Solar power in space: Vanguard 1

Today is an interesting anniversary: the sixtieth anniversary of solar power in space. On 17 March 1958, the American satellite Vanguard 1 entered orbit, becoming the fourth satellite ever to do so, and the first to use solar power. Vanguard 1 was small enough to be held by a person in one hand – 1.5 kg (3 lbs) in mass and 16 cm (6”) in diameter, or 76 cm (30”) wide including the antenna aerials. Altogether, Vanguard 1 had 6 silicon solar cells which generated about 1 watt in total. For comparison, the power produced by a typical rooftop solar PV system in 2018 is several thousand times greater.

Why did the first satellites use electrical power? Primarily, to send radio signals back to Earth. The first satellite ever to reach orbit, the Soviet satellite Sputnik 1, broadcast radio signals at 20 MHz and 40 MHz which could be detected on Earth, even by amateur radio users. The radio signals provided additional proof that the satellite was really in orbit around the Earth (it could also be seen with large telescopes), and allowed observers to measure its position and trajectory. The power to provide this radio signal came from batteries, which allowed it to broadcast radio signals for 21 days before the batteries went flat.

This radio communication was one-way only. Early satellites could not receive communications from Earth, and were essentially a battery, radio transmitter, and an antenna. The second and third satellites, the Soviet Sputnik 2 and US Explorer 1 also used batteries to power radio signals, which lasted somewhat longer (Explorer 1 had a lower power mode that lasted 105 days). Vanguard 1 had two radio transmitters. One transmitter (at 108 MHz) was powered by a battery, which lasted for 20 days. The second transmitter (at a slightly higher radio frequency, 108.3 MHz) was powered by the (as yet unproven in space) solar cells, and that broadcast for over six years, or over 23,000 orbits of the earth, before going silent.

Vanguard 1 schematic (Image credit: NASA)

Vanguard trajectory (Image credit: NASA)

Satellites and spaceflight were one the first uses of solar power in which – environmental reasons aside – it was clearly cheaper, more reliable, and more practical than other sources of electrical power. Generation of electricity on Earth, then and today, is most commonly done with a combustion engine. On Earth, oxygen is in the air everywhere and fuel can usually be found, whether it is wood, coal, natural gas, or some other fuel. Photovoltaic cells at that time were incredibly expensive, and their intermittent output was difficult to manage since rechargeable batteries were also very expensive.

In space, solar power had clear advantages. Combustion in space requires that both fuel and oxygen (or another oxidant) be brought up from the Earth in tanks. For example, the Saturn V rocket engines that sent humans to the moon had tanks of liquid hydrogen and liquid oxygen. (Those engines were obviously used to make the rocket move, not to generate electricity). Non-rechargeable batteries could not provide power for long without a lot of “chemical fuel”. In space, above the clouds, solar power was more or less constant the whole time that the panels were not behind the Earth. No fuel needed to be carried up. Satellites typically orbited the earth every few hours, so that when rechargeable batteries did start to be used with solar panels, they were small compared to those needed to last the entire long night on earth.

What happened to Vanguard 1? Although its radio no longer transmits, Vanguard 1 continues to orbit the Earth today, at an altitude between 600 and 4,000 km, going around the Earth approximately every 2 hours. It is now the oldest object made by humans to still be in space. Sputnik 1 and Sputnik 2 reentered the atmosphere after around one year after launch, and Explorer 1 reentered in 1970. Vanguard 1 is in a very stable orbit, and is predicted by NASA to remain in orbit for another 180 years. Several websites track its location (Satflare, n2yo). You can see where Vanguard 1 is right now on this map provided by Satflare:

3D globe current position of Vanguard 1, by Satflare

As a final note, in researching this article I came across some amazing audio recordings of Vanguard 1 transmissions made by amateur radio enthusiast Roy Welch in 1958 and 59. (The signals have been modified to bring them into audible frequencies). Roy Welch wrote that he believed that the variations in frequency were due to the satellite spinning around, varying the light exposure to the solar cells. The one from 1959 I find quite eerie:

Vanguard 1 signal recorded by Roy Welch (link).

It is quite something to listen to the recording and imagine the tiny Vanguard satellite, moving high above the Earth, broadcasting its radio signal, and slowing turning around in the sunlight.


Icarus

“Icarus” is a documentary on Netflix. You should watch it, it’s very good. There’s no need to look up more about it, it’s better to just watch the movie.


