Space Sunday: water, spaceplanes and clockwork rovers

TRAPPIST-1 compared in size to our own Sun. Credit: NASA.

Since the February 2017 announcement on the discovery of seven rocky planets orbiting the nearby red dwarf star TRAPPIST-1, multiple studies have been conducted to ascertain whether any of the planets might harbour conditions suitable for life. The nature of their parent star would suggest this to be unlikely. However, an international team utilising the Hubble Space Telescope (HST) to study the TRAPPIST-1 system believe they’ve found evidence that some of the planets have the right conditions to allow liquid water to exist.

Vincent Bourrier, from the Observatoire de l’Université de Genève in Switzerland, and his team used the  Space Telescope Imaging Spectrograph (STIS) to study the amount of ultraviolet radiation each of the TRAPPIST-1 planets receives. If there were too much UV light, no water could survive on the surface because the water molecules would break up and escape through the top of the atmosphere as hydrogen and oxygen gas.

The team found that the inner planets in the system – TRAPPIST-1b and 1c – receive so much UV radiation from their sun, they may have lost more than 20 Earth-oceans worth of water in the course of their history, estimated to be between 5.4 and 9.8 billion years old. Thus, they are almost certainly devoid of water, and their surfaces are likely sterile. However, the findings also suggest the outer planets in the system – including the three within TRAPPIST-1’s habitable zone, may have lost less than three Earth-oceans’ worth of water throughout their history, and could possibly still possess liquid water, making them more amenable for life to rise.

As well as suggesting some of the TRAPPIST-1 planets may have liquid water present, the study has broader implications for the potential of other exoplanets harbouring life. Up to 70% of the stars in the Milky Way are believed to by M-class red dwarfs – and the majority of rocky exoplanets thus far found are orbiting such stars. So this study might indicate that many more of the exoplanets orbiting such stars could support liquid water and, perhaps, conditions suitable for life. However Bourrier and his colleagues emphasise that the study is not conclusive, and further research is needed to determine if any of the TRAPPIST-1 planets are actually watery.

SNC Prepares Dream Chaser for Glide Flight Testing and UN Mission

Sierra Nevada Corporation (SNC) carried out a “captive / carry” test of a Dreamer Chaser Cargo vehicle test article on August 31st, 2017. The flight, with the vehicle slung beneath a helicopter forms the first step towards the Dream Chaser Cargo carrying out glide flights and landings.

During the test, SNC collected data on the vehicle’s performance in flight, including operation of radar altimeters, air data probes and other systems that cannot be fully tested on the ground. The captive /  carry test followed a series of ground tests where the vehicle was towed behind a truck down a runway at speeds of up to 100 kph to ascertain its ground handling on landing.

The Dream Chaser Cargo test article is lifted aloft by helicopter in a captive/carry test. Credit: Sierra Nevada Corporation

SNC developed Dream Chaser to transport astronauts to and from the ISS. However, NASA selected capsule designs by SpaceX and Boeing. After a protest over the decision, filed with the U.S. Government Accountability Office, failed, SNC turned their attention to other potential uses for Dream Chaser.

One of these has been the development of a cargo variant to service the International Space Station (ISS) alongside existing resupply contractors,  Orbital ATK and SpaceX, and in 2016, NASA confirmed Dream Chaser Cargo has been selected to fly resupply missions to the ISS between 2019 and 2024.

On July 19th, 2017, it was announced that SNC had signed a contract with United Launch Alliance for the first two launches of these resupply missions, using the Atlas 5 552 launch vehicle. The first launch is scheduled for 2020 and the second in 2021, although NASA has yet to formally order any Dream Chaser flights.

A Dream Chaser Cargo vehicle will also be used in 2021 to launch the first United Nations mission into space. The United Nations Office of Outer Space Affairs (UNOOSA) said an agreement between them and SNC to fly the dedicated Dream Chaser mission is part of a broader effort by the office to increase access to space to emerging nations.

The mission will be open to all nations, but with a particular emphasis on those that don’t have the capabilities to fly their own experiments in space. UNOOSA are in the process of soliciting payload proposals with a goal of selecting payloads by early 2018 so that the winning countries have time to build them for a 2021 launch.

Unlike the majority of Dream Chaser Cargo missions, which will focused on ISS resupply work, the UNOOSA flight will see the vehicle placed in orbit around the Earth, and SNC have indicated the vehicle will be capable of operating freely in orbit for extended periods of time, should the UN desire a longer mission.

While billed as the UN’s first space mission, the Dream Chaser flight is part of UNOOSA’s Human Space Technology Initiative, launched in 2010 with the goal of providing developing countries the possibility to access space in microgravity conditions. Currently, the initiative includes two other major projects. The first is a cooperative project with the Japan Aerospace Exploration Agency (JAXA), designed to give developing nations the opportunity to launch cubesats from the ISS. Another programme, to be operated in cooperation with China’s space programme, will allow UN-backed missions to be flown aboard China’s space station, when it becomes operational in 2020.

