Space Sunday: a farewell to Spitzer, capsules, stars and space planes

A composite image of NASA’s Spitzer Space Telescope. Credit: NASA

The end of January 2020 brings with it the end of a 16-year mission to explore the galaxy in the infra-red, as the Spitzer Space Telescope (SST) is shut down.

Launched in 2003, Spitzer was one of NASA’s four Great Observatories, following in the footsteps of the Hubble Space Telescope and the Chandra X-ray Observatory. Its infra-red vision has allowed Spitzer to peer through the dusty reaches of the cosmos to witness stellar nurseries, provide insight into the deaths of stars and the very formation of the universe, and increase our understanding of the structure of galaxies and the nature of black holes.

Spitzer operated as planned for 5.5 years – three years longer than its initial primary mission – until a lack of coolant prevented the telescope from operating within its planned low temperature range. A switch to a warmer operating mode allowed the telescope’s mission to be extended another 10.5 years, albeit it with only two of its sciences instruments able to function in the higher temperature range.

NASA’s four space-based Great Observatories. Credit: NASA

The official reason for ending the mission, even though the two remaining IRAC instruments remain operational, is issues of balancing operational requirements with those of power generation and communications. Spitzer occupies a similar orbit to Earth but is moving more slowly; as the gap between them widens, so to does the triangle formed by the Sun, Earth and the telescope, and it has now reached a point where in is impossible for the telescope to maintain both line-of-sight communications with Earth and keep its solar panels pointing to the Sun to generate power. Add to this the need to orient the telescope to observe study targets, and operating the telescope has become an increasingly complex and fuel-costly dance.

In 2017, NASA attempted to spin-off the telescope’s operations and management to academic institutions in 2017, but was unsuccessful. So, on January 29th, Spitzer will transmit to Earth the last of the data it has gathered, then on January 30th, it will be put into a hibernation mode, oriented in a permanent “sun-coning attitude”. In theory, it would be possible to recover the telescope from this state at some point in the future, except for the fact that the custom ground system for operating Spitzer is to be dismantled after the telescope has been shut down.

Overall, the cost of the Spitzer mission from launch to this final close-out will have been US $1.3 billion, a modest price for the wealth of data the mission has returned to Earth: over 8,700 scientific papers related to Spitzer’s discoveries and data have been published. However, the shut down will effectively bring space-based infra-red observations of the galaxy around us to an end – at least until the James Webb Space Telescope commences operations. This is expected to launch in 2021.

The telescope has made many discoveries beyond the imaginations of its designers, such as planets outside our solar system, called exoplanets, and galaxies that formed close to the beginning of the universe. We have a lot of new questions to ask about the universe because of Spitzer. It’s very gratifying to know there’s such a powerful set of capabilities coming along to follow up on what we’ve been able to start with Spitzer.

– Michael Werner, Spitzer project scientist, NASA Jet Propulsion Laboratory

China Prepares to Test Launch Its Next Generation Crew Vehicle

In 2018, I first wrote about China’s upcoming “next generation” crewed space vehicle that will eventually replace the Soyuz-derived Shenzhou craft. Since then, work has been proceeding with the design, with structural test articles being rigorously tested together with the vehicle’s parachute and landing systems, while the first flight-ready unit has also been under development and assembly.

The first of China’s next generation crew capsules being mated to its Service Module. Credit: CAST

The new craft mirrors both the the Apollo Command and and Service Module approach to crewed space systems and Boeing’s CST-100 Starliner. Like the former, it comprises a conical crew capsule supported in space be a cylindrical Service Module equipped with a single large motor and designed to provide the capsule with power and life support whilst in space. The Service Module is also thought to offer two variants: a small version for operations in Earth orbit, and a larger unit to help support missions further afield – such as to the Moon.

Like Boeing’s Starliner, the capsule is designed to carry up to 6 crew, or a combination of crew and cargo, and can be re-used up to 10 times. At the end of each flight, it will make a dry land touchdown using both parachutes and air bags.