Ok, if you want a bit more information, then – without spoilers – here it is. “Icarus” begins as a documentary about an American amateur cyclist, Bryan Fogel, who in 2014 injects himself with testosterone, steroids and other drugs to win a gruelling cycle race in the French Alps. At the same time, he learns how to pass drug checks from sports scientists: how to store his “clean” urine during pauses in his doping protocol, how the tests work and how to beat them. He films everything he does – the idea of his movie is to find out if taking performance enhancing drugs really is as effective at helping you win and widespread, and if avoiding detection is as easy as some people say.

Before he began deliberating taking drugs, Fogel was already a very good amateur cyclist. He had competed in the Haute Route race in the Alps in France the year before, over the same routes in the French Alps as the Tour De France, and he had finished in 14th place out of 440 riders. Nevertheless, he felt the very best riders on the race were way better that there was a huge, insurmountable gap in speed and endurance between the winners and himself. Fogel had been a huge fan of Lance Armstrong, he had been disappointed when Armstrong was exposed as a cheat, and he wondered how much of a difference drugs can make.

As Fogel injects drugs, his strength and endurance increase. He meets different sports scientists, most of whom work professionally to try and catch drug cheats, and who think this idea is crazy, but who are curious to see if can be done, and offer some suggestions. He cycles faster, further, training for the next Haute Route event. Eventually, Fogel is introduced to Grigory Rodchenkov, the director of the Russian anti-doping agency, and chats to him on the computer via Skype. Rodchenkov is an odd, cheerful character, enthusiastic about helping Fogel win, and tells him specific details about how to cheat and get away with it: how many grams of this drug or that drug, how many days to wait after taking a particular drug before taking a urine sample, how to combine different drugs. It isn’t at all clear why Rodchenkov wants to help so much, how he knows all this stuff, and why he is so confident that it will work and not be detected.

So far, this all a great movie … and then the story changes. It becomes a much bigger, and even more interesting story and … well, you should watch the movie, I recommend it.


Oh, and once you have seen the movie, here is a good interview with Bryan Fogel at vulture.com


Where to cut the tape

In the 1980s and 1990s, radio journalists would record interviews on reel to reel tape machines. Standard equipment on assignment was a “portable” reel to reel tape machine the size of a suitcase and carried over the shoulder, as well as a bakelite microphone in the shape of an ice cream scoop.

Back at the studio, the interview needed to be edited for broadcast. To edit the interview, you would cut the magnetic tape at the start and end of where you wanted the cut, and then use sticky tape to join the two ends of tape back together.

How do you know where to cut the tape? It is black magnetic audio tape, about the width of a finger, featureless. If you were a beginner, you could use a white pencil to mark the start and end. But after a few years, you developed a feel for where to cut.

My dad Peter was a radio journalist for the ABC (Australian Broadcasting Corporation) for more than twenty years, and the purpose of this article, really, is to a memory of him. When I was about ten years old, he was the presenter of “Australia Tonight”, which went to air each weeknight at 10pm all around Australia. Something that I loved was that, if our family was going away for the weekend, on Friday evening my mum would drop me off in the city at the ABC studios with my dad. We would have a few hours together at the studios before the program went to air. The building was almost empty at that time. My dad would edit the interviews he had prerecorded that day. He would listen to the audio, rewinding and fast-forwarding to different places (which made a wonderful squealing sound in which you could still hear the voices sped up). Then he would pull out one, two, three arm-lengths of tape, casually cut out a section of tape and join the ends together.


Tupaia, Polynesian navigator and translator, biography by Joan Druett

This post is about an excellent book that I read recently, Tupaia, by Joan Druett, that tells the story of the life of Tupaia, a Polynesian master navigator and priest who lived in the 1700s. Tupaia navigated by sail across the islands of the Pacific, finding the way over weeks of travel on the enormous blue ocean using patterns in the stars, clouds, ocean currents, the flight paths of birds, and all the traditional expertise of Polynesian voyagers.

