Space Sunday: Hops, glows, plans and Perseids

SpaceX SN5 rises from its launch stand at the SpaceX Boca Chica, Texas, centre. Credit: SpaceX

SpaceX once again heads this week’s column after the Starship SN5 prototype became the first of the units to successfully make a “hop” into the air and back again, travelling some 150 metres up and several tens of metres sideways to navigate its way from launch platform to landing pad.

The flight of the “flying spray can” – the nickname derived from the vehicle’s cylindrical form topped by the nozzle-like 23 tonne ballast mass – only lasted around a minute once the Raptor engine fired, but the hop represented a huge leap forward for SpaceX in their development of the Starship vehicle.

As I noted in July, SN5’s unusual shape is due to it only comprising the section of the vehicle containing its fuel tanks, single raptor engine and landing legs. It lacks any upper sections (replacing by the ballast block) and the aerodynamic surfaces that will give Starship a lifting body capability during atmospheric operations. These will all be present in future prototypes, But for SN5, they are not currently required, as its initial flight(s) are purely about testing Starship’s ability to make a vertical descent and landing.

A starship cutaway showing the fuel tanks and engine bay (outlined in red) that form the prototype vehicle SN5, and the upper cargo / habitation space and aerodynamic surfaces that are not included on the current prototype. Credit: WAI (with additional annotation)

The successful test flight took place on Tuesday, August 4th – an attempt on Sunday, August 2nd was cancelled  due to unfavourable weather in the Boca Chica, Texas, area. Engine ignition came at 23:57 UTC (18:57 local time), the prototype rising vertically, but canted at a slight angle. This  was due to the initial prototypes being designed to operate with three Raptor motors, by SN5 is currently only fitting with one, offset from the vehicle’s vertical centreline, so the vehicle is canted (with the ad of the top ballast block) to compensate for the offset thrust from the motor, with small reaction control system (RCS) jets near the base and top of the vehicle occasionally firing to help maintain a stable flight angle.

As the craft rose, the Raptor motor was also gimballed (moved around like you move a joystick on a game controller, a common practice for rocket motors to allow them to use directed thrust to adjust a flight trajectory), vectoring its thrust so it could translate across to the landing pad for a successful landing.

Prototype nose cones being fabricated at Boca Chica. Credit: NASASpaceflight.com / BocaChicaGal

SpaceX released a video afterwards the flight showing the highlights. In it, SN5 can be seen lifting off, trailing a plume of vented cooling gas, the RCS jets visible as they fire to help maintain stability. The footage also clearly shows the Raptor’s offset exhaust plume moving as the motor in vectored, as well as the craft maintaining a brief hover at the apex of its flight before descending sideways and down towards the landing pad.

Cameras at the base of the vehicle show the landing legs being deployed, as well as a small, non-hazardous fire on the Raptor motor, likely the result of dust blown into the engine space at lift-off that subsequently ignited. This “inside” camera and one on the SN5 hull then captured the moment of landing and engine shut down.

Prototypes SN6, 7, and 8 are in development, and some of these will fly with the aforementioned forward / upper sections and flight surfaces in loftier (literally) and more complex flight tests. Currently, it not clear how many more flights SN5 will make. However, Musk has already indicated he would like to have Starship use a more “Falcon Like” set of landing legs to provide broader support when landing on uneven planetary surfaces, so SN5 might by used to test new landing leg configurations alongside testing of other prototypes.

The Green, Green Glow of Mars

At midnight on the twelfth of August, a huge mass of luminous gas erupted from Mars and speed towards Earth … As I watched, there was another jet of gas.

– “The Narrator”, Jeff Wayne’s Musical Version of War of the Worlds

The night-time glow of Mars (ultraviolet wavelengths only). Credit: NASA

OK, so we’re not about to face an invasion of Martian fighting machines, but a green glow in Mars’ atmosphere has been causing some excitement of late, thanks to a new animated video released by NASA that uses data gathered by the Mars Atmosphere and Volatile Evolution (MAVEN) orbiter.

The green glow – only visible in ultraviolet wavelengths – has actually been known about for some time, having first been observer by the European Space Agency’s Mars Express mission more than three years ago. It is created when winds carry gases down to denser regions of the atmosphere, a movement that speeds up a reaction produces nitric oxide (NO), which gives the glow under ultraviolet light.

Why the night side of Mars glows. On the planet’s day side, molecules are torn apart by energetic solar photons. Global circulation patterns carry the atomic fragments to the night side, where downward winds increase the reaction rate for the atoms to reform molecules. The downwards winds occur near the poles at some seasons and in the equatorial regions at others. The new molecules hold extra energy which they emit as ultraviolet light. Credit: NASA/MAVEN/Goddard Space Flight Centre/CU/LASP

The glow is approximately as bright in the ultraviolet as Earth’s Aurora in the visible spectrum, so it is a shame it is invisible to the naked eye, as it would make for a spectacular show for future astronauts.

What is interesting about the MAVEN data however, is that it reveals that during the spring and autumn periods, the glow pulsates three times very Martian night, just after local sunset, the first much brighter than the second and third.

Travelling at some 300 km/h as they ripple through the tenuous Martian atmosphere, the pulsations reveal the importance of planet-encircling waves in the Mars atmosphere. The number of waves and their speed indicates that Mars’ middle atmosphere is influenced by the daily pattern of solar heating and disturbances from the topography of Mars’ huge volcanic mountains.

