Categories: Astronomy

Astronomy Without A Telescope – The Only Way Is Up

Escaping a gravity well is never an easy proposition. Unlike other kinds of wells there are no walls, so your options are ilimited. Over the years we humans have experimented with a variety of ways of getting out – with varying levels of success.

Trying to build your way out was first attempted – at least allegorically – with the Tower of Babel which (again allegorically) did not go well. Even with today’s engineering, it remains a dubious prospect. The relatively new Burj Khalifa in Dubai has managed to scale only 830 metres. The official defintition of where ‘space’ starts is 100 kilometres (or 60 miles).

Firing yourself out of a cannon or strapping explosives to your throne in the case of Wàn Hù, generally described as a minor official of the Ming Dynasty circa 1500, is similarly fraught with problems. See the Mythbusters episode Ming Dynasty Astronaut to see how that worked out.

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Even if you do survive the initial blast, the huge acceleration required to achieve a projectile escape velocity of 11.2 kilometers a second from sea level will kill you anyway. And there’s also an issue of atmospheric drag – since the air in front of you will be superheated, your already Gforce-demised self will get cremated on the way up.

It would all be so much easier if someone could just throw down a rope. Various people have been attributed with first thinking up the space elevator – but it was probably Konstantin Tsiolkovsky – involving getting a base station into geostationary orbit and then lowering down from it kilometre-lengths of a carbon nanotube cable that we’ll be inventing any day now.

: The last Saturn V launch (with Skylab 1) in May 1973

So for the moment at least, we are stuck with good old-fashioned rockets – for which we can also thank Mr Tsiolkovsky, amongst others. Although achieving a zero to 11.2 kilometers a second velocity at sea level will kill you – if you can get a bit of altitude at a lower acceleration rate, the escape velocity from that altitude will be lower. So as long as you can launch with enough fuel to keep gaining altitude, you can keep on applying this logic until you eventually escape the gravity well. We’ve done it with robotic spacecraft, but we’ve never done it with people.

Before I start sounding like a Moon landing denier, remember the Moon is still orbiting within Earth’s gravity well. Lagrange points 1 and 2, about 1.5 million kilometres away mark the edges of the Earth’s gravity well. L2 is perhaps the better target since you could use the Earth’s shadow to reduce your exposure to solar radiation. At 1.5 million kilometers, it’s about four times the distance to the Moon, so a one month round trip maybe. It’s still challenging and you’ll still collect a hit from cosmic rays – but nothing like the potentially suicidal two year round trip to Mars. So, if we can get past this obsession with landing on things, wouldn’t it be a wothwhile goal to try and finally get someone out of the well?

Steve Nerlich

Steve Nerlich is a very amateur Australian astronomer, publisher of the Cheap Astronomy website and the weekly Cheap Astronomy Podcasts and one of the team of volunteer explainers at Canberra Deep Space Communications Complex - part of NASA's Deep Space Network.