Category: Aviation & Aerospace

Jerry Elliot High Eagle: Saving Apollo 13

Apollo 13 Mission patch of three golden horses travelling from Earth to the moon
Image by NASA Public domain via Wikimedia Commons

Jerry Elliot High Eagle was possibly the first Native American to work in NASA mission control. He worked for NASA for over 40 years, from the Apollo moon landings up until the space shuttle missions. He was a trained physicist with both Cherokee and Osage heritage and played a crucial part in saving the Apollo 13 crew when an explosion meant they might not get back to Earth alive.

The story of Apollo 13 is told in the Tom Hanks film Apollo 13. The aim was to land on the moon for a third time following the previous two successful lunar missions of Apollo 11 and Apollo 12. That plan was aborted on the way there, however, after pilot James Swigert radioed his now famous if misquoted words “Okay, Houston … we’ve had a problem here”. It was a problem that very soon seemed to mean they would die in space: an oxygen tank had just exploded. Instead of being a moon landing the mission turned into the most famous rescue attempt in history – could the crew of James Lovell, Jack Swigert and Fred Haise get back to Earth before their small space craft turned into a frozen, airless and lifeless space coffin. 

While the mission control team worked with the crew on how to keep the command and lunar modules habitable for as long as possible (they were rapidly running out of breathable air, water and heat and had lost electircal power), Elliot worked on actually getting the craft back to Earth. He was the “retrofire officer” for the mission which meant he was an expert in, and responsible for, the trajectory Apollo 13 took from the Earth to the moon and back. He had to compute a completely new trajectory from where they now were, which would get them back to Earth as fast and as safely as possible. It looked impossible given the limited time the crew could possibly stay alive. Elliot wasn’t a quitter though and motivated himself by telling himself:

“The Cherokee people had the tenacity to persevere on the Trail of Tears … I have their blood and I can do this.” 

The Trail of Tears was the forced removal of Native Americans from their ancestral homelands by the US government in the 19th century to make way for the gold rush . Now we would call this ethnic cleansing and genocide. 60, 000 Native American people were moved with the Cherokee forcibly marched a 1000 miles to an area to the West of the Mississippi, thousands dying along the way.

The best solution for Apollo 13, was to keep going and slingshot round the dark side of the moon, using the forces arising from its gravity, together with strategic use of the boosters to push the space craft on back to Earth more quickly than on those boosters alone. The trajectory he computed had to be absolutely accurate or the crew would not get home and he has suggested the accuracy needed was like “threading a needle from 70 feet away!” Get it wrong and the space craft could miss the Earth completely, or arrive too fast to reenter earth’s orbit and return through the atmosphere.

Jerry Elliot High Eagle, of course, famously got it right: the crew survived, safely returning to Earth and Elliot was awarded the President’s Medal of Freedom, the highest American honour possible, for the role he played. The Native American people also gave him the name High Eagle for his contributions to space exploration.

Paul Curzon, Queen Mary University of London

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RADAR winning the Battle of Britain

Plaque commemorating the Birth of RADAR
Image Kintak, CC BY-SA 3.0 via Wikimedia Commons

The traditional story of how World War II was won is that of inspiring leaders, brilliant generals and plucky Brits with “Blitz Spirit”. In reality it is usually better technology that wins wars. Once that meant better weapons, but in World War II, mathematicians and computer scientists were instrumental in winning the war by cracking the German codes using both maths and machines. It is easy to be a brilliant general when you know the other sides plans in advance!. Less celebrated but just as important, weathermen and electronic engineers were also instrumental in winning World War II, and especially, the Battle of Britain, with the invention of RADAR. It is much easier to win an air battle when you know exactly where the opposition’s planes. It was down largely to meteorologist and electronic engineer, Robert Watson-Watt and his assistant Arnold Wilkins. Their story is told in the wonderful, but under-rated, film Castles in the Sky, starring Eddie Izzard.

****SPOILER ALERT****

In the 1930s, Nazi Germany looked like an ever increasing threat as it ramped up it’s militarisation, building a vast army and air force. Britain was way behind in the size of its air force. Should Germany decide to bomb Britain into submission it would be a totally one-sided battle. SOmething needed to be done.

