Space Sunday: total eclipse and exoplanet update

2016 total eclipse Credit: NASA Exploratorium webcast

On Monday, August 21st, the continental United States will experience its first total eclipse of the sun for 38 years (the last total eclipse visible from the USA having occurred in 1979). Providing the weather holds good along the path of the eclipse, an estimated 220 million people will be able to see the event – providing they take the proper precautions.

An eclipse is a periodic event, occurring when the Moon passes between the Sun and Earth and either fully or partially occults (blocks) the Sun’s light. This can happen only at new moon, when the Sun and the Moon are in conjunction as seen from Earth, in an alignment referred to as syzygy. There are actually four types of eclipse:

  • Partial – this occurs when the Sun and Moon are not exactly in line with the Earth, and so the Moon only partially obscures the Sun. Partial eclipses are virtually unnoticeable in terms of the sun’s brightness, as it takes well over 90% coverage to notice any darkening at all.
  • Annular – occurs when the Sun and Moon are exactly in line with the Earth, but because of the variations in the Earth’s distance from the Sun, and the variations in the Moon’s distance from the Earth, the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring, or annulus, surrounding the dark disk of the Moon.
  • Total – occurs when the dark silhouette of the Moon completely obscures the intensely bright light of the Sun, allowing the much fainter solar corona to be visible. The complete coverage of the Sun’s disk by that of the moon – referred to as totality – occurs at its best only in a narrow track on the surface of Earth.
  • Hybrid (also called annular/total eclipse) – this shifts between a total and annular eclipse. At certain points on the surface of Earth, it appears as a total eclipse, whereas at other points it appears as annular. Hybrid eclipses are comparatively rare.

The last total eclipse took place in March 2016, and was visible from South/East Asia, North/West Australia, the Pacific and Indian oceans. The 2017 event will be visible in partial forms across every continent except Antarctica and Australia. However, the path of totality will only be visible across the continental United States.

Although totality slices through the U.S., partial phases of the eclipse touch on every continent except Antarctica and Australia. Credit: Michael Zeiler / The Great American Eclipse – click for full size

The path of totality will run from Oregon to South Carolina, as will be around 113 kilometres (70 miles) wide, offering people along it an unrivalled opportunity to view the eclipse  – weather permitting -, providing the right precautions are taken.

The most important aspect of viewing an eclipse “live” is never look directly at the Sun, even during the period of totality; you should at least use a solar filter or viewer. However, if you don’t have one or the other or any specialised kit, the best way to see the eclipse in the flesh is via pinhole projection. For those who are unable to see the eclipse first-hand, there are a wide variety of ways to watch the event on television or the Internet, including:

  • NASA Total Eclipse live stream is providing options to watch through NASA Edge, NASA TV, Ustream, YouTube and more. NASA’s Facebook page. These will show images of the eclipse, from 11 spacecraft, three aircraft and from more than 50 high-altitude balloons, and the astronauts on the International Space Station.
  • Slooh, the on-line community observatory, will run a webcast starting at 12:oo noon EDT (1600 GMT), as a part of a 3-day celebration of the eclipse.
  • The Virtual Telescope Project is hosting a free online observing session with views of the total solar eclipse beginning at 13:00 EDT (17:00 GMT).
  • The Eclipse Ballooning Project will be broadcasting live views of the eclipse from the edge of space via more than 57 cameras sent up on weather balloons.
  • CNN and Volvo will be providing a 360-degree view of the eclipse with 4K resolution from different locations along the eclipse path. The stream will also be viewable in virtual reality, which people can navigate by moving a phone or virtual reality headset. The live stream begins at 12:03 p.m. EDT (16:03 GMT).
  • ABC will air a two-hour special on the eclipse starting at 13:00 EDT (17:00 GMT). The broadcast will also be available on Facebook Live and YouTube

There are a number of terms common to eclipses which are worth mentioning for those who wish to follow the event, but are unfamiliar with the terminology. These include:

