Space Sunday: of rockets, moons, carbon and telescopes

Blue Origin, the private space company founded by Amazon billionaire Jeff Bezos has become the first company to successfully launch a rocket into space – and return all elements of the vehicle to Earth for re-use.

The flight, carried out in West Texas, took place on Monday, November 23rd. It comprised the company’s New Shephard capsule, being flown in an uncrewed mode, and a single stage, recoverable booster is powered by an engine also developed by the company.

Unlike SpaceX, Orbital Sciences, Boeing and Sierra Nevada Space corporation, all of whom are directly pursuing rocket and space vehicle designs capable of orbital flight, Blue Origin is taking a more incremental approach, with efforts focused on the sub-orbital market “space tourism” market. The company is looking to build a cost-effective launch system capable of lifting small groups of paying passengers into space on ballistic “hops” which allow them to experience around 4-5 minutes of zero gravity before returning them to Earth.

The November 23rd flight saw the uncrewed New Shephard vehicle hoisted aloft by the booster system which reached a speed of Mach 3.72, sufficient for it to impart enough velocity to the capsule so that it could, following separation, continue upwards to an altitude of 100.5 kilometres (329,839 feet), before starting its descent back to the ground and parachuting to a safe landing.

Following capsule separation, however, the booster rocket Also made a control descent back to Earth, rather than being discarded and lost. The design of the booster – which Blue Origin call the “propulsion module” to differentiate to from a “simple” rocket – means it is semi-capable of aerodynamic free-fall, and won’t simply topple over and start tumbling back to Earth. At 6.5 kilometres (4 miles) above the ground, a set of eight drag brakes are deployed to slow the vehicle, with fins along the outside of the module allowing it to be steered. At 1.5 kilometres (just under 1 mile) above the landing pad, the unit’s motor reignites, further slowing it to a safe landing speed and allowing it to precisely manoeuvre itself onto the landing pad.

Highlights of the actual test flight, mixed with computer-generated scenes of the New Shephard capsule carrying a group of tourists on their sub-orbital hop was released by Blue Origin on November 25th.

One of the first to congratulate Blue Origin on their flight was Elon Musk, the man behind SpaceX, which is also pursuing the goal of building a reusable rocket system, but had yet to achieve a successful recovery of the first stage of their Falcon 9 booster. However, as Musk pointed out, there are significant differences and challenges involved in bringing a sub-orbital launch back to Earth and a booster  which has to reach far higher velocities in order to lob a payload into orbit, as SpaceX is already doing.

Not that Blue Origin doesn’t have orbital aspirations; both the “propulsion module” and New Shephard are designed to be integrated into a larger launch vehicle capable of placing the capsule into orbit.  The November 23rd flight itself marks the second attempt to launch and recover both New Shepard and the propulsion module; in April 2015, the first attempt succeeded in recovering the capsule, but a failure in the drag brake hydraulic system on the propulsion module resulted in its loss.

Martian Moon Starting Slow Breakup?

Mars has two natural moons, Deimos and Phobos. Neither are particularly large; Deimos is only 15 × 12.2 × 11 km in size, and orbits Mars once every 30 hours;  Phobos measures just 27 × 22 × 18 km, and orbits the planet once every 7 hours and 39 minutes. Both exhibit interesting properties, in that Deimos is slowly moving away from Mars, and may even break from Mars’ influence in a few hundred million years.

Phobos, however is doing the reverse; it is gradually closing in on Mars at a rate of about 2 metres (6.6 ft) every 100 years. This means that over time, it is being exposed to greater and greater gravitational forces as it approaches its Roche limit.

It had been thought that Phobos would eventually collide with Mars, but such is the minimal amount of tidal torquing it is able to exert on Mars, it seems more likely that as Phobos enters into its Roche Limit, it will simply break up and possibly form a small ring around the planet. In fact, the process may have already begun.

That’s the conclusion drawn from a study of numerous grooves found in the surface of Phobos, which was published in November 2015.

For a long time, these groves were thought to be the result of shock waves cracking the surface of Phobos following a collision with another rocky object which created Stickney, a massive impact crater 10 km across located at one “end” of Phobos.

However, the new study shows that the grooves are mostly symmetric to the point on Phobos directly facing toward Mars, strongly suggesting that the Martian gravity is slowly but inexorably “stretching” Phobos and that the grooves are the stress pattern resulting from this process, and that the little moon is slowly starting to break apart.

The complete break-up isn’t going to happen any time soon, however. The study suggests optimal time period of Phobos to break apart will be some time between 20 and 40 million years from now – and might not occur for another 50 or 60 million years. When the break-up does happen, however, it is liable to occur in just a matter of weeks, and will result in the formation of a ring of debris around Mars which could last for up to 100 million years.

This is because that, far from being solid underneath its outer crust, Phobos is thought to be made from coalesced lumps of rock, dust and other debris. The evidence for this comes from Stickney crater itself, which covers around one-sixth of Phobos’ surface. Such is the force required to form a crater of this size, it is believed that if Phobos has a solid interior, it would have been completely shattered by the impact. That it didn’t suggests the moon’s interior must be fragmented, allowing it to absorb the huge force of the collision without being smashed apart.

Thus, as Phobos is pulled apart by gravitational forces, it is thought that the smaller, lighter material of the moon’s surface crust and looser, lighter materials from its interior will accrete around Mars, forming the ring, while the larger heavier elements will, over a slightly longer period, be pulled down into the planet’s atmosphere, where they’ll either burn up, or “strafe” the equatorial regions in a series of meteor strikes.

