Juggling Molecules on Mars

So much of what we come into contact with is made of four elements – carbon, hydrogen, oxygen and nitrogen – the main elements of living systems. Add phosphorous and sulphur and you have what comprises 98% of all living systems.

The chemistry for juggling these four atoms – C, H, O, N – has been around for a long time.

Engineers and scientists have been confident enough in the chemistry and the various ways of manipulating them to propose various sets of reactions for use in gathering resources out in the vast reaches of space, as part of human exploration. This is part of a wider field of study called In Situ Resource Utilisation (ISRU), which has formed a key part of plans to explore other part of the solar system, particularly Mars, for the better part of two decades.

In the Mars Direct concept Robert Zubrin proposed using the well known Sabatier reaction:

CO2 + 4H2 => CH4 + 2 H2O

To react hydrogen with the Martian atmosphere to produce methane and water – very useful things to have on the red planet. The methane would be stored and kept for use as rocket fuel.

Methane and oxygen are a handy combination. In terms of chemical rocket propellant candidates, the Specific Impulse (Isp) of Methane and Oxygen at 3700 m/s is second only to Hydrogen and Oxygen at 4500 m/s (to convert to seconds of impulse multiply by 0.102).

Meanwhile the water from the Sabatier reaction would be split via very familiar electrolysis reaction:

2 H2O => 2H2 + O2

The idea was that only the hydrogen would need to be transported to the Red Plant. H2 weighs a lot less than CH4, freeing up space and payload for the 6 months transit to Mars.

Various test rigs were constructed on Earth, using analogues of the Martian atmosphere, which has been well characteristed since Viking. Mars has a lot of CO2 – more than 95% of the atmosphere – and a nice analogue of the Martion atmosphere right down to the low pressure could be similated for the rig. The CO2 is initially absorbed onto zeolite (an ever popular sorbent) under conditions simulating the Martian night. During the Martian ‘day’ the CO2 desorbs and passes into the Sabatier reaction vessel with the H2, which is heated to 300C. Reaction then occurs in the presence of the right catalyst (in this case pebbles of ruthenium on alumina). The water from the reaction is condensed out and passed to the electrolysis unit.

Still awake?

OK. Not surprisingly scientists and engineers planning Mars missions were concerned about overly complex systems forming such major part of a critical path.

Current plans for ISRU on Mars revolve around direct dissociation of the Martian atmosphere i.e.

2 CO2 => 2 CO + O2

[BTW if you could pull off this reaction at room temperature on Earth you would be an instant billionaire]

The current Mars Design Reference Mission proposes the production of oxygen on Mars through direct dissociation. Methane will be transported directly from Earth, with the ascent vehicle still using the tasty combination of methane and oxygen in its rocket engines.

So how is the CO2 pulled apart? There are many contenders, all of which uses a lot of energy. On Mars that energy is currently planned to be delivered by a 30 kW fission power system.

The front-runner for CO2 dissociation is thermal decomposition, followed by isolation of the O2 using a zirconia electrolytic membrane at high temperatures.

This system was developed for its first flight demonstration as the Oxygen Generator Subsystem (OGS) on the defunct Mars Surveyor Lander, which would have been launched in 2001 (but was cancelled following a string of Mars mission failures – Mars Climate Orbiter (1999), Mars Polar Lander (1999), Deep Space 2 Probes 2 (1999). That was a bad year. ).

The OGS was to demonstrate the production of oxygen from the Martian atmosphere using the zirconia solid-oxide oxygen generator hardware. This unit was designed to electrolyze CO2 at 750C (1382 F). The Yttria Stabilized zirconia material – once a voltage is applied across it – acts as a oxygen pump allowing the O2 to pass through it and be collected. The plan was to run the unit about ten times on the surface.

As I mentioned there were various contenders for the process. Such as molten carbonate cells, which operate around 550C with platinum electrodes immersed in a bulk reservoir of molten carbonate. Personally, the engineer in me shudders at the thought of trying to manage any sort of molten system that remotely.

The final system for CO2 decomposition used on Mars is probably still a work in progress. It will be interesting to see what develops there.

The fact is the initially proposed Sabatier reactions did not produce enough O2 to react with the methane, so some form of CO2 splitting process was still required.

