Space Sunday: rockets, exoplanets and alien oceans

rion AA2, July 2nd 2019The Orion test article lifts-off from Space Launch Complex 46 at Cape Canaveral Air Force Station at the start of Ascent Abort-2, July 2nd 2019. Credit: NASA

NASA’s Orion Multi-Purpose Crew Vehicle passed a significant test on its way to its first crewed launch (due in 2022) on July 2nd, 2019, as it completed a flight test of the capsule’s launch abort system (LAS).

The LAS is a system designed to pull a crewed capsule clear of a malfunctioning rocket during an ascent to orbit, hopefully saving their lives in the process. As such, it is a significant system that must be tested and cleared for use before crewed flights can commence with a new launch vehicle.

For the Space Launch System (SLS), NASA is following its traditional approach, with the LAS designed to “pull” a crew capsule clear of launch vehicle. It does this by placing a special fairing over the capsule that has a tower extending from its top, fitted with three motors. This has always been the traditional approach to US LAS systems – by contrast, Russian LAS systems generally sit below the capsule and are design to “push” it away from a malfunctioning rocket.

The Orion / SLS launch abort system (LAS). Credit: NASA

The July 2nd test – called the Ascent Abort-2 (AA-2) mission – was a critical test flight, designed to test the LAS at the point in an ascent to orbit when the Orion / SLS combination will be subjected to the highest aerodynamic stresses – the so-called period of “Max-Q” – that occurs during a rapid ascent into space.

To achieve this, NASA mounted an Orion structural test article – basically an Orion capsule sans its flight systems – contained within a LAS fairing onto the motor stage of an MX Peacekeeper ICBM, and launched it into the Florida skies in a early morning ascent designed to last some 55 seconds.

In that time, the rocket was expected to reach an altitude of 9.5 kilometres (31,000 ft) and a speed of Mach 1.3, at which point the abort sequence would trigger.

As it turned out, the MX rocket motor ran “hot”, accelerating a little faster than anticipated, so reaching its assigned separation altitude 5 seconds early. Nevertheless, the abort sequence initiated correctly, and the powerful abort motors on the LAS fired, generating 181,400 kg of thrust, hauling the Orion free of the ascent motor unit.

Once a clear separation from the still ascending motor stage had been achieved, the attitude control motors at the very top of the LAS fired, flipping it and Orion over. The middle jettison motor then fired, separating the LAS from the Orion.

During an actual abort sequence, the Orion would then re-orient itself so it would be falling heat shield first, allowing its parachutes to be deployed in preparation for a splashdown. However, for the AA-2 flight, the test article did not carry a parachute system. Instead, and like the LAS, the capsule was allowed to fall back into the Atlantic, hitting it at an estimated 480 km/h (300 mph) and breaking up. Just before it did so, however, it ejected 12 bright orange data recorders not unlike those so-called “black boxes” used by aircraft. These contained critical data recorded during the 3 minute 11 second flight, and which will be assessed post-mission to confirm everything did go an planned.

That was a spectacular test we all witnessed this morning. It was really special for the programme; a really big step forward to us. It was a really great day all around – weather and the vehicle. One of the most important parts of the test was to see how the attitude control motor performed. The internal motor pressure was rock solid, straight line and it had excellent control characteristics. Everything we’ve seen so far looks great.

– Mark Kirasich, NASA’s Orion Programme Manager

Orion AA2, July 2nd 2019The Orion test article climbs into the early morning sky over Cape Canaveral Air Force Station at the start of Ascent Abort-2, July 2nd 2019. Credit: NASA

The US has never has to use the LAS on an actual mission. However, there is no guarantee this will always be the case, and circumstances where a LAS must be used are not unkown – as the Soyuz M-10 mission in October 2018 demonstrated (see Space Sunday: of Soyuz aborts and telescopes). Therefore, passing this test was critical if  Orion and SLS are to achieve the flight goals required for NASA’s programme – Project Artemis – to return humans to the surface of the Moon.

