Teams forming walls to shelter their cars from the wind in the Coober Pedy control stop
A brief update from Day 4: Great sun today, but worse headwinds than yesterday. The top five spots in the Challenger class seem pretty locked in and the leaders will finish early tomorrow. The Cruiser class is... a bit of a mess.
In the Challenger class, Innoptus remains in the lead and ended the day well south of Port Augusta. Twente managed to close the gap from 27 minutes at Erldunda yesterday, to 16 minutes at Coober Pedy early today, and 14 minutes at Glendambo afterward... but the gap had once again widened to 30 minutes again at Port Augusta and appeared largely unchanged through the remainder of the day. Barring an extended breakdown, it seems extremely unlikely that Twente will be able to take the lead now that both teams are deep into the area approaching Adelaide where traffic is heavier and overtaking is increasingly difficult.
Two hours behind the battle for the lead, Brunel remains ahead of Michigan. Michgian made up 13 minutes between Erldunda and Coober Pedy, and another 7 minutes between Coober Pedy and Glendambo, but are still a hair over an hour behind Brunel. Again, barring breakdowns, these two seem fairly fixed in position.
In 5th place is Sonnenwagen, about 45 minutes behind Michigan as of the Glendambo control stop and hours ahead of Tokai. Tokai was briefly in 5th place, having finally passed Sonnenwagen yesterday after a long chase, when they were stopped for about two hours early today due to suspension issues. Tokai fell back to 7th behind Top Dutch before getting back on the road, but they were able to regain 6th place soon after Coober Pedy.
About an hour and a half behind Top Dutch, JU is currently edging out Kogakuin and Durham in a 3-way battle for 8th place. This is a very tightly contested spot to watch tomorrow and into early Friday!
Eclipse is fairly firmly in 11th place with over an hour of space ahead and behind them as of the Erldunda control stop. Behind them are Western Sydney, who are finally making a bit of a run and have opened up a 40 minute gap over αCentauri, Goko, and Blue Sky. These are the last Challenger teams remaining on the course - Chalmers, Adelaide, Halmstead, and Wakayama all had to finally throw in the towel and put the cars on the trailers today.
In the Cruiser class... between the bad sun yesterday, the bad headwinds yesterday and worse ones today, and the fact that Tennant Creek to Coober Pedy was the longest and most challenging leg of their race, none of the Cruisers were able to drive all the way to Coober Pedy. Apollo was forced to drop yesterday, Solaride put it in the trailer early today, and then Ascend... and finally Minnesota and Sunswift threw in the towel at nearly the same time today and loaded the cars onto the trailers in Marla so that they could make it to Coober Pedy before the end of the day.
Now that every single Cruiser team has failed to complete the course, it's a bit unclear what happens now. In one of the various group chats, someone pointed out that a strict reading of the regs gives us a method to determine the winner, but that no one actually gets awarded the cup?
I guess Eindhoven gets to keep it for another two years despite deciding to do some solar offroading in Morocco this year rather than attending WSC?
Anyway, it appears that the winner will be determined by the performance of the cars that finished the Darwin to Tennant Creek leg, plus their practicality scores at the finish line. It's unclear what the Cruiser cars are all going to do for the rest of the event? They have a fresh grid charge and two days to drive down to Adelaide, but none of what they do from here on out counts in any way, so I guess they just chillax and party together for the rest of the drive? I have some thoughts about this competition format - that are basically unchanged since the scoring formula was revised for the 2017 event to use a target arrival time instead of rewarding faster elapsed times - but we'll save that discussion for after the event.
Hey folks - I'm chilling out at the Marla Traveller's Rest tonight at the conclusion of the third day of WSC 2023, and what a race it's been. For an at-a-glance race summary of the Cruiser Class, check out this chart from Tony at Scientific Gems:
Chart via Scientific Gems "Two speeds are shown for each team: the first is the average speed since Darwin; the second (in brackets) is the average for the last leg."
The first day this year was a great day for solar racing. The second day saw increasing amounts of smoke along the course dimming the skies (a few team members told me they spend the second night sleeping in N95s), and a front rolled north over our position on the second night bringing in headwinds, cooler weather, and patchy clouds for the third day that I am told will persist tomorrow.