So there are some things we can do to juggle molecules when we get to Mars.

Is everyone out there looking forward to getting to the Red Planet and grappling with what we find there? Who thinks we should not go? And why not?

Planet-Hunting Goes to the Next Level

This really is the age of planet-hunting. The number of confirmed exoplanets now exceeds 800, and there are more than 2,700 other candidates waiting for entry into the hall of fame. When you consider how far away some of these suckers are, it really is astounding.

Up until now we have been able to get estimates of orbit,  general size and mass. Combined with knowledge of star type, this has enabled astronomers to place the exoplanets in relation to the ‘Goldilocks’ or habitable zone, where liquid water is possible (seen as a likely precursor for the development of life (as we know it, Jim)).

Now the analysis of these targeted systems has gone to the next level. Astronomers are beginning to install infrared cameras on ground-based telescopes equipped with spectrographs. This will enable tell-tale signatures of key molecules to be detected. One key feature of this work is figuring out ways of blocking the glare of the planet’s adjacent star. NASAs planned James Webb Space Telescope will also use a similar strategy to study the atmospheres of planets a little bit bigger than Earth.

Two factors can improve the view. Young planets have more heat left over from their formation, increasing the infrared signal for the spectrographs. The other approach is to look at planets further out from their stars, helping to isolate their spectra from the star’s light. Of course looking that far out means starting with Jupiter-sized planets, but astronomers hope to be able to refine their technique to allow the atmospheric compositions of smaller – and older –planets to be examined.

The Holy Grail is finding an Earth-sized planet in the habitable zone with molecules that indicate the probable presence of life. We might have to wait for the proposed Terrestrial Planet Finder before we can crack this.

Still, it’s pretty exciting stuff!

Watching the Asteroids

Asteroids are always intriguing. Little planetoids that fly around the solar system in mysterious orbits, often swinging dangerously close to Earth. It’s that element of the unknown as well as the potential threat to life on Earth that always ensures their popularity.

There is a lot of work going on behind the scenes in modelling asteroid orbits and tracking them. The NASA Near-Earth Object Observations Program – dubbed Spaceguard – detects, tracks characterises both asteroids and comets passing by Earth (anything inside 28 million miles of Earth is regarded as Near-Earth). It uses both ground and space-based telescopes. This information is used to predict their paths, and to determine any potential hazard.  At any given moment some of the world’s most massive radar dishes are on the case.

A new space-based asteroid-hunting telescope is being planned. NASA scientists recently tested the Near-Earth Object Camera – a key instrument. That will be interesting to watch for, potentially doing for asteroids what Kepler did for planet-hunting.

One favourite way to get to know an asteroid is hitting it hard with another object (not recommended in personal relationships). Those collisions can tell us a lot about their structural integrity and composition. Trying to get that little probe to actually hit anything travelling at hypervelocity (11,000 km/h or above) is a feat in itself.

Knowing where an asteroid will be, and its structure and composition are vitally important things to know if we plan to move asteroids around or want to explore them for valuable materials.

Potential targets can be quite small – as tiny as 50 metres wide. One little-known complication of creating a scientifically significant impact is that they can also have their own little family of tiny moons orbiting around them. Trying to track down those secondary orbiting bodies can be a challenge, but critical to the success of any ultimate impact.

At least with asteroids you do not have the complication of jets of material firing into space, which you have with comets. These can upset imaging and guidance systems.

One likely candidate is the asteroid 1999 RQ36, which is the target of a NASA mission called OSIRIS-Rex. The currently slated launch date is September 2016, with the ‘landing’ in 2023 (now that’s long-term planning). Not only do the NASA scientists need to co-ordinate the impact, they have to ensure that the OSIRIS-REx spacecraft, with its crucial observing instruments, can monitor the results of the impact from a safe distance. This little craft will do a loop around Mars then close with its target at the rate of 49,000 km/h (8.4 mi/s). Needless to say mission scientists will be executing several deep space manoeuvres to refine its position during its approach. The spacecraft’s own automatic navigation system will take control only two hours from impact, executing three planned corrections at 90min, 30min and 3min from the impactor ‘landing’. At this point the spacecraft will be a mere 2,400 km away from RQ36. Cosmic spitting distance!

