Space Sunday: commercial crew test flights & exoplanets

An artist’s impression of the SpaceX Crew Dragon IFA test as the SuperDraco pushes the Crew Dragon away from a malfunctioning launch vehicle. Crew: NASA / Mack Crawford

Sunday, January 19th, 2020 saw SpaceX complete a major test that should help bring their Crew Dragon vehicle much closer to the point where it can commence carrying crews to / from the the International Space Station (ISS).

The test, referred to as a in-flight abort (IFA) test saw an uncrewed Crew Dragon vehicle launched from Launch Pad 39A at Kennedy Space Centre atop a Falcon 9 rocket in what was primarily a test of the vehicle’s launch abort system, is designed to push the capsule and its crew clear of a malfunctioning launch vehicle. However, the flight also served as an opportunity to test a further update to the vehicle’s descent parachute system (marking the first time this particular type of parachute had been used on a flight) and for SpaceX to further refine its crew recovery procedures for meeting returning Crew Dragon vehicles.

All the early indicators from the test are that everything ran as expected. Following lift-off and ascent, and at 84 seconds into the flight and an altitude of around 19 km, the first stage engine cut-off triggered the simulated malfunction, causing the abort system to release the clamps attaching the Crew Dragon to the dummy upper stage of the Falcon 9, the SuperDraco engines simultaneously firing, each one generating some 16,000 lbs of thrust. These immediately powered the Crew Dragon clear of the booster, travelling at a speed of over Mach 2, just as they would when trying to get a crew away from a malfunctioning rocket during an operational launch.

The moment of lift-off: the thrice-used Falcon 9 booster with a dummy upper stage topped by the Crew Dragon test vehicle, rises from Pad 39A. Credit: NASA

With the capsule detached, the Falcon 9 continued its own ballistic flight upwards, but the open end of dummy upper stage effectively functioned like a large, open-mouthed air brake, putting huge stresses on the vehicle. These caused the booster to break up, the remaining fuel on-board igniting in an explosion the test team had been expecting.

The SuperDraco motors fired for just 10 seconds. However, this was more than enough to put the craft on its own ballistic trajectory, allowing it to reach a peak altitude of around 40 km three minutes into the flight. Shortly ahead of reaching that point, the service module – referred to as the trunk, and designed to provide power and life support to the vehicle –  was jettisoned. Then as the capsule reached the zenith of its flight, the smaller Draco manoeuvring motors fired, stabilising it as it started its descent back towards Earth, enabling the drogue parachutes to deploy.

This pair of small parachutes allowed the vehicle to properly orient itself and act as a trigger for the release of the four main parachutes – as the drogues are jettisoned, they pulled clear a hatch covering the main parachute bay, just below the docking port that forms the nose of the Crew Dragon, allowing them to deploy, slowing the craft and bringing it down to a safe splashdown.

2:24 into the flight and the service module trunk is jettisoned from the Crew Dragon. Credit: SpaceX / NASA

For crew recovery operations, SpaceX make use of two specially-equipped ships, GO Searcher and Go Navigator. Originally leased by the company from Guice Offshore (hence the GO in the name) for use in the recovery of Falcon Payload fairings, Go Searcher was extensively refitted in 2018 to manage recovery operations for Crew Dragon, gaining a new radar system for tracking incoming Crew Dragon vehicles, a new crew recovery area and medical facility for post-flight check-ups of returning crew, and an upper deck helipad for emergency medivac. Go Navigator completed a similar refit in 2019.

Ahead of the test flight, GO Searcher departed SpaceX’s facilities at Port Canaveral, and took up a loitering position on the edge of the expected splashdown zone some 30 km off the coast of Florida. Following splashdown, teams aboard rigid-hulled inflatable boats (RHIBs) raced to the capsule to start the work of safing the craft and securing it ready for recovery. During normal flight recovery work, the recovery vessel and its crew will additionally have the services of Air Force Detachment-3 to call on, an emergency team of divers and personnel trained for astronaut recovery operations. For this flight, once the capsule has been recovered the the GO Searcher’s stern deck, it will be returned to SpaceX’s facilities along with the recovered parachutes for study.