Eclipse Types (Moon and Sun not to scale). Credit: Cmglee
  • The umbra, within which the object in this case, the Moon) completely covers the light source (in this case, the Sun’s photosphere).
  • The antumbra, extending beyond the tip of the umbra, within which the object is completely in front of the light source but too small to completely cover it.
  • The penumbra, within which the object is only partially in front of the light source.
  • Photosphere, the shiny layer of gas you see when you look at the sun.
  • Chromosphere, a reddish gaseous layer immediately above the photosphere of the sun that will peak out during the eclipse.
  • Corona, the light streams that surround the sun.
  • First contact, the time when an eclipse starts.
  • Second contact, the time when the total eclipse starts.
  • Third contact, the time when the total eclipse ends.
  • Fourth contact, the time at which the eclipse ends.
  • Bailey’s beads, the shimmering of bright specks seen immediately before the moon is about to block the sun.
  • Diamond ring, the last bit of sunlight you see right before totality. It looks like one bright spot (the diamond) and the corona (the ring).

A total eclipse occurs when the observer is within the umbra (they are standing in the shadow cast by the Moon); an annular eclipse when the observer is within the antumbra, and a partial eclipse when the observer is within the penumbra.

As well as the passage of the Moon between the Earth and Sun, there are a number of Earthly effects to look for if you are in the path of totality, such as a the 360-degree sunset. This may also be accompanied by an “eclipse wind” as temperatures suddenly drop. And, of course, there is the rousing of nocturnal animals, fooled by the darkness, followed by a false dawn as the Moon moves away from between the Earth and the Sun, and an accompanying dawn chorus.

The period of totality lasts only a few minutes but offers a superb opportunity for observing the Sun and its corona – hence why NASA is using a chain of three aircraft to “chase” the eclipse as the Moon’s shadows travels at an average speed of 3,683 km/h (2,288 mph) west-to-east, enabling them to carry out an extended study of the corona.

The Moon’s shadow on Earth, as seen from the International Space Station on March 29th, 2006 as it passes over southern Turkey, Northern Cyprus and the Mediterranean Sea. Credit: NASA

As a point of historical interest, August 21st marks the 103rd anniversary of the 1914 total eclipse, which was seen from Scandinavia through to Turkey, the middle east and India. It was the subject of a number of expeditions being sent eastwards to the Baltic and Ukraine by Britain and other European nations with the intention of studying it – only for the conflagration of the First World War to erupt.

The war foiled attempts by a British expedition which intended to use the eclipse as a means to measure relativity; however, it did give rise to another mystery: whether or not a film of the eclipse apparently made in Sweden in 1914 is the real deal or not. If it is, it might be the oldest surviving footage of an eclipse.

If you are on the path of totality, and plan to view the eclipse, do please take the proper precautions and I hope the weather cooperates with you. I’ll be following things on-line.

 

Continue reading “Space Sunday: total eclipse and exoplanet update”

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Space Sunday: Voyager at 40

Voyager: 40 years on. Credit: NASA

August 20th 2017 marks the 40th anniversary of the launch of Voyager 2, which with its sister craft Voyager 1 (launched on September 5th, 1977) are humanity’s furthest-flown operational space vehicles, with Voyager 1 being the most distant human made object from Earth, at some 140 AU (AU= astronomical unit, the average distance between the Earth and the Sun; 140 AU equates to about 20.9 billion kilometres / 13 billion miles).

Despite being so far away from Earth, both craft are still sending data back to Earth as they fly through the interstellar medium in the far reaches of the solar system (the Pioneer 10 and Pioneer 11 craft which pre-date the Voyager programme by some 5 years, ceased transmissions to Earth in January 2003 and September 1995 respectively, although Pioneer 10 is the second most distant human made object from Earth after Voyager 1).