Where Has All the Carbon Gone, Long Time Passing?

The atmosphere of Mars has been making all the news lately, As I recently reported, NASA’s MAVEN space vehicle has been able to confirm how the solar wind is stripping away millions of tonnes of tonnes of gases from Mars’ upper atmosphere every day. Over the aeons,  this has contributed to the overall thinning of the Martian atmosphere, reducing it from being able to support a warm, wet environment on the planet’s surface to the cold, frigid desert we see today.

However, in order for the conversion to be possible, even over millions of years, it has long been thought that other processes must be at work on Mars. Most notably, in order for it to have been warm, wet and dense enough Mars’ atmosphere must have once have been rich in carbon dioxide, and it had been thought that solar stripping would never be sufficient to carry all that carbon dioxide away. Instead, it had been theorised that much of the carbon dioxide might have been absorbed into Martian surface material and rocks, where it would form carbonates.

The problem with this theory is that despite extensive surveying from orbit using spectral analysis and investigations be rovers and landers on the surface, the volume of carbonates found in Martian rocks and samples is nowhere near enough to account for this being the case. So the puzzle has remained: where did all the carbon go?

Now a new model has been put forward which not only explains why there are significantly less carbonates in the Martian rocks than expected, it also explains precisely what happened to the carbon, why the carbon remaining in the atmosphere is in the ratios we see today and, as if that weren’t enough, a measure of just how dense Mars’ ancient atmosphere might have been around 3.8 billion years ago.

In the new model, carbon dioxide (CO2) was generated deep inside the planet in the ancient past, and released directly by volcanism into atmosphere, increasing density and pressure. Once there, it could exchange with the polar caps, passing from gas to ice and back to gas again, and also dissolve into surface waters, which in turn gradually percolated down into the Martian subsurface as the atmosphere thinned, leaving behind carbonate deposits.

But rather than being massively deposited in this way as the atmosphere started to thin due to the solar wind, the CO2 itself became a factor in atmospheric loss through a process called ultraviolet photodissociation.

essentially, carbon dioxide high in the Martian atmosphere would be struck by the Sun’s ultraviolet light (hv in the diagram) and undergo a series of chemical changes, resulting in the formation of carbon-12 (12C in the diagram), and carbon-13 (13C). Carbon 12 is light enough to easily be lost to space, and while heavier, carbon-13 can also be lost to space, but in smaller amounts.

What’s interesting here is that the model predicted that this fractionation, as it is called, would over a period of around 3.8 billion years, give rise to precisely the ratios of carbon-12 to carbon-13 seen in the Martian atmosphere today.Thus, it would seem that most of the ancient carbon dioxide in Mars’ atmosphere was actually lost to space, the result of both the fractionation process and the influence of the Martian wind. Hence why significant deposits of carbonates have never been found under the planet’s surface. What’s more the model shows that back at the time Mars started losing its atmosphere, it very probably had an atmospheric density roughly equal to that of present day Earth.

James Webb Gets first Mirror

We’re all familiar with the Hubble Space Telescope (HST), which earlier this year celebrated 25 years of operations in Earth’s orbit. In 2018, the HST is due to be superseded by the James Webb Space Telescope (JWST),  a joint Canadian – European – American undertaking named after the second NASA Administrator of the Apollo era.

The JWST is intended to replace both Hubble and the Spitzer Space Telescope to provide unprecedented resolution and sensitivity from long-wavelength visible to the mid-infrared. It is also a telescope that has faced may issues and problems, including dramatic cost overruns, actual cancellation by the US Congress in 2011, despite both Europe and Canada footing a considerable portion of the bill, only to be re-instated when it dawned on Congress that the core expenditure meant that by that time 75% of the telescope was already in production.

The result of a gestation, development and design period of 17 years, JWST is completely unlike Hubble Not only is it much larger – the primary, segmented mirror is 6.5 metres across (compared to Hubble’s 2.4 metre diameter mirror) – it is also designed not to operate in Earth orbit, but at the Sun-Earth L2 Lagrange point.

Lagrange points, L-points, or libration points) are celestial positions in an orbital configuration of two large bodies where the combined gravitational attraction of the two bodies provides precisely the centripetal force required to orbit with them – so an object places at a Lagrange point can remain stable relative to the two large bodies. In all, there are 5 Lagrange points.  The first three are on the line connecting the two large bodies and the last two, L4 and L5, each form an equilateral triangle with the two large bodies.

The Sun-Earth L2 position means that the JWST will be places some 1,500,000 kilometres (930,000 mi) beyond the Earth, which it will orbit the Sun in synchrony with the Earth, and only require a single shield to block both heat and light from the Sun and Earth.

Also unlike the HST, the primary mirror on the JWST isn’t a single reflective surface. As noted above, it is segmented, and will eventually comprise 18 individual hexagonal sections which will work together to provide a light collecting area 5 times greater than that of Hubble. During the third week of November 2015, the first of these mirror segments were installed onto the JWST’s mirror backplane assembly. Complete installation of all 18 mirror segments is expected to be completed by April 2016, after which the telescope’s science package will be integrated into the assembly. If all goes according to plan, the JWST should be launched via a European Ariane 5 rocket from the  Guiana Space Centre in Kourou, French Guiana, in October 2018.

Once launched, JWST is expected to operate for at least 5 years, and hopefully up to a decade. However, as it is not equipped to be serviced by visiting astronauts, it is unlikely to enjoy a similar length of operations to that of Hubble.