Two Spacecraft Crash into Moon Mountain!

Yes, really! But not by accident.

On December 17 2012, NASA’s twin GRAIL (Gravity Recovery and Interior Laboratory) spacecraft were steered into a mountain near the Moon’s north pole. Both were about the size of a washing machine with a mass of around 200 kg (440 lbs). The aim here was to squeeze one last bit of science out of the spacecraft and take a look at the Moon’s interior.

The crashes alone could not achieve that. The twin impacts created twin plumes, but another spacecraft had to be on hand to analyse what the nature of these implied for the Moon’s composition. In this case it was NASA’s Lunar Reconnaissance Orbiter (LRO).

In the case of the NASA team driving the LRO it was a mad scramble to get the spacecraft into position to observe the impacts. LRO’s team had only three weeks’ notice of the ultimate position of the two GRAIL’s resting places and had to make sure their baby was on hand to focus on the columns of ejecta.

LRO was about 160 km (100 mi) from the lunar surface when the two spacecraft made impact. Because the site was in shadow at the time of the impact the LRO had to wait until the plumes rose high enough to be in sunlight before making its observation. In this case, the LRO used the LAMP instrument (Lyman Alpha Mapping Project), which is an ultraviolet imaging spectrograph. The LAMP saw mercury and enhancements of atomic hydrogen in the plume.

The results are interesting because the presence of mercury was also noted from the LCROSS (Lunar Crater Observation and Sensing Satellite) impact in October 2009, however that impact was at the bottom of the Moon’s Cabeus crater, which has not seen sunlight in an estimated billion years and is likely to be quite cold.

Now two craters around 4-6m in diameter dot the side of the unnamed mountain at an elevation of around 700m above the surrounding plain, around a third of the way up the 2,500m tall massif. Each has a faint, dark ejecta pattern. The dark ejecta is unusual since  impact craters on the Moon are usually bright. One theory is that the dark pattern is a result of the spacecraft remnants being mixed with the local materials.

If Elon Musk can get the price of space travel down by his claimed factor of 100, then maybe I can send my old washing machine up to the Moon for a scientifically relevant impact. Now that would be something.

Who Shrank the Shuttle?

If you see a picture of the X-37B unmanned spaceplane, you would be forgiven for mistaking it for a slightly modified Space Shuttle. If you look closer you realise it’s a mini-version of a Shuttle, around 9m (29ft) in length and 5 tonnes (11,000 pounds), with a payload of your average pickup truck.

Here is a picture of it in its hanger [CREDIT: space.com].

 X-37B mini shuttle

Looks awesome. I like the V-shaped rear wings. Looking at this I’m thinking all that money spent in Shuttle development wasn’t as wasted as I thought.

Two have been built so far (reportedly), and one has been in orbit around Earth since December, although no one knows exactly what it’s doing up there.

The X-37B went into orbit on top of an Atlas 5 rocket from Florida’s Cape Canaveral on December 11 2012. The current mission is designated Orbital Test Vehicle-3 (OTV-3), as the third classified mission under the US Air Force’s X-37B program.

The little robotic vehicle is on the USAF’s books as USA-240.

The vehicle lands on a strip, just like its bigger (defunct) cousin, but even more impressively it does so autonomously. Pretty cool, huh? I thought maybe I could sneak into the back in a spacesuit for some spacewalking next time it goes up, but then realised I could never hope to pack enough oxy-mix – the little craft was up in orbit for 469 days for OTV-2. That’s a long time to hold your breath.

OTV-2 ended on a special strip at Vandenberg  on June 16 last year, although the jury is out as to whether OTV-3 will end there or back at the good old shuttle strip at Kennedy Space Centre.

Anyone heard anything about what the X-37B’s doing up there?

Astronomical Visitors – Hello 2012 DA14

Next Friday a 46m (151 feet) diameter asteroid is going to be making a fly-by of Earth. The microscopic aliens who inhabit the little world, roughly the mass of an aircraft carrier, have prepared their miniature cameras to get nice snaps of the weird ‘big people’ below as we go about our daily lives. We’ll be watching too.

