How fast

In response to a very good question ™ posed by one of my students, a response. First, the question:

Question

How fast do spaceships or probes or satellites go? How long would it take for them to reach the closest star? The center of the galaxy?

Answer

The Voyager space probes, launched in the late 1970s, went to visit Jupiter and would eventually travel outside of our solar system. It’s actually approaching the Oort Cloud, and the true boundary of the system, called the Heliopause.

Voyager is travelling at about 56 000 km/h [1]. A different source cites a maximum velocity of 62 856 km/h [2]. It’s hard, sometimes, to decipher all of the conflicting information. At any rate, it will reach Proxima Centauri in about 19 000 years. Yawn.

More recently, the New Horizons space probe left Earth at a speed of 58 016 km/h, which is also quite impressive. [3] After passing close by Jupiter, and using something called gravity assist, it was accelerated to a speed of 83,700 km/h. [4] Even more impressive.

However, that’s not the whole story. (Neither is this example, as you will soon see.) The Pioneer 10 probe, sent out in 1972, was also accelerated by Jupiter. It reached a speed of 173 000 km/h. Faster yet.[5]

But there is… another. Launched in the mid 1970s by Germany (and the US), Helios was sent to orbit the Sun. Being accelerated by a mass that’s ten times that of Jupiter means a bit of a boost. Up to 240 000 km/h [6] (wikipedia says 252,792 km/h, but with no sources).

That seems to be the record. And it would take about 4 500 years for it to reach Proxima Centauri. If it were pointed towards there, that is.

What’s Dextre doing?

Your daily gratuitous Dextre (from APoD):

What’s the world’s most complex space robot doing up there? Last week, Dextre was imaged moving atop the Destiny Laboratory Module of the International Space Station (ISS), completing tasks prior to the deployment of Japan’s Kibo pressurized science laboratory. Dextre, short for the Canadian-built Special Purpose Dextrous Manipulator, has arms three meters in length and can attach power tools as fingers. Behind Dextre is the blackness of space, while Earth looms over Dextre’s head. The Kibo laboratory segment being deployed during space shuttle Discovery’s trip to the ISS can be pressurized and contains racks of scientific experiment that will be used to explore many things, including how plants brace themselves against gravity, and how water might be inhibited from freezing in cells under microgravity.