A Soyuz vehicle suffered a minor loss of cabin pressure whilst docked at the International Space Station (ISS), causing a bit of a fuss in some sectors of the media.

At around 19:00 Eastern Standard Time on August 29th, 2018, ground controllers noted a loss of atmospheric pressure in the orbital module of a Soyuz MS-08 docked to the station. While some media outlets reported the ISS crew “scrambled” to locate and patch the source of the pressure loss, the drop was so slight mission controllers decided to allow the 6-man crew to continue their sleep period aboard the station, and did not inform them of the issue until they were woken up at their scheduled time.

A Soyuz vehicle docked with the ISS (a second Soyuz is just visible, top reight of this image). The pressure leak occurred in the spherical orbital module directly attached to the space station. Behind this is the earth return module (and primary compartment for cosmonauts and astronauts when flying Soyuz) with the white section at the rear, with the solar panels, is the vehicle’s propulsion and power module. Credit: NASA / Roscosmos.

The leak was ultimately traced to a 2mm hole through the skin of the Soyuz module. A temporary fix was made using tape while the crew awaited instructions from Earth on how best to affect a more permanent repair. This actually highlighted a difference in approach between American astronauts and engineers and their Russian counterparts in handling situations.

The Americans – including Expedition 56 Commander Drew Feustel – were keen to explore and test options on Earth before determining on a curse of action out of concern that if options were not tested, then a repair could result in additional damage to the Soyuz. Russian engineers, however, proposed just the one approach to making the repair, and ordered the two Russian cosmonauts on the ISS – Oleg Artemyev and Sergei Prokopyev – to make the repair without any Earth-based testing, handling the situation entirely in Russian and using an interpreter to keep NASA personnel appraised of progress.

After completing the work, Artemyev and Prokopyev reported bubbles forming in the patch, but were instructed to leave it in place to harden over 24 hours. At the time of writing, the path appears to be holding, with no further leaks reported. The damaged Soyuz had been scheduled to make a return to Earth in December 2018 (each vehicle generally spending around 6 months berthed at the ISS alongside another Soyuz so they can be used as “lifeboats” by a station crew should they have to abandon the station for any reason), but as a result of the incident, mission controllers are contemplating using the vehicle in October, when three of the current ISS crew are due to return to Earth.

As the leak occurred in the Soyuz orbital module, it does not pose a threat to a crew: the module is only used during the time a Soyuz is en route to the ISS to give the crew a little more space. On a flight back to Earth the module is jettisoned along with the power and propulsion module, leaving the crew to return in the “mid-ships” Earth return capsule.

The cause of the leak is still being investigated, but suggestions are that it may have been a MMOD – a MicroMeteoroid (tiny piece of orbiting rock weighing less than a gramme but travelling at high-speed) or a piece of Orbital Debris (tiny fragment of debris from a space mission). Such strikes have occurred with the ISS in the past, but if this is the cause of the Soyuz leak, it will be the first time such a strike has directly resulted in a loss of atmospheric pressure either aboard the station or a vehicle docked with it, something that will add to concerns as to the amount of natural and human-made debris circling Earth.

SpaceX Talks BFR and Mars

At the 21st Mars Society International Convention held in August 2018, Paul Wooster, Principal Mars Development Engineer, SpaceX provided a further overview on the company’s plans for sending humans to Mars using their upcoming BFR – Big Falcon Rocket, desitned to be the most powerful launch system yet flown, and fully capable of lifting 100 tonnes to low Earth orbit – and then delivering it onwards to the Moon or Mars.

The BFR – note the tiny human figure, to scale. Credit: SpaceX

BFR is intended to be a two-stage, fully reusable vehicle, comprising a massive first stage core  which can make a automated flight back to Earth and land in the same manner as the first stage of the Falcon 9, and a payload carrying upper stage – which can double as a transport vehicle (and which SpaceX simply refer to as “the ship”). This much has been known for some time. However, in his presentation, Wooster filled-out more aspects of the likely Mars mission profile.