NASA now hope to use the Imaging Ultraviolet Spectrograph (IUVS) on MAVEN – the instrument that recorded the pulsations – to view the night glow as it occurs around the limb of the planet, rather than from directly overhead, as this may reveal more above vertical movements and interactions within the various layers of the Martian atmosphere.

Above: the night-time atmosphere glows and pulsates in a NASA animation using data from the MAVEN orbiter. A deliberate false-colour mapping designed to visually enhance the data gathered, it shows brightenings in the atmosphere measured by MAVEN’s Imaging UltraViolet Spectrograph from an altitude of 70 km. The planet’s surface has been added for reference. Three night glow brightenings occur over one Mars rotation, appearing on the left side of the animation.

China Update

China’s Tianwen-1 Mars mission performed its first course correction on August 1st, 230 hours into its mission and 3 million km from Earth, The manoeuvre can a few days after the mission captured a monochrome image of Earth and the Moon using one of the vehicle’s navigation sensors. CASC stated.

A low resolution image of the Earth / Moon system captured by the Chinese Tianwen-1 Mars mission on July 27th, 2020, when the spacecraft was some 1.2 million kilometres from Earth. Credit: CNSA,

With Tianwen-1 now en-route to Mars, China’s focus has turned to their orbital and lunar ambitions. The China Academy of Launch Vehicle Technology (CALT) has indicated that the 22 tonne Tianhe core module of the nation’s first space station (as opposed to orbital laboratory) is on course for a 2021 launch. At the same time, CALT confirmed that work has started on the Shenzhou-12 mission, which will carry a crew of three into space atop a Long March 2F rocket soon after Tianhe-1’s launch, and will rendezvous with it as part of the space station construction work, and carry out assorted tests on the module.

At the end if July 2020, the China National Space Administration (CNSA) issued a call to schools and universities for experiments that might form a part of the ambitious Chang’e 7 lunar mission, and an asteroid and comet exploration project tentatively named ZhengHe.

An image said to be the core stage of the Long March 2F rocket that will launch the Shenzhou-12 mission to the Tianhe core module of China’s upcoming space station in 2021. Credit: CALT

Chang’e 7 is due to continue China’s south lunar exploration programme, with a launch targeted for 2024. It’s a multi-part mission comprising an orbiter, a lander, a rover and a “flying probe”, supported by a communications relay satellite to be placed in a halo orbit in the L2 position beyond the Moon – a technique China has used with the Queqiao relay satellite operating with the Chang’e-4 lunar far side mission.

The mission will carry a total of 23 experiments intended to conduct a detailed survey of the environment and resources in the lunar south polar region. The mini-flying probe will carry out in-situ observations of a permanently shadowed crater, carrying a water molecule and hydrogen isotope analyser payload designed to establish the amount of ice frozen within the crater. The lander and rover will carry a combination of payloads from earlier Chang’e missions, whilst as a part of its work, the orbiter will carry out high-resolution stereo-mapping of the Moon’s south pole as a precursor for future human missions.

ZhengHe, named for the 15th century naval explorer and admiral, will target near-Earth asteroid 2016 HO3 (aka 469219 Kamoʻoalewa). It will collect 200-1,000 grams of samples from the asteroid and return to Earth within 2-3 years of launch, delivering the samples using a re-entry canister as the vehicle swings past Earth.

An Artist’s impression of the ZhengHe mission approaching asteroid 2016 HO3 using a solar-electronic ion drive. Credit: CNSA

The primary goal of the mission is to reveal the characteristics and evolution mechanisms of typical small celestial bodies. It will also study the interaction of these bodies with solar wind, and perform lab analysis on samples. The spacecraft will physically land on the asteroid, fixing itself there so it can drill a sample from the asteroid. It will also launch a mini-rover and orbiter to carry out remote sensing and provide complementary information for sampling.

After returning its sample to Earth, ZhengHe will use our gravity the throw it on towards 133P/Elst-Pizarro / 7968 Elst Pizarro, an object that displays the characteristics of both a comet and an asteroid, hence the double designation. It should reach that body in the mid 2030s, possibly firing a penetrator / mass spectrometer into it, so we might might better understand its physical characteristics.

It’s August – So Get Ready for the Perseids

Every July / August, the Earth passes through a haze of stellar debris left by Comet 109P/Swift-Tuttle. The result is of this passage is the Perseid meteor shower, is one of the brightest meteor displays one can see in the northern hemisphere. The shower tends to last around a month, from July 17th (ish) through to August 24th.

This year, the peak period for activity should be August 12th and 13th, when between 60 and 100 meteors an hour might be visible streaking across the night sky. In Europe, the best time to see them is after midnight, while America gets it a little easier and earlier. To check time in your location try timeanddate.com, which should give local observation times.

Observing the Perseids: the blue oval marks the radiant – apparent point of origin – from which that should appear in clear night skies.

As the Moon is in its last quarter phase only rising at around 01:00 local time some 42º from the shower’s radiant (apparent point of origin in the night sky), which sits in the north-east sky between Camelopardalis and Perseus (the constellation from which they take their name), “seeing” opportunities should be reasonably good, assuming clear skies for those of us in Europe and North America.

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