Space Sunday: rockets and rovers

SpaceX is planning the maiden flight of its Falcon Heavy booster to take place in January 2018 – with an unusual payload. Credit: SpaceX

Elon Musk has announced the first payload that will be flown aboard the SpaceX Falcon Heavy, together with an ambitious goal in mind.

The maiden flight of the new heavy lift launcher had been expected to take place in December, as a part of an ambitious end-of-year five launch schedule. However, in tweets on Friday December 1st, 2017, Musk indicated the Falcon Heavy flight will now take place in January 2018. When it does, and if all goes according to plan, be sending Musk’s own car on its way to Mars – and possibly beyond.

Announcing the push-back on the Falcon Heavy launch

A car might sound a weird payload, but it is entirely in keeping with SpaceX’s tradition; the first Dragon capsule test flight in 2010 carried a giant wheel of cheese into space.

The first tweet on the launch also underlines Musk’s own uncertainty about its potential success; he has previously stated that he expects the first flight of the Falcon Heavy may end in a loss of the entire vehicle, simply because of the complexities of the system.

And the announcement about the payload and its (initial?) destination.

Comprising three Falcon 9 first stages strapped together side-by-side and firing 27 main engine simultaneously at launch means the vehicle will be generating a tremendous amount of thrust requiring all three stages to work smoothly together. They’ll also be generating a lot of vibration during the rocket’s ascent through the denser part of the Earth’s atmosphere. Only so much of this can be simulated and modelled; a maiden flight is the only way to find out where the remaining issues might lie.

However, if the launch is successful, it will be spectacular, involving the recovery of all three Falcon 9 stages to safe landings back on Earth. It will also boost Musk’s car towards Mars – which raises a question. Does SpaceX aim to orbit the car around Mars, or will the mission simply be a fly-by?

Elon Musk and his Tesla Roadser. Credit: Tesla.

Any attempt to achieve Mars orbit would require some kind of propulsion system to perform an orbital insertion burn, something which adds complexity to the mission. However, given Musk’s ambitions with Mars, placing even such an unusual payload into Mars orbit could yield valuable data for SpaceX. The car weighs 1.3 tonnes, so the total mass launched to Mars – car (likely modified somewhat, although the stereo will – according to Musk – be playing David Bowie’s Space Oddity during the ascent) payload bus, propulsion system, fuel, some kind of science system (why orbit Mars only to pass up the opportunity to gather data?) – could amount to around double that, if not more.

Musk’s comment about the payload being in “deep space for a billion years” seems to suggest the mission might by a fly-by, sending the car onwards and out across the solar system and beyond. Again, with a science payload sharing the space with the car, this could generate useful data. Either way the launch of such an unusual payload is likely to require additional US Federal Aviation Authority (FAA) approval; it will certainly require a launch license – which the FAA has yet to grant.

NASA Turns to Lunar Rover to Help With Next Mars Rover Mission

I’ve followed the Mars Science Laboratory (MSL) mission, more generally referred to as the Curiosity rover mission since 2012, tracking the discoveries made and the ups and downs of the mission. Overall, the rover has carried out some remarkable science and made a range of significant discoveries concerning ancient conditions within Gale Crater on Mars and the overall potential for the planet to have been able to potentially support microbial life at some point in its history.

But there have been hiccups along the way – computer glitches, issues with some of the rover’s hardware, and so on. These included was the 2013 discovery that Curiosity’s wheels were starting to show clear signs of wear and tear less than a year into the mission. The discovery was made during a routine examination of the rover’s general condition, carried out remotely using the imaging system mounted on Curiosity’s robot arm.

This image taken on April 18th, 2016 (Sol 1,315) by the Mars Hand Lens Imager (MAHLI) camera on the rover’s robot arm revels areas of damage on Curiosity’s centre left wheel, the result of periodically traversing very rough terrain since the rover arrived on Mars in 2012. Credit: NASA/JPL

The images captured of the rovers six aluminium wheels, each some 50 cm (20 inches) in diameter, revealed tears and a number of jagged punctures in one of them (above), the result of passage over the unforgiving, uneven and rock-strewn surface of Mars. While damage was not – and has not – become severe enough to threaten Curiosity’s ability to drive, at the time they were found, it did cause mission planners to revise part of the rover’s mission as it drove along the base of “Mount Sharp” near the centre of the crater, in order to avoid traversing a region shown from orbit to be particularly rugged. Since then, care has been taken to avoid exposing the rover to particularly rough areas of terrain.

