Space Sunday: SpaceX and a rapid round-up

Starship SN7 rises briefly through a cloud of super-cold nitrogen gas after the base of the tank ruptured during a deliberate over-pressurisation teat, June 23rd. Credit: LabPadre

SpaceX has had a busy week. Following the loss of the Starship prototype SN4, the company has been pushing ahead with the construction of prototypes SN5 and SN6 – one of which is likely to complete the first flight tests for the vehicle.

These prototypes look a little odd to some, resembling little more than steel cylinders. This is because SpaceX is currently focused purely on the vertical ascent / decent capabilities of the vehicle, and for this they only need the section of the hull that contains the fuel tanks and the raptor motors. Experience in flying the smaller Starhopper vehicle demonstrated there is no need to include the vehicle’s upper sections or the dynamic flight surfaces – although these will be added as the test flights become more ambitious and broader in scope.

Starships SN5 and SN6 under construction at the SpaceX Boca Chica Midbay building: Credit: SpaceX

Also following the destruction of the SN4 prototype, the company started work on the SN7 vehicle. This caused some speculation as to where it might fit in the test vehicle series. Might it be the start of a prototype that does go on to include the said upper sections and flight surfaces? Was it being built in case SN5 or SN6 went the way of SN4 and SN3?

As it turned out, SN7 was constructed specifically for further tests on tank pressurisation. On June 15th, 2020 the tank, mounted on a test stand was filled with liquid nitrogen (used in testing because it mimics the super-cold temperatures of the propellants the tanks will eventually contain, and so exposes the tank to the same temperature stresses, but if the tank ruptures, it will not explode) to its maximum pressure. It resulted in a slight leak developing, which was repaired. Then, on June 23rd, the tank was once more filled with liquid nitrogen – but this time to a pressure well beyond it would have to face when in use during a launch.

With nitrogen gas still roiling on the ground, Zeus, the robot dog (arrowed) goes in to check the area around the wrecked SN7 tank. Credit: LabPadre

The results were spectacular: an initial rupture occurs in the lower half of the tank, instantly expand into a tear along its base seam that released the liquid nitrogen in such bulk and pressure that it instantly vaporised en masse, venting with a force that lifted tank and test stand sideways off the ground. Immediately after the incident, SpaceX deployed their newest team member, Zeus.

A robot “dog” developed by Boston Dynamics (which they generically call “Spot”), Zeus is being used by SpaceX to assess potentially hazardous situations around the Boca Chica test site – in this case, the ground conditions following exposure to so much liquid nitrogen that took time to completely boil off. In typical SpaceX humour, the company has even erected a large Snoopy-style dog house on the grounds that’s allegedly the robot dog’s home.

And aerial view: the remnants of SN7 can be seen on their side, the test stand attached. The grey area “below” it is the concrete base on which it stood. A second test stand sits “above” the wreck. Credit: RGV Aerial Photography

One of the reasons for taking the test beyond limits was to check the steel used in SN7’s construction. Earlier versions of the Starship prototypes had been built with 301 stainless steel, but the company has opted to switch to the stronger 304L, and the degree to which the tank stood up to the test is being seen as indicative that the 304L is structurally a better choice.

Also during the week, NASA announced that the Crew Dragon currently docked with the International Space Station will likely return to Earth at the start of August 2020, with its crew of Robert Behnken and Douglas Hurley. Its return will pave the way for the first “operational” crew Dragon launch, which will carry astronauts Michael Hopkins, Victor Glover, Shannon Walker (commander) and Soichi Noguchi to the ISS at the end of August or early September.

Starship prototype SN5 being raised on to its test stand. In the foreground is the Spacehopper. Credit: BocaChicaGal

In a separate announcement, the agency further indicated that in a change to their requirements, they will in future allow SpaceX to make use of re-used Falcon 9 first stages in Crew Dragon launches. Previously, the agency had specified that each crewed mission must take place using a new Crew Dragon and new Falcon 9 launcher. The change came after a second Falcon 9 first stage successfully completed its fifth launch and landing.

Local Red Dwarf Offers Best Chance to Study Exoplanet Atmospheres

Gliese 887 is a red dwarf star some 11 light years away. While it is much dimmer than our Sun and about half its size, it has been of significant interest to astronomers because it is a relatively calm example of red dwarf, or M-Type, stars, and far less prone to violent solar events. This means that if any planets were to be orbiting it – and M-Type stars are the most populous in the galaxy and therefore prime candidates for exoplanets – they could well be able to retain any atmospheres they might have developed. What’s more, data from almost 20 years of observation has suggested Gliese 887 is “wobbling” in its spin, mostly likely as a result of it being influenced by the gravities of planets orbiting it.

