Rosetta and Philae – The afterglow of “that day”.

In a previous post I asked the question if Rosetta and Philae would rekindle the public’s imagination, like comet ISON had done previously.

Well …..blimey !!!!

The answer I’m completely happy to say …. is an unequivocal YES !!!

The first peak in excitement came with Philae’s inital release and start of its journey down to the comets surface. Pictures release later showed a wonderful image (captured with Rosetta’s OSIRIS camera) of the fully deployed Philae lander beginning its descent to the surface.

ESA_Rosetta_OSIRIS_NAC_Farewell_Philae_crop-1024x489

Set to be a future iconic image ….Philae just after departing Rosetta imaged by Rosetta’s OSIRIS camera.

From then on, the tension just ramped up and up.
So many questions for us all to grip our collective chair arms and repeatedly refresh our twitter feeds for …

  • did it land and whether or not it was successful?
  • did the harpoons fire?
  • did the ice screws in the feet grip the surface?

Then a little later, with many theories expounded, alternate hypotheses proposed and conjecture from all angles we found out our favourite little lander had bounced……not just once, but twice!

philae-bounce

Philae’s bounce after landing and subsequent resting place. Image courtesy ESA.

 

By this point, the social media world had gone bonkers. My own twitter feed looked like the London stock exchange ticker and I could barely keep up with the volume of posts.
I was elated.
Not just because they had accomplished “something wonderful” (to paraphrase Dave Bowman from 2001!) by managed to successfully “soft-land” a probe on the surface of a comet 300,000,000 km from earth but that the whole world was sitting up and not only taking notice but joining in and celebrating the landmark scientific success.

Just about every major news broadcast carried the landing as its lead story – just wonderful.

Eventually its was discovered that Philae had settled (at the end of its second bounce) in a shaded area of the comets surface, next to a rock wall. Limited battery life, experimental processes, streaming data and the lack of sunlight to charge the lander via the solar arrays led to the inevitable end that everyone had been dreading. The apparent “death” of little Philae. Sad to watch but expertly managed by the team at ESOC, the bittersweet moment arrived where battery charge was exhausted and Philae went into stasis – all systems powered down into standby or “idle mode”.

What a rollercoater ride!

And according to the ESA Rosetta project director, it might not be over yet !
It has been suggested that as the comet gets closer to the sun, there is a chance that little Philae may yet awaken as more sunlight falls upon is solar panels.
Only time will tell and for now its down to the scientists to process the amazing amount of data gathered by the lander in its short active period on the surface.

But what now? ….is there more? ….what comes next?
Is there a legacy of such a marvellous achievement that can be built on?
I believe most strongly that the answer is YES!
I really hope that the afterglow of such an amazing project is long lasting and bears fruit in the form of further and sustained interest in not only space but in the wider arena of STEM related subjects.

Advertisements

Comets Comets Comets – Will Rosetta & Philae recapture the public’s imagination?

Last year, at the very end of November, the world of space and science revelled in the spotlight for a while as comet C/2012 S1 (ISON) passed close to earth, passing round the sun, only to disappear in a few lingering wisps of cometary debris.

ison

Comet ISON’s pass round the Sun.

During this perihelion pass, I (like many others) was glued to a multitude of scientific newsfeeds from NASA, ESA and other users in my own twitter feed. For the self-confessed astrogeek in me, no Hollywood blockbuster even came close to the will it or won’t it debate!

For a short period of time comet ISON captured the imagination of the world’s media, both social and mainstream, and gave a huge boost to the place of science in pop culture.
This was however, shortlived (as usual) and science soon returned to its comfortable old armchair at the back of the hall.

But there’s a newcomer on the horizon! Another opportunity for science (and space in particular) to be thrust back into the limelight, and it comes in the form of a well travelled space probe called Rosetta.

Rosetta

Artists impression of the Rosetta spacecraft.

Launched in March 2004 aboard an Ariane V, the Rosetta mission has taken over 10 years to reach its goal – another comet!
This one, called 67P/C-G (Churyumov–Gerasimenko), is a large icy rock that completes its eliptical orbit of the sun once every 6.45 years.

After it’s incredible journey into the outer solars system, Rosetta reached the comet on 6th August 2014, becoming the first spacecraft to go into orbit around a comet.

Comet_on_3_August_2014

Close up detail of comet 67P/Churyumov–Gerasimenko.

Lets just take a moment here to let this sink in …… we’ve successfully managed to launch a space probe, guided it to perform four gravity assist manoeuvres (around earth three times and Mars once) to gather enough speed, precisely calculate the position of a lump of rock and ice in the vastness of space, wake the space probe after ten years in sleep mode, in order to not only greet the comet at over 600 million km from earth but enter into orbit with the nucleus at a distance of just 30km!
Thats just incredible!
Absolutely incredible!