The asteroid, poetically dubbed 2012 DA14 in accordance with the naming convention, will pass within 27,680 km (17,200 mi) of Earth. Geosynchronous orbit is at 36,000km, so this visitor will actually pass between the orbit of various GPS and TV satellites and Earth. NASA scientists assure there is no chance of collision.

It will zip past at around 27,000 km/h (17,500 mph), and should be visible through binoculars and telescopes.

The best viewing location will be Indonesia, but Australian watchers should get a pretty good view as well. It will be visible from around 0624 Australian Eastern Daylight Time (i.e. Sydney, Melbourne, Canberra etc) on February 16 – that 524am for us Brisbanites (that’s our Saturday morning). The asteroid should be visible as a small star moving against the background of stars.

A telescope at NASA’s Marshall Space Flight Center in Huntsville will broadcast its view of the event from 6pm to 9pm USA ET on February 15.

Conventional wisdom says that asteroids of around 50m in diameter pass by Earth every 40 years or so, but are only expected to impact the Earth around every 1200 years.

The asteroid is thought to be similar in size to the object that exploded over Tunguska, Siberia, in 1908. The shockwave levelled hundreds of square kilometres of forest. Whether an asteroid makes impact or detonates in mid-air is down to its composition. The Tunguska explosion was thought to result from a rocky asteroid, as opposed to more metallic asteroids that have more structural integrity and stay intact up to impact.

This is the closest approach on record to Earth for an asteroid of its size.

Observations from the fly-by will hopefully gives clues on the asteroid’s composition and structure.

Any plans to watch the asteroid fly past?

Slingshots and Cosmic Coincidences

It’s easy to get dizzy thinking of humanity reaching out into the Universe. Especially if you have a head full of space opera with FTL drives, wormholes and other ‘standard’ transportation techniques.

No wonder it feels disappointing in the extreme to watch the progress of us Earth-dwellers into the local space.

Our first steps into the solar system will be much along the lines of what has gone before. Chemical propulsion will likely remain the standard for planetary lift-off for some time to come. If we are lucky, perhaps we can satisfy the EPA and use Nuclear Thermal Rockets, which might double the available impulse. Reentry will remain much more economical with technology used since the space race – i.e. heat shields and parachutes – while space vehicles of the like of the Shuttle will retire to museums.

When it comes to getting around the solar system, again we will probably be relying on chemical propulsion – all the currently proposed manned Mars missions are based on this. Again NTR rockets may offer potential in the future if the safety concerns can be addressed. For missions where time is not no much of an issue, electric rockets (ion drives) with their highly respectable exit velocity of 30 kilometers per second are capable of bringing spacecraft to high interplanetary velocities (but their low thrust means they will never get us to orbit).

Here’s where the slingshot manoeuvres come in. These have been used to great success in the early interplanetary probes such as the Voyagers. Basically, these rely on the principle of conservation of momentum. The same principle as slamming a cue ball into a billiard ball to get the billiard ball in the pocket. The momentum is transferred from the cue ball into the billiard ball but the momentum of the whole system stays the same. In this case it is the angular momentum of the two bodies movement around the sun that is conserved. The tiny spaceship takes a low trajectory over a big planet like Jupiter, and is shot out of the planet’s gravitational field at ninety degrees to its original direction of travel. The spaceship is now on a new trajectory that does not centre on the sun, and its angular velocity has increased by the same amount as Jupiter’s Sun-orbital velocity of 13 kilometers per second (while Jupiter’s angular momentum decreases by a minuscule amount).

Voyager 1 used a gravity slingshot manoeuvre to get to its present velocity of 17 kilometers per second. (Try not to think about the fact that it would take 70,000 years at this speed to reach our closest stellar neighbours.)

If a spaceship can apply thrust during a slingshot manoeuvre it can capitalise on the orbital mechanics even further. If a probe approaches the sun within 1.5 million kilometers along a parabolic solar orbit, then increases its velocity by 2 kilometers per second, it will leave the Solar System at an impressive 41 kilometers per second.

NASA’s Mariner 10, which performed flybys of Mercury in 1974 and 1975 relied on Venus gravity-assist manoeuvres to get it into position.