While the initial response ot the flight has been positive, post-flight review is expected to take several weeks, and NASA has pointed out that there are still a number of additional tests that need to be completed ahead of crewed flights.

The GO Searcher, of of the crew recovery ships now operated by SpaceX, undergoing sea trails following her 2018 sea trials. the ship was used to to recover the IFA Crew Dragon capsule. Credit: NASA

There are some additional system-level tests of the spacecraft’s upgraded parachutes still needed to be completed, as well as other reviews of the spacecraft. [But] stepping through that [abort test] together and making sure that we’ve dotted all the i’s and crossed the t’s before our crew demonstration flight is very, very, important We’ve got work to do, but, honestly, getting this test behind us is a huge milestone.

– NASA Commercial Crew Programme manager, Kathy Lueders

As such, no date has been confirmed for the first crewed flight – officially called Demo-2, and which will see a 2-man crew fly a Crew Dragon to the ISS, where it will remains for approximately two weeks before they return to Earth. However, should the post-flight IFA test analysis prove positive, speculation is the Demo-2 flight could be staged as early as March, with “operational” flights starting later in 2020. In the meantime, the test flight can be followed in the video below, which has a start time set to just before the Falcon 9 ignites its main engine.

Continue reading “Space Sunday: commercial crew test flights & exoplanets”

Space Sunday: stars, a rover, a planet and a round-up

A Cataclysmic variable star, with the large main sequence “donor” star to the left, and the white dwarf “primary” taking mass from it, on the right. Credit: Mark A. Garlick

At the end of 2019, I wrote about the speculation around Betelgeuse and its recent behaviour (see: Space Sunday: a look at Betelgeuse). However, when it comes to a star going nova or supernova, there is a candidate out there that will more than likely do so before the end of this century.

V Sagittae, a variable star in the constellation Sagitta that is actually a binary system some 1100 light years away. In particular, it is in a class of stars called cataclysmic variables (CVs). These comprise a large, ordinary star orbiting a much smaller white dwarf at a distance where the white dwarf (referred to as the primary) distorts the larger (called the donor), drawing off mass to form an accretion disk around itself.

Usually, material at the inner edge of this disk heats as a result of both increasing density and proximity to the primary, causing dwarf nova outbursts, resulting in the pair to suddenly brighten. In some cases the material drawn into the primary can trigger a nova explosion or even a Type Ia supernova explosion, which would completely destroy the white dwarf.

Sagitta (the Arrow) is a constellation on the edge of the “Summer Triangle” defined by Vega (in Lyra), Deneb (in Cygnus), and Altair (in Aquila). The Arrow consists of five stars in an arrow-shape, pointing right at V Sge. Image Credit: Schaefer et al 2019.

However, the V Sagittae is amongst the most extreme group of CV stars, with the donor star almost 4 times as massive as its companion, and an extremely hot star. The material being drawn off of it is correspondingly hot (around 12,000ºK), and on contact with the white dwarf is either being accreted, building up the white dwarf’s mass and heat, or violently accelerated away in an extreme solar wind. This wind irradiates the inner hemisphere of the donor, further heating it, fuelling a circle of activity that is seeing mass transferred between the two at an ever-faster rate.

Checks back through archival images show the binary has been steadily brightening for around a century – and the rate of brightening has been accelerating. The net result of this is that astronomers believe V Sagittae is now in the closing decades of this life: over the next several decades, it will continue to brighten and the mass transfer accelerate further. Around the 2080s this will reach a point where the donor will spiral into the primary, triggering a catastrophic nova – one so powerful it could, with the assistance of the extreme solar wind, border on a supernova event.

Astronomers studying the system are so confident of their findings, they are prepared to to put a year on when the collision and subsequent explosion will occur: 2083 ±16 years.