The 14-tonne (l) and 20-tonne next generation Chinese crewed vehicles – remarkably similar to Boeing’s CST-100 Starliner. Credit: Beijing Institute of Space Mechanics and Electronics

On January 20th, the flight test vehicle arrived at China’s Wenchang Satellite Launch Centre on Hainan island in the South China Sea. It will be integrated with a Long March 5B launch vehicle – currently China’s most powerful booster – ready to for an uncrewed flight that will carry it some 8,000km from Earth before returning and making a soft landing. This first flight could take place as early as April 2020.

The vehicle has yet to be given an official name, and no date has been given for its possible entry into service. However, it is seen as a key component in China’s upcoming new space station – construction of which may also start this year – and in their human Moon exploration programme.

Betelgeuse Continues to Dim

Over the last several months, the red giant variable star has been dimming in our night skies, leading some to speculate whether or not we might be about to witness it having gone supernova. In writing about the phenomena December 2019 (see: Space Sunday: a look at Betelgeuse), I noted that while Betelgeuse will likely go supernova some time in the next 100,000 years, the current dimming coincides with two of the star’s periods of dimming being at their lowest points of brightness, so most astronomers believed we’d witness the star to brighten again.

However, since that time, the star has continued to get dimmer – albeit at a slower rate than the closing months of 2019, which might suggest a reversal might be forthcoming – and the astronomers who first reported the current dimming, Edward Guinan and Richard Wasatonic, have also now noted that the star’s temperature has apparently fallen by 100 Kelvin.

A chart marking Betelgeuse’s dimming, showing the sharp decline in late 2019 / 2020. Credit: AAVSO – AAVSO Light Curve Generator 2

Is this further evidence that Betelgeuse is approaching supernova? Most astronomers still think not. Over the last 20 years the star  – or at least is surrounding corona – has shrunk by about 15%; were the star be approaching supernova, it would likely expand its already massive size prior to a rapid collapse – although Guinan and Wasatonic believe Betelgeuse may have increased size by around 9% since September 2019. So what is happening?

One suggestion is that as well as the current dimming be the result of two of Betelgeuse’s cycles coinciding, it could also be the result of a cloud of gas and dust is interfering with the amount of light we’re seeing from the star. In short, as Betelgeuse burns its fuel, it loses mass, weakening its gravitational hold on its outer edges, allowing clouds of gas escape into the region around the star, and this might be contributing to the current uncharacteristic dimming episode – and may also interfere with data on the star’s temperature and size. Given this, Edward Guinan in discussing Beteleqeuse in the last few days, elieves that the dimming will “reverse” itself Betelgeuse will start to brighten again.

SpaceX Would Like to “Catch” Returning Crew Dragon Capsules

Having just completed a successful in-flight abort (IFA) test as they move steadily towards commencing crewed flights to and from the International Space Station (ISS) with their Crew Dragon capsule, SpaceX is already looking down the line at ways to achieve re-usability with the vehicle.

Unlike Boeing’s CST-100 Starliner capsule, which makes a return to land at the end of a mission, Crew Dragon makes a more traditional splashdown in the ocean. This lowers the complexity of individual flights, but due to the higher safety requirements enforced for crewed flights the exposure to salt water makes refurbishing individual Crew Dragon vehicles more complex than is the case with the Cargo Dragons SpaceX use to ferry cargo to and from the ISS and which are routinely plucked out of the sea and refurbished for further flights. So as they start crewed flights, SpaceX will use a new Crew Dragon vehicle for each mission it flies.

If a salt water splashdown could be avoided, then refurbishing a Crew Dragon for re-use becomes easier. To this end, SpaceX CEO Elon Musk has made a novel proposal: catch returning Cargo Dragons in a net.