The Messenger probe to Mercury – the first probe to visit the planet in 30 years – went into orbit around Mercury on the 18th March 2011. It was the first space craft ever to do so. So far its found significant water in the planet’s exosphere, evidence of past volanic activity and evidence for a liquid planetary core. To get some idea of the crazy orbital scheme required to get it there, here is a diagram of its journey since launch.

Messenger Since Launch
Talking about cosmic coincidences, has anyone noticed that the gravity of both Mars and Mercury is 38% of Earth standard? I had to check that twice. Given the fact that Mercury may have water in its dark side craters (its tidally locked), it makes you think of the possibilities.

The other one that always gets me is that both the Moon and the Sun are exactly the same angular size in the sky.

What other cosmic coincidences have you noticed?

Weird Planets

exoplanet

This year has produced some amazing discoveries in the planet-hunting arena.

Notable among these is the announcements of more ‘super-Earths’.

The planet HD 40307g is the most distant from its sun of six planets found in its system, and takes 200 days to orbits its star. At seven times Earth-mass, bets are on as to whether this planet is rocky or a Neptune-like world. Astronomers put it at about 50:50. The system is around 42 lightyears away. Not only does it orbit in a habitable zone, the target system is also close enough to potentially image directly in the future using the next generation of space-based telescopes. Bring it on!

Gilese 163c is another planet in its stars habitable zone, also estimated at seven times the mass of the Earth. The planet orbits a red dwarf slightly dimmer than old Sol and zips around it in 26 days [red dwarfs are the most common star type in the Milky Way].

Other discoveries showed planets where you least expect to find them – in multiple star systems. Solving multiple-body problems like that give even the most brilliant mathematicians a severe headache. But that does not stop us from seeing what’s out there.

The gas giant PH1orbits a pair of stars that are part of a four-star system [in this case it would orbit the centre of mass of the two stars]. The first planet found in a four-star system. It is bigger than Neptune, and easily big enough to host rocky moons approaching Earth-size. Unfortunately its location makes it too hot for liquid water – its temperature is estimated to range between 251C to 340C (484-644F).

The best thing about PH1 is that it was discovered by two amateur astronomers as part of the Planet Hunters program. So non-professionals get to play too!

A number of binary systems with planets have now been found, some with planets near the habitable zone, such as Kepler-34b and Kepler 35b. Each would get that double-star sunrise, just like Tatooine. Both planets are big, and around 5000 lightyears from Earth. So no exploring just yet.

As for the closest planet, that is a rocky planet orbiting Alpha Centauri B, 4.2 lightyears from Earth. No need to pack the swimsuit – unless you like doing laps in lava. It orbits its sun in a little over 3 days at a distance one tenth of Mercury’s orbit. Ouch.

Find more info and some good pics here.

What were your favourite discoveries of the year?

Opportunity Still Rolling on Mars

Almost nine years old and still going strong – Opportunity – one of the twin rovers sent to Mars almost a decade ago is still turning its robotic wheels on the red planet. It is continuing its mission to learn about the history of wet environments on Mars.

Spirit and Opportunity were the twin rovers that exceeded all expectations by hanging on well past their planned life and going above and beyond the call of scientific duty. Both landed in January 2004. Each had a primary mission of 90 Martian sols (92 days in Earthspeak).  So Opportunity at 3244 days of mission life is a long-lived explorer indeed.

Spirit got bogged in soft soil on 1st May 2009 and finally gave up the electronic ghost on 22nd March 2010 (2695 days) after long and valuable service.

Opportunity has been exploring a crater-rim where orbiting Mars spacecraft have detected traces of clay minerals that may indicate a wet, non-acidic geology with favourable conditions for life. The hill its investigating – Matijevic Hill – is on the western rim of Endeavour Crater, a 22km wide impact crater dating back more than 3 billion years. This impact site is of particular interest to scientists because deep rocks have been pushed to the surface within reach of the intrepid rover. One of the puzzles to solve is sorting out the age of local outcrops.