The Voyager programme stands as one of the most remarkable missions of early space exploration. Originally, the two vehicles were to be part of NASA’s Mariner programme, and were at first designated Mariner 11 and Mariner 12 respectively. The initial Mariner missions – 1 through 10 – were focused on studying the interplanetary medium and  Mars, Venus and Mercury (Mariner 10 being the first space vehicle to fly by two planets beyond Earth – Venus and Mercury – in 1974). Mariner 11 and Mariner 12 would have been an expansion of the programme, intended to perform flybys of Jupiter and Saturn.

A drawing of the Voyager vehicles. Credit: NASA/JPL (click for full size)

However, in the late 1960s Gary Flandro, an aerospace engineer at the Jet Propulsion Laboratory (JPL) in California noted that in the late 1970s, the outer planets would be entering a period of orbital alignment which occurs once every 175 years and which could be used to throw a series of probes out from Earth, which could then use the gravities of the worlds they encountered to “slingshot” them on to other targets. This led to the idea of a “Grand Tour” mission: sending pairs of probes which could use these gravity assists to fly by Jupiter, Saturn, Uranus, Neptune and Pluto in various combinations.

Funding limitations eventually brought an end to the “Grand Tour” idea, but the planetary alignment was too good an opportunity to miss, and so elements of the idea were folded into the Voyager Programme, which would utilise Mariner 11 and Mariner 12. However, as the mission scope required some significant changes to the vehicles from the basic Mariner design, they were re-designated as Voyager class craft.

(As an aside, the Mariner class is the longest-lived of NASA’s space probe designs; as well as the ten missions of the 1960s and 1970s which carried the design’s name,  the Mariner baseline vehicle – somewhat enlarged – was used for the Viking 1 and Viking 2 orbiter missions to Mars, and formed the basis of the Magellan probe (1989-1994)  to Venus and the Galileo vehicle (1989-2003) which explored Jupiter. And uprated and updated baseline Mariner vehicle, designated “Mariner Mark II”, formed the basis of the Cassini vehicle, now in the terminal phase of its 13-year study of Saturn and its moons.)

Each of the Voyager mission vehicles is powered by  three plutonium-238 MHW-RTG radioisotope thermoelectric generators (RTGs), which provided approximately 470 W at 30 volts DC when the spacecraft was launched. By 2011, both the decay of the plutonium and associated degradation of the thermocouples that convert heat into electricity has reduced this power output by some 57%, and is continuing at a rate of about 4 watts per year.

To compensate for the loss, various instruments on each of the vehicles have had to be turned off over the years. Voyager 2’s scan platform and the six instruments it supports, including the vehicle’s two camera systems, was powered-down in 1998. While the platform on Voyager 1 remains operational, all but one of the instruments it supports – the ultraviolet spectrometer (UVS) – have also been powered down. In addition, gyro operations ended in 2016 for Voyager 2 and will end in 2017 for Voyager 1. These allow(ed) the craft to rotate through 360 degrees six times per year to measure their own magnetic field, which could then be subtracted from the magnetometer science data to gain  accurate data on the magnetic fields of the space each vehicle is passing through.

However, despite the loss of capabilities, both Voyager 1 and Voyager 2 retain enough power to operate the instruments required for the current phase of their mission – measuring the interstellar medium and reporting findings back to Earth. This phase of the mission, officially called the Voyager Interstellar Mission, essentially commenced in 1989 as Voyager 2 completed its flyby of Neptune, when the missions as a whole was already into their 12th year.

A plume rises 160 km (100 mi) above Loki Patera, the largest volcanic depression on Io, captured in March 1979 by Voyager 1. Credit: NASA/JPL

Voyager 2 was launched on August 20th, 1977. Of the two vehicles, it was tasked with the longer of the planned interplanetary missions, with the aim of flying by Jupiter, Saturn, Uranus and Neptune. However, the latter two were seen as “optional”, and dependent upon the success of Voyager 1.

This was because scientists wanted the opportunity to look at Saturn’s moon Titan. But doing so would mean the Voyager craft doing so would have to fly a trajectory which would leave it unable to use Saturn’s gravity to swing it on towards an encounter with Uranus. Instead, it would head directly towards interstellar space.

