Space Sunday: Kepler, China, and a voyage to the Sun

An artist’s rendering of Kepler in its heliocentric orbit. Credit: NASA

In March 2018, I reported that NASA’s exoplanet hunting Kepler mission might be drawing to a close. The end of the mission was threatened when engineers confirmed that the observatory was showing signs of running out of fuel.

Responsible for locating 70% of the 3,750 exoplanets discovered to date, Kepler was launched in 2009 and has been one of the most successful missions NASA has run. Unfortunately, as a result of a change to its operational parameters following the failure of two of the four reaction wheels used to hold it steady while observing distant stars, the observatory has had to increase its use of its propellant reserves. As a result, on July 2nd, 2018, NASA Kepler was ordered into a “no-fuel-use safe mode” after telemetry reported an “anomalous” drop in fuel pressure in the spacecraft.

The observatory will remain in this mode until August 2nd, 2018, when it is due to use its manoeuvring jets to orient itself so it can transmit the data collected on its last observational campaign – the 18th in its extended mission – to Earth via the Deep Space Network. During the time between now and August 2nd, engineers will attempt evaluate the status of the spacecraft’s propulsion system to determine if it has sufficient fuel left to allow it to resume observations in what is called Campaign 19, scheduled to begin August 6th, 2018.

Kepler has been tremendously successful by any measure. In addition to its impressive raw planet tally – liable to raise as there are still more than 2,000 planet candidates still to be vetted – the data gathered by Kepler since 2009 seems to suggest that 20% of Sun-like stars host a roughly Earth-size planet in the habitable zone — that just-right range of distances where liquid water could exist on a world’s surface.

During its primary mission, from 2009 through May 2013, Kepler stared at about 150,000 stars simultaneously, hunting for periodic dipping in their brightness that might indicate a planetary body moving in front of them. Since 2014, it has been engaged on its extended K2 mission, comprising a series of observational campaigns lasting 80 days apiece, each focused on a slightly different area of sky.

However, if this is the beginning of the end for Kepler, it’s not the end of our exoplanet hunting efforts: if all is proceeding as planned, the Transiting Exoplanet Survey Satellite, launched in April, 2018, should be taking over the task – although admittedly, news on its “first light” image, which was due in June, has yet to be released.

China’s Super-Heavy Launch and Reusable Rocket Capabilities

Speaking during an event in China at the end of May 2018, Long Lehao, a chief designer with the China Academy of Launch Vehicle Technology (CALT), gave an update on two of China’s new launch vehicles: the Long March 9 super booster and the partially reusable Long March 8 rocket.

The Long March 9 – referred to as the CZ-9, or Changzheng 9 in Chinese – is slated to enter service in 2030, and is central to China’s interplanetary ambitions. It is also a huge increase in scale a capability for the nation’s launch systems. The core three-stage rocket will stand 93 metres tall, using a 10-metre diameter first stage. It will be assisted at launch by four 5-metre diameter strap-on boosters – these alone being the same diameter as China’s Long March 5, currently the country’s most powerful rocket. The most powerful variant of the vehicle will be capable of launching 140 tonnes to low-Earth orbit (LEO), 50 tonnes to the Moon and around 44 tonnes to Mars.

China’s Long March 9 (CZ-9), flanked by launch vehicles past and present, including Russia’s never successfully flown N-1 lunar rocket from the 1960s. Via: Wikipedia

By comparison, NASA’s Space Launch System (SLS) vehicle will have a core stage 8.4 metres in diameter, with its most powerful variant (Block 2) capable of placing 130 tonnes into LEO, and SpaceX’s BFR with a 9-metre diameter core and be capable of putting 150 tonnes into LEO.

In his presentation, Long confirmed the first CZ-9 is slated for launch in 2030 – around the time the Block 2 variant of the SLS is due to fly. One of the first missions earmarked for the super booster is an automated Mars sample return mission, with crewed lunar missions also on the cards for the vehicle. In addition, the CZ-9 could be used to deploy a system of solar power satellites the Chinese government and military are said to be considering.

Meanwhile, the Long March 8, based on the core of China’s current mid-range launcher, the Long March 7, is expected to make its first flight in 2021. Capable of lifting a more modest 8 tonnes to LEO, the first stage of the booster is designed to be reusable, employing a similar methodology to SpaceX’s Falcon 9 first stages to return to Earth and land.

An artist’s impression of the Long March 8 first stage about to make a soft-landing at the end of a launch flight. Credit: Shanghai Academy of Spaceflight Technology

While the payload capacity of the Long March 8 might sound small, it is ideal for typical satellite payloads. More to the point, the use of the Long March 7 first stage means the system could be “upgraded” to work with that vehicle, which is capable of placing 13 tonnes into LEO.

China has also revealed more on the technologies it is developing for future crew-carrying spacecraft, with successful tests of the new parachute system that will be used in conjunction with the county’s next generation crew-carrying space vehicle, which will replace the current Shenzhou capsules derived from Russia’s Soyuz vehicle.

The new crew vehicles will be somewhat similar to the American Apollo Command and Service Modules and Boeing’s CST-100 Starliner, comprising a crewed “command module” and a supporting “service module”. They will come in two variations, a 20 tonne version a 14 tonne variant, with either capable of carrying between 4 and 6 crew depending on the mission profile. Each would be used as part of larger missions to the Moon, Mars and deep space.

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

A test mock-up of the new capsule was flown atop a Long March 7 in 2016. A further test-flight, possibly with a full test version of the craft, is due to be launched by a Long March 5 booster in 2019. This might also involve the use of the new parachute system.