JWST to Study “Ocean Worlds”

Due for launch in October 2018 atop a European Ariane V booster, NASA’s James Webb Space Telescope (JWST) is essentially the successor to the Hubble Space Telescope (HST). With a primary mirror over 2.5 times the diameter of Hubble’s, the JWST will be 100 times more powerful than its predecessor, and will be capable of looking over 13 billion years in time. This will allow it to probe the first light of the Universe from the Big Bang, examine other galaxies and probe extra-solar planets in nearby star systems.

In addition, JWST will be used to study Jupiter’s moon Europa and Saturn’s moon Enceladus, which have been selected for study by some of the scientists who have been developing the telescope, and whoy will be among the first to use the telescope once it becomes fully operational, around 16 months after its launch. These two moons are of specific interest because of their potential to harbour liquid water oceans, warmed by heat rising from the moons’ core through thermal vents on the floors of their respective ocean floors – vents which might be pumping chemicals and nutrients into the water around them which might allow life to arise.

Artist rendering showing an interior cross-section of the crust of Enceladus, which shows how hydrothermal activity may be causing the plumes of water at the moon’s surface. Credits: NASA-GSFC / SVS, NASA/JPL / Southwest Research Institute

JWST will not be able to see into the two moons to confirm this, but it will be able to study the geyser-like plumes erupting from the southern hemispheres of both. The plumes on Enceladus have been known about since 2005, periodically erupting to deliver water vapour and organic chemicals to replenish Saturn’s outermost E ring. Similar eruptions on Europa have been imaged since 2012.

To study Europa, the science team will use JWST’s near-infrared camera (NIRCam) to image the moon’s surface in high-resolution in a search for hot spots that indicate the locations of a plume and its associated geological activity. Once a plume is located, the near-infrared spectrograph (NIRSpec) and mid-infrared instrument (MIRI) will be used to determine its composition.

As Enceladus is too far away for JWST to image its surface in high-resolution, the scientists will perform a direct analysis of the molecular composition of the southern hemisphere plumes – if they are active at the times observations are made – and perform a broad analysis of the moon’s surface.

It is hoped that the surveys will find evidence of organic signatures in any plumes rising from either moon, such as methane, ethanol and ethane. Doing so will help better characterise the active regions of both moons, and potentially help pinpoint locations that will be of interest for future missions, such as NASA’s Europa Clipper mission, expected to launch sometime in the 2020s in an attempt to determine if Europa is habitable.

A “Clockwork” Rover on Venus?

Venus is an inhospitable world. It’s surface temperature averages 462 °C, and the atmospheric pressure at the surface is some 92 times greater than here on Earth. The atmosphere is 96.5 percent carbon dioxide and highly sulphurous. It forms dense sink, trapping heat in what is often called a runaway greenhouse effect.

The proposed Venus “clockwork” rover: the AREE. Credit: NASA/JPL

While we have studied Venus from orbit – notably by NASA’s Magellan mission, which extensively observed the planet and mapped its surface via radar between 1990 and 1994 – missions to the surface have not been overly successful. The only missions to successfully operate on the surface of Venus were the Soviet-era Venera and Vega programmes – and these only survived for between 23 mins and two hours.

The reason for this is a combination of the high temperatures and atmospheric pressure place considerable strain on the structure of surface probes, while the sulphur in the atmosphere quickly corrodes electronic systems. To counter both – particularly the corrosive effect of the atmosphere on electronics, Jonathan Sauder, a mechatronics engineer at NASA’s Jet Propulsion Laboratory, has put forward the idea of sending a “clockwork” rover to Venus.

Called the Automaton Rover for Extreme Environments (AREE), the vehicle would be almost entirely analogue in nature, actually using the Venusian wind to power its computer system. First proposed in 2015, and now receiving further study, the rover would be around 1.5 metres (just under 5 ft) tall, and comprise a heavyweight, tracked frame containing the wind turbines used to drive. Radar targets on the rover’s top would be periodically pinged via radar to send data using Morse code. While very little sunlight reaches the surface of Venus, solar panels would be included on the rover to provide supplemental power.

The AREE rover (with and Apollo astronaut to give an idea of scale). Wind would be channelled through the rover’s body for primary power. Rotating targets on top could be “pinged” by radar, sending data as Morse code. Credit: NASA/JPL

Regarded as an automata – a mechanical, self-operating machine capable of performing sequences of operations and instructions – AREE has the same pedigree as clocks and a heritage stretching back 2,300 years to the Antikythera mechanism, an ancient Greek analogue computer and orrery used to predict astronomical positions and eclipses for calendar and astrological purposes. In developing the AREE idea over a number of years, Sauder acknowledges the inspirational role played by the mechanism and by the wind-propelled Strandbeest creations of Dutch artist Theo Jansen in his thinking.

Like the Strandbeest, AREE was originally conceived as a “walking” rover using multiple legs. However, as we have little detailed knowledge of the kinds of surface terrains a rover on Venus might encounter, tracks were eventually chosen as the optimal means of locomotion for the rover.

The vehicle has yet to be officially adopted and funded as a mission, but were this to happen, it would be the first surface mission sent to Venus since the Cold War era – and the first steampunkesque space mission ever flown.

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