Half-Planet, Half-Star

Discovered in 2012, GJ3470b is a “mini-Neptune” planet orbiting a red dwarf star called Gliese 3470, 100 light years from our Sun. Occupying an orbit some 6 million km (3.7 million mi – roughly one-tenth of the distance between the Sun and Mercury) from its parent, the planet has a mass of around 12.6 Earths.

None of this is particularly unusual; as I’ve noted in past Space Sunday articles, M-type stars are the most common type of star in the galaxy, and mini-Neptune type planets account for around 80% of the exoplanets discovered to date. Nevertheless, recent studies have revealed GJ3470b to be a very unique world.

GJ3470b, its atmospheric composition, and its relative location to its parent star. Credit: NASA, ESA, and L. Hustak (STScI)

The presence of an atmosphere around the planet was detected fairly soon after its discovery and prompted astronomers to take a prolonged look at it. To do this, they combined the Hubble and Spitzer space telescopes to examine the planet’s atmosphere for a total of 20 transits in front of its parent star.

These observations, using the light of the star passing through the planet’s atmosphere during the transits, allowed the astronomers to gather data on the composition of GJ3470b’s atmosphere. What was discovered came as a huge surprise.

It has been expected that the observations would reveal an atmosphere somewhat similar to Neptune’s, but such was the depth to which they could measure, it quickly became clear that GJ3470b has an almost pristine atmosphere of hydrogen and helium surrounding a large solid core.

The presence of hydrogen and helium may not sound too unusual – after all, the four gas giants of our solar system have atmospheres largely made up of those two gases. However, they also have amounts of other, heavier elements – methane, nitrogen, oxygen, ammonia, acetylene, ethane, propane, phosphine, etc., – none of which showed up in any of the spectral analyses performed by Hubble and Spitzer. This makes GJ3470b’s  atmosphere closer in nature to that of the Sun or a star than it does to a planet, leading to it being dubbed “half-planet / half-star” in some quarters, and making it the most unique exoplanet yet discovered.

Unlike our our solar system, which has its giant giants sitting far from the Sun, many exosystems have their gas giants relatively close to their parent star. As this has generally been considered a region where such planes couldn’t form (as the star would be sucking up all the matter needed for them, it had been assumed such gas giants had formed at a greater distance from their parent, and then gradually migrated closer over the millennia.

However, Gliese 3470 is a comparatively young star – a mere two billion years old (less than half as old as the Sun). This is thought to be far too short a time for GJ3470b to have formed further away from its parent and then gradually spiralled inwards to its current orbit. Plus, if it had formed further out from its star, then by rights its atmosphere would contain detectable traces of the other elements mentioned above.

So, the theory is, GJ3470b managed to form out of the same cloud of primordial material that gave birth to its parent star, and at the same time. Only the star was able to gain mass and gravity faster, compressing its core to the point where fusion commenced and it ignited. At that moment, the disk of gas around the star and planet was pushed outwards, denying the planet the opportunity of further growth and leaving it very similar to how we see it today, further increasing its uniqueness among the exoplanets we’ve so far discovered.

Caught on Camera: the X-37B

I’ve written on numerous occasions about the US Air Force’s super-secret X-37B “mini shuttle”, and it’s back in the news again in a rather novel way.

Infographic on the US Air Force X-37B (courtesy of space.com)

Originally developed as a project between NASA and Boeing Aerospace, the Orbital Test Vehicle (OTV), as it is more formally known, was transferred to the US Department of Defence in 2004.

An uncrewed vehicle, it is launched atop either an Atlas V or SpaceX Falcon 9. Two have been known to have been built so far, undertaking five separate missions, the last of which is still in progress, having lifted-off in September 2017, while a sixth is due to launch in December.

These missions have been largely carried out under a veil of secrecy, with few details being released to the public. This had led to a lot of speculation about the X-37B’s real purpose, with theories ranging from it being some form of specialised spy vehicle to it being a space weapons platform even to the idea of it being a “space bomber”, able to swoop down into the atmosphere to bomb targets on Earth.