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Space Sunday: exoplanets and launch systems

An artist’s impression of Ross 128. Credit: ESO / M. Kornmesser

The European Southern Observatory (ESO), responsible for finding a planet orbiting the Sun’s nearest stellar neighbour, Proxima Centauri (see here for more), has now discovered another exoplanet orbiting a nearby star.

The star in question is Ross 128, a red dwarf located in the constellation of Virgo. As I’ve previously noted, red dwarf stars tend to be extremely violent in nature. Their internal action is entirely convective, making them unstable and subject to powerful solar flares, generating high levels of radiation in the ultraviolet and infra-red wavelengths which can leave planets like the one orbiting Proxima Centauri or those orbiting TRAPPIST-1 unlikely to support life.

However, Ross 128 is different. It is a “quiet” red dwarf; it experiences less in the way of flare activity, meaning any planets orbiting it will be exposed to less radiation and stellar wind. In particular, the planet discovered by ESO could potentially be habitable.

The planet, designated Ross 128 b, was discovered using the ESO’s High Accuracy Radial velocity Planet Searcher (HARPS), located at the La Silla Observatory in Chile. HARPS uses measurements of a star’s Doppler shift in order to determine if it moving back and forth, a sign that it has a system of planets. The data gathered by the instrument allowed astronomers to confirm Ross 128 b is a rocky world, with roughly 35% more mass than Earth, orbiting Ross 128 at a distance of about 0.05 AU, and with a period of 9.9 Earth days.

Measurements of Ross 128’s likely radiative output, combined with the planet’s distance from the star put it on or near the star’s habitable zone – the region around a star where a solid body planet might have both an atmosphere and liquid water on the surface. It receives around 38% more light from its star than Earth does from the Sun. This has allowed the team making the discovery to estimate that Ross 128 b’s equilibrium temperature is likely somewhere between -60 °C and 20 °C – close to what we experience here on Earth, making it a temperate planet.

That Ross 128 is a “quiet” older red dwarf, less prone to violent outbursts, means Ross 128 b may well have retained any atmosphere which may have formed around it. Whether or not Ross 128 b has an atmosphere has yet to be determined; if it does, given the planet is likely to be tidally locked, with the same same side always facing towards its star, any atmosphere the planet may have could be subject to extreme weather.

Even so, given what is currently known about Ross 128 b, were it to have an atmosphere and liquid water on the surface, it would be the closest potentially habitable exoplanet to Earth so far discovered. This alone means Ross 128 b is liable to be the subject of a lot of additional study over the coming months.

Nor is this the first time Ross 128 has been in the news this year. In July 2017, Abel Méndez, an astrobiologist at the Arecibo Radio Telescope, reported that on May 12th, 2017, during a 10-ten observation of Ross 128, the telescope received a 10-minute wide-band radio signal “almost periodic” in natures, and which decreased in frequency.

While some were quick to link this event with the November discovery of Ross 128 b, it’s worth pointing out that Arecibo, the Green Bank Telescope in West Virginia and the Allen Telescope Array (ATA) in northern California, have all spent time listening to Ross 128 without any of them hearing any repeat of the signal. Currently the most widely accepted explanation for the May 2017 signal is radio frequency interference from a satellite orbiting the Earth.

A Lava World with an Atmosphere?

And staying with exoplanets, 55 Cancri e, also named Janssen, has also been in the news this week.

One of the few exoplanets discovered prior to the Kepler mission, it is one of five planets orbiting 55 Cancri A, the G-class main sequence star which forms one half of the binary star system 55 Cancri, some 41 light years away from the Sun, in the constellation of Cancer. At 7.8 Earth masses, and with a diameter almost 50% that of Neptune, it has the distinction of being the first “super-Earth” discovered in orbit around a main sequence star similar to the Sun.

