Model rocketry is a gateway drug for STEM. I bought my son an Estes model rocket kit when he was about 11. Now he is studying aerospace and astronautic engineering at university.
There are some fantastic model rocketry competitions for youngsters. There is one running in the UK right now (Google 'UKROC') and equivalent ones in the USA, France and Japan. Plenty of guidance is available and it isn't dangerous if you are sensible. We entered a team into UKROC 2 years running and had an amazing time.
bayouborne 1 days ago [-]
I'm 66, and when I myself was 10 or 11 my friends on my street and I were completely obsessed with the Estes rocket and Cox .049 U-control scenes. Most of us were lucky enough to have engaged fathers and once the standard craft were assembled and flown, we all browbeat them mercilessly for more information for mods, shortcuts, hacks etc. My dad grew very wary of the 'Why can't we' type questions. I had modified a C-type engine Big Bertha rocket with an extra long transparent payload module which set the stage for various kidnappings of lizards, frogs, praying-mantises, eggs, multiple 1 and a quarter inch sockets, etc (all returned to earth unharmed, if not un-rattled). The nichrome wire igniters were troublesome for most of the kids. Bulky and expensive (for 4th graders) lantern batteries were hard to come by. We found we could steal D-cells from flashlights, hack cardboard tubes from paper towel rolls, reinforce with electrical tape, and make passable energy sources from that, etc. But all of that required questions from the closest available parent about voltage and series/parallel connections, as well as other questions about CG when modding the rockets themselves, etc. I think your STEM comment is very much on-point. None of my friends thought we were learning anything at the time. We were mostly just jazzed about doing fun stuff that had the potential for tearing itself apart in mid-air. I know the advent digital everything makes modeling systems for kids [Kerbal,etc] probably pretty trivial now, but actually crashing things in spectacular fashion IRL had/has it's own visceral rewards.
hermitcrab 1 days ago [-]
My son enjoyed Kerbal Space program. But, fun[1] and educational as that is, it couldn't match the thrill of launching a real home-made rocket to ~1000 feet.
> WARNING – Extreme care must be exercised in flying a whoosh rocket and students must be supervised when using this type of rocket.
Only surpassed by the time I tried to grab a falling soldering iron by the tip this is the source of the worst burn I've ever received. I cannot stress how vicious an ignited alcohol mixture in a container can be.
maccam912 2 days ago [-]
What went wrong?
timewizard 2 days ago [-]
Something in my childhood I presume. In this specific case, you see how they depict the long necked "BBQ" style lighter? That's a /really/ good idea.
kbenson 2 days ago [-]
> Something in my childhood I presume.
LOL, I can empathize quite a bit, as someone that has a nasty burn scar on my hand caused by a glob of melted saltpeter and sugar from an accidental ignition of a concoction I was cooking one fourth of July in my youth.
s1artibartfast 2 days ago [-]
A lot of good lessons to be learned from KNO3. An early lesson was not to melt it and incorporate fuel on a kitchen stove. Next lesson was how to build a outdoor brick stove. Then we learned a couple pounds would fill up several square blocks with dense smoke and burn a hole through blacktop.
Not sure how we made it through our youth without learning what the inside of a jail cell looked like, but I suppose things were different before 9/11.
kbenson 2 days ago [-]
> An early lesson was not to melt it and incorporate fuel on a kitchen stove.
That was, indeed, an aspect of the problem I alluded to before. I have made it a few times before, and I was going to use the gas grill outside, but it seemed to be acting up, and I didn't trust it, so I thought it would be "safer" to move inside.
Combine that with me iterating on a few different batches with "improvements", such as lining the bottom of the pan with tinfoil so I could lift it out, and then next making an extra large batch... well multiple lessons were learned that day, including how to deal with insurance companies from some shrewd negotiating from my parents, given most the entire kitchen needed to be replaces and the entire house needed to be scrubbed floor to ceiling.
> Not sure how we made it through our youth without learning what the inside of a jail cell looked like, but I suppose things were different before 9/11.
