SPOILER WARNING!!!

 cootha_escape

From the Book

As Will tipped forward off the platform, a blinding column of light shot into the sky. At first he dropped like a stone, hurtling headfirst towards the meadow underneath the tower. Then, as the wind picked up and the wings flared, he started to move forward. Below him the mountain top pulsed and birds and bats rose screaming into the air. Just as he was about to crash into the treetops, the ground below collapsed, pulling them down with it. Branches whipped at his face as he shot out over the disintegrating cliff face.

Only then did he realise he didn’t have a parachute.

The Problem

Will is stuck at the top of Mt Cootha with only minutes left until the nuke he’s left deep under the mountain explodes, taking him and everything else with it. His only chance is to escape the zone of destruction – but he’s got very limited options!

He’s just made it onto the top of the mountain and there’s only six minutes (by the time he makes it to the shed) until the nuke goes off. He has a couple of possible options for escape – a bike, a wingsuit – and no time to make a considered decision.

The Bike

bike_escape
Copyright OpenStreetMap Contributors

Will finds a bike in a shed. He knows from the sign he saw earlier that it’s 500 metres to the nearest road up a stairway. He can make a quick and dirty calculation on how far he’ll be able to get away using a bike:

Time to make it up the stairs = distance / stair climbing speed carrying a bike

Will can estimate that he can run, slowly, up the stairs carrying the bike – so 10 km/hr:

Time to make it up the stairs = 500 metres / 10 km /hr

Converting into consistent units:

Time to make it up the stairs = 500 metres / 10000 m / hr

Time to make it up the stairs = 500 metres / 2.78 m / s

Time to make it up the stairs = 180 seconds

Time to make it up the stairs = 3 minutes

Taking 3 minutes to get up the stairs leaves him with 3 minutes to ride downhill as fast as he can. He can calculate approximately how far he’ll get in 3 minutes of fast flat and downhill riding (the top of the mountain is flat) by estimating an average speed of 50 km/hr:

Distance ridden = time x speed

Distance ridden = 3 minutes x 50 km / hr

Once again converting everything into consistent units:

Distance ridden = 180 seconds x 13.9 m/s

Distance ridden = 2500 metres or 2.5 km

Will thinks this isn’t far enough to have any reasonable chance of escaping the blast zone. So his next and only option is to grab a wingsuit, and try flying off the mountaintop.

The Wingsuit

What we’re going to do here is work out whether it is remotely possible Will could escape from the top of the mountain. I’m not going to give any certainties because a) we’re going to have to guesstimate a lot of the relevant parameters and b) because you’ll have to read Book 2 in the series to find out for sure!

Can Will Climb High Enough to Not Hit the Ground?

wingsuit_glide_path

A wingsuit takes approximately 10 – 15 seconds to reach its “flying” stage where it moves forward about 2.5 units for every 1 unit it falls. During this time the fall rate of the flyer accelerates to a maximum fall speed (perhaps around 100 km/hr downwards) then reduces to a slower fall rate (maybe around 45 km/hr). In total the wingsuit flyer may fall about 200 – 300 metres during this stage.

The towers at the top of Mt Cootha are only about 150 metres tall. Luckily:

Looking down, Will could see the point where the trees stopped at the drop-off and then re-appeared on the slope below, running downhill towards the quarry.

There’s a drop-off below the tower where the mountain drops away before sloping downhill towards the quarry. This drop-off means that Will may be able to fall for those 10-15 seconds without hitting anything, even though he is only moving forward slowly at first. But he’d definitely need to climb to near the top of the tower.

One way in which the nuke helps Will is that the mountain top drops away below him as he jumps off the tower – leaving him with a greater vertical distance to fall before hitting anything.

How Far Can Will Fly?

Will jumps from the tower with between 1 and 2 minutes until the nuke goes off. A wingsuit flight reaches a maximum sideways speed of maybe 120 km/hr after about 10 seconds of flight. If we are optimistic and say Will has up to 110 seconds (two minutes less the 10 seconds required to accelerate to full sideways speed) of flight time, how far can he fly?

Distance covered = sideways speed x time

Distance covered =  120 km/hr x 110 seconds

Standardize units:

Distance covered =  33.3 m/s x 110 seconds

Distance covered =  33.3 m/s x 110 seconds

Distance covered =  3670 m

Interestingly, because Will has far less time with the wingsuit than the bike, he can’t cover that much more distance (even though the wingsuit is much faster). However, the wingsuit has one other significant advantage – it flies in a straight line, unlike the bike which must follow the curvy mountain road. This means he can get further away from ground zero, giving him a higher chance of survival.

curved_versus_straight

Landing the Jump

Will realizes as he jumps that he doesn’t have a parachute. He still has a chance however – wingsuit flyers have landed and survived without a parachute, albeit into cardboard boxes. His best chance lies in landing on a surface with the same slope as his fall, which (if he flies the suit properly) is a ratio of about 2.5 to 1. There’s a hint of possible landing sites earlier in the book:

The road ahead curved in a large arc, the mountain on one side, a lake on the other. Spotlights lit up the quarry walls, cut deep into the side of the mountain. Each cutaway was separated by a sloped section covered in enormous tarpaulins, glistening in the rain. It reminded Will of the water slides he’d slid down when he was a kid.

If Will is able to land on the slippery tarpaulin downslope he might stand a chance. The ideal landing site might look something like this in profile – matching Will’s angle of fall at the start and gradually flattening out:

 landing_site