When it happens, the normally faint V Sagittae will be between Venus and Sirius in brightness – not as bright as any supernova from Betelgeuse by any means, but it will be bright enough for even casual observers of the night sky to notice it – although it will be somewhat short-lived as a “new star”; after a month or so, it will dim down once more. The explosion itself will totally destroy whatever was left of the donor star at the time it occurred, with the primary likely converted into a red giant with a core of degenerate electron matter, surrounded by a hydrogen burning shell in turn layer surrounded by a vast halo of mostly hydrogen.

Happy Anniversary Yutu-2 and Chang’e 4

China greeted the New Year with some impressive lunar milestones. January 3rd, 2020 the Chang’e 4 mission to the lunar far side achieved its first anniversary of surface operations, while its Yutu-2 mini-rover completed its 13th lunar day of science operations.

Yutu-2 in particular has proven impressive. Designed to have a primary mission of 90 days, it has survived a full year of operations, which include the little rover having to put itself to sleep for 14 out of the 28 days of a lunar day in order to survive the cold lunar night, and it is still going strong. In that time, it has travelled 357.7m, the longest distance travelled by any vehicle on the lunar surface.

January 3rd, 2019: a shot of the Yutu 2 rover’s wheels ahead of the rover being commanded to roll off the Chang’e 4 lander (l) and as it slowly drives away from the lander (r). Credit: China National Space Administration via Xinhua News Agency

In during so, the rover has revealed a great deal about the composition of lunar soil – regolith – within the South Pole Aitken-Basin, including about materials that are believed to have originated from deep inside the lunar mantle. This has helped scientists understand more about the composition, formation, and evolution of the Earth-Moon system. It’s anticipated that Yutu-2 will continue these  explorations, helping to better understand the Moon’s composition and locate accessible resources that might be used in establishing and operating a permanent lunar base.

Chang’e 4 is part of a broader Chinese Lunar Exploration Programme, which includes the Chang’e 5 sample return mission scheduled for launch towards the end of 2020. It will be followed by a second sample return mission in 2024, (Chang’e 6), while Chang’e 7 will continue and extend the work of Chang’e 4, and Chang’e 8, scheduled for a 2027 launch, will test technologies and lay the groundwork for a crewed mission.

Continue reading “Space Sunday: stars, a rover, a planet and a round-up”

Space Sunday: things to watch for in 2020

An artist’s impression of ESA Solar Orbiter over the Sun. Credit: ESA

2020 is promising to be a busy year for space flight and astronomy, so I’m liable to have an even harder time sifting through all that is going on when trying to cover some of the more interesting / unusual events and missions taking place. So for the first Space Sunday of the year, I thought I’d look at some of the more notable events for the year; I can’t promise to cover all of them as the year progresses, but I’m aiming to get to as many as I can!

Spaceflight

Apollo 13

April 1970 marks the 50th anniversary of Apollo 13, probably the second most famous of the Apollo lunar missions on account of what went wrong and the eventual successful return to Earth of the 3-man crew of James Lovell, Jack Swigert and Fred Haise. Apollo 13 was the only Apollo mission to take place in 1970, and I’ll be covering the mission nearer its anniversary.

ISS: 2020 Years of Continuous Human Presence

November 2020 will mark the 20th anniversary of a continuous human presence aboard the International Space Station (ISS).

While there had been five Space Shuttle flights to the ISS between 1998 and 2000, none constituted a continuous human presence at the station. However, on November 2nd 2019, two days after launching from the historic Gagarin Start launch pad (used to launch the first human in space / to orbit the Earth, Yuri Gagarin) at Baikonur Cosmodrome in Kazakhstan, the 3-man crew of Expedition 1, transferred from their Soyuz TM-3 vehicle to the ISS to start a 136-day stay at the station.

The crew that marked the start of a permanent human presence in space aboard the ISS: Expedition 1 crew William Shepherd (c), Flight Engineer Sergei K. Krikalev (l, later commander of Expedition 11), and Soyuz Commander Yuri P. Gidzenko (r)

The crew of NASA astronaut (and mission commander) William Shepherd, and cosmonauts Yuri Gidzenko and Sergei K. Krikalev were not alone during their stay, being joined by the crews of space shuttles Endeavour (STS-97) and Atlantis (STS-98) during missions to further the assembly of the station. The Expedition 1 crew eventually departed the ISS on March 18th, 2001, aboard the shuttle Discovery, which had arrived on March 10th, both as a part of the assembly operations and to deliver the Expedition 2 crew who replaced Shepherd, Gidzenko and Krikalev.

