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Saturday, 18 August 2018

Reposted: Answers for Authors: What's fire fighting in space like?

Above: Some footage of the FLEX 2 experiments, part of a series of experiments to better understand fire in space. Oddly beautiful, isn't it?

To understate things hugely: Being stuck in a burning building is not fun. That’s why we have a heroic body of people called the fire service who do the ‘save you from a burning building’ thing.

In a space there’s no fire brigade, and outside is only slightly less deadly than the fire - which means an astronaut crew has nowhere to run, and no-one to help them in a major fire. And it's not like they never happen: In 1994, on the Russian Mir space station, a cosmonaut thought he’d beaten a small fire out with a jumpsuit (I assume a spare, unless naked firefighting in space is the best way to do it). Moments later he was horrified to find the the fire had just jumped into the jumpsuit, and was cheerily burning its way back out through it.
Jerry Linenger, an American astronaut aboard Mir, described fighting a larger fire in 1997: 

"As the fire spewed with angry intensity, sparks – resembling an entire box of sparklers ignited simultaneously – extended a foot or so beyond the flame’s furthest edge. Beyond the sparks, I saw what appeared to be melting wax splattering on the bulkhead opposite the blaze. But it was not melting max. It was molten metal. The fire was so hot that it was melting metal." 

Above: The Mir space station. One day someone will made a movie about it. That movie will include fires, the station getting rammed by a space freighter, and lots of cross-lingual swearing.
People began realising that fire in space has different rules, and space agencies spent a lot of time studying it. And it’s much, much worse than we thought:

Fire is generally hard to fight in space, partly because it can become freaking invisible: On Earth hot air rises, pulling the waste products and the flame itself into a relatively well confined (and hence easy to spot) cone. In space the flame has no such guide, so it spreads in a diffuse fashion that spreads out the light it emits – so much that it becomes almost undetectable. For the same reasons, fire is also less predictable in space: On Earth it will tend to spread upward faster than it does any other direction, but in space it spreads in all directions. 

Above: On the left is a normal flame, and on the left is a flame in space. Courtesy of the Discovery channel.
Oh but it gets worse: In space a fire will change how it operates to fit its circumstances, reacting to its environment. Fire wit limited oxygen in space will, rather than simply going out, split itself into many tiny ‘flamelets’. The flamelets use much less oxygen than a single flame front, move quickly and independently, will each then go it’s own way until one finds a new source of fuel and oxygen, and will cover more ground by dividing and multiplying where they can. The effect has been reproduced on Earth by keeping a fire sandwiched between glass and metal sheets, suggesting that the effect is linked to the different way air moves under microgravity.

To make the job of a space firefighter even harder, fire in space also needs less oxygen, and can stay burning at a lower temperature, making it much less likely to burn itself out. In experiments, fires have even been seen to carry on burning in an 'impossible' fashion: Still combusting after they’ve been apparently extinguished, via some unknown mechanism.

So how do you put a space fire out for good?

The Fire Industry Association put this question to astronaut Time Peake (link to their article here). He said: 

“We have procedures that deal with each case depending on the severity of the situation. In the most serious cases, we would don breathing apparatus and fight the fire using either CO2, water mist or foam fire extinguishers. We would also try and locate the power source and remove electrical power (electricity is most likely to be the cause of a fire on board). The smoke detectors trigger an automatic response from the ISS to shut down all ventilation systems, so as not to feed oxygen to the fire and to reduce the spread of smoke throughout the station."
 
Here's Chris Hadfield demonstrating some of their fire safety equipment... if by demonstrating you mean 'playing with it, and using it as a musical instrument':

 

If all else fails, the ISS always has at least one man rated spacecraft docked to act as a life raft. However the crew operate on a very, very strict ‘prevention is better than cure’ policy*: Anything going up to the ISS is tested to make sure it's completely non flammable - that's done by pressing a heated filament against it in a ventilated, sealed, box. When an experiment or mission absolutely must carry something flammable up there the crew do everything humanly possible to keep it away from any sources of ignition.

