Space Sunday: rockets, landers, FRBs and the Moon

The Long March 5B booster heads towards orbit, carrying China’s next generation crew capsule on its first (uncrewed) flight, Tuesday, May 5th. Credit: China TV

China has successfully completed an uncrewed test-flight of its next generation of space vehicles that will support future crewed operations in Earth orbit and be a part of missions to the Moon – and possibly beyond.

The new craft – which resembles the Apollo command and service module (CSM) combination used by NASA in the 1960s and early 1970s (or, if you prefer, Boeing’s current CST-100 Starliner capsule and service module) – was launched atop a Long March 5B rocket, China’s most powerful launch vehicle, on Tuesday May 5th. From the launch pad at the Wenchang launch site on the southern island of Hainan, the vehicle took 8 minutes to rise to its initial orbital separation altitude, where it successfully entered orbit. A second payload – that of a cargo return capsule also undergoing tests – also successfully separated from the booster.

A significant difference between the new crew capsule and China’s Soyuz-derived Shenzhou is in the use of three, rather than one, parachutes, during descent to landing. Credit: CASC

While the crew capsule test vehicle would remain in space for several days, allowing it to complete a series of automated tests, the cargo capsule – designed to return equipment and experiments from China’s upcoming space station – had been due to return to Earth on Wednesday, May 6th. Unlike the crewed vehicle, the cargo unit is designed to use an “inflatable” heat shield during re-entry.

Called a “ballute” (a portmanteau of balloon and parachute), this approach to inflatable systems was initially developed in the last 1950s as a parachute-like braking device optimised for use at high altitudes and supersonic velocities. In the 1960’s, ballutes were included as part of the astronaut escape system in NASA’s Gemini missions. More recently, a number of organisations and countries have been looking at there use as re-entry systems as they are lighter and potentially less complex than conventional re-entry systems.

The capsule on the ground, the white thermal protection of the hull scorched after re-entry, the airbags used to soften the impact of land deflated. The open compartment to the right is one of the airbag containers. Credit: Xinhua

In this instance, it appears the ballute may have failed. Following re-entry, the China National Space Agency (CNSA) announced the cargo vehicle has suffered an “anomaly” that was being investigated – with no further information forthcoming.

The crew capsule, however, completed its mission entirely successfully, performing a number of orbital manoeuvres, testing the deployment of the vital solar panels and carrying out a series of communications tests.

The extended orbit of the vehicle carried it some 8,000 km altitude – greater than that of the Orion uncrewed flight test in 2018. This meant it would be able to make an atmospheric entry at speeds matching a return from the Moon – putting the heat shield to its ultimate test.

Ths initial de-orbit burn took place on Friday, May 8th, at 5:21 UTC, after which the capsule separated from its service module. Following a successful atmospheric entry, the vehicle deployed three main parachutes to make the descent over the planned Dongfeng desert landing area. Shortly before landing, self-inflating airbags were deployed to soften the impact, which occurred at 5:49 UTC. In all, the vehicle spent more than 2 days and 19 hours in orbit.

When crewed flight commence, the vehicle will be capable of carrying a combination of crew and cargo, with a minimum of 3 crew (and up to 500 kg of cargo, if required) required for a launch and operation of the vehicle, with a maximum of 6 (or 7 according to some Chinese sources) crew. The core of the capsule is designed to be used over a maximum of ten flights, with the heat shield being completely replaced after each flight, with the side thermal protection system also being refurbished.

The success of the flight, together with that of the Long March 5B – making its first launch – has been reported as now opening the door to a slate of 11 missions revolving around space station construction, with CNSA indicating they plan to complete space station construction by the end of 2022.

However, one side-effect of this flight is that the 20-tonne core stage of rocket also reached orbital velocity. It is expected to make an uncontrolled re-entry into the atmosphere on Monday, May 11th, the largest man-man object to date to do so. Any elements surviving re-entry should splash down in the Indian ocean.

FRB Origins Confirmed?

In radio astronomy, a fast radio burst (FRB) is a transient radio pulse lasting no more than a few milliseconds. Their cause has been subject to a lot of debate since their first detection in 2007; many appear to be extra-galactic in origin, leading to suggestions they originate with black holes or magnetic neutron stars (magnetars) or are even a sign of extraterrestrial intelligence.

A key reason FRBs are difficult to study is because most radio telescopes are highly focused in their “view” of the sky, so an FRB must be directly in that field of view in order to be detected; something that’s hard to achieve, as we have no means of predicting when they might occur. Also, despite being highly concentrated, the strength of the signal reaching Earth has been described as 1,000 times less than from a mobile phone on the Moon, so they can be lost amongst “background noise” radio telescopes must deal with.

However, in 2017, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) interferometric radio telescope came on-line. It has a much wider field of view than other radio telescopes, allowing it to potentially record far more FRBs. On April 28th, CHIME detected a pair of millisecond FRB bursts from the same portion of the sky as magnetar SGR 1935+2154.

An artist’s impression of outbursts resembling solar coronal mass ejections from a a magnetar. Credit: S. Wiessinger

This suggested the pair of bursts might have originated from that star, thus confirming the theory that such stars are the source of FRBs. What was more, this particular pair of bursts were of a power that a) suggested their origin was within our galaxy; b) allowed astronomers to use the dispersion measure (DM) of both bursts to determine their point of origin. DM measures how much a radio signal’s frequency is dispersed across as a result of interference – in this case, defraction due to interstellar gas – allowing the probable point of origin to be calculated.