Tupaia was born on the island of Ra’iatea around 1725, and was trained in navigation at the fare-‘ai-ra’a-upu schools of learning. When he was about 30, he was badly injured fighting invaders from the island of Bora Bora, stabbed in the back by a spear with a stingray barb point, nearly died, and fled to Tahiti. There, Tupaiai was a priest of the god ‘Oro, and consort of a noblewoman called Purea. In 1769, in Tahiti, Tupaia joined the Endeavour voyage with Captain James Cook and sailed to New Zealand, Australia, and Indonesia. During that voyage he painted several remarkable pictures, including the first known picture to show a meeting between Maori and Europeans – a Maori man and a British man trading a lobster for a piece of cloth. The picture is reproduced on the book cover:


It is an extraordinary story, which is full of events and moments that I find myself thinking about again and again, trying to imagine as different people in the story, and wondering what it would have been like to be there.

For example, imagine being on the beach at Te Kuri o Paoa on New Zealand’s North Island in October 1769, for the first formal meeting between Maori and the crew of the Endeavour, a few days after the Endeavour had first sighted the land. The Maori and the Europeans faced each other on the beach, the Maori in flax and fur cloaks, the British officers in red and navy jackets. The mood would have had tension, curiosity, anger, apprehension. The day before, there had been an encounter between a smaller group of Europeans and four Maori men, which had led to threats, confrontation and fighting. A Maori man named Te Maro had been shot and killed by a British man named Samuel Evans, the coxswain on the Endeavour. The next day, during this more formal meeting, Te Maro’s dead body still lay there on the beach between the two groups. The British marines marched in formation to the beat of a drum, presented arms. The Maori performed a haka, with ritualistic chants and challenges. Captain Cook announced in English who they were and what they were doing. Neither the Maori or the British understood the language of the other.

And then, Tupaia stepped out from amongst the British group, and spoke to the Maori in his own language, and amazingly, he and the Maori could understand each other well, and spoke almost the same language. Nobody there had expected this. Tupaia and the Polynesians had no knowledge about Maori people and the land of New Zealand, and while the Maori had legends about their migration from islands a long time ago, there had been no contact for hundreds of years, and no expectation that anyone from those now mythical islands would one day appear.

Or imagine the friends of Te Maro, the three young men, sitting in their village on the evening after he was shot, the day before the formal meeting, grieving for their friend. Eating kumara, palm root and fish – familiar foods in the familiar place they had known all their lives. Wondering about the strange men, in the strange clothes, with the strange language, from the strange ship, with strange and deadly weapons. What did they want? What would happen next?

When Tupaia spoke in an understandable language the next day, the .The Endeavour sailed all around the North Island and South Island, and throughout the voyage Tupaia acted as negotiator and translator. He made possible meetings and trades that went much better for everyone than had he not been there. Episodes of bad faith, mistrust, and violence did occur, but there can be no doubt it would have been different and certainly worse without Tupaia. Tupaia was honored by the Maori for his learning and culture, including new legends they had not yet heard. When the Endeavour returned for a second voyage of New Zealand, Tupaia’s fame had spread, and across the land, Maori people asked for him and were sad to learn that he had died.

The book Tupaia tells a fascinating history. It is complicated and sad in many places. I really know very little of this history, and I should learn more, and also acknowledge the privilege and remoteness I have from it. The author Joan Dreutt has done what seems to me an excellent job in researching as many sources as exist today, but of course there is still much left unknown about Tupaia, that is uncertain and must be imagined. Tupaia is not nearly as well known as he should be – I had never heard of him before reading the book. It is a story worth knowing, and I highly recommend the book.


Logbooks of childcare

My daughter will start school next month, and this week she went to her old child care for (almost) the last time. At the end of the day she brought home two large ring binder folders.

They were logbooks of her time at childcare. Until they came home that day, I didn’t know they existed or that the childcare teachers were making them each day. The books are full of notes, photos, artwork in clear plastic pockets, stories and quotes from the children. Many of the pages I had seen in the daily email, but here it was all collected in a book. There is something from almost every day she was at childcare – over three years of memories. Looking through it now I can see:

  • Photos of the children mixing paints and finger painting
  • Stories about learning the names of fruits
  • Paintings and drawings
  • A story my daughter told the class about a time we rode our bikes along the creek to the cafe with chickens in the garden
  • A painted cardboard boomerang
  • Photos of the children making cupcakes
  • Many things covered in glitter
  • My daughter talking about a picture she made: “I am drawing roads and flowers …these are the foot prints.”

It is an extraordinary gift to have received. A gift which is full of memories and photos, which took work over several years. I am not that good with paper records, the sort of person who is not prefers to keep records as files on my computer where I can search them electronically. The discipline and diligence of the staff amazes me, in creating physical paper records for each child, adding to each book each day, moving them around as each child moves from room to room over different years, and I am grateful for it.