Until there's a real space fire service it will stay the nightmare enemy for astronauts - but we're getting better at understanding and controlling it, and it's turning out to be an amazing thing to study (even aside from the terrible danger)...

* Because you don't want to tell your boss you broke the ISS and left it to explode now, do you? Unless you're Sandra Bullock.


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Monday, 30 July 2018

Answers for Authors: Could an astronaut really grow their own food? (re-posted)


Want to support the future science and engineering? You can do so through one of these charities:

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The Association for Science Education 

Yes. Yes they can. 

In fact, the future of salad in space looks multi-coloured, crunchy, and even good enough to protect against the space crazies. 

I mean... I'm not saying they might not prefer rare steak. But stuffing a cow into a rocket isn't easy.

Disclaimer: Not a real space cow.
Nor would mucking one out be, although sending living things into space to see what weird things happen to them is a long and horrifying tradition. In fact it's how the story of fruit and veg in space begins: America was shooting seeds of maize, rye and cotton above the atmosphere, well before NASA came along, on V2 rockets capture from Nazi Germany. 

This wasn’t a simple case engineers imbibing a bottle of scotch and wondering ‘what can we do with this rocket thing then? ’ To prove who was the smartest country to the world, they wanted to put a human into space. Having them come back horribly mutated, screaming insane, or just plain dead would not net anyone a Christmas bonus - so they needed to see what effects space would have on living tissue.  A lot of critters were eventually sent up...

Above: All the space critters, courtesy of Space.com.

...but plant seeds were actually the starting point - you don’t need to put anything very complicated or expensive in the rocket to monitor what happens to them, just see if they grow when they get back to Earth. Slightly to everyone’s surprise, seeds sent into space grew perfectly normally*, and sending seeds was established as a cheap and simple way to test a destination. When Apollo 14 went to the Moon Loblolly Pine, Sycamore, Sweetgum, Redwood, and Douglas Fir seeds went along. They were planted back on Earth, to see if being on the Moon had done them any damage: It hadn’t. 

In botanist's heads an idea started to grow (not fertilised by poo, but enthusiasm): Although space was seen as a domain of shiny machines, square jawed heroes, and mutilated animal remains, there might be room for plant biology experiments up there. Not just to see how mucked up a plant that can’t tell which way up is gets, but because… 

Well… actually, yes: Seeing how mucked up plants get without gravity is a genuinely useful way to find out more about them. It’s using a change in gravity - something that's hard to do properly here on Earth** - to investigate plant biology, growth, and development.  

After a years of nagging, the Soviet Salyut 7 space station crew grew some Arabidopsis plants in microgravity - they flowered, and the idea caught on: An experiment on the US Skylab spacestation studied the effects of gravity and light on rice plants, the SVET-2 Space Greenhouse successfully achieved seed to seed plant growth in 1997 aboard space station Mir, the Bion 5 satellite carried Daucus carota, Bion 7 carried corn.... and so on. 

Above: The Skylab space station. Courtesy of NASA.

Once the first plants had flown more things to research became apparent. 

If you're just looking for a run down on where in the solar system we might grow plants one day.... you can probably skip the next bit. But for those with an interest in more technical details here's a quick cross section of some of the phenomena and experiments affecting plants in space:

  • Microgravity makes it easier for plants to move – plants move on Earth (just jump on youtube and look for videos of plant movements following the Sun over the course of a day), but microgravity allows movements too small to be noticed on Earth to show up, revealing things about plants circulatory systems and some movements we don’t understand the meaning of yet. 
  • Microgravity also influences how water moves through the soil – instead of flowing downwards it gathers close to the entry point, turning some parts of the soil into watery slurry, and leaving others parched. 
  • Plant research continued on the International Space Station, using flowers grown on a nutrient-rich gel in clear petri plates. That’s not just to make it all more sci-fi, the idea was to watch how the roots grew. We know that plants generally do sense gravity, and that’s why they know to send roots down and shoots up. To do this they use starchy structures called amyloplasts – these are denser than the cytoplasm (jelly stuff inside the cell) so they sink to the bottom of the cell under gravity, giving it an idea of which way to grow. Yet plants with fewer of them still figure out up and down eventually – so even on Earth we know sensing gravity isn’t the whole story. The space flowers confirm this: They showed growth patterns thought to be gravity dependant, so it seems that some plants can read other indicators to which way their shoots and roots should grow. 
  • Some plants definitely don’t like space as much as others: Their roots grow in the wrong direction without gravity, and the second generation of canola seeds grown aboard the International Space Station were pretty sickly. 
  • Potatoes grew the same in space as they do on Earth, as do many others, but lack of gravity also works on plants in indirect ways: Like humans they need constant ventilation, or they could end up suffocating in a bubble of their own waste gasses.  
  • How are those plants that thrive doing so? The alternative cues they follow include moisture, nutrients, and light. A study of how the plant’s use various kinds of genes in microgravity backs that idea: The University of Florida grew the A. thaliana plant on the ISS, and found that plants in microgravity used ‘adaptive strategies’ - like increasing their expression of genes associated with light perception in the leaves. Understanding those strategies could help us to create strains specifically adapted to space, but (in an uncharacteristic move of co-operation by mother nature) many plants seem to find solutions themselves. 

All this experimentation has born fruit (or at least tomatoes, which I'm still confused about): An experiment snappily named ‘Biomass Production System’ was used on the ISS, and later the VEGGIE system (Vegetable Production System). Plants tested in VEGGIE included lettuce, Swiss chard, radishes, Chinese cabbage and peas. American astronauts first ate plants grown in space on August 10, 2015 when their crop of Red Romaine was harvested. 

Above: The ISS crew  harvesting crops from the station's greenhouse.

Well done NASA. 

Although Russian cosmonauts have been eating their own crop since 2003, so presumably the Russian word for ‘sissies’ may have been muttered through mouthfuls of lettuce and salad. For several years. 

OK, that’s on a space station, in a nutrient gel. True colonies are another story, though. If off-Earth colonies want to grow, or if they can’t recycle every last atom of waste, they'll need additional nutrients. So will Lunar soil, for example, support plants? 

On the face of it, the Moon isn’t a great farming prospect. The utter lack of air is a wee bit of a problem – but if we domed over a section, melted some lunar ice, and filled the dome with  atmosphere… would we get crops, or just damp dust? Well NASA  provides a lesson plan (here), so you can do some experiments yourself.

Researchers have tried growing plants in simulated Lunar and Martian soil - their mineral composition is similar to volcanic Earth soils. Wieger Wamelink and colleagues at the University of Wageningen, in the Netherlands, grew a veritable salad – wheat, tomato, cress and mustard – for 50 days with no added nutrients. The plants even grew better in the simulated Mars soil than in poor quality Earth soil, and the Lunar soil simulant was comparable to the poor quality Earth soil. According to Rober Ferl, who does similar research at the University of Florida:

“Get to Mars or the Moon and, yes, plants will pull minerals from whatever soils we give them. Any atoms that plants pull [out of the soil], we don’t have to pack.”  

Above: A prototype lunar greenhouse at the University of Arizona

Any people with a biochemistry background reading that have just gone ‘Huh?'

Why ‘Huh?'

Because life is based on four main chemical elements: Carbon, Hydrogen, Oxygen and Nitrogen (CHON). In Earth soils these are abundant as organic matter. But the soils of the Moon and Mars are very poor in organic matter, as their soil is essentially ground up rock. 

So where are these plants getting their CHON from? 

It turns out that many species of plant simply don’t need their CHON as organic matter. The right bacteria in the soil can extract those elements from the rock particles, which have CHON in them as chemically bound compounds. The plants then feed off the bacteria. For example, plants need nitrogen in it's reactive form - and the missing reactive nitrogen could be made by using ‘nitrogen fixing’ plants and bacteria. So to make Lunar soil fertile we may just need to add a sprinkling of microbes.  

We'll have to wait for future missions to see if the plants hold up on real alien soils - possibly more of a worry would be the heavy metal content of both soils - metals like aluminium and chromium that damage plant growth. These could be cleaned out in any number of ways, but it adds a layer of difficulty.