Ms Tree (still bearing her former name of Mr Steven) being equipped with larger nets for the capture of Falcon 9 payload fairings – and which might in the future – be used to catch returning Crew Dragon capsules. Credit: Pauline Acalin

The net in question is the giant one carried aboard two of the SpaceX recovery vessels, Ms Tree (formerly called Mr Steven) and Ms Chief. These ships are currently being used to try to catch the payload fairings from outgoing Falcon 9 launches, which after being jettisoned during launch, use their shape like a lifting body to drop back into the denser atmosphere where parasails can be deployed, allowing them to drift down either to a gentle splashdown or – more preferably, again to avoid exposing them to salt water (and even sinking) – to a capture by one of the two recovery ships.

So far, SpaceX has only captured a fairing in this manner on two occasions, one of which is recorded in the video below. However, as they gain greater proficiency and raise their success rate, Musk suggests the same technique might be used with returning Crew Dragon vehicles.

A video of Ms Tree making a second successful fairing recovery, August 2019

The approach would require NASA’s approval before being attempted with a crewed vehicle, and it would seem likely that such an approach would not be attempted until well into Crew Dragon flights – and potentially then only after there have been proof-of-concept attempts to recover Cargo Dragon craft using the ships’ nets.

A Space Plane Dies, Another Get Promoted

In 2018 I wrote about the US Defence Advanced Research Projects Agency’s (DARPA) plans to develop a cargo-capable, sub-orbital space plane that could deliver single or dual payloads to orbit piggyback-style. Referred as XSP, the programme saw Boeing selected to lead Phases 2 (vehicle development) and Phase 3 (test flight operations commencing in 2020), with US $146 million being granted by DARPA for Boeing to kick-start Phase 2.

Dubbed the Phantom Express, Boeing’s proposed system comprised a 30m long vehicle with a 19m wingspan designed to launch vertically and land horizontally, and with the capability of being launched and recovered 10 times in as many days as a part of DARPA’s rapid launch response programme.

An artist’s impression of DARPA’s Experimental Space plane XS-1 and dubbed the “Phantom Express” by the project’s sole contractor, Boeing, lifting a piggyback payload to the edge of space. Credit: Boeing

However, on January 22nd, 2020, Boeing pulled out of the project “with immediate effect”. No reason for the decision has been given, but Boeing’s departure effectively kills the XSP programme, with DARPA already turning to other projects.

Meanwhile, Exodus Space Corporation, a start-up company whose principals include former managers and engineers at SpaceX, Lockheed Martin and NASA, has formally announced its intention to develop and operate and ambitious two-stage, multi-propulsion aerospace plane they are calling the AstroClipper.

Claiming they have had the vehicle in development “in private” for the ten years, Exodus is now seeking investors to provide financing for the project.Their first aim to to develop a technology demonstrator by 2022. Called AstroClipper Pico, and the size of a drone, it would be designed to fly within the Earth’s atmosphere and then be followed by a larger vehicle, the AstroClipper Nano, capable of delivering 1,200 kg of cargo to orbit. From this, the company plan to move to developing and flying the full-scale craft, the passenger variant of which, they claim, will be able to carry up to 20 passengers into space – and around the globe – some time in the 2030s.

The video below explains how the system will work. However, it presents some significant technical complexity. The first stage of the vehicle, for example, will have three separate propulsion systems: conventional turbojets, hypersonic ramjets and rocket motors. The upper stage is simpler, however, using a conventional rocket propulsion system to achieve orbit, while relying on its lifting body shape to achieve atmospheric entry and allowing it to glide to a runway landing.

It’s an ambitious project, one that is going to require a lot of financing, but Exodus CEO Miguel Ayala believes the company can achieve its targets.

We’ve worked on vehicles, spacecraft and aircraft. We’re a very experienced leadership team. We also have an extended team of around 40 people that helps us with different aspects of our technology … we do have a big team we’re going to draw from. Once we get funded, we have the people in line to start getting to the work.

As such, it will be interesting to see if / when the company’s concept leads anywhere.