Also being tested is a system claimed to be a “breakthrough” technology for getting large space vehicles safely to the surface of Mars. Called the Inflatable Reentry and Descent Technology (IRDT), it uses airbag / ballute systems to integrate the functions thermal protection, deceleration, and landing systems. It is in some ways similar to the Low-Density Supersonic Decelerator (LDSD) tested by NASA to help decelerate a vehicle as it enters the Martian atmosphere, but if the statements about IRDT prove accurate, it is potentially far more capable.

LDSD’s range of operations are around 1.3-1.5 tonnes; IRDT is being designed to work with landers of up to 15 tonnes. Essentially, it is designed to be inflated around the base of a vehicle entering Mars’ atmosphere, both shielding it from the heat of entry, and then acting as an “aerobrake”, decelerating the craft sufficiently to allow parachutes to be deployed. A second element of the system, forming a set of airbags is designed to inflate and cushion a craft on landing, reducing the reliance retro-rockets, which add mass to the vehicle.

China’s inflatable entry, descent and landing systems: the IRDT test article, designed to test the aerodynamic stability of an inflatable heat shield (l) and an inflatable landing cushion for a large-scale capsule (r) being tested by the Beijing Institute of Space Mechanics and Electronics. Credits: China Academy of Space Technology

The IRDT tests took two forms, the first saw a saucer-shape vehicle, representing a ballute-like decelerator was used to test the atmospheric handling of an inflatable ballute, and its effectiveness in slowing a test vehicle. The second test involved dropping what appears to be a model of the new capsule system from a test rig to test the rapid deployment and cushioning effect of the landing airbags.

Experts have pointed out that the photos alone make it hard to assess either part of the system; but it will be interesting to see how IRDT continues to be developed.

Virgin Signs Agreement for European Operations

Virgin Galactic and Virgin Orbit have signed a series of agreements with the Italian space agency and various Italian companies that could pave the way for both companies to operate services from Italy.

The agreements build on a series of initial memoranda of understanding signed between Virgin and the Italian companies involved – Altec and Sitael – and discussions between Virgin Galactic (technically an American company and so subject to US laws on technology exports) and the US State Department to Virgin allow them to use their systems from foreign soil.

Virgin Galactic: planning to operate its SpaceShipTwo vehicle from southern Italy. Credit: Virgin Galactic

The first set of agreements help pave the way for Virgin Galactic and its sister company, The Spaceship Company, to build and operate facilities at the Taranto-Grottaglie airport in the southern part of Italy, from which they hope to operate a WhiteKnightTwo carrier aircraft and a SpaceShipTwo sub-orbital vehicle, for both space tourism and space research flights.

This partnership could see Virgin Galactic launch the first person in history into space from Italian soil — and in fact from any European territory. Together, we will help to expand opportunities for science, industry and the millions of people who dream of experiencing space for themselves.

– Sir Richard Branson, Virgin Group founder.

The second, and separate, set of agreements open the way for Virgin Orbit to also operate from Taranto-Grottaglie airport, flying their LauncherOne air-launched, two-stage rocket system, intended to place payloads between 300 kg and 500 kg in polar, Sun-synchronous orbits. The rocket is launched by flying it to altitude under the wing of a modified 747 aircraft, where it can be released to allow its own rocket motors to lift it to orbit, massively reducing the amount of fuel the rocket must carry.

Virgin Orbit is also looking to operate its air-launched LauncherOne system from southern Italy. Credit: Virgin Orbit

The agreements are not a firm commitment for Virgin to operate either Virgin Galactic or Virgin Orbit out of Italy, nor do they indicate when operations for either might start. These points will require the signing of formal contracts between the various parties involved.

Solar Probe Steps Closer to Launch

NASA’s Parker Solar Probe took a further step towards its upcoming August 2018 launch with the re-installation of its revolutionary heat shield.

Named for astrophysicist Eugene Parker, who in 1958 predicted the existence of the solar wind – the stream of charged particles flowing constantly from the Sun -, the mission is billed as the “first to touch the Sun”, as the spacecraft will come to within 8.86 solar radii (6.2 million km / 3.85 million mi) of the Sun’s photosphere (or “surface”). This will allow it to collect unprecedented data about the inner workings of the Sun’s corona.

The heat shield is a vital component of the mission; at its closest approach to the Sun, the probe temperatures on the heat shield will reach almost 1370oC (2,500oF), more than enough to put it out of commission. However, the shield will help keep the vehicle’s temperature at a relatively “cool” 30oC (85oF).

It achieves this by being constructed of two panels of superheated carbon-carbon composite sandwiching a lightweight 11.4 cm (4.5 in) thick carbon foam core, filled with air, allowing it to store vast amounts of heat which can be radiated away when the spacecraft is further away from the Sun in its elliptical orbit. In addition, the Sun-facing side of the heat shield is sprayed with a specially formulated white coating designed to reflect as much of the Sun’s energy away from the spacecraft as possible.

An artist’s impression of the Parker Solar Probe passing over the Sun’s photosphere. Credit: NASA / JHU/APL

The re-installation of the heat shield – technically referred to as the Thermal Protection System, and which was briefly attached to the spacecraft in 2017 during testing at the Johns Hopkins Applied Physics where both were constructed – marked one of the final steps in preparing the vehicle for launch.

I’ll have a full report on the Parker Solar Probe in these pages ahead of its intended August 2018 launch.