So it was decided that Voyager 1, which although launched after Voyager 2 would be able to travel faster, would attempt the Titan flyby. If it failed for any reason, Voyager 2 could be re-tasked to perform the fly-past, although that would also mean no encounters with Uranus or Neptune. In the end, Voyager 1 was successful, and Voyager 2 was free to complete its surveys of all four gas giants.

Along the way, both missions revolutionised our understanding of the gas giant planets and revealed much that hadn’t been expected, such as discovering the first active volcanoes beyond Earth, with nine eruptions imaged on Io as the vehicles swept past Jupiter. The Voyager missions were also the first to find evidence that Jupiter’s moon Europa might harbour a subsurface liquid water ocean and to return the first images of Jupiter’s tenuous and almost invisible ring system. Voyager 1 was responsible for the first detailed examination of Titan’s dense, nitrogen-rich atmosphere, and Voyager 2 for the discovery of giant ice geysers erupting on Neptune’s largest moon, Triton. In addition, both of the Voyager vehicles added to our catalogues of moons in orbit around Jupiter and Saturn, and probed the mysteries of both planet’s atmospheres, whilst Voyager 2 presented us with our first images of mysterious Uranus and Neptune – and thus far remains the only vehicle from Earth to have visited these two worlds.

This is the last full planet image captured of Neptune. Taken by Voyager 2 on August 21st, 1989, from a distance of 7 million km (4.4. million mi). A true colour image white balanced to reveal the planet under typical Earth lighting conditions, it shows Neptune’s “Great Dark Spot” and surrounding streaks of lighter coloured clouds, all of which persisted through the period of Voyager 2’s flyby. More recent Hubble Space Telescope images suggest the “Great Dark Spot”, initially thought to be a possible cloud / storm formation, similar to Jupiter’s Great Red Spot, has vanished, leading to speculation that it may have actually been a “hole” in a  layer of Neptune’s layered clouds. Credit: NASA/JPL

The flyby of Neptune also sealed Voyager 2’s future. Scientists were keen to use the flyby of the planet to take a look at Triton, Neptune’s largest moon. However, because Triton’s orbit around Neptune is tilted significantly with respect to the plane of the ecliptic, Voyager 2’s course to Neptune  had to be adjusted by way of a gravitational assist from Uranus and a number of mid-course corrections both before and after that encounter, so that on Reaching Neptune, it would pass over the north pole, allowing it to bent “bent” down onto an intercept with Triton while the Moon was at  apoapsis – the point furthest from Neptune in its orbit – and well below the plane of the ecliptic. As a result, Voyager 2 passed over Triton’s north pole 24 hours after its closest approach to Neptune, its course now pointing it towards “southern” edge of the solar system.

Continue reading “Space Sunday: Voyager at 40”

Space Sunday: Curiosity’s 5th, Proxima b and WASP-121b

On August 6th 2016, NASA delivered the Mars Science Laboratory (MSL) to the surface of Mars in what was called the “seven minutes of terror” – the period when the mission slammed into the tenuous Martian atmosphere to begin deceleration and a descent to the surface of the planet which culminated in the Curiosity rover being winched down gently from a hovering “sky crane” and then lowered until its wheels made firm contact with the ground.

The “seven minutes of terror” actually had a double meaning. Not only did it represent the time MSL would smash into Mars’ atmosphere and attempt its seemingly crazy landing, at the time of the event, the distance between Earth and Mars meant it took seven minutes to be returned to mission control from the red planet. Thus, even as the initial telemetry indicating the craft was entering the upper reaches of Mars’ tenuous atmosphere was being received, mission controls knew that in reality, the landing had either succeeded or failed.

Obviously, the attempt succeeded. Everything worked flawlessly, and Curiosity was delivered to the surface of Mars at 05:17 GMT on August 6th, 2012 (01:17, August 6th EDT, 22:17 PDT, August 5th). In the five years since that time, it is helped revolutionise our understanding of that enigmatic world – as well as adding somewhat to its mystery.