With the bursts recorded on April 28th, the DM showed they originated some 30,000 light years away – the same distance SGR 1935+2154 is from Earth. Thus, we have our first confirmation that FRBs are likely generated by neutron stars – although further confirmation is obviously required. In the meantime, this initial confirmation may help determine how FRBs are generated.

Perseverance and Integrity Packed for Their Mars Trip

Engineers at NASA’s Kennedy Space Centre in Florida have begun packing the Mars 2020 Perseverance rover and its accompanying Integrity Mars Helicopter ready for their trip to Mars, the lift-off of which is due to occur during a 3-week launch window that opens on July 17th.

“Percy”, the Perseverance Mars rover, in its stowed configuration, sits underneath the “sky crane” decent unit. 1: “Sky crane” frame; 2: retro-rocket fuel tanks; 3: retro-rockets; 4: Perseverance’s wheels. Credit: NASA/JPL

It’s a complicated process that requires placing the rover in its “folded” configuration, then carefully mounting it under the “sky crane” decent stage that will use retro-rockets to hover over the surface of Mars and then gently winch the rover down to the surface, the wheels deploying along the way. Once the wheels touch the ground, the which cable will detach and the “sky crane” will then fly away from the landing zone before making a crash landing.

Attaching the rover to the descent stage is a major milestone for the team because these are the first spacecraft components to come together for launch, and they will be the last to separate when we reach Mars. These two assemblies will remain firmly nestled together until they are about 20 metres over the surface of Mars.

– David Gruel, the Perseverance rover assembly, test,
and launch operations manager

The rover and “sky crane” inside the aerodynamic backshell. 1: rover chassis; 2: “sky crane” instrumentation; 3: rover wheels (6); 4: Mars helicopter (under the rover chassis); 5: “sky crane” rockets (4 pairs); 6: interior of the backshell. Credit: NASA/JPL

After mating the sky crane and rover, engineers then had to carry out a series of checks to ensure all of the connections between the two were correct, and the various pyrotechnics ready for arming. After this, the combination of rover and sky crane were mated inside the aerodynamic “backshell” that will – along with the base plate and atmospheric heat shield – enclose the rover and sky crane during the 6-month flight to Mars and protect them during entry into the tenuous Martian atmosphere.

The work mating the rover and sky crane to the backshell was completed on April 29th. Final checks and tests will be carried out in May before the final step of mating the heat shield to the vehicle is completed. Once this has been done, and the necessary checks and test completed, the “stack” will be ready for mating to the cruise stage – a circular unit that supplies the rover and its lander systems with the necessary power whilst also monitoring them. Once that has been done everything will be set for integration with the payload launch shrouds of the Atlas V 541 rocket that will send Perseverance and Integrity on their way to the Red Planet.

The “Impossible” Moon

This moon might look a little funny to you, and that’s because it is an impossible scene. From two weeks of images of the waxing moon, I took the section of the picture that has the most contrast … aligned and blended them to show the rich texture across the entire surface.

– Andrew McCarthy

It is a stunning image of the Moon, carefully composited to reveal just about every major crater visible from Earth and blended so as to show a consistent terminator (the dividing line between the side of the Moon lit by the Sun, and the side away from it).

The Moon by Andrew McCarthy. A blending of the best images of the Moon taken over a 2-week period, this composite presents the lunar surface in amazing detail. Credit: Andrew McCarthy

Within it, we see the sunlit face of the Moon to the right, and the dark side to the left, with the bright splash of the impact crater Copernicus left-of-centre and lying towards the terminator. Further to the left and standing out brightly on the darker side of the Moon is the bright spot of the crater Aristarchus. Both of these craters are brighter than those around them as they are, relatively speaking, much more recent.

Above the bright Copernicus lies the dark bruise of Mare Imbrium (Sea of Rains) and just to the right of this, Mare Serenitatis (the Sea of Serenity) and Mare Tranquillitatis (Sea of Tranquillity). These three areas were the landing points for Apollo missions 15, 17, and 11 respectively. At the bottom of the image is the bright splash of the 108 million-year-old Tycho crater.

We might never be able to see the Moon like this naturally, but Andrew McCarthy’s composite is nevertheless a remarkable image.

US Readies 6th X-37B Flight

The sixth mission of the U.S. Air Force’s reusable, uncrewed X-37B spaceplane is scheduled to launch on May 16th, 2020, from Cape Canaveral Air Force Station, Florida.

Three views of X-37B OTV 2 by Giuseppe De Chiara

The super-secret “mini-shuttle”, which can be launched atop either a United Launch Alliance (ULA) Atlas V vehicle or a SpaceX Falcon 9 and make an aircraft-like landing on a suitable runway, has been subject to many rumours and conspiracy theories since its first flight in 2010. In all, two of the craft are known to exist, and each of the five missions flown to date have been of increasingly longer durations, with the 5th in the programme lasting an astonishing 779 days before it came to an end in late 2019.

Officially billed as “an experimental test program to demonstrate technologies for a reliable, reusable, uncrewed space test platform for the U.S. Air Force”, the 8.9m long vehicle in fact carries a mix of classified and NASA experiments during its flights, and the 6th mission will see the most experiments yet to be carried aloft by an X-37B. Many of these will be carried in the vehicle’s payload bay; however, this mission will see the first flight of a “service module” attached to the rear of the vehicle, increasing its overall payload capacity.

During the mission, the spaceplane is expected to deploy FalconSat-8, a small satellite carrying five science experiments of its own. Developed by students at the US Air Force Academy, FalconSat-8 is an educational, rather than outright military project, and its five experiments reflect this. Also making a trip on the spaceplane will be NASA experiments to study the effects of radiation on seeds and materials used to grow food in space.