But the best is yet to come.

Scheduled for the 12th November, the second part of the Rosetta mission gets underway and involves a passenger that Rosetta has carried on its epic journey. No a passenger in the form of a person but a small robotic lander called Philae. This will detach itself from the main body of the spaceprobe and, if all goes well, achieve something that has never been achieved before, a controlled decent and landing on a cometary surface.  WOW!

Rosetta_Philae_Artist_Impression_Close_4k

Artists impression in the detached lander “Philae” on approach to the comet’s surface.

Immediately after touchdown Philae will deploy harpoons to anchor itself to the cometary surface and commence a series of scientific experiements to look at the comet’s surface and sub-surface composition as well as the plasma and magnetic environments of the nucleus.

For some people,that will not be exciting at all.
For others (myself included) it will be an incredible feat of science and engineering and marks a spectacular acheivement in space exploration.

No mater into which camp you fall, I just hope that the mainstream media give this endeavour the attention it deserves.

Comet Tales – Exciting ISON

Now that all the excitement has died down a little, I felt it only right that poor old ISON got at least one blog post from me, to commemorate its passing.
I, like many others (my fellow astro-obsessed people), watched intently the journey of comet ISON over the last couple of weeks of November to today in early December, culminating at the very end of November (perihelion on the 28th) in ISON’s passage around the sun and thence to its final demise to naught but a wisp of dust and particles (although speculation still abounds!).

ison

A time-lapse image of comet ISONs perihelion.

This information above probably comes as no great shock to anybody.
Anyone into space and astronomy was watching.
However ……
I feel I have to comment on the unpresidented activity that ISON’s slingshot round the sun caused. I for one was glued to my twitter feed, the helioviewer website and the NASA and ESA feeds of LASCO, SOHO and STEREO data.
It was joyous to behold !
….. but not because of ISON itself but of what it caused. The huge level of interest in this space based phenomena. A surge of tweets and posts, as so many like-minded science lovers looked on, and speculated, postulated and discussed.
But it became more than just the science community, for a time ISON entered the domain of the common man and sought to complete almost as a celebrity. It was trending on twitter, discussed on local radio stations and given plenty of attention in the national media and television.
How wonderful that science could be brought to the fore and engage so many people by the travel of a lump of icy rock that began its journey from the very farthest reaches of our solar system over a million years ago.

C/2012 S1 (ISON) ….. I salute you !

Top Ten Astrophysics Misconceptions Explained

This post is born out of a conversation between students during a lecture on the life cycle of stars and harvests many comments gathered over years working in schools and colleges. Some of the list also came from suggestions made by friends on Twitter. It’s by no means a definitive list, just the top ten I picked.

They say that “kids say the funniest things” but that’s not always true. When it comes to common misconceptions about space and astrophysics, it’s just as likely to be the adults 🙂

So here we go on a countdown of the top ten.

No. 10 – Planetary Nebulas make planets.

crab-nebula

The Crab Nebula

Our first misconception (and the one that started it all off). A planetary nebula is the remnant of a star that, at the end of its life, has burned all of its fuel and shed or pushed off its outer layers. The rest of the star then collapses inward leaving a small dense core called a white dwarf star. During this process, strong stellar winds drive the expanding gasses and this coupled with large amounts of emitted ultraviolet radiation, cause the clouds of gas and dust to glow. Initially called “planetary” nebulae by early astronomers (namely William Herschel), thinking their round appearance resembled the recently discovered planet Uranus.
The emitted material from these nebulae will eventually spread across space until it mixes with other stellar matter and once more begins to clump together initiating the formation of other stars.

No. 9 – “Empty” Space

Another one I reckon just about everyone will have heard. “Space is a vacuum and the gap between planets and stars contains nothing”.
Wrong again I’m afraid. Although it doesn’t contain very much, space is not empty. Scientists have now realised that every square metre of “space” contains at least a few atoms of matter – primarily a plasma of hydrogen and helium as well as varying quantities of the ubiquitous neutrino. However, the story does not stop there as many cosmologists are now looking at the possibilities of dark matter and dark energy to fill these spaces, that could account for as much as 80% of the mass-energy of the universe !

No. 8 – Black Holes part I – Travelling through and out of the other end.