To call the mission a success is not an exaggeration; within weeks of its arrival inside the 154 kilometre (96 mile) wide Gale Crater, Curiosity was examining an ancient riverbed en route to a region of the crater dubbed “Yellowknife Bay”. It was there the rover made its first bombshell discovery: analysis of the area showed that billions of years ago it was home for the ideal conditions to potentially kick-start microbial life. It was, in essence, the achievement of mission’s primary goal: to identify if Mars may have once harboured the kind of conditions which might have given rise to life.

This 360-degree view was acquired on August 6th, 2016, by Curiosity’s Mastcam as the rover neared the “Murray Buttes” on lower “Mount Sharp”. The dark, flat-topped mesa seen to the left of the rover’s arm is about 15 metres (50 ft) high and about 61.5 metres (200 ft) long. Credit: NASA/JPL / MSSS

For the first year following its arrival on Mars, Curiosity continued to survey the regions relatively close to its landing zone, finding more evidence of a benign ancient environment. Then it started out on the next phase of its mission: the long traverse towards the massive bulk of “Mount Sharp” – officially called Aeolis Mons. A huge mound of rock deposited against the crater’s central impact peak, “Mount Sharp” rises from the crater floor to an altitude of some 5.5 km (3 mi), and imagining from orbit strongly suggested its formation was due, at least in part, to the presence of water in the crater at some point in Mars’ past.

The 8 km (5 mi) trip took the rover a year to complete, in part due to its relatively slow speed, in part due to the fact is had to travel a good way along the base of “Mount Sharp” to reach a point where it could commence an ascent up the slope; but mostly because there were a number of points of interest along the way where the mission scientists  wanted to have a look around, investigate and sample.

Mount Sharp as seen from Curiosity, on January 24th, 2017. The light grey banding befpre the sandy coloured slopes is the clay unit the rover will reach in about 2 years. In front of it is the “Vera Rubin Ridge”, the next location for study by the rover. Credit: NASA/JPL / MSSS

For the last three years, the rover has been slowly making its way up “Mount Sharp”, climbing around 180 metres (600ft) vertically above the surrounding crater floor and visiting numerous points of interest – such as “Pahrump Hills”, the mixed terrain where “Mount Sharp” merges with the crater floor. Along the way, Curiosity has both confirmed that “Mount Sharp” was most likely the result of sedimentary deposits laid down during several periods of flooding in the crater before the water finally receded and wind action took over, sculpting the mound into its present shape down through the millennia.

The lakes within Gale crater may have actually been relatively short-lived, perhaps lasting just 1,000 years at a time, but Curiosity has shown that even during the dry inter-lake periods, water was very much a feature of Gale Crater, finding evidence of compressed water channels within the layers of rock which sit naturally exposed on “Mount Sharp’s” flanks.

In December 2014, NASA issued a report on how “Mount Sharp” was likely formed. On the left, the repeated depositing of alluvial and wind-blown matter (light brown) around a series of central lakes which formed in Gale Crater, where material was deposited by water and more heavily compressed due the weight of successive lakes (dark brown). On the right, once the water had fully receded / vanished from the crater, wind action took hold, eroding the original alluvial / windblown deposits around the “dry” perimeter of the crater more rapidly than the densely compacted mudstone layers of the successive lake beds, thus forming “Mount Sharp”

Alongside the sedimentary layering of the mudstone comprising “Mount Sharp” and the compressed and long-dry water channels, a further sign that the region was once water rich comes in the form of the mineral hematite, which Curiosity has found on numerous occasions. Right now, the rover is making its way towards a feature dubbed “Vera Rubin Ridge” which orbital analysis shows to be rich in this iron-bearing mineral which requires liquid water to form. Beyond that is a clay-rich unit separating the hematite rich ridge from an area which show strong evidence for sulphates. These are also indicative of water having once been present, albeit less abundantly than along “Vera Rubin Ridge”, and thus hinting at a change in the local environment. Currently, Curiosity is expected to reach this area in about two years’ time, after studying “Vera Rubin Ridge” and the clay unit along the way.