An artist’s impression of super-Earth exoplanet 55 Cancri e and its parent star. Credit: NASA/JPL

Discovered in August 20o4, the planet has been subject of extensive study. As the closest planet to its parent, it takes 2.8 days Earth days to complete one orbit, and is tidally locked, always keeping the same side facing its parent. A study of the planet using the Spitzer space telescope in 2013 led astronomers to the conclusion 55 Cencri e is likely carbon planet, dominated by lava flows on its sunward side. In 2016, observations using the Hubble Space Telescope indicated the planet may have a thin hydrogen and helium atmosphere with suggestions of hydrogen cyanide.

However, an international team led by Cambridge University in the UK, has been re-examining the data gathered by the Spitzer space telescope. Using an improved model of how energy would flow throughout the planet and radiate back into space, their findings indicate that temperatures on the “dark” side of the planet average 1,300 to 1,400 oC (2,400 to 2,600 oF), much closer to to the average 2,300 oC (4,200 oF) on the sunward side than previously thought.

These finding suggest 55 Cancri e has a far denser, more complex atmosphere than had been thought, one which acts as transfer mechanism for circulating heat around the planet. What’s more, this atmosphere may well contain nitrogen, water vapour and even oxygen—molecules found in our atmosphere, too—but with much higher temperatures throughout.

The overall conditions on the surface of the planet preclude free-flowing water or the opportunity for life to arise, but they also present a further mystery. Given its proximity to its parent star, in theory 33 Cancri 2e’s atmosphere should have been stripped away aeons ago by the solar wind. so there are still mysteries with the planet yet to be resolved.

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Space Sunday: SLS, Falcon and Dream Chaser

Orion’s first deep space mission, EM-1 will be an extended uncrewed flight to cislunar space, officially targeted for June 2020, but which may still make a December 2019 lift-off. Credit: NASA

NASA has provided an update on the first integrated launch of the Space Launch System (SLS) rocket and Orion spacecraft.

Planned as an uncrewed mission, Exploration Mission-1 (EM-1), planned as a flight to cislunar space and back, is a critical test on the road to NASA’s human deep space exploration goals, designed to verify the SLS / Orion’s capabilities in handling missions between Earth and the Moon.

The update comes after the completion of reviews of both the Space Launch System and the Orion vehicle systems – the latter of which took place on both sides of the Atlantic, given the Orion’s Service Module, which is providing the vehicle with power and propulsion, is being built by the European Space Agency. NASA initiated the reviews as a result of early studies, which raised concerns over meeting a December 2019 launch date as ambitious, leading to the agency pushing it the launch back to June 2020.

EM-1 will utilise the “Block-1” Space Launch System booster, with a 70-tonne payload capability. Credit: NASA

As a part of the update, NASA points to June 2020 still being the planned launch date, but indicates it is also working to keeping the December 2019 launch a possibility, providing no significant setbacks or issues arise, as several of the risks indicated in the earlier report have not been realised. However, even if EM-1 still achieves the 2019 launch date, the follow-up EM-2 mission, which will carry a crew into space, will still take place in 2023, rather than 2021 as originally planned, to allow additional time for the development of the SLS Block 1B launch vehicle which will be used in that mission.

As part of the recent reviews, and in order to help meet the December 2019 launch opportunity, the update indicates that a flight test of the  Orion’s launch abort system, critical to SLS operations, and must occur prior to EM-1, have been brought forward to April 2019. Known as Ascent-Abort 2, it will validate the launch abort system’s ability to land the crew safely during descent, and also help ensure that the agency can remain on track for the EM-2 crewed flight in 2023.

To build the SLS and Orion, NASA is relying on several new and advanced manufacturing techniques, including 3D printing, which is being used to fashion more than 100 parts for the Orion capsule.  In Germany, integration of the first Service Module is progressing. Recently, the 24 orientation thrusters were installed, complementing the eight larger engines that will back up the main engine, and more than 11 km of cables are being laid and connected to send the megabytes of information from the solar panels, fuel systems, engines, and air and water supplies to the module’s central computers.