Hollywood has a lot to answer for when it comes to space misconceptions and this is one of them. If you’ve seen the Disney film “The Black Hole” or more recently “Interstallar”, then you know what I’m talking about. However, contrary to sci-fi film makers predictions, space travel through a black hole is not possible ……. well not yet anyway. The matter shredding tidal forces and infinite density of the singularity at the centre of a black hole would merely add any object’s mass to the mass of the black hole, effectively destroying it in the process.
However, I felt I ought to qualify the “not yet” part with additional explanation. There are some recently floated theories and papers dealing with principles that may yet yield results in the field of black hole travel, although the commonly held opinion is that these theories still currently sit firmly in the realm of science fiction.

No. 7 – Saturn’s rings.
(suggested by @SaturnSheila)

saturn_during_equinox

A picture of Saturn taken by the Cassini orbiter.

There are two common misconceptions about the ring system of the solar system’s second largest planet. The first is that the rings are made of rocks. They are not! Although this is the most common answer given when asking people what they think Saturn’s ring are made from. In reality, 99% of the ring material is ice. It is this fact that allows us to get such a good view of the rings, as the ice is very good at reflecting the sun’s light. Each ring is made of chunks of ice ranging in size from about a millimetre to over ten metres in length. Each of the rings can be as thin as three metres in depth to over a kilometre.
The second misconception is that the rings have gaps in them where there is an absence of ring material. However, it just seems that way to the observer. In reality, all the rings have varying densities and even the bands that appear to us as gaps are actually populated with ice, just at a very low density.

No. 6 – The moon shines or gives out light.
(suggested by @DrLucyRogers)

Quite a common misconception this one. A lot of people gaze up at earth’s natural satellite and see how bright it is in the sky without actually realizing that what they are actually seeing is reflected sunlight – and not very much of it at that !!! moon2A surprising fact about the moon is that it only reflects approximately 12% of the light that hits it from the sun. This is primarily due to the fact that the moon is essentially a large lump of dull grey rock. That last bit is probably a disservice to the moon as I’m sure we all agree it can be breathtakingly beautiful when showing us different phases and during the differing metereological conditions of the changing seasons.
Beautiful as it can be, it doesn’t change the fact that the moon is not a “luminous” object . It emits no light of its own!

No. 5 – The Far side of the Moon – “Doesn’t the moon rotate?

The second of our lunar based misconceptions checks in at number 5 in our top ten.
So to what are we referring when we say “the far side of the moon”.
Well …. seen from the earth the moon does not appear to rotate as we see the same part of the moon all year round. This led to the misconception that the moon doesn’t rotate.
Fortunately, it does. The effect is caused by a phenomenon called tidal locking in which the tidal forces of the earth have altered the rotation of the moon causing the time taken for the moon to rotate once to be the same length of time as it takes the moon to complete one orbit of the earth. The result of this is the fact we only ever see the same bit of the moon even though it is rotating.
Numerous conspiracy theories existed concerning the far side of the moon but were mostly debunked in the late 60s early 70s after numerous missions from both Russia and the US returned high resolution imagery of the far side.

No. 4 – Black Holes part II – “Nothing escapes the pull of a black hole, not even light.”
(The “Cosmic Vacuum Cleaner” analogy)

Well …… thats partially true but we’ll still deal with it as a misconception. It is true that once the event horizon is breached, not even light can escape from falling into the physics defying, matter crushing, depths of the space-time singularity in the black hole’s centre. The story does not end there however as there are a couple of other factors that we need to consider.

cygnus-x1-black-hole

An artist’s rendition of the Cygnus X1 black hole showing polar jets and the accretion disk pulling material off the nearby blue supergiant HDE 226868.

Jets! – Not the baseball team, not even the fast moving aircraft either. These jets are “Relativistic Jets”. These occur at the poles of the black hole throwing plasma thousands of light years in to space and are thought to form due to the complex dynamics of the twisting magnetic fields and super high temperatures of the accretion disk focusing these beams along the rotation axis of the black hole (see pic). Realistically, we perhaps shouldn’t really consider these being emitted from the black hole itself though.
The other thing that escapes a black hole is something called Hawking Radiation. Not for the scientifically feint-hearted, this quantum effect relates (in incredibly over-simplified terms) to the escape (therefore emission) of one half of a virtual ‘particle / anti-particle’ pair formed just above the event horizon and brought into being by the black hole’s massive gravitation.

No. 3 – “Its hotter in July because the earth is closer to the sun.”
(suggested by @DrLucyRogers)

The notion that the whole earth moves closer to the sun in summer is a fallacy. The four seasons (no, not the hotel :)) are driven by the fact the the earth’s axis is off vertical by 23.4 degrees.
This slant causes different parts of the earth to be closer to the sun at various times of the year, giving us our seasons. During July, the Northern Hemisphere of the earth tilts towards the sun giving us our summer and away from the sun in December giving us the cold weather of winter. Unsurprisingly, the opposite is true for the Southern Hemisphere who have their winter in July and summer in December.

