Space Sunday: the Sun’s twin, going to the Moon & SpaceX

The three proposals for NASA’s Human Landing System vehicles under consideration of the US Artemis programme. Left: the Dynetics lander / ascent vehicle; centre: the modified SpaceX Starship; right: the National Team’s descent / ascent modules. Credit: NASA

In late April, NASA awarded funding to develop human landing systems for the agency’s Artemis lunar programme to three commercial groups: SpaceX, Dynetics and the so-called “National Team” of Blue Origin, Lockheed Martin, Northrop Grumman and Draper.

All three are taking different routes to supply vehicles capable of landing humans on the surface of the Moon and then returning them to lunar orbit for onward transit to Earth. For the initial mission, which NASA has time-tabled for 2024 – a highly ambitious date – one of the three vehicles must be capable of delivering a crew of two to the south polar regions of the Moon and then back to orbit.

On August 20th, 2020, the National Team delivered a full engineering mock-up of its proposal lander / ascent vehicle to NASA’s Johnson Space Centre (JSC).

For those familiar with the Apollo lunar lander, the National Team’s vehicle is a veritable monster, standing over 12 metres (40 ft) in height. It comprises three elements: a descent element that physically lands on the Moon and that is topped by the ascent element, both of which are helped down to the lunar surface by a transfer element.

The National Team design. From left-to-right: the transfer vehicle (Northrop Grumman), the descent module with the ladder and landing legs (Blue Origin), and the Ascent stage (Lockheed Martin). Credit: Blue Origin

It’s a combination of vehicles that build on a definable heritage. The descent element is being designed by Blue Origin using the technology the company has been developing over the last three years for its automated lunar lander, Blue Moon.

The ascent stage, meanwhile, is being developed by Lockheed Martin leveraging technology used in NASA’s Orion Multi-Purpose Crew Vehicle (MPCV), the capsule vehicle that will be used to ferry crews to and from Lunar orbit. Finally, the transfer stage uses technology and elements from Northrop Grumman’s automated Cygnus resupply vehicle serving the International Space Station (ISS).

The newly delivered mock-up will remain at JSC through until early 2021. It will be used by NASA engineers and astronauts to ascertain how the vehicle works, what is required, and helping engineers within the National Team to validate the team’s approach to getting crew, equipment, supplies, and samples off and on the vehicle.

In all, the three contractors were awarded a total of US $967 million that would be used to meet the costs of the first 10 months in developing each of their proposals of a Human Landing System (HLS). Of the three, the National Team took the lion’s share of the funding, some US $579 million. As well as delivering the engineering mock-up to JSC, the National Team is also preparing for a certification baseline review of their proposed design, with NASA expected to release a draft of the call for proposals for the next phase of the programme in early September.

For their design, Dynetics is also working with Draper and with Sierra Nevada Corporation, the developers of the Dream Chaser space plane. Their design is the smallest of the three proposed HLS vehicles – and potentially the most flexible. It is effectively a two-stage craft comprising a core lander / ascent vehicle of a squat design, supported by “drop tank” units that provide fuel for the initial stages of descent to the lunar surface, and which are jettisoned as their supplies are used.

The core craft is designed to carry crew or cargo down to the surface of the Moon and return crews back to orbit to rendezvous with an Orion MPCV or the Lunar Gateway. In addition, the uncrewed cargo variant is designed so that once cargo has been unloaded, it can be utilised as an additional module for a lunar base, providing a means for the base to be routinely expanded.

SpaceX – a surprise receiver of funding for HLS – is proposing the use of a modified version of its Starship vehicle, one sans aerodynamic surfaces, as these will not be required for operations to / from the surface of the Moon.

It is expected that NASA will de-select one of the proposals in early 2021, allowing the remaining two to continue. However, there has been a crimp put in plans: NASA requested some US $3.3 billion specifically to fund the HLS programme in fiscal year 2021, but under the proposed House budget, only US $670 million is allocated to HLS development, and the Senate’s budget proposal may not significantly raise this.

Was the Sun Once Part of a Pair?

A theory published in the Astrophysical Journal Letters on August 18th, 2020, dips into the theory that the Sun was once part of a binary pair.

The theory itself isn’t new: the Sun was one of a number of stars formed around the same time in the “local cluster”, and so may well have been twinned with another early in its life, before the gravitational influences of other stars in the cluster forced them apart. In fact, in 2018, astronomers from the Instituto de Astrofísica e Ciências do Espaço in Portugal announced they may have discovered it in the form of star HD 186302, some 184 light-years away – although this has yet to be proven.

An artist’s impression of the Sun (foreground) with its former twin. Credit: unknown

In the new publication, scientists from Harvard University point to the Oort cloud – a complex combination of a ring of icy planetesimals (the Hills Cloud) and a larger, more distant sphere of such objects, both of which lie beyond the heliosphere, as indicative that the Sun once had a companion.

Conventional thinking has it that the Oort cloud formed from debris left over from the formation of the solar system and its neighbours. However, models designed to show this have been unable to produce the expected ratio between scattered disk objects within the Hills cloud and outer Oort cloud objects. But if a relatively close stellar companion is introduced to the mix, modelling the formation of the Oort cloud elements and the distribution of objects within them becomes clearer, the paper’s authors claim.  Not only that: it may actually help explain how life on Earth started.