Since then, there have been 61 Expedition crew rotations, with the total number of crew on the ISS at any one time varying from between three and six people (allowing for overlaps between individual Expeditions), with some individual astronauts and cosmonauts participating in more than one rotation.

Commercial Crew Flights

The year should also mark the resumption of crewed flights between US soil and the ISS for the first time since the space shuttle ceased operations in 2011. Crews are due to start flying to the station around mid-2020 using the SpaceX Crew Dragon vehicle (which has already completed a successful uncrewed flight to/from the ISS), and the Boeing CST-100 Starliner (which was unable to rendezvous with the ISS during its first orbital flight).

SpaceX Crew Dragon (l) and the Boeing CST-100 Starliner: crewed lights to the International Space Station in 2020. Credit: SpaceX / Boeing

No formal dates have been given on when Crew Dragon and Starliner will start routine to the ISS, both both are expected to complete one crewed “test flight” in “early” 2020 before transitioning into “operational” flights, with the Boeing test flight possibly lasting a full 6-month crew rotation.

For SpaceX, there is one remaining critical flight test that must be completed prior to any crewed flights. This will be a flight test of the Crew Dragon’s launch abort system, and is due to take place on or just after January 11th, 2020.

NASA Artemis 1

Formerly known as Exploration Mission-1 (EM-1), NASA’s Artemis-1 mission is being targeted for a late 2020 launch as a part of the US space agency’s goal to return humans to the surface of the Moon, possibly by 2024. This mission will be the first flight of NASA’s new super booster, the Space Launch System (SLS), which will be used to send an uncrewed Orion Multi-Purpose Crew Vehicle on an extended 3-week trip to cislunar space, including a week actually orbiting the Moon, before making a return to Earth.

Before the mission can take place, there are a number of critical tests the SLS system must undergo before it can be declared ready for launch, including a major engine firing test for its first stage engines. As such, whether or not Artemis-1 takes place depends on the outcome of these tests.

Space Tourism

It is anticipated that both Virgin Galactic and Blue Origin will commence sub-orbital flights into space for fare-paying tourists before the end of 2020. Neither company have formally committed to dates for their first flights, but Virgin Galactic has already commenced providing training and pre-flight health and diet advice for the first of the estimated 2,500 people who have made at least a significant down payment of their tickets.

An unusual view of Virgin Galactic’s VSS Unity about to land at the Mojave Air and Space Port in California in February 2019. Credit: Gene Blevins / Reuters

Blue Origin, meanwhile, have been ramping up their New Shephard booster / capsule launches with a series of uncrewed science and test flight in readiness for also flying their own crews and passengers.

Mars Opposition

Mid-2020 will see Mars and Earth make a relatively “close” approach to one another – something that happens every 26 months -, marking it as the most advantageous time to launch missions to the red planet. So the year should see four individual missions launched, involving multiple countries.

NASA Mars 2020: NASA’s latest (and still-to-be-named) Mars rover vehicle is due to be launched on July 17th. Of the same class of large, nuclear-powered rover as Curiosity, Mars 2020 is due to land in Jezero Crater on February 18th, 2021. However, while similar to Curiosity, the Mars 2020 rover has a very different mission – to seek out direct evidence of past life on Mars, and has very different capabilities.

An artist’s impression of the Mars 2020 rover. note the revised instrument package on the rover’s arm. Credit: NASA

In particular, the rover has a completely new instrument system on its robot arm, and will be capable of depositing sealed sample containers on the surface of Mars, which will be collected and returned to Earth by a proposed future mission. In addition, it will carry the first vehicle designed to fly on Mars in the form of a small helicopter drone.