Ha, probably true, especially since my recipe came from a copy of the anarchist cookbook my older brother happened to have (and I wouldn't be surprised if you happened upon it the same way). It's got a lot of dangerous stuff in it, but honestly, as a tool for sparking curiosity it works pretty well.
dhosek 2 days ago [-]
I grew up with a (stolen, of course) copy of Steal this Book in the house.
dhosek 2 days ago [-]
As a grade school kid, I was taken to the police station for making a bomb with a couple friends. Fortunately for us, no charges were pressed (presumably because we didn’t manage to ignite the bomb and it was the 70s).
hermitcrab 2 days ago [-]
I met someone on holiday whose brother has been blinded for life by a pipe bomb he and a friend made. So the risks of messing around with that sort of thing are very real. Better to couple youthful enthusiasm with some adult oversight. It can still be a lot of fun (see my comments on youth rocketry competitions elsewhere in this discussion).
Please don't post comments saying that HN is turning into Reddit. It's a semi-noob illusion, as old as the hills.
qoez 2 days ago [-]
I'm aware of this rule but I think it's clearly not true that quality hasn't degraded over time. Look at any pg thread from 2014 https://news.ycombinator.com/item?id=21233848 Anyway I get that commenting this isn't the best use of space but I still think it's true (I also suspect not being allowed to call this out is not helping the quality).
My high school chemistry teacher did this a few times with a water cooler bottle. In fact, the morning of our graduation, we were having breakfast at the school when he walked on stage holding a water cooler bottle and a lighter. I think he must have used too much alcohol that time because it blew out the bottom of the bottle and the rest of it shot several feet in the air.
Retr0id 2 days ago [-]
"too much alcohol" tends to make it less explosive because the oxygen ratio becomes suboptimal.
hermitcrab 2 days ago [-]
I'm not sure it is a good idea to do that indoors.
blacksmith_tb 2 days ago [-]
Possibly not, though that larger polycarbonate water bottle is quite heavy, compared to the 2 liter PET soda bottles NASA is suggesting for outdoor firing, and it looks like the "nozzle" is the uncapped mouth, which would also help to keep it from hitting the ceiling.
hermitcrab 2 days ago [-]
I would be more worried about setting fire to the building.
Just seems like a totally unnecessary risk. But I have been called a 'safety Nazi'.
ggm 2 days ago [-]
Nearly took out a <5yo kids eye with a bottle rocket showing off. Not my kid either. (he was safely out of distance a bit wiser) Haunts me still.
Rockets are fun. With one remaining eye explain to mummy and daddy how this happened again.
hermitcrab 2 days ago [-]
Water bottle rockets have a surprising amount of energy. I managed to hit myself in the chest with one, after only a couple of pumps, and it fair knocked the wind out of me.
We also did some messing around with coke/butane rockets. These could easily knock teeth out and I made my son wear his full face cycling helmet before handling them.
Model rockets with solid fuel motors obviously require an even greater level of respect.
Loughla 2 days ago [-]
Solid fuel at least is more controlled. You can ignite them from a very safe distance.
I've never been hurt by an actual rocket motor, but I thought I lost a finger with the woosh rocket that exploded. . . Luckily just a cut and some burns and not on my face.
hermitcrab 2 days ago [-]
Solid fuel motors are quite hard to ignite. So they are pretty safe from that point of view. But:
Once the motor is ignited, nothing will put it out. Not even immersion in water.
The motors are not made to NASA standard and don't always do the expected thing.
Model rockets with solid fuel motors can go 1000s of feet. If they come down in one piece without a parachute (which does happen). You don't want to be under it.
They can set fire to dry ground. I've seen it happen.
None of the above are an issue if you are being sensible, following guidelines and paying attention.
TeMPOraL 1 days ago [-]
Also: solid fuel motors may be quite hard to ignite for launch, but solid fuel itself is damn easy to ignite when you're making it yourself. Take care, keep containers pointing away from your face at all times, and generally FIRE HAZARD.
Also: a bad fuel mixture will clog your nozzle with "solid combustion residue", as we called it with my friend, leading to the infamous rapid unplanned disassembly (the motor will promptly explode), so if you value your life and not being in prison, never ever use metal containers for it. Thin PVC pipe dangerous enough in case of RUD, but is much less likely to kill you.
(Obviously, I too somehow survived childhood unharmed...)
hermitcrab 1 days ago [-]
Bear in mind that making solid fuel motors without a licence is also illegal in some countries (such as the UK).