No. 2 – A comet’s tail always trails out behind it showing where it’s come from.

comet

Comet Hale Bopp showing two distinctive tails.

Wrong again but this is a very common misconception, hence it’s high ranking here at number 2 on the top ten. A comet is comprised on a solid ball of rock and ice and is a leftover piece of “stuff” from the earliest times in the formation of the solar system. Thought to originate in the Oort Cloud on the very edges of our solar system, they tend to have very large elliptical orbits around the sun. At the furthest distances from the sun the comets is just a fast moving icy rock.
When the comet begins its approach towards the sun, solar radiation causes vaporisation in this nucleus resulting in the ejection of dust and gas forming a glowing cloud around the nucleus, called the “coma”. As the comet closes the distance to the sun the tail forms. Comets usually have two tails and not one as many people think. Both tails are expelled from the comets nucleus by the solar wind. The first tail, the ion tail (type I tail), is a jet of ionised particles that always points directly away from the sun. The other tail, the dust tail (type II tail), isn’t as strongly affected by the solar wind and so curves back somewhat, toward the comet’s path.
If we think now about the comet having already gone round the sun and starting its long journey back to the edges of the solar system, the tail (still stretching directly away from the sun) will be in front of it! – although constantly reducing as time passes and the comet gets further from the sun.

No. 1 – There is zero gravity in space!
(suggested by @Rebecca_George and many many students over the years!)

Here it is. The final misconception in our top ten. In number one position – “Once you get into space there is zero gravity!”

Many people looking at the astronaut in the picture could be forgiven for thinking this is true but that’s why it’s number one in the list. Its completely false! (but a little difficult to explain simply)

Gravity exists between all objects with mass.

Although gravity is the weakest of the fundamental forces (the others being electromagnetism and the strong and weak nuclear forces) the masses of objects involved, at least on a cosmic scale, are gigantic and consequently the effects of gravity are far reaching – holding the planets in orbit around the sun, the satellites in orbit around the earth and it can recall comets from the farthest reaches of the solar system.

space-walk

NASA astronaut undertakes EVA.

With this in mind and looking again at the astronaut in the picture – ask yourself …… is he really in zero gravity ??

The obvious question now becomes why does he look and behave “like” he’s in zero gravity ?? Well, we’re back to mass again and the confusion between the terms zero gravity and weightlessness.
The astronaut is, of course still, affected by the force of gravity. Its just that he has no point of reference, no counter force (like the ground beneath his feet), to give him the impression of weight – hence he feels weightless.
Weightlessness is a bit or a misnomer and should be more correctly termed microgravity. The astronaut is not actually weightless, because the Earth’s gravity is holding him and his spacecraft in orbit. He is actually in a state of free-fall, much like jumping from an airplane except that he is moving so fast horizontally (about 5 miles per second or 8 kilometers per second) that, as he falls, he never touches the ground because the Earth curves away from him.

And there we have it, ten of the best space based misconceptions.
All comments / views / discussion welcome 🙂

Space Debris – Some creative thinking and “out there” solutions.

Quite a few people talk about the dangers of space debris. It trends on twitter in cycles and is a hot topic in the space world.
So, given my the exposure to the topic (mainly by the peeps on twitter) I did a little reading and then let my overactive imagination loose on the problem, well …. a section of the problem anyway.

Impression of space junk in LEO and higher orbits

Lets first set the scene. Space debris, or space junk, is the ever-increasing collection of used rocket stages, defunct satellites, and collision fragments that circle the planet. The problem is mainly found in low earth orbit (LEO) but not exclusively.
Wow, there’s a lot of crap up there !!!

So why is it such a problem?? Well…. with the amount of junk that’s now up there the low earth orbit is becoming a very packed place and if we don’t do something about it soon, spaceflight and in fact any launches, even to put satellites in orbit, will prove very difficult. With so many objects in the same or overlapping orbits, the chance of collisions is on the increase. The main problem with this is that an impact between two pieces of debris, generates even more debris and can even create clouds of debris. This resultant net increase in the amount of debris raises the probability for further impacts, with propagation runaway becoming a real possibility (the Kesseler Syndrome).

There have been numerous suggestions of how to remove the larger pieces (spent rocket stages and old satellites etc.) most of which relay on having another satellite intercept the junk and attach either an active thrust device (ion engine or conventional thruster) or a passive inductive drag device such as a solar sail. Other methods include laser ablation to induce momentum and setting off small thermonuclear devices to vaporise unwanted debris.
These methods are the most likely ones to be used, barring the thermonuclear option (probably!).