Continue reading “Space Sunday: things to watch for in 2020”

Space Sunday: a look at Betelgeuse

Astro photographer Alan Dyer captured this image of Orion on December 21st, 2019. Betelgeuse (top left) appears to be the same brightness as Bellatrix (top right). Normally, Betelgeuse is the 10th brightest star in our sky and Bellatrix the 27th. Credit: A Dyer

The constellation of Orion is one of the most familiar in the night skies. It is marked by a number of notable features, containing as it does three of the brighter stars in our night sky: Rigel: the 6th brightest star visible from Earth, and serving as Orion’s left foot; Betelgeuse, the 10th brightest, and serving as Orion’s right shoulder (so diagonally opposite Rigel); Bellatrix, the 26th brightest star in our sky, and sits at Orion’s left shoulder; and three  galaxies – the Orion Nebula, the Messier 43 nebula, the Running Man Nebula – all of which can be found in Orion’s “sword”.

Orion  – or more particularly – Betelgeuse – has been occupying a lot of the astronomy-related news cycles of late, with speculation that we might be witnessing the star’s potential move towards a cataclysmic supernova event.

Before I get down to the nitty-gritty of why Betelgeuse has astronomers all a-twitter (quite literally, given the amount of Twitter chat on the subject), some details about the star. Classified a M1-2 red supergiant, Betelgeuse has a very distinctive orange-red colouration that can again be seen with the naked eye. However, it’s exact size is hard to determine, because it is both a semiregular variable star, meaning the brightens and dims on a semi-regular basis as it physically pulses in size, and because it is surrounded by a light emitting circumstellar envelope composed of matter it has ejected.

This means calculations over the years have given many different estimates of the star’s size, suggesting it is roughly 2.7 to 8.9 AU in diameter (1 AU = the average distance between the Earth and the Sun). This means that were the centre of Betelgeuse to be placed at the exact centre of the Sun, then its “surface” would be at least out amidst the asteroid belt between Mars and Jupiter, or lie somewhere between Jupiter and Saturn!

A diagram showing the approximate size of Betelgeuse compared to our solar system. Credit: unknown

That Betelgeuse is pulsating and has a cloud of material around it, also makes it difficult to pin down its precise distance from us. However, the most recent estimates suggest it is most likely around 643 light years from Earth, with a possible variation of around +/- 146 light years.

Re giant stars are of a type that have a comparatively short life, generally no more than 10 million years at the most (compared to our Sun’s anticipated 9-10 billion years lifespan), with Betelgeuse estimated to be about 8.5 million years old. This is because these stars burn through their reserves of fuel at a high speed, although a temperature lower than typically found with Sun-type stars. Eventually, they reach a point where the temperatures generated by the nuclear process is insufficient to overcome the huge gravity created by their size, and they suddenly and violently collapse, compressing to a point where the pressure is so great, they explode outwards even more violently, tearing away most of their mass in an expanding cloud of hot gas called a nebula, leaving behind a tiny, dense core – or even a black hole.

However, while this final collapse and explosion takes place suddenly, the period leading up to it can be marked by observable changes in a star – and this is the reason for the excitement around Betelgeuse.

Comparison chart showing Jupiter, Wolf 359 – a red dwarf star (often featured in this column) – Rigel, , Betelgeuse and the biggest stars so far discovered. Credit: unknown

Over the last 20+ years Betelgeuse’s radius has shrunk by 15%. While this has not massively altered the star’s brightness over that time, it is still an astonishing amount of mass to lose over so short a period. More recently, however, there has been a further change in the star that has caused excitement: since mid-October 2019, Betelgeuse has gone through a stunning drop in its apparent magnitude – or brightness as seen from Earth’s location – dropping from being the 10th brightest object in our night sky to around the 27th, bringing with it a complete change in Orion’s appearance in our skies.

This sudden drop in brightness has been seen by some as a possible indicator that Betelgeuse may have gone supernova, and we’re now waiting for the light of the actual explosion to reach us. Such has been the interest, reference has been made to monitoring neutrino detectors for the first signs of an explosion. This is because whereas photons have to escape a star’s collapse, neutrinos don’t, and so will reach us ahead of any visible light; so a sudden increase in the number of them detected coming from the region of the sky occupied by Betelgeuse could be indicative of it having exploded.