An artist’s impression of Gliese 887c (closest) and Gliese 887b orbiting their parent star. Credit: Mark Garlick

In 2018, researchers from spent 80 continuous nights observing the star using the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument at La Silla Observatory in Chile. They then took the data they gathered and carried out a careful comparative study with 20 years of data gather in observing it. Their findings, recently published, led them to conclude there are at least two “super Earth” planets orbiting the star.

The first planet, called Gliese 887b, is about 4.2 times Earth’s mass and is just 6.8% of an astronomical unit (AU) from its parent. The second, Gliese 887c is about 7.6 times Earth’s mass and orbits 12% of an AU from the red dwarf. Both are moving rapidly around their parent: Gliese 887b taking just 9.3 terrestrial days to complete an orbit, and Gliese 887c some 21.8 days.

Despite their closeness to the star, the relative calm of Gliese 887 means that both planets could well have atmospheres. However, they are well inside the star’s habitable zone, so are unlikely to be life bearing. Even so, thanks to the relative brightness of their parent, and it’s relative proximity to Earth, they could offer a first-class means for astronomers to learn about exoplanet atmospheres. What’s even more exciting is that the data suggests a third planet in orbit within them, one that is likely to be within the star’s habitable zone.

More work is required to confirm this third planet, but the data has already indicated that Gliese 887 will be a prime target for study by the James Web Space Telescope, once launched.

Virgin Galactic Complete 2nd Spaceport Guide Test

On Thursday, June 25th, Virgin Galactic completed their  second successful glide test with VSS Unity over Spaceport America in southern New Mexico.

The test saw the vehicle carried to an altitude of 15,545 metres by its carrier aircraft VMS Eve before being released. The craft then descended at speed, reaching Mach 0.85, and was put through a series of manoeuvres before making a safe landing at the spaceport. The next stage will be powered flight test, which will in turn be followed by passenger-carrying flights – although the company hasn’t committed to a date when these will start. Currently, 600 people have purchased tickets to fly on Virgin Galactic’s sub-orbital hops.

Space Tourists Trips to ISS Now with Space Walks

Space Adventures, a U.S. space tourism company, has booked two passenger seats on Russian Soyuz capsules heading to the International Space Station in 2023, where one of the tourists flying to the station will take part in a space walk.

The company had already reached an agreement with Energia, a part of the Russian Roscosmos space agency, to fly two tourists to the ISS in 2021. Under the new arrangement, two more tourists – yet to be signed-up – will visit the space station four 14 days, during which one will participate in a 90-minute EVA.

Ticket prices have yet to be announced, but between 2001 and 2009, Space Adventures offered flights to the ISS at between US $20 and $35 million. In 2006, the tapped on a US $15 million fee for a similar space walk opportunity, but no such flight was ever made.

As well as offering trips on Soyuz to the ISS, Space Adventures has purchased four seats on SpaceX Crew Dragon for 5-day flights into space that will not include an ISS rendezvous, for an undisclosed price per seat. The company believes the first of these flights could take place early in 2021.

“Percy’s” Launch: Further 2-Day Delay

The launch of the Mars 2020 rover Perseverance has been further delayed until “no earlier than July 22nd”.

Originally scheduled for departure from Earth on July 17th, the launch was initially pushed by to July 20th due a ground system equipment issue. The more recent delay came about as a result of a contamination issue as the rover, packed into its aeroshell and heat shield and attached to is cruise module, was being integrated into the payload fairings of its Atlas V launch vehicle.

Left: the Mars 2020 within its payload fairings. Right: the ULA Atlas V during its “wet test” on June 22nd. Credits: NASA / United Launch Alliance

The launch window for the mission extends through until August 11th, which leaves plenty of time for a successful launch to be made in order for the rover to reach Mars in February 2021. In the meantime, the Atlas V launch vehicle has completed a successful launchpad “wet dress rehearsal”, loading the tanks with fuel and testing them.

Axiom Space picks Thales Alenia to Build Space Station Modules

In January, NASA, agreed to allow Axiom Space to construct a new module that will increase the habitable space aboard the International Space Station.

An artist’s impression of the Axiom Station. Credit: Axiom Space

Subject to additional agreements, Axiom plan to launch up to two further modules to the ISS, where they will reside until the station is “retired” (de-orbited) in 2030.

When this happens, the Axiom modules will be detached to remain in orbit, where they will be joined by a power and thermal module with an airlock to form what is planned to be the world’s first commercial space station.

On June 24th, 2020, Axiom announced that they had contracted Thales (Thaa-Lez) Alenia, European’s largest maker of satellites and the company responsible for the European module on the ISS, to build both the habitation module to be launched in 2024, and a second unit, called Node One.

Once operational, the Axiom station will be continuously occupied by at least one astronaut, and will be used for a range of commercial space research activities and space tourism.