Space Sunday: flying water tanks, telescopes and weird rocks

The “Flying Water Tank”, aka “R2D2’s Dad”, otherwise know as the Starhopper – rises to 120m (500ft) during its second major test flight, August 27th, 2019. Credit: SpaceX

SpaceX successfully flew their Starhopper vehicle – designed to prove the viability of their upcoming Starship space vehicle – on August 27th, in its most complex test flight to date.

The Starhopper craft, dubbed “the flying water tank” on account it both lacks its conical nose (damaged beyond repair during a storm at the start of the year) and the fact it was fabricated for SpaceX by a company that specialises in building water tanks, lifted off from a pad at SpaceX’s test site in Boca Chica, Texas, rising vertically to a height of 150 metres (488 ft) before translating to horizontal flight to crab across to another pad at the test facility and then descended under power to touch down once more.

While the flight lasted less than a minute, it has, according to Musk, paved the way for two dramatic follow-up flights. As well as the Starhopper vehicle, SpaceX is currently building two full-size Starship prototypes – “Mk 1” is being built at Boca Chica, with “MK 2” under construction in Florida. It appears that the “Mk 1” vehicle will be used for the 20km flight.

Starship Mk 2 on the left of the image, standing upright and with additional elements nearby, under construction in Cocoa, Florida. Credit: SpaceX

Musk’s announcement of a potential attempt to reach orbital altitude drew questions on whether SpaceX plan to use their Super Heavy  – essentially the “first stage” for Starship launches – with one of the Starship prototypes, or just make the attempt with the Starship on its own. In the past, Musk has indicated that a fuelled but unladen Starship should have the power to achieve orbit, but that would presumably be using all six of an operational Starship’s Raptor engines. By comparison, the Starhopper has a single Raptor motor and the Starship Mk 1 and Mk 2 craft will have 3 Raptors – at least initially.

As it stands, the “first generation” of Starship / Super Heavy is designed to be 9m (29 ft) in diameter and stand around 118m (390 ft) tall on the launch pad. Super Heavy is to be powered by 31 Raptor engines and the 48m tall Starship by 6 Raptors. Together, SpaceX stated that they will be capable of lifting around 100 tonnes of payload to orbit, with Starship capable of reaching the Moon or Mars with that payload or up to 100 crew and passengers.

All of that is pretty mind-boggling. If possible, it will make Starship / Super Heavy the most powerful launch system ever built in terms of thrust. But SpaceX is apparently going to go beyond that. Following the Starhopper test, and responding to a question, Musk indicated that a “next generation” craft based on Starship / Super Heavy could follow in “several years”. While planning a follow-up to Starship / Super Heavy is not surprising, the scale of the follow-up version is: in a further tweet, Musk suggested it will be 18m (60 ft) in diameter – twice that of Starship / Super Heavy.

Mathematics tells us that doubling the diameter of a circle quadruples its area. This means that if the current ratio of dimensions for Starship / Super Heavy is retained, the “next generation” version would stand a mind-boggling 230 m (780 ft) tall and have eight times both the surface area and propellant tank volume of the current Starship / Super Heavy. All of which leads to a fuelled launch mass of around 40,000 tonnes.

An artist’s impression of a future “next generation” Starship / Super Heavy launch combination compared to SpaceX’s current family of launch vehicles, the current (2018) and previous (2016 and 2017) BFR designs. This assumes the “next generation” vehicle will have Musk’s stated 18m diameter and retain the same proportions as the current Starship / Super Heavy combination. Credit: Teslerati.

At such a size and mass, the new vehicle would require 100 Raptor motors just to get off the pad – or a system of engines several times more powerful. Take the noise and vibration issues this would introduce to the system, and I’ll say that it just isn’t going to happen. In the meantime, Musk is promising a public update on the status of Starship / Super Heavy on September 28th, 2019.