In particular he covered the planned architecture for SpaceX’s missions, and on some of the core requirements for missions – such as developing ISRU – in-situ resource utilisation – capabilities for sustaining a human presence on Mars. ISRU involves using local materials – Martian surface material, water ice beneath the surface, and so on – to provide an outpost on Mars with building materials, with the means to grow crops, to the production of water and oxygen – and even the fuel needed to fly some of their transport vehicles back to Earth. It’s an approach first popularised by Mars Society founder Dr. Robert Zubrin, who demonstrated how spacecraft on Mars could be refuelled using little more than 6 tonnes of hydrogen carried from Earth and the CO2 in Mars’ atmosphere. For their part, SpaceX plan to use water obtained from sub-surface ice deposits on Mars rather than hydrogen, but the process is the same – and using ice also provides people on Mars with wter and oxygen as well.

The SpaceX Mars Architecture. Ships bound for Mars (either cargo or crew carrying) are placed into low Earth orbit, where they are refuelled by up to 3 “tanker” versions of the BFR. Then then depart Earth for Mars, where they use aerocapture and land, delivering their cargo / crew to the surface. Those ships destined to return to Earth then use local resources to refuel ahead of a return to Earth. Credit: SpaceX

In support of this, SpaceX has been developing the Raptor engine, specifically designed to be powered by a liquid methane / liquid oxygen mix of propellants. The prototypes of this engine have undergone a total of 1,200 seconds (20 minutes) of ground-based test firings, in which they have demonstrated the motor is exceptionally capable and powerful, generating 3 times the thrust of the Merlin 1D motor used to power the Falcon 9 / Falcon Heavy.

The baseline mission profile for getting to Mars comprises an initial two flights of cargo vehicles, each carrying 100 tonnes of equipment and supplies – including the equipment needed to manufacture water, oxygen and fuel on Mars. These would be followed two years later (26 months being the period between the optimal times for launching to Mars) by 2 crew vehicles and 2 further cargo vessels. The former would carry an unspecified number of people to Mars and become their habitats / base of operations as they undertake initial development of the base, with the cargo vehicles further equipment  and supplies. This schedule would be continued until such time fuel stocks start allowing for the crew vehicles to start making return trips to Earth – which both allows personnel to return home and further reduces mission costs as each “ship” is designed to fly up to 12 times – and surface construction allows for personnel to start living in facilities built on Mars with local resources.

SpaceX envision “the ship”, the upper stage of the BFR, as being able to perform a wide range of missions, including (clockwise from top left): placing very large cargoes into almost any orbit around Earth, orbital construction and support, missions to Mar and, bottom left, to the Moon. Credit: SpaceX

It’s a massively ambitious proposal – but organisations such as the Mars Society and others have laid much of the foundational work, and SpaceX is clearly looking to others to help solve some of the critical issues around living on Mars: how best to obtain / use local resources (and there are plenty of them); how to deal with the Martian dust, which could be a significant contaminant / health hazard if not properly mitigated; how to manage radiation issues whilst on Mars, and so on. However, what the company really has yet to publicly address is how they will handle matters of radiation during the Earth / Mars and Mars / Earth flights, particularly with regards to minimising the effects of galactic cosmic rays (GCRs), which as I’ve mentioned in past Space Sunday reports, is potentially a greater issue to crews than solar radiation, as it is much harder to mitigate.

It’s unlikely that SpaceX will achieve their aspirational dates of 2022 and 2024 for their first flights to Mars with BFR (I would doubt they would be in a position to do anything until the latter half of the 2020s). But at a time when NASA seems intent on swapping an Earth orbiting space station for one in an extended lunar orbit in the hope of kick-starting lunar exploration which may “someday” allow humans to travel beyond the Moon, it is refreshing that SpaceX is attempting to harness their own abilities and international knowledge and research in an effort to carry us directly to Mars.