The clearest image we have of Betelgeuse, captured by the European Southern Observatory’s Atacama Large Millimetre/sub-millimetre Array (ALMA). Credit: ESO / NAOJ/NRAO / E. O’Gorman / P. Kervella.

Continue reading “Space Sunday: a look at Betelgeuse”

Space Sunday: Starliner’s first orbital flight

Ignition: the United Launch Alliance Atlas V topped by an uncrewed Boeing CST-100 Starliner vehicle lifts-off from Space Launch Complex 41 at Canaveral Air Force Station on its uncrewed Orbital Flight Test mission. Credit: ULA / Boeing

On Friday, December 20th, 2019, NASA and Boeing, together with launch partner United Launch Alliance (ULA), attempted to undertake the first flight of the Boeing CST-100 Starliner commercial crew transportation system to the International Space Station (ISS).

I say “attempted” because while the first part of the mission went precisely to plan and the Starliner successfully reached orbit, a software issue left it unable to reach the ISS. However, while this prevented a core mission objective from being met – that of rendezvousing and docking with the ISS – it did not leave the mission a failure: the ascent to orbit was successful, with a lot of data gathered on the vehicle’s performance, and further data could be gathered while on-orbit and during the vehicle’s return to Earth – also a critical part of the test.

The vehicle was uncrewed for this test flight, but is carrying a range of cargo – including Christmas gifts for the ISS crew; tree seeds that will be planted on Earth after the mission to mark it; a mannequin fitted with a host of sensors to measure the stress placed on a human body during the flight to orbit (the mannequin is called “Rosie the Rocketeer” in reflection of “Rosie the Riveter”, the iconic role model for U.S. women working in factories and on production lines in WWII, and a Snoopy soft toy “zero gee indicator” – Snoopy is the mascot for NASA’s Artemis programme to return humans to the Moon.

The Atlas V, dual Centaur and CST-100 vehicle stack. Credit: ULA

Things started off well enough: following a near-perfect count down, the core booster of the Atlas V and its two strap-on  solid rocket motors ignited precisely on time at 11:36:43 UT (06:36:43EST) on the launch pad of Space Launch Complex 41 at Cape Canaveral Air Force Station, and the vehicle lifted off smoothly into the still-dark early morning sky.

Due to the need to keep the vehicle within a 3.5 G limit during ascent, the Atlas V rose into a “flat” trajectory during its climb, the two solid rocket boosters being  jettisoned some 2 minutes into the flight, the core stage motors continuing to burn for almost three more minutes before BECO – Booster Engine Cut-Off – was called. Shortly after, the core stage of the Atlas V separated from the Centaur upper stage, allowing it to fire its twin RL-10A motors – marking the first time a twin-engined Centaur had been used with the Atlas V booster. Again, the additional power provided by the additional motor was required to push Starliner toward orbit, running for seven minutes in the process.

It was after the Starliner has separated from the Centaur upper stage that the major problem occurred. At this point, the vehicle was supposed to orient itself and then fire the main engine on the service module to push itself into an initial orbit that would allow it to complete further engine burns to both raise its orbit and circularise it, allowing the Starliner to catch-up and rendezvous with the ISS.

However, that initial burn failed to occur on time. Instead the vehicle continued to fire its attitude control thrusters while ignoring commands from Earth to fire the the service module’s motor. Some seven minutes passed before the engine was ignited, allowing Starliner to achieve its initial orbit – but by that time its was “off course” in relation to where it needed to be in order to catch up with the ISS, and had used too much attitude control system fuel to be able to make necessary course corrections and achieve any form of rendezvous with the ISS.

The Boeing Starliner space vehicle experienced an off-nominal insertion. The spacecraft currently is in a safe and stable configuration. Flight controllers have completed a successful initial burn and are assessing next steps. Boeing and NASA are working together to review options for the test and mission opportunities available while the Starliner remains in orbit.

