University of Cape Town Team Breaks World Water Rocketry Record (uct.ac.za) 35
New submitter Cycliclogic writes: A team of engineers based at the University of Cape Town recently had their record breaking flights of their water powered rocket Ascension III ratified by the Water Rocket Achievement World Record Association. This record is for a single stage rocket power purely on pressurized water. Two launches must be completed within two hours, the record being set at the mean above-ground altitude of the two flights. The record now stands at a whopping 2723 Feet (830m). You can watch videos of the launches here. (Warning: they're loud.)
0.8 km down... (Score:4, Interesting)
...only 152.2 km to go.
In all seriousness, I wonder what they could achieve with a multistage version.
Re:0.8 km down... (Score:4, Interesting)
I know someone who did far better. (Score:4, Interesting)
Back in the 70s. Bought a 10,000psi stainless cylinder at surplus. Screwed on a fin set, nozzle and burst plate he constructed. Then filled it 80% with water before building a bonfire around it.
They drank beer until the pressure plate popped out at about 8,000 psi.
They were walking around, stomping out fires in the dessert when a group of nice airmen in a Huey invited them to come and talk. They denied everything.
Apparently Russian launch detection satellites saw the flight. He claims they made 10k meters+.
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Did his brother by any chance strap a JATO to his old Dodge???
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All stories like this are suspicious. But I believe him, Berkeley ME, right age, right attitude.
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Seems Cape Town Team broke rules too (Score:2)
Seems the team in the fine article did as well. Carbon Fiber is not ductile plastic.
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TFA (Score:4, Funny)
I just scanned the articles and didn't see what sort of tank pressures these things use.
Also, do I have to use a tank of water? Or can I make my own as I go? One tank of LH2, one of LO2 .....
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I wonder if you have to charge it with air, or if you can charge it with hydrogen or helium gas to pressurize it?
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So, I'm super curious to hear what you think pressurized hydrogen or helium would provide that pressurized air would not.
1) Lower mass. Air at STP is 1.2 g/L. Hydrogen is 0.09 g/L. Looking at the contest rules the pressure vessel has to contain 20% water, so most of the volume is gas. A lighter gas lets you either use more pressure while staying under the 1500 gram limit, or have less dead weight for a given bottle/propellant quantity (whichever way you want to look at it).
2) Non-ideal gasses have different compressability. Not my field, so I can't calculate it, but it's significant enough that the rules forbid it for th
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So, I'm super curious to hear what you think pressurized hydrogen or helium would provide that pressurized air would not.
1) Lower mass. Air at STP is 1.2 g/L. Hydrogen is 0.09 g/L. Looking at the contest rules the pressure vessel has to contain 20% water, so most of the volume is gas. A lighter gas lets you either use more pressure while staying under the 1500 gram limit, or have less dead weight for a given bottle/propellant quantity (whichever way you want to look at it).
2) Non-ideal gasses have different compressability. Not my field, so I can't calculate it, but it's significant enough that the rules forbid it for this reason. You have to use air.
But doesn't the gas form part of the reaction mass? And therefore using a lighter gas would give less thrust? Eg might sulfur hexafluoride be better?
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But doesn't the gas form part of the reaction mass? And therefore using a lighter gas would give less thrust? Eg might sulfur hexafluoride be better?
No, these are water rockets. The reaction mass is water. :)
Even if the gas was reaction mass you'd probably want a light gas. A heavy gas might have better impulse per mole or per liter, but lighter gasses will provide more impulse per gram. At some point the larger pressure vessel will add more mass than you're saving on the gas, but I'd expect the optimal gas to be closer to the hydrogen end of the spectrum. Take that with a grain of salt though because I haven't made any attempt at the math.
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Per rule 1, the 1500 gram limit is "dry" meaning not including fuel which would presumably also mean not including the compressed air. It's the compress-ability that really matters here. You could get a lot more energy into compressed hydrogen than compressed air. But it's against the spirit of the competition.
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Rule 2: Rocket must use compressed ambient atmospheric air as its energy. Other gasses have much higher compression ratios and there needs to be a baseline so the record is fair to all. (see section II for special rules regarding bottled air).
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Rules say has to be "Mainly Water" and nothing "that might harm the environment"
Obligatory Danger Warning: this rocket gives off Hydrogen Hydroxide!
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Water can power rockets? (Score:2)
Lets ban water, so the terrorists cant built water-rockets.
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Try logging in before you read the articles.
Also serious contenders for... (Score:2)
The most egregious abuse of the Wadsworth constant.
Seriously. Eleven and a half minutes? The Shuttle used to take less time to get into orbit than this thing sat there doing nothing.
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Re: Also serious contenders for... (Score:2)
What's a stomp rocket?