WFIRST and JWST Move Forward

NASA has confirmed that the telescope assembly for the Wide Field Infra-red Survey Telescope (WFIRST) mission passed its preliminary design review (PDR), and can now move forward to finalising the telescope’s final design.

Due for launch in the mid-2020s, WFIRST is designed to operate in a halo orbit around the Sun-Earth Lagrange point (L2)  1,500,000 km (930,000 mi) from Earth, where it will help uncover some of the biggest mysteries in the cosmos. Its telescope system will play a significant role in this, providing the largest picture of the universe ever seen and with the same depth and precision as the Hubble Space Telescope (HST).

That it has survived to this point is a mark of the mission’s importance: the Trump Administration has twice tried to cancel the programme, citing some spurious reasons  – one being WFIRST’s “expense”, despite the fact the WFIRST is one of the most cost-effective projects NASA has undertaken as it repurposes a lot of “spare parts” developed for HST.

NASA’s Wide Field Infrared Survey Telescope (WFIRST) will fly in the mid-2020s and provide astronomers with the most complete view of the cosmos to date. Credit: NASA Goddard Space Flight Centre / CI Lab

The telescope will be equipped with both a wide-field imager instrument and a coronagraph. The former is similar in nature to the imaging system carried by HST, but with 100 times the sensitivity. It will be used to map the presence of mysterious dark matter, which is known only through its gravitational effects on normal matter. WFI will also help scientists investigate the equally mysterious “dark energy,” which causes the universe’s expansion to accelerate, and will survey our own galaxy as a part of the overall search for exoplanets.

The coronagraph will also be used in the hunt for exoplanets. It will block light from stars to allow direct imaging of any planets and dust disks orbiting them.

The science enabled by our telescope is extraordinary. We are asking, ‘what is the fate of the universe?’ by looking at how the expansion of the universe is accelerating, and we are asking, ‘are we alone?’ by looking for exoplanets in neighbouring planetary systems.

– Jeff Kruk, project scientist for WFIRST

WFIRST’s search for exoplanets will in part be carried out in partnership with NASA’s other major new telescope, the James Webb Space Telescope (JWST). This massive and complex project has faced its share of issues, including cost-overruns and delays, but is due to be launched in 2021. Like WFIRST, JWST will operate in a halo orbit around the Sun-Earth L2 position, directly opposite to the Sun relative to Earth where it will carry out a range of science activities, including seeking out and examining exoplanets.

The James Webb Space Telescope as it will look when fully deployed and operating at the Sun-Earth L2 position. Credit: NASA

On August 28th, NASA confirmed the two major sections of the telescope – the primary reflector and the science instruments that are together referred to as “the observatory”, and the “bus” / sun shield that form the lower section of the telescope, have been joined together.

The “bus” is the section of the telescope that includes the power and control systems and solar arrays, while the sun shield is a large hull-like system of expanding layers designed to protect the telescope and the science instruments from the light and heat of the Sun, and reflected light from Earth and the Moon. Both elements have up until now been subject to assembly and testing independently to one another, so mating them is seen as a significant step along the road to readying JWST for launch.

For the operation, the sun shield was opened out , and the observatory, with the main reflector dish is its folded and stowed configuration was lowered into the bus unit. Once in place, mechanical connections were made between the two and in the coming weeks, the electrical and power connections will be made and tested.

JWST assembled and seen from the front. The large primary reflector, comprising hexagonal elements, is shown in its folded configuration and mounted on the mission power bus. In the foreground is part of the sun shield element of the telescope with its 5 layers compressed into their stowed position. During launch, this shield, which extends either side of the observatory, is folded up against the reflector assembly, hence the two latching arms in the foreground. Credit: NASA / Chris Gunn

In the coming months, the completed telescope will be put through a number of tests. The first of these will be to ensure the sun shield can be properly deployed. This involves raising the sun shield into its launch configuration, in which it encloses the observatory, then commanding it to lower and then fully deploy its layers. Providing this is successful, and during 2020, the entire assembly will then be subjected to further acoustic and vibration tests to mimic the conditions of launch and ascent through the Earth’s atmosphere to ensure nothing shakes loose.