None are likely to be true – the X37-B really is, as the US DoD states, a vehicle for testing reusable space technologies, but the theories have encouraged a lot of amateur satellite trackers to take a particular interest in trying to find as it orbits the Earth.

One such individual in Dutchman Ralf Vandebergh. He actually caught sight of the X-37B in early June and used that sighting to calculate when he would be best placed to capture it on film – only to have the spaceplane fool him.

When I tried to observe it again [in] mid-June, it didn’t meet the predicted time and path. It turned out to have manoeuvred to another orbit.

– Ralf Vandebergh on photographing the X37-B

Fortunately for Ralf, his calculations were enough for get other people in his group of satellite trackers involved, and together they were able to relocated the X-37B, allowed Ralf to photograph it as it passed almost directly overhead on June 30th and July 2nd.

The X37-B as photographed through a 10-inch telescope by Ralf Vandeburgh. Credit: R. Vendeburgh

Admittedly, captured through a modest 10-in telescope, the images aren’t that spectacular – but the X-37B is only 9 metres long, and was some 330 km  / 200 mi above Ralf. But with a little post-processing they are enough to show the little vehicle’s open payload bay and certainly add to the X-37B’s mystique.

Enceladus Likely the ‘Perfect Age’ for Life

Saturn’s moon Enceladus is one of several icy worlds within the solar system that likely harbours a vast ocean beneath its icy crust. We know this because the Cassini mission spotted geysers of vapour bursting out of the ice of the moon’s south polar ice, and following daring passes through these plumes, rising hundreds of kilometres, the spacecraft was able to obtain samples that confirmed they comprised water vapour.

A dramatic line of plumes spray water ice and vapour from the south polar region of Saturn’s moon Enceladus. Cassini’s first hint of this plume came during the spacecraft’s first close flyby of the icy moon on February 17, 2005. Credit: NASA/JPL / Space Science Institute

It is believed the ocean is kept liquid as a result of Eceladus being constantly “flexed” by the gravities of Saturn and its other moons, a process that generates frictional heat deep within the Moon’s core, and giving rise to the ridges and fracture lines seen in the ice of the Moon’s surface.

Such flexing is also likely to affect the seabed of the moon’s ocean, probably giving rise to hydrothermal vents that allow more heat from the moon’s core to escape. Such vents on Earth are sources of chemical energy and elements such as carbon, nitrogen, hydrogen and oxygen – the essential building blocks of life. This had led to speculation that Enceladus might have basic life of its own; it all depends on just how old its ocean really is.

For example, if the oceans is just a few tens of millions of years old, then it’s unlikely there would have been enough time for the elements ejected into the water by the vents to combine and create life. Thus, trying to estimate how long the ocean has been active has been of particular interest to scientists. The problem is, we don’t actually know how old Enceladus and many of the other moons of Saturn actually are.

So a team from NASA’s Goddard Space Flight Centreset out to see if they couldn’t work this out. They did this by running  simulations tusing data gathered by the Cassini mission to try to work out how old Enceladus and for other moons – Mimas, Tethys, Dione, and Rhea might be, by tracking back their probable evolution. These simulations suggest that Enceladus is likely to be one or two billion years old.  What’s more their modelling suggests the ocean natually developed as a part of the moon’s evolution, rather than being the result of some orbital mishap that occurred aeons after Enceladus formed, thus adding to the idea that basic life many have started there.

However, the team admit there are some differences in the results of the simulation and the data gathered by the Cassini mission, and so they are trying to refine their modelling further. Bur even if it is only a reasonable estimate, their finding add weight to the arguement that Eceladus is definitely worthy of detailed future study.

Congratulations to Jodrell Bank

Congratulation to Jodrell Bank, the UK’s famous radio telescope on being awarded UNESCO World Heritage Site status on Sunday, July 7th, 2019.

Credit: Jodrell Bank

Read more here: A UNESCO World Heritage Site.