– Kelly Kaplan, Boeing’s spokesperson, after the planned automated engine burn failed

According to initial investigations, it is believed that the mission clock aboard Starliner overseeing all of the vehicle’s automated flight operations – including triggering the engine burn – had incorrect data, causing it to believe the service motor had fired, and thus triggering use of the attitude control system.  While the issue left Starliner unable to reach the ISS, mission controllers were able to order the vehicle to complete two additional engine burns to put it into a near-circular 250km high orbit, where a range of tests on the vehicle have been made, and from which it could complete its planned EDL – entry, descent and landing.

A couple of important points to highlight here is that had the vehicle been carrying a crew, they would not have been in any danger – in fact, they would likely have been able to correct the initial burn failure, allowing the rendezvous with the ISS to take place.

The stages of a Starliner’s return to Earth. Credit: Boeing

With the issue understood – if not the cause known – the decision was taken to complete the planned orbital tests and then bring the Starliner back to Earth  and a landing at the White Sands Missile Range, New Mexico on Sunday, December 22nd. These orbital test included testing the navigation systems and the vehicle’s flight handling, and communications (including establishing a link with the ISS).

Landing commenced with Starliner turning itself around and using the service module’s motor in a de-orbit burn. This took place at 12:23 UT (06:23 CST at the White Sands landing ground) on December 22nd, slowing the vehicle sufficiently for it to start a decent into the denser part of the Earth’s atmosphere. Three minutes after this, the service module was detached and left to burn-up in the upper atmosphere.

The capsule, protected by a double heat shield system – referred to as the forward heat shield (protecting the upper part of the vehicle: the airlock and the landing system parachutes) and the base heat shield (at the base of the capsule and designed to protect it from the full heat of atmospheric entry) and covered in a thermal protection system – reached “entry interface” some 20 minutes later. This is the point where the atmosphere becomes dense enough to generate friction around the vehicle, both heating up and slowing the vehicle down. At this point, Starliner was some 15 minutes away from landing.

Continue reading “Space Sunday: Starliner’s first orbital flight”

Space Sunday: tiny stars & giant planets, and an interstellar visitor

An artist’s impression of the Neptune-sized world orbiting white dwarf WDJ0914+1914,. While the star is “dead” it is still hot enough for its solar wind to be slowly ripping away the planet’s outer atmosphere, most of which is lost to space, while some of it swirls into a disc, itself accreting onto the white dwarf, further heating it. Credit: ESO / M. Kornmesser

When a star like our own reaches the end of its life, two things happen: first, in a desperate attempt to keep itself burning after using its hydrogen and helium, it expands outwards into a red giant as it burns heavier elements in turn (our Sun will expand to a size sufficient to consume Mercury, Venus and Earth) before it collapses into a hot, white dwarf, a fraction of its former size (perhaps no bigger than the Earth).

But what of any gas giants orbiting the star well beyond the limits of its red giant expansion? What happens to them following the star’s collapse to a white dwarf? Do they simply continue until such time as their own internal heating fails? Might they have some additional interaction with their former parent?

A team from Warwick University, England, appear to have the answer. They’ve discovered a Neptune-sized planet some 4 times larger than its white dwarf host star, and the two have entered into what is – at this point in our understanding of such situations – a unique relationship.

The star is called WDJ0914+1914 and is some 2,000 light years away. Whilst reviewing data on it gathered by the Sloan Digital Sky Survey (SDSS), the astronomers came across something odd: the star was apparently giving off oxygen, sulphur and hydrogen emissions. While the oxygen was to be expected – by this time in a star’s life most of what is left is actually oxygen and carbon – the hydrogen and sulphur simply shouldn’t have been there.

Turning to the Very Large Telescope (VLT), the Warwick team found the emissions corresponded to to a ring of gas surrounding the star. At first they thought they had discovered a binary system in which the mass of one star was being drawn off by the other, forming a dust ring around both. However, further analysis revealed the composition of the disc matches the deeper layers of planets in our own Solar System like Neptune and Uranus, suggesting a planetary body still exists orbiting the star and material from that planet is feeding the disc, allowing it to survive.