Providing the schedule can be maintained and no significant issues occur, JWST should be launched atop a European Ariane 5 rocket in March or April 2021, gently deploying and testing itself as it makes a 16-day voyage out to the Sun-Earth L2 position, where it is expected to operate for a minimum of 5 years.

The Moon: Chandrayaan-2, and Yutu-2 Makes “Weird” Find

India’s Chandrayaan-2 mission successfully completed its fifth and final lunar orbit manoeuvre on Sunday, September 1st, setting the stage for the release of the country’s first lunar lander.

Lunched on Monday, July 22nd, the Chandrayaan-2 lunar orbiter, which carries a lander / rover combination, has spent the time since launch spiralling away from Earth prior to being captured by the lunar gravity well, where it has gradually been circularising its orbit in readiness to release the lander, called Vikram, in honour of Vikram Sarabhai, regarded as the father of the Indian space programme, and which in turn carries the Pragyan rover.

The Vikram lunar lander under construction at India’s Space Research Organisation (ISRO). Credit: ISRO

The lander / rover combination is scheduled to detach from the orbiter on Monday, September 2nd in readiness to make a soft landing in the Lunar south polar region on Friday, September 6th  / Saturday September 7th, the descent being deliberately slow, and almost entirely self-guided.

Once on the Moon, the lander will communicate both directly with Earth and the orbiter. It will also facilitate communications with the Pragyan rover, which will be deployed within hours of touch-down. Between them, the lander and rover carry 5 science experiments designed to examine the environment around them (the orbiter carries a further 8 experiments), with both are expected to operate for around 14 days.

Providing the landing and subsequent rover deployment are successful, Vikram and Pragyan will become the second lander / rover combination to be currently operating on the lunar surface, the others being the Chinese Chang’e-4 lander and the Yutu-2 rover. These arrived in the south polar region of the Moon’s far side in January 2019. Since then, they have been operating successfully, surviving the intense heat of the Lunar day by periodically going to “sleep”,  a mode that turns off their more sensitive systems through the most intense period of each lunar “day”.

Yutu-2 takes a snap of its tracks and the Chang’e-4 lander during mission day 7, June / July 2019. Credit: China Lunar Exploration Project

Since its arrival on the Moon, the little Yutu-2 rover has been exploring the area around the lander, covering a distance – through until the end of July 2019, of some 271m (890 ft) – and along the way it has discovered something “weird”.

On July 28th, when the mission team was preparing to order the rover into one of its “sleep” cycles, a small crater was spotted in one of the images returned by the rover, which seemed to contain material with a colour and lustre unlike that of the surrounding lunar surface. The image so intrigued the mission team, that following the rover’s nap, the planned drive was abandoned, and instead, Yutu-2 was instructed to carefully approach the crater.

The small crater where Yutu-2 spotted usual material. Credit: China Lunar Exploration Project

This it did by using a mix of direct commands relayed from Earth and its own self-guidance system. Once close enough, Yutu-2 examined the deposits with its Visible and Near-Infra-red Spectrometer (VNIS). So far, mission scientists haven’t offered any indication as to the nature of the coloured substance, stating only that it is “gel-like” and has an “unusual colour.” One possible explanation, outside researchers have suggested for the material, is that it is melt glass created from a meteorite striking the surface of the Moon; however, until the Chinese release more information, nothing can really be verified.

It’s not the first time odd material has been found on the Moon: during Apollo 17, geologist Harrison Schmitt discovered orange-coloured soil near the mission’s Taurus-Littrow landing site in 1972. Returned the Earth for study, the samples he and mission commander Gene Cernan gathered appear to have been created during an explosive volcanic eruption on the Moon some 3.64 billion years ago.