Selfies from Mars: how Curiosity has weathered the dust on Mars over five years – the dates are given as Sols – Martian days, top left and the locations where the pictures were taken. Credit: NASA/JPL

Throughout the last five years, Curiosity has remained relatively healthy. There has been the odd unexpected glitch with the on-board computers, all of which have been successfully overcome. There has been some damage to the rover’s aluminium wheels. This did give rise to concern at the time it was noted, resulting in a traverse across rough terrain being abandoned in favour of a more circuitous and less demanding route up onto “Mount Sharp”. But overall, the wheels remain in reasonably sound condition.

The one major cause for concern at present lies with Curiosity’s drill mechanism. Trouble with this first began when vibrations from the drill percussive mechanism was noted to be having a negative impact on the rover’s robot arm.

More recently – since December 2016, in fact – all use of the drill has ceased, limiting Curiosity’s sample gathering capabilities. This has been due to an issue with the drill feed motor, which extends the drill head away from the robot arm during normal drilling operations, preventing the arm physically coming into contact with targets. Attempt to rectify the problem have so far been unsuccessful, so engineers are loot at ways to manoeuvre the rover’s arm and place the drill bit in contact with sample targets, avoiding the need to use the feed motor.

So with five years on Mars under its belt, and barring no major unforeseen incidents, Curiosity will continue its mission through the next five years, further enhancing our knowledge of Mars.

Continue reading “Space Sunday: Curiosity’s 5th, Proxima b and WASP-121b”

Space Sunday: ninja space stations, Falcons, Dragons and ET

The cislunar Deep Space Gateway with an Orion Multi-Purpose Crew Module approaching it. Credit: NASA

Lockheed Martin has announced it will build a full-scale prototype of NASA’s proposed Deep Space Gateway (DSG), a space habitat occupying cislunar space. The facility, which if built, will be both autonomous and crew-tended, and is intended to be used as a staging point for the proposed Deep Space Transport NASA is considering for missions to Mars, as well as for robotic and crewed lunar surface missions.

DSG is part of a public-private partnership involving NASA in developing technologies for carrying humans beyond low Earth orbit called Next Space Technologies for Exploration Partnerships (NextSTEP). A Phase I study for the facility has already been completed, and the full-scale prototype will be constructed as a part of the Phase II NextSTEP habitat programme, which will examine the practical issues of living and working on a facility removed from the relative proximity of low Earth orbit, outside of the relative protection of the Earth’s magnetic field and subject to delays of up to 3 seconds in two-way communications.

“It is easy to take things for granted when you are living at home, but the recently selected astronauts will face unique challenges,” said Bill Pratt, Lockheed Martin NextSTEP program manager.

“Something as simple as calling your family is completely different when you are outside of low Earth orbit. While building this habitat, we have to operate in a different mindset that’s more akin to long trips to Mars to ensure we keep them safe, healthy and productive.”

The proposed Gateway, which if built would likely enter service in 2027/2028, will be designed to make full use of the Orion Multi-Purpose Crew Module as its command and control centre, and will also use avionics and control systems designed for the likes of NASA’s MAVEN mission in order around Mars and the Juno mission at Jupiter, which will allow the facility to operate in an uncrewed automated flight mode around the Moon for up to seven months at a time.

NASA’s MPLM mission logo. Credit: NASA / Marshall Space Flight Centre

The core of the prototype will be the Donatello Multi-Purpose Logistics Module (MPLM), originally designed and built for flights aboard the space shuttle and capable of delivering up to nine metric tonnes of supplies to the International Space Station (ISS). Two of these units, Leonardo and Raffaello flew a total of 12 missions to the ISS between 2001 and 2011, with Leonardo becoming a permanent addition to the space station in early 2011. And if film and comic fans are wondering, yes, the modules were all named after a certain band of mutant ninja turtles – hence the MPLM mission logo (right).

