How high is space, how far can you fall with a parachute, where is the Project Calliope satellite going to be, and where does the hard radiation from the sun get nasty? Gathered for the first time in one place is our High Altitude Explorer's Guide.

A typical airplane cruises at 9km (6 miles) up, around 30,000 feet. Military jets (from the SR-71 onward to modern planes) can hit over 30km (19 miles) up, over 100,000 feet.

Can you parachute from that height? Yes, in 1960 Joseph Kittinger set the record at 31.3km (19.5 miles), or 102,800 feet. Felix Baumgartner is trying this year, 2010, to freefall from 36km (over 22 miles), an 118,000 feet fall.

But those aren't 'space'. In the US, "space" begins at 80.4km (50 miles), or 264,000 feet. General international consensus sets a similar limit for the start of space as 100km (62 miles), or 380,000 feet.

"Low Earth Orbit" (LEO), where many satellites live, goes from 160km (100 miles, 525,000 feet) to 2,000km (1,240 miles, 6.5 million feet). In LEO, we have some sample objects to look at.

Our own Project Calliope satellite will be 230km up (143 miles, 755,000 feet). The International Space Station (ISS) cruises higher up, from 278km (173 miles, 912,000 feet) to 460km (286 miles, 1.5 million feet).

Starting above the 'space' limit but a bit before LEO, the inner Van Allen Belts, which magnetically shield the Earth's surface from high energy particles, extend from 100km (62 miles, 33,000 feet) up to 10,000km (6,200 mil, 3.3 million feet).

And geostationary orbits are at 35,786km (22,236 miles, 117.5 million feet). These geosynchronous orbits, lined up above the Earth's equator, have an orbital period equal to one day, so they 'hover' over the same spot of the Earth.

Alex

Tuesdays at The Satellite Diaries and Friday at The Daytime Astronomer (twitter @skyday)

A typical airplane cruises at 9km (6 miles) up, around 30,000 feet. Military jets (from the SR-71 onward to modern planes) can hit over 30km (19 miles) up, over 100,000 feet.

Can you parachute from that height? Yes, in 1960 Joseph Kittinger set the record at 31.3km (19.5 miles), or 102,800 feet. Felix Baumgartner is trying this year, 2010, to freefall from 36km (over 22 miles), an 118,000 feet fall.

But those aren't 'space'. In the US, "space" begins at 80.4km (50 miles), or 264,000 feet. General international consensus sets a similar limit for the start of space as 100km (62 miles), or 380,000 feet.

"Low Earth Orbit" (LEO), where many satellites live, goes from 160km (100 miles, 525,000 feet) to 2,000km (1,240 miles, 6.5 million feet). In LEO, we have some sample objects to look at.

Our own Project Calliope satellite will be 230km up (143 miles, 755,000 feet). The International Space Station (ISS) cruises higher up, from 278km (173 miles, 912,000 feet) to 460km (286 miles, 1.5 million feet).

Starting above the 'space' limit but a bit before LEO, the inner Van Allen Belts, which magnetically shield the Earth's surface from high energy particles, extend from 100km (62 miles, 33,000 feet) up to 10,000km (6,200 mil, 3.3 million feet).

And geostationary orbits are at 35,786km (22,236 miles, 117.5 million feet). These geosynchronous orbits, lined up above the Earth's equator, have an orbital period equal to one day, so they 'hover' over the same spot of the Earth.

Alex

Tuesdays at The Satellite Diaries and Friday at The Daytime Astronomer (twitter @skyday)