There’s more to the soil story: The Moon and Mars don't have the most fertile soils off Earth, the asteroids do. Specifically, carbonaceous or “c-type” asteroids, which are  packed with organic compounds and highly nutritious for plants. Michael Mautner, of Lincoln University in New Zealand, came up with a very direct way to test that: He grew edible plants in material from c-type asteroids, which had fallen to Earth as meteorites. He simply ground up the meteorite, added water, and seeds, and waited. 

Then he did something scientists don’t do often: He ate his results. 

While he was waiting his space salad to grow he also analysed the nutrient content of these meteorites, and calculated that a 200-kilometre-wide space rock could provide enough fertiliser to sustain 10,000 people for a billion years. That's pretty incredible, and the really good news is that asteroids are tiny, low gravity, places. Most of them you could jump right off of so mining their fertile soil, or shipping crops grown on one, shouldn’t be a problem. Michael Mautner got a meal from space, and a potentially revolutionary scientific result - just for doing a bit of gardening.

Not bad for grinding up some rocks. 

Above: Comet 67-P, as seen by ESA's Rosetta space probe. True it looks like a gigantic flying poo, but, being loaded with both water (as ice) and organic molecules  we could be looking at prime farming real estate.

What about water? Plants are fairly addicted to the stuff. Mars might have a little native liquid water, but it’s probably incredibly salty, and very scarce. The Moon has none at all, except in extremely unusual circumstances***. But both worlds have ice in abundance, and since we’d need to enclose crops in a warm greenhouse anyway...

 In fact China's recent Chang'e 4 mission did exactly this, successfully growing plants in a small greenhouse inside the lander - so all this is no longer just theory. 

The benefits of growing food in space aren't just physical, it  also improves an astronaut's psychological state. We probably shouldn’t be surprised at that, since so many cultures have independently adopted a green shoot as a symbol of hope – but giving astronauts a routine that involves long term responsibility to care for something living seems to be a big part of it too:
  
"It was surprising to me how great soybean plants looked," NASA astronaut Peggy Whitson wrote in one of her Letters Home while she was aboard the space station. "I guess seeing something green for the first time in a month and a half had a real effect. I think it's interesting that my reaction was as dramatic as it was."

Given the psychological dangers of space – the effects of extreme isolation, monotony, boredom, and space radiation induced dementia - a space garden seems like a very good idea.

Above: The first ever Zinnia in space. It's probably confused.

Are there any unknowns? Yes, plenty - the biggest thing we haven’t yet really tested is the effects of reduced gravity. That seems like and odd worry, considering how we’re able to get plants to grow with no gravity at all, but the devil is often in the details – what if by some quirk of biology there’s a ‘black zone’ around 1/6th G (the surface gravity of the Moon) which plants really don’t like? NASA has plans to test that by just sending plants there and just... seeing how they grow.  

Could a lone astronaut grow enough food to live on? Maybe - a lot would depend on where they were, and their exact circumstances. But, as far as growing crops in space generally goes.... I'd have to say yes.

In fact, in the long run, it's hard to see how astronauts will be able to avoid it.

* A disaster for animal rights, as that meant the animals were up next.
 
**On Earth changing gravity is pretty difficult – we have centrifuges but keeping a plant growing inside a spinning centrifuge for months on end isn’t easy – and the plant still has Earth’s gravity acting on it. Devices called clinostats can be used to spread gravity’s effects across all possible directions, but that isn’t exactly the same as taking gravity away.

*** There’s been speculation that an major asteroid strike into a large ice deposit could form a short lived bubble of atmosphere that would allow liquid water to persist for a few seconds



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Answers for authors: What is the view like from different parts of our galaxy? (re-posted)



To answer this we first need a quick bit of galactic geography:
Go out on a really dark, clear, night, far from any artificial lights, give your eyes time to adapt to the darkness, and look up. You will probably see many more stars than you’re used to and, stretching across the sky from horizon to horizon, a long band of faintly lowing fuzziness: That's the Milky Way, the galaxy that our Sun, our solar system, and this planet are part of.
 