The rover drove 354 metres around the hill in a counterclockwise circuit for its initial reconnoitre. This initial survey will be used by mission scientists to determine the best place for further investigation. Two areas of particular interest were identified: Whitewood Lake shows a light-toned material that scientist believe may contain clay, while Kirkwood contains small spheres with composition, structure and distribution that are different from iron-rich sphericules (aka blueberries) Opportunity saw at its landing site.

The final target for further investigations has not been chosen. Meanwhile Opportunity is flexing its robotic arm, ready for action.

Curiosity, Opportunity’s  newer, larger cousin, is also having fun. Here is an article about the organic non-signal that NASA was eager not to announce. To me, this is strangely reminiscent of the Viking ‘false positive’ – anyone remember that one?

Titan – Archvillain’s Lair

Still continuing my fascination for Saturn’s moon Titan this week. This time adding local power production to my sketch for the habitat.

But first a few other fun facts.

Using a variety of instruments aboard the Huygens probe scientists have been able to recount a by-by-blow of all 10 second of its bounce, wobble and slide across the surface of Titan.

At first contact the probe made a dent 12cm deep before bouncing onto Titan’s flat surface. They estimate the 200 kg probe hit the surface with the impact speed of a ball dropped from around waist height on Earth. Just think about that for moment – the effect of Titan’s reduced gravity. I find that awesome.

The analysis is so precise, scientists then report the probe tilted by 10 degrees, slid about a foot across the surface and came to its final resting place – where it wobbled back and forward four to five times. (Of course what they don’t realise is that a local Methanomorph – who had the sh*t scared out of him by the appearance of this strange object – kicked the Probe five times in sheer frustration.)

You can see an animation of the landing here.

Recent radar images from Cassini – orbiting Titan – reveal a circular feature described as a ‘hot cross bun’. This tasty region, which is 70km long, is characterised by surface fractures, with steam – possibly from rising magma below the surface, driving the uplift.

Having a think about where you would want to set up a habitat on Titan, I realised heat would be a premium. So you would set up either in a geologically active area like the ‘hot cross bun’ or perhaps near the mouth of an active volcano – just like the old Archvillain’s Lair!

OK, before you tell me I’m crazy, remember that things are very cold on Titan, around -179 C (-290F). The volcanic ‘lava’ is actually a liquid ammonia and water mixture. At the surface pressure of 1.45 atmospheres or 147 kPa (~21 psi) that means water is boiling at a slight elevation of 106C (~224F). [If you want to check out this boiling point elevation effect, find yourself a set of steam tables and look at the Saturated Water section.]

Perched up on the rim of the volcano, you would have a nice source of heat, and also a source of liquid water. Of course you would probably need to drive piles down to a nice solid foundation of ice or rock to keep your hab steady.

What you also have is a power Engineer’s dream – a temperature difference! Forget the portable nuclear reactor you brought to power things while you set up, now you can generate electricity directly from the ‘lava’.

You could operate a modified Rankine cycle using local materials for the working fluids. You would need to bring the key components with you (turbines etc), but you could use ammonia (R717) as the working fluid. Ammonia has a critical point at 132C. So you could fit a conventional cycle say between the temperatures of 106C and 10C – which would give you a theoretical cycle efficiency of around 25%. Not that great, but straightforward.

But what about using liquid methane as well? If you mixed liquid methane from the surface with the water ‘lava’ (50:50), you would end up with a methane-water-ammonia mixture with a temperature of around -79C. Now, because the ambient temperature is so low (-179C), you can theoretically operate a power cycle to recover heat right down to this temperature. The theoretical efficiency of recovering heat between 100C and -70C is 46%, much better. You could improve this by playing the proportions of the mix.

Of course you would have to do something tricky with the working fluid to allow this, perhaps by using a binary mixture of methane and ammonia.

You could pump the hot water from the volcano mouth, then generate power while you cooled the water using the ammonia cycle, then get even more power by mixing some of this water with methane. Rejecting heat from the working fluid would be a snap, given the low ambient temperature.

If you are interested,  here are the temperature Vs entropy diagrams for methane and ammonia. A typical steam-based Rankine cycle on a T-s diagram looks like this:

You would probably need to set up your Lair on the northern hemisphere of Titan, the only place where vast hydrocarbon seas have been observed.

Next week – sailing ice boats on methane seas. . .