With the SLS booster, welding has been completed on all the major structures for the mission and is on track to assemble them to form the largest rocket stage ever built and complete the EM-1 “green run,” an engine test that will fire up the core stage with all four RS-25 engines at the same time.

EM-1 will see a crew-capable space craft travel further from Earth than at any point in time since the dawn of the space age. Following launch, the vehicle will commence a 4-day flight to cislunar space, where it will remain in extended orbit around the Moon, before making a 4-day return to Earth.

SpaceX Looks to Falcon Heavy Launch and Operational Return of Pad 40

With NASA still looking at a potential of December 2019 for the maiden launch of the Space Launch System rocket, SpaceX is preparing for a December 2017 maiden flight of their new launch system, the Falcon Heavy. Originally scheduled for November 2017, the launch is now pencilled for December 29th, 2017 and will be one of five launches SpaceX plan to round-out the year.

SpaceX Falcon Heavy, slated for a December 29th maiden flight. Credit: SpaceX

The Falcon Heavy, when operational, will be capable of hoisting a maximum payload of 63.5 to low Earth orbit, although the more usual LEO payload limit will be around 55 tonnes. It will also be capable of lobbing 14 tonnes to the Moon, 10 tonnes to Mars and even 3.5 tonnes to the outer solar system.

The maiden flight, however, will carry little more than a dummy payload, but it will hopefully include the recovery of the three Falcon 9 rockets which make up the core of the Falcon Heavy.

Two of these rockets form “strap on boosters” for the Falcon Heavy, and are jettisoned first. If all goes according to plan, these will perform automated “boost back” manoeuvres and fly themselves to safe landings.. The central booster will continue until its fuel is almost expended, then separate from the upper stage, perform its own boost back manoeuvre and return to Earth.

Eventually, SpaceX plan to make Falcon 9 and Falcon Heavy fully reusable with the addition of a “fly back” upper stage as well.

Also in December, SpaceX plan to re-active their launch facilities at Launch complex 40 at Canaveral Air Force Station alongside Kennedy Space Centre, Florida. This has been out of commission sine September 1st, 2016, when a Falcon 9 booster exploded on the pad during a pre-launch test, completely destroying itself, its payload and severely damaging the pad.

Since that time, SpaceX’s east coast operations have been confined to launch complex 39A at Kennedy Space Centre, which will be used for all Falcon Heavy launches and – eventually – for the launch of the SpaceX Interplanetary Transport System.

Despite Canaveral Pad 40 being out of service, SpaceX has achieved its highest cadence of launches to date in 2017, and hopes to be able to commit to an even higher rate of launches in 2018 using both pad 40 and pad 39A.

The first scheduled flight from the repaired pad 40 should be a commercial cargo resupply services mission to the International Space Station (ISS), and subject to NASA approval, might utilise a previously flown Falcon 9 first stage.

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Space Sunday: when neutron stars collide

When neutron stars collide: an artist’s impression of the point when two neutron stars collided in the galaxy NGC 4993, 130 million years ago, and which are now increasing our understanding of neutron stars and the universe. Credit: SF/LIGO/Sonoma State University/A. Simonnet

Around the world on August 17th, 2017, some 70 telescopes and observatories – including the Laser Interferometer Gravitational-Wave Observatory (LIGO), responsible for confirming the existence of gravitational waves (see here and here for more) – quietly turned their attention on the same spot in the constellation Hydra.

“I don’t think it’s out of the question that this is the most observed astronomical event ever. It’s a thrilling notion, and a little overwhelming,” said LIGO spokesperson David Shoemaker. “We’ve got somewhere between a quarter and a third of all the world’s astronomers working with us.”

The reason? Hours earlier, an observatory in Chile had detected gravitational waves followed by a burst of gamma radiation – potentially the signature of two neutron stars colliding far beyond our galaxy. If so, the detection would be the first time gravitational waves have been observed originating from something other than the merger of two black holes. Hence, an alert was issued to observatories around the globe, resulting in the massed focusing on instruments on that single point in space.