This thing - although this is a long exposure that intensifies the light in the image. It doesn't look much like a swirl of stars from Earth, as we're inside the disk

It’s a collection of hundreds of billions of stars, at least that many planets, comets, nebula, and much weirder things with names like ‘magnetars’, ‘pulsars’, ‘white dwarfs’ that sound like they came straight out of an early draft of superhero comic. It's actually shaped like the swirl of cream in a coffee mug - and we can divide it into three bits:

  • The central bulge / galactic core: The centre of the swirl, the core is made of a mix of stars of all ages. It's also one of the oldest neighbourhoods, and has both a lot of old stars and clusters of very young stars, and gas clouds primed for new star growth. Everything is very close packed (less than half a light year between stars on average, often much closer). The bulge is about 5,000 light years in radius, and has at least two gigantic black holes in the centre, one of which is the supermassive Sagittarius A* black hole, our galaxy's central black hole which weighs as much as 4,300,000 Suns. 
  • The disc/arms: The arms of the swirl. About 60,000 light years in radius, and around 1,000 light years deep where the Sun is, it's mainly made of young to middle age stars. Beyond the edge of the disk is a mysterious ring of stars and gas surrounding it, with a radius of 75,000 to 80,000 light years, called the Monocerous ring. 
  • The galactic halo: This is where my coffee metaphor runs out completely, unless you’ve brewed your coffee in weightlessness and then spilled it – these are, well, wispy bits outside the main galaxy. They are made of widely spaced gas and stars, floating above or below the plane of the disk in a rough ball, stretching to a radius of 130,000 lightyears. Although the stars and gas are incredibly sparse there, set within the halo are locales called globular clusters: Round clusters of hundreds of thousands of ancient stars, which are often separated from each by less than the width of our solar system.
Let’s assume I’ve got a ship fast enough, and well supplied enough, to go around the galaxy and stop in each section. What would my human eye see? 

The galactic disk: 
A map of the galactic disk, showing the spiral arms. Courtesy of Universe Today.

The nice thing about figuring out the view from the galactic disk is I live in it: Earth is located in the 'Orion spur' - a sub arm of the disk about 25,000 light years from the galactic centre. So there's lots of information to go on...

After my eyes have some time to adjust to the darkness the Milky way is a rough, very broad, band of faintly glowing fuzz stretching across the sky. In the direction of the constellation Sagittarius I can see a bulge in the band, with dark gaps in it - that's the direction of the galactic core. The gaps are dark nebula, blocking light from that direction out. 
I can't actually see the galactic core - there's too much gas, dust,and intervening stars in the way. What I see is the result of the disk getting slightly thicker in that direction.
If I look about with care I see the occasional dim fuzzy blob of a star forming nebula (like the one on Orion’s belt), and glittering collections of blue stars - open clusters. 

Above: The Pleiades, a cluster of young stars still wearing the remains of the nebula that created them.

The stunning colours I've seen in pictures from space telescopes are nowhere to be seen because, well, my eye isn't a space telescope. But it's good enough to make out some things: Above and below the plane of the galaxy I can see the Magellanic Clouds - smaller galaxies that orbit the Milky Way - as broader fuzzy patches well away from the galactic centre.


The galactic centre: 
Above: Incredibly densely clustered stars near the galactic core, Courtesy of the European Southern Observatory.
The stars of the core are densely packed, often living within fractions of a light year of each other, and many of the biggest and brightest are either huge, ancient, red stars or clusters of equally bright, young blue ones. The bright, close clustered, stars around me stop anything outside the galactic centre being  visible - the core seems to be the whole universe.

The sky is much, much brighter than on Earth: A lot of these stars are as bright as Venus from Earth – some are as bright as a full moon all by themselves. How bright is that in total? It’s very had to tell exactly, because clouds of gas and dust keep us from getting a really good count and the brightest stars wash out the fainter ones… but a back of the envelope calculation suggests the sky would glow with at least 1/300 the the brightness of the Sun from Earth**.