Donatello was a more capable module than its two siblings, as it was designed to carry payloads that required continuous power from construction through to installation on the ISS. However, it was never actually flown in space, and some of its parts were cannibalised to convert Leonardo into a permanent extension to the space station. In its new role, Donatello will form the core habitat space for the DSG prototype, and will be used as a testbed for developing the living and working space in the station, which will also have its own power module and multi-purpose docking adapter / airlock unit.

The Phase II development of the DSG is expected to occur over 18 months. Mixed Reality (augmented reality and virtual reality) will be used throughout the prototyping process to reduced wastage, shorten the development time frame and allow for rapid prototyping of actual interior designs and systems. The results of the work and its associated studies will be provided to NASA to help further the understanding of the systems, standards and common interfaces needed to make living in deep space possible.

The DSG is one of two concepts NASA is considering in it attempts to send humans to Mars. The second is the so-called Deep Space Transport (DSH). This is intended to be a large vehicle using a combination of electric and chemical propulsion to carry a crew of six to Mars. It would be assembled at the Deep Space Gateway.

While having a facility in lunar orbit does make sense for supporting operations on the Moon’s surface, when it comes to human missions to Mars, the use of the DSG as an assembly  / staging post for the DST actually makes very little practical sense. Exactly the same results could be achieved from low Earth orbit and without all the added complications of lunar orbit rendezvous. The latter simply adds an unnecessary layer of complexity to Mars missions whilst providing almost no practical (or cost) benefits, and perhaps again demonstrates NASA’s inability to separate the Moon and Mars as separate destinations – something which has hindered their plans in the past.

Musk Walks Back SpaceX Aspirations

SpaceX CEO and chief designer, Elon Musk has walked back on expectations for the initial lunch of the Falcon Heavy booster and on longer-terms aspirations for the Dragon 2 crew capsule.

Musk: a successful maiden flight of the Falcon Heavy “unlikely”. Credit: Associated Press

Speaking at the International Space Station Research and Development Conference held in Washington DC in mid-July 2017, Musk indicated that a successful maiden flight of the Falcon Heavy rocket is extremely unlikely. He also indicated that the company is abandoning plans to develop propulsive landing techniques for the Dragon 2 when returning crews to Earth from the ISS – and to achieve a soft landing on Mars.

Falcon Heavy is slated to be the world’s most powerful rocket currently in operation when it enters service in 2018, capable of lifting a massive 54 tonnes to low Earth orbit – or boosting around 14 tonnes on its way to Mars. Designed to be reusable, the rocket uses three core stages of the veritable Falcon 9 rocket – one as the centre stage, two as “strap on boosters” either side of it.

But computer modelling has revealed that firing all 27 motors on the stages (nine engines apiece) at launch has dramatically increased vibrations throughout the vehicle stack, making it impossible to gauge by simulation whether or not the rocket will shake itself apart without actually flying it. Hence Musk’s statement that the maiden flight of the Falcon Heavy  – slated for later in 2017 – is unlikely to achieve a successful orbit. However, telemetry gathered during the flight – should the worse happen – will help the company more readily identify stresses and issues created by any excessive vibration, allowing them to be properly countered in future launches.

Once Falcon Heavy is fully operational, all three of the core stages are intended to return to Earth and achieve a soft landing just as they do when used as the first stage of a Falcon 9 launch vehicle, and SpaceX is also working to make the upper stage of the Falcon 9 / Falcon Heavy  recoverable as well.

Also at the conference, Musk announced SpaceX will no longer be using propulsive landings for the crewed version of their Dragon 2 space capsule, due to enter operations in 2019 ferrying crews two and from the ISS, operating alongside Boeing’s CST-100 Starliner capsule. Initial flights of the Dragon 2 were intended to see the vehicle make a “traditional” parachute descent through Earth’s atmosphere followed by an ocean splashdown – the technique currently used by the uncrewed Dragon I ISS resupply vehicle.

