Posts Tagged Space travel
The answer to that question quite obviously relies on the reader, I’m in London for example. You could be in a town nearby, or across the country or for all I know thousands of miles away. But we can group together where we live, if you are reading this in Brighton or Dunstable then we could say we both live in the south of England. If you’re reading this in York or Leicester we could stretch it and say we both live in England. We can play this game for a little while before we inevitably come to the conclusion “we all live on Earth”, but where exactly is that?
Our pale blue dot is flinging itself around the campfire we call the Sun at around 30km per second (London to New York in 3 minutes). We share this Sun with seven other planets; Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune along with five dwarf planets; Ceres, Pluto, Haumea, Makemake, and Eris. Along with a few score moons, a couple of asteroid belts and a sprinkling of comets we all make up the solar system together. It’s hard to get round just how big the solar system is, there isn’t even a definitive boundary with clouds of asteroids extending for trillions of kilometres around our Sun. But that number “trillions of kilometres” is meaningless, let’s face it, I could have said billions or zillions for all the connection it has with our lives. In light of this I’d like to share an analogy I often use…
Imagine the distance between the Earth and the Sun (some 150 million kilometres) and shrink it right down to just one metre. At this scale the Earth is just 80 millionths of a metre wide (about the size of ten red blood cells side by side). The Sun is little bigger than a marble at 9 thousandths of a metre. 40cm from the Sun we find Mercury and just 30cm beyond that we have Venus. Within our metre sized orbit the Moon is nearly 2mm from our bacteria sized Earth, about the size of two grains of sand. This is the furthest mankind has ever gone in our universe. It took years for thousands of geniuses and billions of dollars to take us just 2mm on our scale. With the solar system shrunk down like this Neptune, the furthest planet, is just 30 metres away from our marble sized Sun. Eris, the furthest dwarf planet doubles that distance at 62 metres. Taking this orbit as the boundary of our system on our scale a football pitch would fit within our entire solar system with a few metres either side to spare. This is our solar system, over 120 metres wide and the furthest we have travelled is just two measly millimetres. But our home doesn’t stop there.
Our solar system is just one of hundreds of billions inside the galaxy we call the Milky Way. If you live in a place with low light pollution you can look up at night and see the disk of our galaxy cutting straight across the dark. Our spiral galaxy is so large that we have to measure it in lightyears, that’s the distance that light (the fastest possible thing, it travels at 299,792.4 kilometres every second) travels in an entire year! In kilometres that’s 9,450,000,000,000,000! In our scale one lightyear is 61km, nearly twice the length of the English channel at it’s smallest width. The nearest star system to us is four times that again! On our little scale where the Sun is a marble and the Earth just a collection of cells wide the Milky Way is 6 million kilometres wide. Even with our horrendously shrunk down scale the length of the Milky Way is equivalent to circling the equator 200 times. This is our home; our town, our country, Earth, every planet we’ve ever seen all of them are there in this galaxy. But if we are being honest, it’s not really our home. Oh no, we’ve barely begun to talk about that…to be continued.
I’ve just watched a fascinating animation of the international space station being assembled. That got me thinking and next thing I knew I was hammering out a blog post.
When I was young I always wanted to be an astronaut. When I was four I went on holiday to Florida and visited the space centre there, from then on I was hooked. I loved rockets and shuttles to the extent that even now if I see a rocket launch on TV I get glow of pride and awe that our species has managed to do this. In my pre-teen childhood I was quite into all the traditionally geeky space stuff like Star Trek and other shows which now if I ever see annoy the hell out of me for two reasons;
Firstly, any TV show that calls itself “science-fiction” typically takes a white-western conservative culture and bolts on shiny tech.
Secondly, flying off to other planets isn’t a dream that is going to be available to us any time soon.
Every now and then I meet someone who admits that they believe the moon landings were a hoax. My second response to this (my first being to try to beat them to death with their own internal organs) is to ask why they think this way. Aside from flag waving, shadows and reflections the only interesting question that is asked is “why haven’t we been back?” The last Apollo mission was nearly forty years ago and since then there hasn’t been any grandiose feats to rival those missions. We live in a world where technological development appears to progress almost exponentially. Moore’s law is a good example of this (transistor numbers on computer chips double every two years) and we see it in our daily lives. The laptop we bought that was state-of-the-art last week was barely second best when we got it home from the store and by now deserves a dusty shelf in some museum. Now I’m not suggesting that space science has not progressed in the last forty years but it’s important to note that in that time space science has not yet developed to the point where it can give us cheap space travel.
At the time of the space race NASA was costing the US 4% of the federal budget. Out of every dollar the US spent 4 cents went to NASA and with this they got to the moon. This is thing about manned space travel, its hideously expensive, it takes a significant cut of a very rich country’s budget and it gives no profit back. I’m not suggesting that we should only commit to projects that have economic benefit (far from it) but the fact is that any manned space travel project requires a fortune in surplus funds (Note: the US didn’t go to the moon because they had some spare change and a twinkle in their eye, they did it for competition and the potential dangers of having a USSR military dominance in orbit).
Space travel is inspiring, it’s romantic but above all its bloody expensive. But all is not lost to the warcries of “cuts”, “audit” and “profit”. As technologies progress and economies grow we may find ourselves again in the position where we have the capability and the will to strive out into space with manned travel. Mars has always been seen as the next step for human exploration but a Mars mission is a world more difficult than a lunar one. Once a ship leaves the protection of the Earth’s magnetosphere (which the moon is within) the intensity of radiation exposure from the sun massively increases. Even more of a problem is the fuel and engine technology it takes to get there, the probes we send to Mars take years and are only making a one way trip.
All current rockets use chemical fuel as a propellent, but this gives a very limited burn time before the fuel runs out. With an equal fuel:rocket ratio our current technologies can give only a few minutes of thrust (for more info see “specific impulse“). There are other technologies being used, some probes use ion thrusters which can burn for months but they give very very low thrust (0-60 in about four days). However all that may be soon to change, the next generation in rocket technology will soon be launching to the international space station. In 2014 a VASIMR rocket will be attached to the side of the station, this type of rocket promises to give high thrust with very long burn times (hours-days). It does this by heating its fuel until it turns into a superhot plasma that it then shoots out of the back of the engine with a magnetic field. If this engine passes testing and gains investment we could be seeing a wave of VASIMR craft capable of taking us back to the moon and across to Mars in just months of travel time rather than years. In addition to this there have been a sprinkling of other technologies proposed such as a plasma bubble generator that would protect the ship from radiation by making a strong magnetic shield to deflect it, and the always jaw-dropping proposal of building a tower to orbit.
Space science isn’t as attractive as it used to be, the middle generation grew up with the images of moonlandings and shuttle launches. We’ve got budget cuts and Justin Bieber. But this isn’t the end of man’s story in space, our science marches on and when conditions are favourable we’ll be able to invest in technologies that will get us back out there. I’d like to think that this lull we are in is just the first interval in a long epic play…and the second act is starting soon.