If that doesn’t sound so bright – the full Moon is juist 1/400,000 the as bright as the Sun, so the sky in the galactic core would be over a thousand times brighter than the full moon. Switching the lights off on my spaceship would still leave me with the equivalent light of bright sunset.

But!

If I head deeper into the core, eventually I come to the heart of darkness: Sagittarius A*, the 4.3 million solar mass black hole our galaxy is centred on. The vast black hole is 'only' as wide across as the orbit of the planet Mercury, but for half a lightyear around it is a swirling doughnut of superhot gas that X-ray telescopes can pick up even from Earth -
the graveyard of stars and planets that passed too close to the hole.

The galactic halo: 
Above: The Andromeda galaxy, in a long exposure photograph that brings out otherwise invisible details. Our galaxy might look similar, from outside. Courtesy of Brian Snyder.
 The galactic halo is pretty lonely place. I’m well outside the galactic bulge and the disk, which are stretched out below me. 

I might have expected to see something like a celestial fried egg in an infinite black frying pan - but then I’m not remembering the view from Earth: There the galaxy is a dim fuzzy band across the night sky, even though I was looking lengthwise through it, with all the accumulated light of the  galaxy on my line of sight. Up here, looking down on the relatively thin galactic disk from a great distance, the only part that is very bright to the human eye is the galactic central bulge: A twinkling, fuzzy edged, blob of a billion stars – from here it’s easily brighter than the full Moon. 

Around it is an ethereal, almost invisible swirl of mist. That’s the galactic disk. You don’t need to take my word that it would be virtually see through: The Andromeda galaxy, that is regularly in the night sky from most locations, and it’s bigger than a full Moon. 

Ever seen it hanging in the sky? 

Above: The Andromeda galaxy, in a long exposure shot that makes it's outer regions brighter, and easier to see. Courtesy of Ted Van.
Probably not – even through a telescope, the only really visible bit is it’s galactic core. The spiral arms are vast, but too thin for our eyes to really make out.  

That said, it’s a dark sky out here: Rather than being separated by five or six light years, as in the spiral arms, the stars out here are separated by hundreds or thousands of light years. For that reason, if you turn so the bright core is behind you, it’s possible to dimly make out the structure of the spiral arms. Other galaxies are also more visible than from Earth, even through the disk of the Milky Way.

Globular cluster: 
A globular cluster - a vast ball of ancient, close packed stars.
 The last stop on our galactic whistle stop tour: These are huge collections of ancient, red stars floating in the galactic halo. Mostly they're located in a shell around the galactic core - and the stars are, if anything, even more tightly packed – big, bright old stars, dating from when the rest of the galaxy was just a huge cloud of gas. I can't see much outside of the cluster, except maybe the galactic core. 
Although this place is as bright as the core, the quality of the light is different: Orange-white, as every star is an ancient red giant or dwarf.
The close stellar quarters means that any planets will have been stripped away from their solar systems - not that there will have been many: Globular clusters are incredibly poor in heavier, planet forming, elements. This is a place where no new stars have been formed for billions of years - in many ways it's a tiny, zombie galaxy in it's own right.

And, finally, I can turn and head back to Earth. Hopefully I didn't leave the oven on... 

**The back-of-an-envelope calculation went: The very central cubic parsec (1 parsec = 3.26 lightyears) of our galaxy is estimated to contain 10,000,000 stars. To get a rough lower limit for how bright that would be, lets assume all those stars are as bright as the Sun (in reality many of them are far, far brighter), and arrange them in a sphere with a radius of 0.825 light years - the average distance from the centre assuming the stars are evenly spaced. Earth is 8 light minutes – 0.000015 of a light year, from the Sun. That means our hypothetical stars are each 55000 times further away from the centre of the sphere than the Sun is from Earth. Luminous intensity decreases with the square of distance, so each of those stars is delivering 1/ 3,025,000,000th of the Sun’s intensity at Earth. Multiplied by 10,000,000 that givs a total brightness, across the whole sky, of 1/302th the brightness of the Sun from Earth. 


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