Herds Of Giant Wombats Grazing

When you walk through the doors of the museum here in Melbourne, there is a gigantic entrance hall which contains the entire skeleton of a blue whale. Walking throughout the Museum, there are dinosaurs and insects, there are gemstones of translucent purple, milky blue, and a thousand other colours. There is an entire native rainforest in a room, with actual plants and trees and a pond full of fish. There is an extraordinary kids play room, with rope ladders going up a series of tunnels to a succession of rooms which go over your head and then back down again to the ground. It takes 20 minutes for a child to crawl from one end to the other, so if you see your kids up there halfway through it, there is nothing to do but watch them and hope they don’t get stuck.

One of my favourite exhibits is the giant extinct wombat, diprotodon.

They were the size of a delivery van, and in life would have weighed over two tons. I like to think about herds of these giants, gently grazing over the western grasslands of Victoria. Imagine golden fields of grass at the end of summer, the long stems waving in the breeze, the sandstone hills of Arapiles in the background, and giant diprotodon thoughtfully chewing on the grass. Several artists have tried to draw what they might have looked like – which is basically a giant wombat, albeit with longer legs (in proportion) than modern day wombats. My favourite illustration is this one by Peter Trusler for the happy smile the artist gave the diprotodon. Trusler also made a beautiful illustration of a palorchestes, another extinct Australian mammal with a long,flexible nose. Here is a interesting video where he talks about the illustration at the Museum’s website here.


Electricity demand response at the Supreme Court (Demand response part 2)

In part 1 of this article, I wrote about the importance of demand response in the electricity industry – i.e., why power companies might choose to pay customers to use less electricity at certain times. Here, I discuss what the right price for demand response would be, and a recent US Supreme Court case over the fundamental economic principles of that price – including the question of whether reducing consumption was equivalent to generation.

When companies offer demand response programs, the offer needs to be simple, compelling and easy to understand for customers. Demand response is typically used only a few times per year, so it is not worth customers spending the time and effort to learn a complex price scheme. You might also ask, what is the point of demand response as a separate scheme? We already have a wholesale market. If the price gets very high, then people will reduce their consumption. There is more that can be said on this, but one point of separate demand response schemes is to target customers who are not able, or not interested, to respond to wholesale market prices in real time. So demand response schemes are offered in different ways that make sense for different customers. In part 1, I described a scheme to pay people cash up front in return giving the distributor Energex the ability to remotely turn down their air conditioner at certain times. Another example will be trialled by the retailer Powershop this summer, supported by The Australian Energy Market Operator (AEMO) and Australian Renewable Energy Agency (ARENA). Powershop will use a smart phone app to tell people to reduce their demand at certain times, with the reward being a certain about of free electricity at other times.

With these indirect schemes, it is often difficult to calculate the exact price in $/MWh being offered to customers. That’s probably fine if both buyer and seller are happy with the deal. But is there are a “correct” price? Given that demand response is something of an alternative to the wholesale market, the correct price probably has to do with the wholesale market price, right?

Let us give a specific example. If a person normally pays $50/MWh for their electricity use, and prices rise to $500/MWh … how much should they be paid if they use less electricity than they normally would?

  • $500/MWh for each MWh of reduced demand (the current price), or
  • $450/MWh (the current price minus the customer’s usual retail price)?

This was argued in a 2016 Supreme court case, where the two sides disagreed on the fundamental economic theory of the question. The case was significant because this was not an example of a buyer and seller mutually agreeing on price, but an example of when the government was forcing power system operators to pay demand response providers a particular price, even if the operators did not agree with that price.

In the case, FERC (the US regulator) had created a demand response program that required energy market operators to pay the current price ($500/MWh in the above example). The EPSA (a generator industry group) was opposed to the demand response scheme, and argued that:

  1. In the EPSA’s view, FERC did not have the legal authority to create a demand response scheme, and
  2. That if FERC did have the authority, then the compensation should be the current price minus the normal price for the customer ($450/MWh in the above example).

What I think was amazing about the case was that all these famous economic professors then wrote submissions to the court, arguing the economic theory of what the price should be. Harvard economics professor Bill Hogan contributed a “friend of the court” brief in support of the EPSA, arguing that FERC was forcing grid operators to overpay for demand response by, in the example above, forcing them to pay $500/MWh.