A hopeful plan was hatched in the mid 1930s to build a death ray to zap pilots in attacking planes. One of the engineers asked to look into the idea was Robert Watson-Watt. He worked for the met office. He was an expert in the practical use of radio waves. He had pioneered the idea of tracking thunderstorms using the radio emissions from lightening as a warning system for planes, developing the idea as early as 1915. This ultimately led to the invention of “Huff-Duff”, shorthand for High Frequency Direction Finding, where radio sources could be accurately tracked from the signals they emitted. That system helped Britain win the U-Boat war, in the North Atlantic, as it allowed anti-submarine ships to detect and track U-Boats when they surfaced to use their radio. As a result Huff-Duff helped sink a quarter of the U-Boats that were attacked. That in itself was vital for Britain to survive the siege that the U-Boats were enforcing sinking convoys of supplies from the US.

However, by the 1930s Watson-Watt was working on other applications based on his understanding of radio. His assistant, Arnold Wilkins, quickly proved that the death ray idea would never work, but pointed out that planes seemed to affect radio waves. Together they instead came up with the idea of creating a radio detection system for planes. Many others had played with similar ideas, including German engineers, but no one had made a working system.

Because the French coast was only 20 minutes flying time away the only way to defend against German bombers would be to have planes patrolling the skies constantly. But that required vastly more planes than Britain could possibly build. If planes could be detected from sufficiently far away, then Spitfires could instead be scrambled to intercept them only when needed. That was the plan, but could it be made to work, when so little progress had been made by others?

Watson-Watt and Wilkins set to work making a prototype which they successfully demonstrated could detect a plane in the air (if only when it was close by). It was enough to get them money and a team to keep working on the idea. Watson-Watt followed a maxim of “Give them the third best to go on with; the second best comes too late, the best never comes”. With his radar system he did not come up with a perfect system, but with something that was good enough. His team just used off-the shelf components rather than designing better ones specifically for the job. Also, once they got something that worked they put it into action. Unlike later, better systems their original radar system didn’t involve sweeping radar signals that bounced off a plane when the sweep pointed at it, but a radio signal blasted in all directions. The position of the plane was determined by a direction finding system Watson-Watt designed based on where the radio signal bounced back from. That meant it took lots of power. However, it worked, and a network of antennas were set up in time for the Battle of Britain. Their radar system, codenamed Chain Home could detect planes 100 miles away. That was plenty of time to scramble planes. The real difficulty was actually getting the information to the air fields to scramble the pilots quickly. That was eventually solved with a better communication system.

The Germans were aware of all the antenna, appearing along the British coast but decided it must be a communications system. Carrots also helped fool them! You may of heard that carrots help you see in the dark. That was just war-time propaganda invented to explain away the ability of the Brits to detect bombers so soon…a story was circulated that due to rationing Brits were eating lots of carrots so had incredible eye-sight as a result!

The Spitfires and their fighter pilots got all the glory and fame, but without radar they would not even have been off the ground before the bombers had dropped their payloads. Practical electronic engineering, Robert Watson-Watt and Arnold Wilkins were the real unsung heroes of the Battle of Britain.

– Paul Curzon, Queen Mary University of London

Postscript

In the 1950s Watson-Watt was caught speeding by a radar speed trap. He wrote a poem about it:

A Rough Justice

by Sir Robert Watson-Watt

Pity Sir Watson-Watt,
strange target of this radar plot

And thus, with others I can mention,
the victim of his own invention.

His magical all-seeing eye
enabled cloud-bound planes to fly

but now by some ironic twist
it spots the speeding motorist

and bites, no doubt with legal wit,
the hand that once created it.

…

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Let the brain take the strain

Cockpit controls
Image by Michi S from Pixabay

Whenever humans have complicated, repetitive jobs to do, designers set to work making computer systems that do those jobs automatically. Autopilot systems in airplanes are a good example. Flying a commercial airliner is incredibly complex, so a computer system helps the pilots by doing a lot of the boring, repetitive stuff automatically. But in any automated system, there has to be a balance between human and computer so that the human still has ultimate control. It’s a strange characteristic of human-computer interaction: the better an automated program, the more its users rely on it, and the more dangerous it can be.

The problem is that the unpredictable always happens. Automated systems run into situations the designers haven’t anticipated, and humans are still much better at dealing with the unexpected. If humans can’t take back control from the system, accidents can happen. For example, some airplanes used to have autopilots that took control of a landing until the wheels touched the ground. But then, one rainy night, a runway in Warsaw was so wet that the plane began skidding along the runway when it touched down. The skid was so severe that the sensors never registered the touchdown of the plane, and so the pilots couldn’t control the brakes. The airplane only stopped when it had overshot the runway. The designers had relied so much on the automation that the humans couldn’t fix the problem.