However, SpaceX had planned to shift Dragon 2 landings from the sea to land – using parachutes for the majority of the descent back through the atmosphere, before cutting the vehicle free and using the built-in Super Draco engines (otherwise used as the crew escape system to blast the capsule free of a Falcon launch vehicle if the latter suffers any form of pre- or post-launch failure). The engines would fire during the last few metres of decent, placing the capsule into a hover before setting it down on four landing legs.

Extensively tested in tethered “hover” flights, propulsive landings would in theory made the recovery and refurbishment of Dragon capsules for future launches a lot easier, lowering the overall operating costs for the capsule. In announcing the decision to scrap the propulsive landing approach, Musk indicated it would have unnecessarily further drawn out the vehicle’s development as SpaceX sought to satisfy NASA’s requirements for crewed vehicle operations.

The decision also affects Musk’s hope of placing a robotic mission on the surface of Mars in 2020. Under that mission, a special cargo version of Dragon 2 – called Red Dragon- would fly a NASA science payload to Mars and use supersonic propulsive landing to slow itself through the tenuous Martian atmosphere and achieve a successful soft landing. This approach was seen as ideal, because using parachutes on Mars is extremely difficult with heavy payloads – NASAs studies suggest parachute on Mars have an upper limit of payloads around 1.5-2 tonnes. A Red Dragon capsule is liable to mass around 8-10 tonnes.

SpaceX have dropped plans to use propulsive landings on both their crewed Dragon 2 vehicles returning from the ISS and on their Red Dragon automated Mars lander (above). Credit: SpaceX

However, Musk no longer believes the use of a propulsive landing mechanism is “optimal” for Red Dragon, and the company has a better way of realising their goal – although he declined to indicate what this might be. Instead, propulsive landing systems would seem to be something the company will return to in the future – particularly given their hopes of placing vehicles massing as much as 100 tonnes on the surface of Mars.

No, ET Isn’t Calling Us

The Internet was agog recently after it was announced some very “peculiar signals” had been noticed coming from Ross 128, a red dwarf star just 11 light-years away. While not known to have any planets in orbit around it, and despite the best attempts of astronomers – including the team picking up the signals at the Arecibo radio telescope, Puerto Rico – news of the signals led to widespread speculation that “alien signals” had been picked up.

The usual signals – officially dubbed the “Weird!” signal, due to the comment made in highlighting the signals in an image – were first picked up on May 12th/13th, 2017. However, it was not until two weeks later that the signals were identified and analysed, the PHL team concluding that they were not “local” radio frequency interference, but were in fact odd signals coming from the direction of Ross 128 – sparking the claims of alien signals, even though the director at PHL and the survey team leader -Abel Mendez – was one of the first to pour water on the heat of the speculation. “In case you are wondering, he stated in response to the rumours, “the recurrent aliens hypothesis is at the bottom of many other better explanations.”

The Weird! signal. Credit: UPR Aricebo

Without drawing any conclusions on what might be behind the signals, PHL liaised with  astronomers from the Search for Extra-Terrestrial Intelligence (SETI) Institute to conduct a follow-up study of the star. This was performed on Sunday, July 16th, using SETI’s Allen Telescope Array and the National Radio Astronomy Observatory‘s (NRAO) Green Bank Telescope. The fact that SETI was involved probably also helped fan the flames of “alien signal” theories. However, initial analysis of the signal and the portion of the sky where it was observed have suggested a far more mundane explanation:  geostationary satellites.

“The best explanation is that the signals are transmissions from one or more geostationary satellites,”  Mendez stated in an announcement issued on July 21st. “This explains why the signals were within the satellite’s frequencies and only appeared and persisted in Ross 128; the star is close to the celestial equator, where many geostationary satellites are placed.”

While certain this explanation is correct, Mendez does note it doesn’t account for the strong dispersion-like features of the signals (diagonal lines in the figure). His theory for this is that it is possible multiple reflections caused the distortions, but the astronomers will need more time to evaluate this idea and other possibilities.

So sorry, no ETs calling out into the night – yet.