I have largely been following along with the teams up at the very front, and the big three up there have been Innoptus (Leuven), Twente, and Brunel (Delft). Innoptus took an early lead on the first day, and between Dunmarra and Tennant Creek they had achieved a >30 minute lead - they departed the Tennant Creek, Barrow Creek, Alice Springs, and Erldunda control stops before Brunel and Twente arrived. They also managed to arrive at Alice Springs just before the end of the second day; the checkpoint there was not scheduled to open until the following morning and the race officials had to scramble to be ready in time for Innoptus's arrival! And speaking of Innoptus, a few people online have been speculating about how much use they are getting out of that retractible fin or if it's mostly just being used for photo shoots. All I can say is that we have overtaken them somewhere between 6 and 8 times, and the fin was extended on all but one occasion...
Further back, Brunel was in second place soon after the start, but began slowing down on the second day of the event and was passed early on by Twente. As we've faced headwinds on the third day of the race, Twente has closed the distance to Innoptus and are almost back to the point they'll be meeting at control stops again - it's very much still anyone's race!
Behind Brunel, Michigan has steadily been catching up. During qualifying, Michigan encountered issues on their hot lap and were forced to start at the very back of the starting grid. I'm told they overtook something like 25 teams on the first day alone... they spend large parts of the first day grouped up with Kogakuin and Top Dutch, and ended the first day at Dunmarra with those two and Tokai. They turned on the gas on the second day and made up quite a bit of time, and although they slowed down in the clouds and headwinds on the third day just like everyone else, they didn't slow down as much as Brunel and have closed from an hour and forty minute gap at Tennant Creek to just under an hour at Erldunda. Barring any mistakes or breakdowns by Brunel, in the distance remaining it will be a challenge for Michigan to close the remaining distance to overtake for 3rd place, but they have a chance...
About half an hour behind Michigan are Tokai in 5th and Sonnenwagen Aachen in 6th.
Tokai has been running a very steady race, they've been comfortably in 5th place for essentially the entire even thus far - momentarily falling to 6th when overtaken by Michigan, but climbing back to 5th after overtaking Sonnenwagen.
Sonnenwagen got the pole position at the start and hung onto 3rd place closely with Innoptus and Brunel up through Katherine, but have slowly and steadily fallen back - by Tennant Creek they had been overtaken by Twente and were in 4th, they had clearly fallen out of the lead group by Alice Springs, they fell to 5th by Erldunda, and were passed by Tokai before the end of the third day.
Behind Sonnenwagen is a 2+ hour gap back to Top Dutch in 7th, another hour and a half or so back to Kogakuin, and the remaining cars are spread out behind. The current running order from 9th onward appears to be JU, Durham, Eclipse, WSU, αCentauri, Blue Sky, Goko, Chalmers, Adelaide, Halmstead, and Wakayama; all other teams appear to have stuck the car on the trailer. Halmstead and Wakayama do not appear to be on a pace to finish the race; we'll see if Chalmers and Adelaide can hang on. There may be some excitement in the back: WSU, αCentauri, Blue Sky, and Goko have been running extremely tightly together for the entire event and 12th appears to be the most tightly contested place in the Challenger class.
On the Cruiser side, right now it's Sunswift's competition to lose. Cruiser teams were supposed to arrive at Tennant Creek at 2:00pm on the second day, and if late they would start accruing a 0.99^(minutes_late) penalty multiplied against their score. Sunswift was the only team that arrived on time, Minnesota was next at 52 minutes late (penalty multiplier of 0.59), Apollo was 63 minutes late (multiplier of 0.53), Solaride was 65 minutes late (multiplier of 0.52), Ascend was 94 minutes late (multiplier of 0.39), SunShuttle was 128 minutes late (multiplier of 0.28), and the remainder appear to be out of the event.
It's especially heartbreaking for Minnesota, who were on a pace to finish before the target time... until they had some sort of issue and parked their car almost a full hour before the end of the first day, putting them off the back of the pack of Cruiser cars. They were the fastest Cruiser car on the second day, but it wasn't enough to make up for the time they'd lost.
It remains to be seen what the external energy usage and person-km for each team are, and of course practicality is a big black box at the finish line, but Sunswift has been carrying four people in the car for almost the entire even and I expect them to do very well on practicality, so it's hard to see how any other team can come back from those penalty multipliers. Of course Sunswift could also have some sort of issue and accrue a large penalty multiplier, but looking ahead to the second stage, Sunswift is the front-running Cruiser team at the end of the first day of the stage and appears to be on pace to hit Coober Pedy by the required 4:30pm time. Minnesota also remains on pace, while Solaride and Ascend slowly slip back, and Apollo apparently has suffered some sort of critical problem and will certainly miss the 5:00pm hard cutoff, leaving only four cruisers left in the running.
Ok - gotta hit the tent and get some sleep for the drive ahead tomorrow. I'll leave you with some photos:
A very confused road train driver trying to enter the Katherine weighstation
Sunset at Dunmarra
Fire and smoke between Barrow Creek and Ti Tree on the second day We could feel the thermal radiation passing this fire from inside our car Innoptus was ahead of us at this point, Twente and Brunel behind
Hello! Long time no see. Sorry about the extended absence... I intended to cover the 2019 World Solar Challenge the way I did in 2015 and 2017, but life got in the way. This year I'm headed back to outback... Even though I haven't been blogging in the lead up to the race, I wanted to get some thoughts down before the start.
So for starters: What are the significant changes to the regs since 2019?
1) Ground clearance/approach angles/etc. WSC continues to try to force teams to drive their cars on and off the highway and the start/end of the race day, rather getting lifted onto the highway and sitting stationary in the lane at the start of the day and parking on the highway to get lifted off to the shoulder at the end. Rather than just stating that "cars must be able to drive off a 50mm vertical drop" as in 2019, now we have a minimum 100mm ground clearance, minimum approach and departure angles, a minimum hump that cars must be able to drive over without high-centering, etc.
2) Wheel count. For the first time since 2011, WSC is allowing three-wheeled Challenger class cars (Cruisers still need 4 wheels). On the one hand, all the cars that I ever worked on were three-wheelers and I was disappointed when WSC started to require four wheels in 2013. On the other hand, given how many off-road excursions happened in 2019, I was very surprised to see this change... it's only going to make the modern skinny monohulls even less stable. WSC *has* added a static stability requirement - cars must be able to be tilted 45 degrees across any two adjacent tire contact patches - but I haven't seen any evidence of a tilt table at scrutineering...
3) No more gallium arrays; allowed solar collectors sizes are only called out for Silicon (unchanged at 4sqm). If a team want to propose using something different, "the materials should have low environmental toxicity; this precludes the use of GaAs, CdTe
and CuInSe2".
4) Here's an interesting one: For the first time (as far as I can tell), WSC is requiring cars to have automatic battery protection systems, not just battery monitoring systems - peep the language changes in reg 2.5.9. I'm assuming Nuna 10 burning down on the finish line in 2019 might have had something to do with this? I guess it's one thing when non-competitive teams burned down outside of Darwin every other race, but a star team burning down in front of news vans outside Adelaide was different matter.
5) License Plate. No more shenanigans with it being inside the canopy and hard to see, NOTHING can be aft of the license plate within a defined cone. I was interested to see if any teams tried shenanigans here, never underestimate a determined aerodynamicist! But the rule is extremely clear and so far I haven't seen anything questionable. Most teams have a very clear location to mount the plate, as seen for example on the back of Twente's car below:
6) Occupant Space. This is the first year that WSC will be using a test fixture that they call "PVC Pat" to inspect the size of the interior.
7) Rear steer: forbidden this year. No using a rear steering system that only operates at extreme steering lock to meet the U-turn reg, no rear steering system to "crab" the car into crosswinds and reduce aerodynamic drag. I'm told that this is in a bid to reduce car speeds - apparently several teams were sailing VERY effectively in 2019. But notably movable aerodynamic devices are not banned...
8) 3.24.6: "If a solar car rolls onto its side or roof then the team must withdraw immediately." It'll be interesting to see how this reg intersects with the three-wheel reg potentially reducing the stability of the cars. Twente apparently already put the car on its side during pre-race testing.
OK regs talk over, let's talk about cars.
The main way these regs seem to be influencing the teams is: More monohull/bullet cars: fully 3/4 of the Challenger entries this year are monohulls. The modern monohull trend started in 2017: that was the first year of the 4sqm array formula, and we saw highly competitive monohulls finish in 2nd and 4th place overall. This result apparently inspired teams - about half the field was in monohulls in 2019, and the vast majority of the "good" teams were, with 7 out of the top 8 finishers being monohulls. But! Until Twente wrecked out and Vattenfall (formerly Nuon, now Brunel) burned down, the three fastest cars were all catamarans, and the overall winner was a catamaran from Agoria. Given that result, why are teams committing further to the monohull concept (including the winning team from 2019)? I think it's mostly down to the 3-wheel rule.
One of the major disadvantages of the 2017/19 4-wheel monohulls over their catamaran counterparts is that the wider monohull has a much larger surface area close to the road - the entire region bounded between the wheels is basically flat against the ground, in relatively dirty airflow. The body also has to stay wide all the way to the rear wheels and can only start to aerodynamically close behind them. The skinny catamaran pontoons can be much shorter front-to-back, minimizing the parts of the car that are down low. But with only three wheels, a monohull's body can start to sweep inward and upward immediately aft of the front pair of wheels, reducing the area of the car that has to be near the ground. Clearly teams think that this is a big enough change to tip the balance in favor of monohulls... Both Twente and Innoptus (formely Agoria, the 2019 winner) have switched from catamarans to monohulls for 2023.
The big outlier is Brunel (formerly Vattenfall, formerly Nuon): Nuna 12 is a three-wheeled "outrigger" catamaran. It has the driver against one side of the car with a wheel fore and aft of the driver as on previous four-wheel cars, but only a single wheel centrally located on the side opposite the driver.
I am genuinely excited about this car, I feel like the sport has been waiting for this design for over a decade. Nuon themselves thought about the idea when the change from laydown cars to upright seating happened with the WSC 2007 regs, you can see an outrigger catamaran concept peeking out in the back of this photo (they ended up choosing the middle concept, setting the tone for the 2007/09/11 generation of cars):
Kansas State also had the same idea around the same time, and got as far as cutting up an old chassis to build a prototype to do some dynamic testing on. Here they are showing that it brakes straight with the driver's hands off the steering wheel:
And here's a video showing that it skids rather than flips in a high-speed turn:
And prior to the mid-2012 regs release mandating 4-wheel cars, I was seriously proposing to my old team that they field a design like this for WSC 2013 - and I know that I wasn't the only person doing do!
Brunel isn't the only team to look at this design for WSC 2023; Durham is also running an outrigger catamaran this year.
It's worth noting that this isn't Brunel's first rodeo with this car design: they built Nuna 11 as an outrigger catamaran for the canceled 2021 World Solar Challenge, and drove it to a 3rd place finish in Morocco in 2021 and a 1st place finish at Sasol in 2022. The car they are bringing to WSC this year is Nuna 12, their second-generation outrigger catamaran. Brunel clearly believes in the concept.
Of course, the same can be said for Twente and Innoptus - they clearly believe in monohulls now, despite being at the top of the field in 2019 with catamarans. That Moroccan race in 2021 that Brunel finished in 3rd with their first outrigger catamaran? Twente won that race with their first monohull car, and Innoptus came in second with their first monohull. Both of those teams have brought new second-generation monohulls to WSC this year as well.
It's going to be a really fascinating race between these teams this year. We also can't forget Michigan, one of the originators of the modern monohull concept back in 2017 and bringing another good looking monohull. Similar to the teams above, Michigan hasn't been resting over the WSC pandemic break - they also built a non-WSC car over the pandemic (although it didn't race anywhere), so the team has worked to keep their skills fresh.
Photo: Ⓒ University of Michigan Solar Car Team (image source)
Worth noting, since you're going to see it on a lot of the monohulls - see the raised nose? It's a very distinctive change from previous monohull designs, and one that is featured on a LOT of the cars this year. I was puzzling over why - maybe there's an aerodynamic reason, but how did every team land on the same aerodynamic feature at the same time? - but then I realized that this is a consequence of the 10° approach angle rule!
This post is getting longer than I planned, so very briefly: All the other teams from the top grouping in 2019 - Tokai, Top Dutch, Sonnenwagen, Kogakuin - are back, with monohulls. Kogakuin of course has some very interesting suspension concepts that I will hopefully be able to get pictures and post about. NITech and Antakari were unable to make it, but Blue Sky, Eclipse, and JU are all back as well. Notably Eclipse is the only WSC 2019 finisher that's coming back with a catamaran, and JU is bringing the only monohull that doesn't have the driver canopy protruding over the solar array. WSU is also back with a monohull - hopefully they won't have a repeat of their very rough 2019 race.
On the Cruiser side of the competition, the big news is that neither Endhoven nor Bochum are attending this year! Eindhoven won all four previous Cruiser classes 2013-2019, and Bochum has historically been a strong competitor. Without the two of them, Minnesota, Sunswift, and Sophie are likely the three strongest competitors in the class this year, although I'm also keeping my eyes on Apollo. There's also a very interesting rule that the teams must upload telemetry about solar energy collected and energy used from the battery at each of the control stops, I'm very curious to see what that data looks like.