Many designers now think it’s better to give some control back to the operators of any automated system. Instead of doing everything, the computer helps the user by giving them feedback. For example, if a smart car detects that it’s too close to the car ahead of it, the accelerator becomes more difficult to press. The human brain is still much better than any computer system at coming up with solutions to unexpected situations. Computers are much better off letting our brains do the tricky thinking.

– Paul Curzon, Queen Mary University of London

This article was first published on the original CS4FN website and a copy is available on page 19 of Issue 15 of the CS4FN magazine, which you can download as a PDF by clicking on the panel below. All of our previous issues are free to download as PDFs here.

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In space no one can hear you …

Red arrows aircraft flying close to the ground. Image by Bruno Albino from Pixabay 
Image by SnottyBoggins from Pixabay (cropped)

Johanna Lucht could do maths before she learned language. Why? Because she was born deaf and there was little support for deaf people where she lived. Despite, or perhaps because of, that she became a computer scientist and works for NASA. 

Being deaf can be very, very disabling if you don’t get the right help. As a child, Johanna had no one to help her to communicate apart from her mother. She tried to teach Johanna sign language from a book. Throughout most of her primary school years she couldn’t have any real conversations with anyone, never mind learn. She got the lifeline she needed, when the school finally took on an interpreter, Keith Wann, to help her. She quickly learned American Sign Language working with him. Learning your first language is crucial to learning other things and suddenly she was able to learn in school like other children. She caught up remarkably quickly, showing that an intelligent girl had been locked in that silent, shy child. More than anything though, from Keith, she learned never to give up. 

Her early ability in maths, now her favourite subject, came to the fore as she excelled at science and technology. By this point her family had moved from Germany where she grew up to Alaska where there was much more support, an active deaf community for her to join and lots more opportunities that she started to take. She signed up for a special summer school on computing specifically for deaf people at the University of Washington, learning the programming skills that became the foundation for her future career at NASA. At only 17 she even returned to help teach the course. From there, she signed up to do Computer Science at university and applied for an internship at NASA. To her shock and delight she was given a place. 

Hitting the ground running 

A big problem for pilots especially of fighter aircraft is that of “controlled flight into terrain”: a technical sounding phrase that just means flying the plane into the ground for no good reason other than how difficult flying a fighter aircraft as low as possible in hazardous terrain is. The solution is a ground collision avoidance system: basically the pilots need a computer to warn them when hazardous terrain is coming up and when they are too close for comfort, and so should take evasive action. Johanna helped work on the interface design, so the part that pilots see and interact with. To be of any use in such high-pressure situations this communication has to be slick and very clear. 

She impressed those she was working with so much that she was offered a full time job and so became an engineer at NASA Armstrong working with a team designing, testing and integrating new research technology into experimental aircraft. She had to run tests with other technicians, the first problem being how to communicate effectively with the rest of the team. She succeeded twice as fast as her bosses expected, taking only a couple of days before the team were all working well together. Her experience from the challenges she had faced as a child were now providing her with the skills to do brilliantly in a job where teamwork and communication skills are vital. 

Mission control 

Eventually, she gained a place in Mission Control. There, slick comms are vital too. The engineers have to monitor the flight including all the communication as it happens, and be able to react to any developing situation. Johanna worked with an interpreter who listened directly to all the flight communications, signing it all for her to see on a second monitor. Working with interpreters in a situation like this is in itself a difficult task and Johanna had to make sure not only that they could communicate effectively but that the interpreter knew all the technical language that might come up in the flight. Johanna had plenty of experience dealing with issues like that though, and they worked together well, with the result that in April 2017 Johanna became the first deaf person to work in NASA mission control on a live mission … where of course she did not just survive the job, she excelled. 

As Johanna has pointed out it is not deafness itself that disables people, but the world deaf people live in that does. When in a world that wasn’t set up for deaf people, she struggled, but as soon as she started to get the basic help she needed that all changed. Change the environment to one that does not put up obstacles and deaf people can excel like anyone else. In space no one can hear anyone scream or for that matter speak. We don’t let it stop our space missions though. We just invent appropriate technology and make the problems go away. 