Here is an extract from Hogan’s brief:

“To offer an analogy, consider a manufacturer that produces an automobile it can sell to a dealer for $20,000; the dealer has agreed to then sell the automobile to a customer at cost ($20,000), but cars are in high demand and another customer wants to buy the car for $30,000. No one would say that the first customer should be paid $30,000 for not buying the car, just because another customer wants it or cars are in short supply. If one customer has a right to buy the car at $20,000, while another is willing to pay $30,000–and lack of supply means that both cannot purchase cars–the dealer could, in theory, sell the car to the second customer and give the first customer the $10,000 difference between the market price and the price at which she has the right to purchase. That would allocate the car to the customer who values it more, while giving the first customer an incentive to allow the second customer to have it. We would never, however, say that the dealer must: (1) pay the manufacturer $30,000; (2) pay the first customer $30,000 (the car’s current value) for not buying the car; and (3) sell the car at $30,000 (again its current value) for a loss. But that is what FERC effectively has done: It provides the first customer with a windfall while requiring [grid operators] to pay twice (to the electricity producer and the non-buyer) for a unit of electricity that they may only sell once for less than the total price paid.”

However, in an earlier affidavit, Professor Kahn of Cornell University argued (and FERC agreed), that reducing demand was equivalent to increasing generation, and should receive the same compensation, meaning that the $500/MWh would be the correct price above. From Kahn’s affidavit:

“Demand response is in all essential respects economically equivalent to supply response; and that economic efficiency requires, that it should be rewarded with the same [price] that clears the market. Since DR is actually–and not merely metaphorically–equivalent to supply response, economic efficiency requires that it be regarded and rewarded, equivalently, as a resource proffered to system operators, and be treated equivalently to generation in competitive power markets.”

What do you think? It is a subtle difference. In the above example, the $450/MWh case is equivalent to the customer buying electricity at their regular price of $50/MWh, and immediately selling it to the market at the market price of $500/MWh, for a profit of $450/MWh, instead of using the electricity themselves.

In the end the Supreme court did not endorse any particular price method. By a 6–2 verdict, the court decided that:

  1. FERC did have the legal authority to run a demand response scheme, and
  2. That FERC also had the authority to set the price in that scheme, and therefore (even though both sides had made good points) FERC’s price should be used.

What do I think? I admit that I am not an expert in these matters – nothing like the experts quoted above – but for what is worth, my view is that Hogan’s argument is correct, and that $450/MWh would be the correct price. From my perspective, demand response by a customer is equivalent to selling their right to use electricity to someone else. To do that, they need to have the right to use electricity, and if they have to pay $50/MWh to obtain that right (and hence receive $450/MWh overall), then that is what they need to do.

However, I acknowledge that there are other benefits to demand response schemes than avoiding wholesale market costs. For example, demand response schemes at times of high network demand also reduce the costs of “poles and wires”, and that the financial benefits of reducing network costs could even exceed those of wholesale costs. (Note that in the air-conditioner example above, the scheme is offered by the distributor Energex (a network operator) rather than the wholesale market operator AEMO). Network costs are recovered very inefficiently in general, mostly through simple charges. A demand response scheme with non-ideal prices could still benefit the public overall. Another submission to the court, from Charles Kolstad, an economist at Stanford University, argued in favour of FERC because the public was better off with demand response than without it, even if the non-ideal FERC method was used. Note that there were also implementation challenges with the EPSA method that I haven’t described, such as the need for the market operator to know the normal price paid the customer. (There are other details which I have omitted, and if you’re interested I recommend reading the references below).

References

Supreme court dockets 14-840 and 14-841

Hogan brief to the court

FERC quotation of Alfred Kahn

Kolstad brief to the court

Supreme Court decision (January 25, 2016)

Scientific American article on the case


Paying people to use less electricity (Demand response part 1)

In the electricity industry, where I work, it is important to keep supply (the energy being provided by the generators) balanced with demand (the energy being used by customers) at all times. If this is not done, the entire system will quickly collapse to and fail to what is called “system black” or “blackout”. This is different to the market for almost every other product or service. Consider, for example, what happens when Apple creates a new model of iPhone, but does not make enough so that everyone who wants to buy one on the day they are released is able to do so. What happens in this case? Well, all the iPhones that are made will be bought by someone, and those people will get to use them. Everyone else who wants to buy one will either have to wait until more phones are made, or buy another kind of phone. If the phone market were similar to the electricity market, an analogous situation would be that if even one person went to the store and could not purchase a new iPhone, then all other iPhones stopped working within a few seconds.