Over the coming days, the data revealed that a collision between two neutron stars in what is referred two as a “kilonova”  – which sits between a star going nova and a super-massive star going supernova.  It marks the first confirmation that neutron star mergers can cause gamma ray bursts. However, there is much more to the event.

Neutron stars are the dense remnants of massive stars that long ago exploded as supernovae. The two stars in question are located in galaxy NGC 4993, 130 million light years from Earth. Originally, these stars were each around 10-20 times the mass of our sun; after each went supernova, they collapsed down to bodies around 16 km (10 mi) in diameter, comprised entirely of neutrons so densely packed, that despite their small size, each still had a mass perhaps twice that of our own Sun.

These two neutron stars, located close together, were gradually drawn together over the course of perhaps 11 billion years by their mutual gravities until they collided, venting huge amounts of energy across the spectrum and space-time in what astronomers call a “multi-messenger event”. It was the arrival of the light waves and gravitational waves here on Earth, 130 million years later, that astronomers from around the world were keen to observe, marking the first time a cosmological event of this nature has been observed in both gravitational waves and light, producing a huge amount of data for researchers to study.

How the kilonova was initially observed through the initial days of visible light observation following the first indication of the collision through to the falling off of light from the initial explosive outburst of energy. Credit: Sarah Wilkinson / LCO.

Thanks to the alert sent out by the Chilean observatory, over 3,500 astronomers and more than 100 instruments  – including LIGO and a the Hubble Space Telescope responded, making the event the first to be observed through the detection of visible light and gravitational waves. Their findings are now being made public, and include some remarkable facts.

These include the first confirmation that neutron star mergers can cause gamma ray bursts – although there is some questions over what this might in fact mean. It also marks the first measurement of the universe’s expansion using gravitational waves.In addition, as the collision was recorded in wavelengths right across the electromagnetic spectrum, from radio to gamma rays, it is the first time a cosmological event of this nature has been observed in both gravitational waves and light. A further result of the observations is that astronomers have witnessed heavy elements being formed from the aftermath of the event.

“People have long suspected that heavy elements were made in neutron star mergers, but this is really the first time we’ve nailed that down,” Andrew Levan, an astronomer at the University of Warwick in the UK. “This merger made something like the mass of the Earth in gold, along with other heavy elements such as platinum, lead and uranium.”

The kilonova as seen from the Hubble Space Telescope a few days after the explosion, tracking it as the initial light faded. Credit: NASA and ESA. Acknowledgement: A.J. Levan (U. Warwick), N.R. Tanvir (U. Leicester), and A. Fruchter and O. Fox (STScI)

It was actually the discovery that heavy elements were being formed in the material resulting from the collision which confirmed the event was an actual collision of two neutron stars. The elements would only be formed if neutrons were being ejected from the two stars to collide with lighter atoms in the surrounding space. Material would only be ejected if the objects in collision each had a surface, something black holes don’t have – they only have an event horizon.

This in turn indicated the event was far closer that the previous five detections of gravitational waves which have occurred since 2015. These have been the result of pairs of black holes merging, none of which have been closer than 1.3 billion light years away. That the gravitational waves were observed alongside of light waves also gave further confirmation of another of Einstein’s general relativity predictions: that light and gravitational waves travel and more-or-less the same speed.

Observations and data gathering continued after the initial explosion was detected, although the light from the collision faded over the 6-8 days following the event, and astronomers are keen to discover what has been left behind. Currently, the region of NGC 4993 where the kilonova occurred is obscured behind a cloud of matter and heavy elements, leading to questions on whether or not the two stars may have merged to form an even larger neutron star, or whether they collapsed into a black hole. Some of those studying the data gathered believe the gamma ray burst recorded after the initial detection of gravitational waves might be indicative of the latter, the result of matter left over from the event and collapse being drawn into the event horizon.

Summing up the significance of the event, astronomer Tony Piro from the Harvard–Smithsonian Centre for Astrophysics said, “The ability to study the same event with both gravitational waves and light is a real revolution in astronomy. We can now study the universe with completely different probes, which teaches things we could never know with only one or the other.”

Continue reading “Space Sunday: when neutron stars collide”