While fusion has long since ended at WDJ0914+1914, the star is still radiating at some 28,000ºC – enough energy to tear material from the upper layers of a planet’s atmosphere. Much of this atmosphere would trail outwards from the planet as a hot plume – which the Warwick team detected – while some would collapse to feed the disc of material surrounding the star.

Putting their calculations together, the Warwick team worked out that the planet – which cannot be directly sighted – is likely to be around the size of Neptune, and it is losing its atmosphere at a rate of around 2,700 tonnes per second to both to the disc of material around the star, and eventually onto the star itself – “feeding” it, if you will. Although this sounds a lot, it actually adds up to a relative small amount given the size of the planet, and so the loss is unlikely to alter its overall structure as the star continues to cool.

This discovery at WDJ0914+1914 is unique at the moment – but it makes the case that other white dwarf stars may also be survived by planets, some of which we may be able to detect using the transiting method of observation (WDJ0914+1914 is simply too dim for this to work). Certainly, the Warwick team’s research has opened the door on this form of research, one that could help with our understanding of exoplanet atmospheres.  It also offers a cold look at the far future (roughly 4.5 to 5 billion years from now) of our own solar system.

New Dates For Commercial Crew Test Flights

NASA has issued new dates for the final test flights for the SpaceX Crew Dragon and Boeing CST-100 Starliner that, if passed, should allow both vehicles to move on towards actually transporting astronauts to and from the International Space Station.

On December 20th, 2019, a United Launch Alliance Atlas V will launch the first CST-100 Starliner into orbit on an uncrewed orbital test flight (OTF) to the International Space Station. As well as testing the Starliner’s avionics and flight systems, the flight will also test a new docking system that is intended to become the “”standard docking system for sending humans to Gateway and to Mars” as a part of the Artemis programme, and used to deliver additional supplies and some Christmas / New Year’s extras to the ISS crew.

The first Boeing CST-100 vehicle being transported from Boeing’s fabrication centre at Kennedy Space Centre on its way to the Space Launch Complex 41 Vertical Integration Facility at Cape Canaveral Air Force Station in readiness for its flight, November 21st, 2019. Credit: Boeing

Also flying on the vehicle will be a flight test dummy christened “Rosie the Rocketeer”, named for “Rosie the Riveter”, the iconic role model for U.S. women working in factories and on production lines in WW II. The dummy is fitted with an array of sensors to measure critical data including G-forces endured during the flight to inform the team about the stresses a human crew will experience during an ascent to orbit on the vehicle. Results from this data, and all telemetry gathered during the flight will help inform NASA and Boeing on the Starliner’s readiness to commence crewed flights.

The vehicle will not spend long at the ISS – it will be undocked on December 28th and make a return to Earth in a full dress-rehearsal for a crewed landing for the CST-100 capsule. Should weather interfere with the planned launch, both December 21st and 23rd offer suitable windows for the launch to take place.

The first Boeing CST-100 mounted atop its United Launch Alliance Atlas V booster at Space Launch Complex 41, Cape Canaveral Air Force Station, December 4th, 2019. Credit: Boeing

Then, on January 4th, 2020, SpaceX is expected to complete an in-flight abort test. For that test, a Falcon 9 will lift off from Launch Complex 39A at Kennedy Space Centre carrying a test Crew Dragon vehicle – which has previously performed  a successful static fire test of its SuperDraco escape motors in November. Around 90 seconds into the flight, and the time of maximum dynamic pressure on the vehicle, the escape system will be triggered, the capsule hopefully escaping the rocket to make a safe splash-down under parachute.

SpaceX had hoped to complete this test before the end of the year, but assorted delays – including that of the CRS-19 resupply mission, which launched earlier in December (see: On the ISS – mighty mice and robots) – meant that target could not be met. If the abort flight test is successful, it should allow NASA and SpaceX to determine when crewed flights to the ISS can commence – an uncrewed test flight of the vehicle to the ISS having been completed in March 2019.

Overall. NASA would like both Boeing and SpaceX to complete their first crewed flights to the ISS – also regarded as test flights – by mid-2020.

Continue reading “Space Sunday: tiny stars & giant planets, and an interstellar visitor”