– Paul Curzon, Queen Mary University of London

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Pepper’s Ghost: an 1860s illusion used in ‘head-up displays’

by Paul Curzon, Queen Mary University of London (first published in 2007)

A ghostly illustration including a woman in historic garb, an ornate candlestick, a grand chair and a mirror with grey curtains pulled back.
Ghostly stage Image by NoName_13 from Pixabay

When Pepper’s Ghost first appeared on the stage as part of one of Professor Pepper’s shows on Christmas Eve, 1862 it stunned the audiences. This was more than just magic: it was miraculous. It was so amazing that some spiritualists were convinced Pepper had discovered a way of really summoning spirits. A ghostly figure appeared on the stage out of thin air, interacted with the other characters on the stage and then disappeared in an instant. This was no dark seance where ghostly effects happen in a darkened room: who knows what tricks are then being pulled in the dark to cause the effects. Neither was it modern day special effects where it is all done on film or in the virtual world of a computer. This was on a brightly lit stage in front of everyone’s eyes…

Stage setup for Pepper’s Ghost, from Wikipedia, Public Domain

Switch to the modern day and similar ghostly magic is now being used by fighter pilots. Have the military been funding X-files research? Well maybe, but there is nothing supernatural about Pepper’s Ghost. It is just an illusion. The show it first appeared in was a Science show, though it went on to amaze audiences as part of magic shows for years to come, and can still be found, for example in Disney Theme Parks, and onstage to make virtual band Gorillaz come to life.

Today’s “supernatural” often becomes tomorrow’s reality, thanks to technology. With Pepper’s ghost, 19th century magic has in fact become enormously useful 21st century hi-tech. 19th century magicians were more than just showmen, they were inventors, precision engineers and scientists, making use of the latest scientific results, frequently pushing technology forward themselves. People often think of magicians as being secretive, but they were also businessmen, often patenting the inventions behind their tricks, making them available for all to see but also ensuring their rivals could not use them without permission. The magic behind Pepper’s ghost was patented by Henry Dircks, a Liverpudlian engineer, in 1863 as a theatrical effect though it was probably originally invented much earlier – it was described in an Italian book back in 1558 by Baptista Porta.

Through the looking glass

So what was Pepper’s ghost? It’s a cliche to say that “it’s all done with mirrors”, but it is quite amazing what you can do with them if you both understand their physics and are innovative enough to think up extraordinary ways to use old ideas. Pepper’s ghost worked in a completely different way to the normal way mirrors are used in tricks though. It was done using a normal sheet of glass, not a silvered mirror at all. If you have ever looked at your image reflected in a window on a dark night you have seen a weak version of Pepper’s Ghost. The trick was to place a large, spotlessly clean sheet of glass at an angle in front of the stage between the actors and the audience. By using the stage lights in just the right way, it becomes a half mirror. Not only can the stage be seen through the glass, but so can anything placed at the right position off the stage where the glass is pointing. Better still, because of the physics of reflection, the reflected images don’t seem to be on the surface of the glass at all, but the same distance behind as the objects are in front. The actor playing the ghost would perform in a hidden black area so that he or she was the only thing that reflected light from that area. When the ghost was to appear a very strong light was shone on the actor. Suddenly the reflection would appear – and as long as they were standing the right distance from the mirror, they could appear anywhere desired on the stage. To make them disappear in an instant the light was just switched off.

Jump to the 21st century and a similar technique has reappeared. Now the ghosts are instrument panels. A problem with controlling a fighter plane is you don’t have time to look down. You really want the data you need to keep control of your plane wherever you are looking outside the plane. It needs not just to be in the right position on the screen but at the right depth so you don’t need to refocus your eyes. Most importantly you must also be able to see out of the plane in an unrestricted way…You need the Peppers Ghost effect. That is all “Head-up” displays display do, though the precise technology used varies.

Satnav systems in cars are very dangerous if you have to keep looking down to see where the thing atually means you to turn. “What? This left turn or the next one?” Use a Head-up display and the instructions can hover in front of you, out on the road where your eyes are focussed. Better still you can project a yellow line (say) as though it was on the road, showing you the way off into the distance: Follow the Yellow Brick Road … Oh and wasn’t the Wizard of Oz another great magician who used science and engineering rather than magic dust.

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Featured image: Cute ghosts image by Alexa from Pixabay