Space Sunday: Dream Chasers Falcons, and spacewalks

The Dream chaser alongside NASA's space shuttle Atlantis
The Dream Chaser flight test article alongside NASA’s space shuttle Atlantis in 2010 (image: NASA / SNC)

NASA has announced a renewal to the current US private sector contracts to provide uncrewed resupply missions to the International Space Station (ISS) – and it came with something of a surprise.

SpaceX and Orbital ATK are the two US companies currently flying cargo resupply missions to the ISS, operating alongside Russian Progress vehicles and the Japanese H-II “Kounotori” Transfer Vehicle. Europe, which previously operated the largest cargo vehicle, the Automated Transfer Vehicle, ended ISS resupply missions in February 2015, and is now focused on supplying NASA with the Orion Service Module.

Both SpaceX, who can both launch and return up to 3.3 tonnes of cargo and trash to / from the space station using their Dragon cargo vehicle, and Orbital ATK,who can transport up to 3.5 tonnes of cargo / trash aboard their Cygnus vehicle (which burns-up on re-entering Earth’s atmosphere) have their resupply contracts renewed from 2019 through 2024, matching the extended lifetime of ISS operations. While this had been expected, the inclusion of a third vehicle, the Dream Chaser vehicle being developed by Sierra Nevada Corporation SNC surprised some.

Dream Chaser was unique among the commercial crew transportation proposals as it was based on a "lifting body" design , allowing to re-enter the Earth's atmosphere and glide to a landing on a conventional runway - aspects which still make it a very flexible vehicle
Dream Chaser was unique among the commercial crew transportation proposals as it was based on a “lifting body” design rather than a capsule system. Although launched atop a conventional rocket, the design allows it to re-enter the Earth’s atmosphere and glide to a landing on a conventional runway, making it an exceptionally versatile craft (image: SNC)

Dream Chaser was originally designed as part of NASA’s Commercial Crew Development (CCDev) programme aimed at having private sector companies provide the means of carrying crews back and forth between the space station and US soil. One of four proposals put to NASA under the programme, it was ruled out of the final selection in September 2014, with SpaceX and Boeing being chosen by NASA despite the fact that on paper, Dream Chaser offered potentially a better deal than Boeing’s CT-100 capsule.

While SNC lodged a complaint with the US Government Accountability Office (GAO) as a result of the decision, citing interference in the selection process by William Gerstenmaier, NASA’s top human exploration official, the GAO upheld the selection of SpaceX and Boeing for the crewed transport vehicles. However, NASA continued to work with SNC on various ideas for Dream Chaser, alongside of SNC looking at other options for the vehicle’s crew carrying capabilities to be put to use.

An artist's concept of the Dream Chaser Cargo docked with the ISS during a resupply flight
An artist’s concept of the Dream Chaser Cargo docked with the ISS during a resupply flight (image: SNC)

The new resupply contract will see SNC provide NASA with the uncrewed “Dream Chaser Cargo” variant of the vehicle, capable of flying up to 5 tonnes of cargo to / from orbit, As with the original crewed variant, the Dream Chaser Cargo will launch atop a rocket, but return to earth to make a conventional runway landing.

How many missions each of the three resupply vehicle types will fly is unknown; vehicles will be selected on the basis of flight / payload requirements and cost. The total cost of the contract, spilt between the three companies, is expected to be US $14 billion over the 5 years.

The Ice Volcanoes of Pluto

Scientists with NASA’s New Horizons mission have assembled the highest-resolution colour view of one of two potential cryovolcanoes spotted on the surface of Pluto, as the spacecraft hurtled by the little world in July 2015.

Informally called “Wright Mons”, the feature is about 150-160 kilometres (90-100 miles) across at its base, and about 4 km (2.5 miles) high. If it is in fact a volcano, it will be the largest such feature discovered in the outer solar system.

The feature has members of the New Horizons science team intrigued on two counts. The first is that there is a very sparse distribution of red material on its flanks. The second is that it apparently only has a single impact crater. This latter point suggests “Wright Mons” is relatively new surface feature on Pluto, while the former might suggest it is active, with ice ejected by eruptions covering the red material over time.

"Wright Mons" (the large dimple in the image on the right) and as seen in context with the rest of Pluto, may be one of two enormous cryovolcanoes on the tiny world (image: NASA/JPL / JHU/APL / SwRI)
“Wright Mons” (the large dimple in the image on the right) and as seen in context with the rest of Pluto, may be one of two enormous cryovolcanoes on the tiny world (image: NASA/JPL / JHU/APL / SwRI)

The images of “Wright Mons” were returned to Earth from New Horizons in November 2015. Since then, data from the Ralph instrument suite aboard the spacecraft has been used to add the colour details to the images, which have been composed into a new mosaic of the feature. If it and “Piccard Mons” are cryovolancoes, then they present further evidence that Pluto was (and might still be) geologically active.

Continue reading “Space Sunday: Dream Chasers Falcons, and spacewalks”