On / by Alex Keen

For the schoolchildren we visit in our Classtronauts program, the highlight is unquestionably the moment of release. Even the most cynical teenagers find themselves swept up in the excitement when we begin the countdown, while primary school pupils are practically whipped into a frenzy, doing dance moves and poses from video games, trying to initiate their own countdowns, running around – we feel a little for the teachers who have to teach them for the rest of the day!

The experience is a little different on our end. We’ve launched hundreds of flights to the edge of space and while it’s always exciting, our focus at that moment is on ensuring our payload electronics are functioning correctly and packing away our launch kit. While for the children, this is the pinnacle of the event, for us it’s the start of a long journey to track and recover our payload.

For us, the most enjoyable part of the day actually comes before the launch site is even set up. As part of our Classtronauts visit, we deliver a presentation about the launch process during the school assembly, which is followed by a Question and Answer session with smaller groups. These are invariably a treasure trove of questions both insightful and silly, and today we’re going to share three of the best questions we’ve had. Any teachers reading, feel free to reference these answers yourselves.

What happens if you send a giraffe to space?

Sending celebrities, family members, classmates and animals into space is a common theme in our Q&A sessions. While it’s hard to decide what’s the most bizarre living thing proposed in these hypotheticals, a giraffe is certainly high on the list.  Anyway…

After getting over the shock of being lifted above the ground, the first thing a giraffe on one of our flights would experience is the cold. At an altitude of just 1000 metres, the ambient temperature is already around 7°C lower than on the ground. For a creature suited to the warm savannahs and woodlands of Africa, this would hardly be a comfortable temperature shift, but it’s still within survivable bounds.

Further up, however, the temperature continues to drop – and as it does, so too does the air pressure. At 8,848m (the height of Mount Everest), the air is about 40% of the density experienced at sea level, meaning it’s harder significantly harder to breathe. At this height, ambient air temperature is below 0°C and will continue to drop for some time. Things do not look good for our giraffe friend!

The boundary for Near Space is defined by the Armstrong Limit, which is an air pressure of 6.3kilopascals. This is the pressure where the boiling point of water is equal to human body temperature (around 37°C). Depending on atmospheric conditions, this pressure tends to be found at an altitude around 18-19km. Above this point, no human can survive without a pressurised suit or capsule.

Now, the body temperature of a giraffe is 1-2°C higher than that of a human, so they’ll reach this point slightly earlier. However, this won’t kill the giraffe, who will already have suffocated.

Will it land on the moon?

Not quite. The balloons we use to conduct our flights are made from a highly stretchy latex, which we fill with a buoyant gas – usually helium, but sometimes hydrogen. They’re designed to expand many times over before bursting, so that the buoyant gas we use can lift them high into the stratosphere into Near Space, which is the closest region of space above the Earth. Near Space extends from 18-19km up to the Karman Line at 100km, which marks the boundary of Outer Space. As the balloon rises, the external pressure drops. This makes the balloon expand as the gas inside exerts a relatively greater force. Eventually, the balloon will be the size of a double decker bus, before the latex can expand no further and the balloon bursts. This usually happens at about 34-38km. The moon is 384,400km away – around 10,000 times the height our payloads reach.

Even if the balloon could stretch indefinitely, it still wouldn’t go to the moon. Eventually, the external pressure is so thin that the gas inside the balloon is equally dense. The combined weight of the system is perfectly balanced by the lifting force of the gas, so the flight system reaches neutral buoyancy and floats. The highest altitude ever recorded on a gas balloon flight is 53km.

To get to the moon, we’d need to use a rocket, which would cost millions and millions of pounds. However, from the peak of our flights, we can still see the curvature of the Earth, the blackness of space and the thin blue line of Earth’s atmosphere on the horizon!

What if a bird flies into the balloon?

Because the balloons are stretched so much during the flight, it’s vital that they don’t get punctured somehow. The balloons are manufactured in a way that ensures they are as close as possible to perfectly even in thickness at every point, so that there are no weak points in the material. We use latex gloves when handling them at launch, to prevent the natural oils on human skin from degrading the latex. We also keep them away from any sharp edges at the launch site, doing everything we can to preserve their integrity until they’re released. But once we let go of them, we have no control over their flight path.  Birds aside, what could happen if our balloons come into contact with an aeroplane or a helicopter?

Well, there are a couple of answers here. Firstly, every flight we launch is logged with the Civil Aviation Authority, who regulate use of airspace in the UK. They give us permission to conduct our launches and issue a Notice to Airmen, which anyone who uses airspace can access and check. We’re able to predict the flightpath of our payload to a very high degree of certainty and we launch only on days when we can be certain we won’t pass through any major commercial flight paths.

Secondly, statistically it’s just not very likely that we will encounter anything. The sky is mostly empty and most other things in the air mostly move horizontally, whereas our payload’s movement is primarily vertical. At the speed we move, we don’t spend more than a minute at any machine or creature’s cruising altitude before we move on. Even without taking any precautions, the odds of our payload encountering a balloon are slimmer than the odds of winning the lottery jackpot – twice.

Let’s get back to birds. They don’t check Notices to Airmen, do they? However, birds are highly adept at avoiding collisions in the air. After all, a flock of a hundred birds can twist and turn and change direction in seconds without a single one bumping into another. What’s more, our balloon is a big, cream-white spheroid. It looks, in fact, quite a bit like a giant egg. And if there’s one thing every bird is afraid of, it’s a bigger bird!

 .  .  .

While these questions might seem a little silly, we always endeavour to answer them honestly, even if we don't know absolutely everything. The Classtronauts program isn't just about giving kids an exciting day away from normal lessons, it's about inspiring them to follow an interest in space. Cultivating and rewarding their curiosity is a vital part of achieving that goal. For more information about Classtronauts, visit the Education section of our website.

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