Oort cloud objects are rich in water ice and the minerals and chemicals essential to starting life. Having a stellar companion for the Sun dramatically increases the amount of perturbations that might ripple through the Oort cloud and send some of its objects to fall into the solar system – and potentially collide with Earth, bring that water and those compounds with them.

The Oort cloud disk (Hills Cloud) and sphere lie beyond the Sun’s Heliosphere. Credit: NASA

The proposal even has implications for the notorious Planet Nine and the ever-evolving debate over its possible existence. Again, in simple terms, not only could the gravitational influence of stellar twin result in the formation of the complexities of the Oort cloud, it could have resulted in one – or more – rogue planetary bodies falling into the Sun’s influence into into highly eccentric orbits and at great distances from the rest of the solar system.

And yes, that is planetary bodies – the Harvard theory suggests that perhaps, and if it is indeed there, Planet Nine might be one of several captured rogue planets, particularly given another study published in the Astronomical Journal suggests that their could actually be more rogue planets in our galaxy than there are stars.

Currently, the Harvard theory is just that – a theory. However, the authors note that the upcoming new generation of space-baae telescopes will do much to increase our knowledge of the Oort cloud and may help in the search for Planet Nine and other far-flung planets caught in the outer limits of the Sun’s gravitational influence.

Yet More SpaceX News

At the rate things are going, I may need to rename this column SpaceX Sunday!

Just a fortnight after Starship prototype SN5 made its first successful flight, prototype SN6 looks set to repeat the feat, possibly on Friday, August 28th, weather permitting.

Starship prototypes SN5 (left, with the ballast weight visible at the top of the upper tank) and SN6 pass one another at the SpaceX Boca Chica facility. Credit: Bocachicagal

The SN6 prototype, which like the SN5 vehicle only comprises the tank section of a Starship vehicle, has already completed its vital cryogenic proof test – filling the tanks with liquid nitrogen to simulate the super-cold temperatures and pressures they will face with fully loaded with fuel for an actual flight, while hydraulic arms apply pressure to the base of the vehicle to simulate the stresses of thrust from an operating engine.

Designed to test the vehicle’s overall integrity and ability to withstand launch pressures without risking fuel and an explosion, SN6 came through with flying colours, and after extensive post-test inspections, engineers started work on installing the vehicle’s single Raptor engine. If things go to plan, the coming week should see the vehicle undergo a post-installation inspection which will be followed by a static fire test of the Raptor engine in the run-up to the flight.

When it comes, the flight is likely to be very similar to the SN5 flight, as Musk has indicated the company would like to get the process of preparing the prototypes and making shorter flights “smoothed out” before moving to more ambitious goals. The latter will include the flight of prototype SN8, which will be the first complete prototype with upper sections, aerodynamic surfaces, and to use 3 Raptor engines. This vehicle, or possible SN9 (now under construction) will make the 20km flight designed to test the full range of the vehicle’s aerodynamic handling, as the animation below shows.

In a further set of milestones, SpaceX successfully completed the seventh launch and recovery of a Falcon 9 first stage on August 18th, when booster B1049 lifted off from Cape Canaveral Air Force Station Launch Complex 40 carrying 58 Starlink satellites and three rideshare payloads from Earth observation company Planet.

Following successful staging, the first stage performed its burn-back manoeuvre and made a successful descent and landing on the autonomous landing ship Of Course I Still Love You. The landing and recovery marked the seventh flight and recovery of the stage – the first Falcon 9 to achieve this.

Drone images of the fairing capture by GO Ms. Tree. Credit: SpaceX

Also following the launch, the recovery ship GO Ms. Tree successfully captured one of the rocket’s payload fairings as it drifted back to Earth under a parasail. While it was the 6th such successful recovery of a fairing – allowing them to be re-used – this one was unique in that it was the first make with the ship operating on autopilot. This allowed it to function in co-ordination with automated adjustments made to the fairing’s parasail to change its course, forward speed, etc., in an attempt to increase the recovery success rate.

Following the success – although GO Ms. Chief, the second recovery ship, failed to snag the flight’s other fairing – SpaceX posted a short video of the recovery set, in typical SpaceX humour, to the strains of elevator musak.

Finally, and also on August 18th, the Crew Dragon capsule destined to complete the company’s first operational mission to the International Space Station (ISS) has been delivered to SpaceX processing facilities in Florida.

Capsule C207 arrived at SpaceX facilities at Canaveral Air Force Station complete with an upgraded Trunk (service module) that carries improved solar cells that will enable Crew Dragon vehicles to remain in space for up to 6 months at a time.

The capsule will now undergo final check outs and testing while at SpaceX’s Florida processing facilities, prior to being mated with its Falcon 9 booster in SpaceX’s Horizontal Integration Facility at Kennedy Space Centre’s Launch Complex 39A. Its launch, carrying four astronauts to the ISS, is currently expected to take place on or shortly after October 23rd, 2020.