Below are some of the thoughts I personally had whilst considering the issue over a couple of days. Some of them are only semi-serious and the others may even verge on the ridiculous. But, thinking about it, being creative, highlighting the issue and talking about it has to be a good thing …… right ??? And before anyone shoots me down, there may well be overlap with a number of other much better ideas already out there. These are just a few of my own (possibly ill-informed) ramblings.

Spider Webs
I was looking at a spider web the other day whilst daydreaming (as you do!). What an elegant design! Super strong thread and highly sticky. What a good way to catch stuff, but could this be translated into a much much larger scale to trap bits of junk in space? I don’t know….. maybe ??
Using monofilament threads made into a net and coated in glue, this could be spread out from an orbital delivery container, using very small thrusters to “pull” the corners apart.
The questions and problems that arise from this are pretty obvious though.

  • The net would need to be massive and collision fragment clouds tend to be spread over a very wide area.
  • The thread would need to be super strong to resist the impact of targets travelling in excess of 15,000 mph
  • The net would have to be very dense, having very small holes, to catch the small stuff

Based on the above, does this render the glue net defunct ?? Hmmmmm…… not necessarily.
Lets say that you made it target specific with regards to debris size and used it only in the area of a cloud that has the highest spacial density of fragments. Maybe some sort of carbon fibre thread could be used. Would the glue be strong enough to hold that fragment even after such a momentary contact? Would the fibres that the net was made of be strong enough not to just be shredded by the impact? The trick would be not necessarily to have the net taut but very very baggy to give the maximum amount of absorption of momentum. Should even a few of the fragments be caught up, the net could then be “encouraged” into a degrading orbit using the thrusters that erected it in the first place.

Catcher’s Mitt
The catchers mitt idea is really just a development of the net, but the material used would be a solid sheet and would need momentum absorbing properties much like a Whipple shield. Whether this would better be a stuffed or spaced variety would be best decided by experimental design and testing. The idea would be to manoeuvre this large shield around inside the debit field orbit to “catch” whatever fragmentary debris were possible until the “mitt” were so degraded by impacts that it lost any further usefulness and itself became a risk of possible fragmentation from impacts.
It could then be manoeuvred into a graveyard orbit or urged into a more rapidly decaying orbit.
DARPA currently have a program codenamed “catcher’s mitt”, looking at tethers and solar sails for altering the orbits of large items of junk.

Interestingly, the previously mentioned solar sails need to be ‘erected’ or expended when in orbit. The net and mitt ideas also require an expanding mechanism technology to deploy them. Although I have mentioned the possibility of using small thrusters for the net idea, another way might be considered. Were the backs of all these sheets and surfaces covered in a web of tiny hollow pipes, a liquid (or maybe a gas) could be pumped through them causing them to unfurl much like the wings of an emerging dragonfly. I’m sure I can’t be the first person to think of this.

Bouncing Rocks and Debrisflectors
The idea behind this last strategy came about after remembering a childhood holiday spent on a pebble beach in the south of England. I can clearly remember throwing fist sized beach cobbles at a large rounded car size lump of rock a good distance away in the sea and then being amazed at how the rocks appeared to bounce or ricochet off the curved surface almost with an apparent complete preservation of momentum.
That was just the seed thought as its really the ricochet bit that is of interest.
Let say that it were feasible to get a relatively strong surface into space (we’ll come back to some ideas in a bit) that could be manoeuvred into the path of the debris – would this be capable of deflecting smaller items back towards the atmosphere to harmlessly burn up on re-entry???
Similarly to the catchers mitt idea, this “debrisflector” would have to be actively manoeuvred around inside an oncoming debris field to intercept the maximum number of objects. This also assumes that the surface could be made hard enough and correctly angled.
One other thought for the debrisflector would be to induce an ultrasonic vibration in the surface. This might then mitigate damage done to the surface by impacts (ricochets) extending the lifespan and usability of the unit.

So how could the reflecting surface be made strong enough to resist impacts and reflect properly, yet lightweight enough to be delivered to orbit in the first place??
One idea would be to use a composite sheet made of some form of metallic surface with a doped and strengthened aerogel backing. It could potentially be delivered in sections and assembled in orbit although this could potentially introduce weak spots at the joins.
The other main issue with reflection is the possibility that the object may not “ricochet” in whole pieces but may create an even worse problem in further clouds of collision spall. The only mitigating factor is that this cloud would then be directed towards the atmosphere for a relatively rapid re-entry.

So ……. a few ideas. None of them great, but maybe it’ll starts someone’s ball rolling. Good luck 😉

%d bloggers like this: