So the most outrageous homework you have had to "help" with so far is... ?

[DanceswithUnix]

Until recently the winner for me would have been last years "Build a model submarine that can dive and surface".

But this half term, for my 10yr old (last year of primary school): "Build a model rocket that can lift off".

The Thames Valley Spaceport project is coming along nicely, but I have to wonder what other parents have ended up doing!

[kalniel]

You've uncovered Britain's plans to compete for cheap space travel contracts!

[DR]

I think we need photographic proof

[jimborae]

In other news "Thames Valley Father & Child Arrested On Suspicion Of Building IED In Garden Shed!"

[Ttaskmaster]

Until recently the winner for me would have been last years "Build a model submarine that can dive and surface".

Hmmm.... How old are you?

You may recall, they used to give away little plastic toy submarines in Kellogg's Cornflakes, that did exactly this. It had a small compartment in the middle with a hole in the bottom. You filled the compartment with a few mm³ of cornflour... or was it baking soda... put the cap on and drop it in the bath.
The thing bubbled a bit and then sank, then rose, then sank again, then rose and kept on until the flour/soda/whatever was exhausted.

But this half term, for my 10yr old (last year of primary school): "Build a model rocket that can lift off".

So... licence to build a proper, actual model rocket like the electronic igniting kits?
Or licence to effectively make a 60mm mortar?

The Thames Valley Spaceport project is coming along nicely, but I have to wonder what other parents have ended up doing!

Mine had to buy me a packet of cigarettes and a bag of animal guts, once...

[peterb]

Until recently the winner for me would have been last years "Build a model submarine that can dive and surface".

But this half term, for my 10yr old (last year of primary school): "Build a model rocket that can lift off".

The Thames Valley Spaceport project is coming along nicely, but I have to wonder what other parents have ended up doing!

Plastic bottle half full of water with a restricted nozzle on the end. Build a rocket superstructure and then use a bicycle pump to pressurise the bottle. Compressed air forces water out. Or use a balloon, or a vinegar/bicarbonate of soda mix (might not react fast enough) or a good mixture of chemical to produce an impulse (!) might be a bit illegal though, and mixing the ingredients safely might be difficult.

Or you good build a ballistic launcher using the afformentioned ingredients as the propellant or just something like a teaspoonful of petrol.

Obviously, you try these at your own risk . Stored energy systems are risky!

Have fun

[Galant]

Plastic bottle half full of water with a restricted nozzle on the end. Build a rocket superstructure and then use a bicycle pump to pressurise the bottle. Compressed air forces water out. Or use a balloon, or a vinegar/bicarbonate of soda mix (might not react fast enough) or a good mixture of chemical to produce an impulse (!) might be a bit illegal though, and mixing the ingredients safely might be difficult.

Or you good build a ballistic launcher using the afformentioned ingredients as the propellant or just something like a teaspoonful of petrol.

Obviously, you try these at your own risk . Stored energy systems are risky!

Have fun

So essentially the Mentos in a Coke bottle thing upside down, you'd just need a way to get the mentos into an inverted bottle.

[DanceswithUnix]

So essentially the Mentos in a Coke bottle thing upside down, you'd just need a way to get the mentos into an inverted bottle.

Nah, not enough energy

We are going for a "soda bottle rocket", launching a 2L Pepsi bottle part full of water hopefully at about 100PSI.

The launcher is largely dry assembled, I need to get the O-ring fitted which isn't trivial but without it the water will escape before launch.

There are lots of plans out there on the internet, but finding the right parts in the UK is hard. For starters, drink bottles need a 21.5mm pipe to fit snugly and the UK standard seems to be 22mm which won't quite fit the bottle. I found Screwfix does a 21.5mm solvent weld pipe which is about perfect, but they don't stock end caps so I have had to modify the usual designs.

I'm about £20 spent so far on this, but my daughter enjoyed sawing up the 3m pipe into lengths so that's a new skill she has already

So peterb was about right, except you don't restrict the nozzle, the faster you dump reaction mass the further up it goes (apparently, we haven't flown yet)!

[peterb]

Baked bean cans with the ends cut off and gaff-taped together (and then bound all over with tape) makes a good impulse launcher for a ballistic launch... (so Im told.. )

[DanceswithUnix]

I think we need photographic proof

Will have to get my son to video the first flights, when we get there. Might need a youtube channel

Hmmm.... How old are you?

You may recall, they used to give away little plastic toy submarines in Kellogg's Cornflakes, that did exactly this. It had a small compartment in the middle with a hole in the bottom. You filled the compartment with a few mm³ of cornflour... or was it baking soda... put the cap on and drop it in the bath.
The thing bubbled a bit and then sank, then rose, then sank again, then rose and kept on until the flour/soda/whatever was exhausted.


So... licence to build a proper, actual model rocket like the electronic igniting kits?
Or licence to effectively make a 60mm mortar?


Mine had to buy me a packet of cigarettes and a bag of animal guts, once...

I had a sub like that (I am mid 40's) and mine was powered by something like alka seltza tablets. The one we made for homework had a tube to blow in to make it surface on demand.

And yes, the launch mechanism is totally open. As part of my initial research I found "Rocket Candy" which is I think a leap too far, I shall stick to the bicycle stirrup pump

Edit to add: Is there still quite a low limit on how many pictures you can upload to Hexus? I think last time I tried I filled it quite fast.

[DanceswithUnix]

Well, here was what was "handed in"



Lots of fun!

[peterb]

Very neat! How high did it fly?

[GoNz0]

Plastic bottle half full of water with a restricted nozzle on the end. Build a rocket superstructure and then use a bicycle pump to pressurise the bottle. Compressed air forces water out. Or use a balloon, or a vinegar/bicarbonate of soda mix (might not react fast enough) or a good mixture of chemical to produce an impulse (!) might be a bit illegal though, and mixing the ingredients safely might be difficult.

Or you good build a ballistic launcher using the afformentioned ingredients as the propellant or just something like a teaspoonful of petrol.

Obviously, you try these at your own risk . Stored energy systems are risky!

Have fun

I Didn't follow the instructions on the booms bangs and fizzes kit my Daughter got, I skipped the water part but still got it about 40 feet up

[DanceswithUnix]

Very neat! How high did it fly?

Very hard to say, and if it ever stops raining I'm sure we can give it another go.

Launched at 40psi with about 1/3rd full of water on a slightly foggy day it was quite hard to see. Was in flight for about 8 seconds, came down so fast the nose was buried in the ground!

There seems to be a slight air leak around the launch mechanism, need to fix that (might need a different o-ring) and then pressure test up to 100psi. That should shift From what I read on the web, the bottles are good for 120psi.

So could have been 30m, could have been 50m, no idea just a dot in the distance so hard to tell. Next time we will have to go prepared with one of these: https://spaceflightsystems.grc.nasa....tracking2.html

Test firing at low pressure 20psi in our back garden, no fins on the bottle (and fins make a huge difference) it was clearing the top of the house.

[peterb]

Very hard to say, and if it ever stops raining I'm sure we can give it another go.

Launched at 40psi with about 1/3rd full of water on a slightly foggy day it was quite hard to see. Was in flight for about 8 seconds, came down so fast the nose was buried in the ground!

There seems to be a slight air leak around the launch mechanism, need to fix that (might need a different o-ring) and then pressure test up to 100psi. That should shift From what I read on the web, the bottles are good for 120psi.

So could have been 30m, could have been 50m, no idea just a dot in the distance so hard to tell. Next time we will have to go prepared with one of these: https://spaceflightsystems.grc.nasa....tracking2.html

Test firing at low pressure 20psi in our back garden, no fins on the bottle (and fins make a huge difference) it was clearing the top of the house.

Excellent, just be careful with that 'O' ring, remember what happened to the space shuttle.....

[DanceswithUnix]

Excellent, just be careful with that 'O' ring, remember what happened to the space shuttle.....

I was actually thinking about that when I was sanding a bit off the O ring. Might have sanded a bit too much off, it was hard to get the bottle on so I kept sanding when I should have just slapped a bit of vasaline on there!