For electricity grid operators, this fact makes it hard to run the power system securely when electricity demand is very high (which may happen only a few times per year, typically on hot days). There is nothing to stop people from connecting additional appliances to the grid. Even though wholesale prices rise very high at these times (over 300 times the average price), most people are either unaware of such prices or any not exposed to them (i.e. the price paid by their retailer rises but the customers themselves have a fixed price). For many kinds of loads, the demand rises automatically without any person even being involved. For example, many air conditioners are trying to cool a building down to a set temperature. If the outside temperature increases, the air conditioners automatically start working harder (therefore using more electricity) in response.

One way that this problem is managed is called demand response, which is essentially paying customers to use less electricity at certain times than they normally would. Sometimes this is done by paying customers directly. Sometimes there is simply an appeal to customers, “Let’s all pitch in and use less power tomorrow afternoon, it will help keep the lights on, and we’ll all share the benefits and reduced costs later.” Here is an example from 2017 in NSW.

When demand response is financially compensated, it is often paid for in indirect or simple ways. As with rooftop PV under the renewable energy target, demand response programs for the masses often pay the entire subsidy upfront in cash, at the time of purchase. For many customers, this is easier to understand, and more compelling, and it means that you don’t have to manage an ongoing financial relationship to pay thousands of people small amounts of money on a regular basis. For example, in Queensland, there is an interesting program called PeakSmart, which is managed by the distributor Energex. When you buy a new air conditioner at the shop, if you opt in to the PeakSmart program, you get up to $400 cash back which helps make the system cheaper. The PeakSmart system allows the distributor to remotely turn down the air conditioner to about half the output. They do this a few times per year, for an hour or so each time. From their annual report:

“We activated our PeakSmart airconditioner technology on 1 and 2 February 2016. On these two days South East Queensland experienced 40 degree temperatures. More than 50,000 air-conditioners were signalled to reduce their demand by approximately 25 per cent between 4.30pm and 5.30pm. More than 25,000 air-conditioners were active at the time and reduced peak demand on our network by 11.2 MW on 1 February and 16.4MW on 2 February. These load reductions are the equivalent of more than 7,200 homes on our network. Surveys completed with participants after the event indicated no impact on comfort.”

From what I can tell, this is a successful and well run demand response program, and is well designed for its target customers.

In the next post, I’ll discuss what is the optimal price to pay for demand response, which is a dispute that went all the way to the US Supreme Court in 2016, with a disagreement about the fundamental economic principles that should be used.


Preparing For Monsters

The other night I helped my daughter to make a cubby from the couch cushions to play in.

Earlier in the night she had got in trouble for putting leaves from the garden into my bed, and then again for messing up my son’s train set. She wasn’t going to get any TV for the next few days, and was grumpy about it.

But later in the evening, things improved. We made a cubby together, helping each other with the walls and a sheet for the roof. A box of Lego and her toy monkey went inside to play with. She wanted to play the game where I pretend to be a monster, growling and stomping around outside the cubby, whilst she is safe inside, which was fun.

After that was done, I went off to do some cleaning. Later she calls out, “Daddy, you need to be the monster again!”.

“Ok, a bit later,” I say.

“I want to play the monster game!”

“I’d rather be friendly. Are you having fun in the cubby?”

“Yes.”

“Oh, what’s the long thing you are making with the Lego?”

“A gun.”

“What’s that gun for?”

“To shoot monsters,” she says.

-


The best of the old and new swings

At another park, upstream from our house, there are two excellent swings which the kids love to play on, one new and one very old.

The old swing has a big diamond head, with the sculpted face of a friendly clown. The whole thing spins round and round, and the chairs swing out wider and wider the faster you go. These swings used to be quite common in Victoria when I was growing up. This one has been recently painted (and possibly serviced), but I’m sure it is at least 30 years old. It is great to lie down with your chest on the swing chair and pretend to be superman, flying through the air.

The new swing is the modern version, in the sense that they are very common, I know at least 6 parks with these swings. There is a big hoop suspended by 4 cables, with netting across the hoop to lie in or sit on. The angled steel beams provide some bounce and spring. I can see why these swings are popular, they are a simple design, overall pretty safe, and a lot of fun to swing on.