That is pretty impressive. Large empty spaces like that are a bit hard to come by in the UK.
krunck 2 days ago [-]
When I was a kid I used to do this with propane. I'd fill it with a propane torch - which is set t mix the C3H8 and O2 to the right proportion - and light it. I would not use a restrictor/nozzle cap because it had plenty of thrust without it.
I survived my childhood unscarred, somehow.
AStonesThrow 2 days ago [-]
Two or three drops of fuel! That's a very counterintuitive contraption! I would really be reluctant as a teacher to bring a flame near something made entirely of plastic... and with no fins or guidance control on a ballistic trajectory? I mean it's an air-filled soda bottle, but still.
I also seem to recall a type of toy vehicle that was propelled by some compressed gas as it slid, suspended along a horizontal wire/string, but I'm drawing a blank regarding the type of propellant right now. It seemed safe enough to use indoors, especially considering the constrained pathway.
I loved water rockets as a kid and I also enjoyed actual model rocketry, except they seemed too hazardous for me to find a launch area where bystanders felt completely safe. Model rocketry is sometimes 90% modeling, and 10% launching them. Estes can make some really precious designs that fly horribly but look great in a Plexiglas cube on your shelf.
I lost most of the ones I built due to poor launch conditions, and while I chose deserted school campuses during vacation or weekends, I didn't make any friends with security patrols there!
userbinator 2 days ago [-]
Two or three drops of fuel!
The stoichiometric AFR for isopropanol is 10.4:1 according to the sources I found. For 1g of fuel you need 10.4g of air which at SSL[1] corresponds to around 8.5L. One drop of fuel does consume several liters of air to burn. The volume difference is really that huge --- and the higher the AFR, the bigger the difference; gasoline engines are around 14.7:1, and diesels go much higher when idling or under light load.
> I also seem to recall a type of toy vehicle that was propelled by some compressed gas as it slid, suspended along a horizontal wire/string, but I'm drawing a blank regarding the type of propellant right now. It seemed safe enough to use indoors, especially considering the constrained pathway.
I've heard of using ordinary rubber party balloons for this.
I have never been to the US, but I wonder if this is equally safe in the EU where plastics regulations appear to have changed the density and feel of drinks containers over the past half-decade or more. They're obviously fine for carbonated drinks, and probably bottle-rocket use too, but I wonder about their structural integrity as a receptacle for alcohol combustion.
hermitcrab 2 days ago [-]
Soda bottles are surprisingly strong. Even if one fails, I think it would probably split, rather than creating dangerous shrapnel (citation needed).
PaulHoule 2 days ago [-]
The patent for the PET soda bottle was granted to one of the Wyeth brothers!
The patent says they are good to 100 psi for regular operation and people pump them up to 2x that when they shoot them up as rockets.
It's fun to make a "chemical pressure bomb" out of that kind of bottle, the classiest way to do that is to use liquid nitrogen, the second classiest way is to put in a pellet of dry ice, if you have no class at all you put in some aluminum foil and either a strong acid ("The Works" drain cleaner) or a strong base (Lye/Sodium Hydroxide) which in either case will evolve hydrogen. [1]
The dry ice version goes off in 30-45 minutes if you put in just the pellet, if you add some hot water it works like a hand grenade and will explode less than a minute, cold water is intermediate. These are dangerous at point blank range
but in my experience harmless 10 feet away. [2] [3] When I was in college my friends and I made a bunch of them and threw them into a vacant lot at night and thought 30 minutes later that we'd failed, but soon we heard a series of loud explosions which caused the neighbors to call the police. The cops drove by and shined a spotlight into the area and we were worried that the last one would go off when he was there but it exploded just after he drove off.
[1] ... and spray dangerous chemicals. Don't do it.
[2] had one blow the bottom out of a small plastic waste basket though and read a report which I couldn't find this time about a high school chemistry teacher who tried this in class and it blew up in a student's hand, blinding him
[3] usually the bottle is torn up such that most of the plastic is in one big piece with jagged edges, today people would worry about microplastic generation
bityard 2 days ago [-]
TFA warned against using bottles other than soda because soda bottles are made to withstand a lot of pressure. Others may or may not.
I don't imagine ANY plastic bottle survives too many lift-offs.
PaulHoule 2 days ago [-]
See https://waterockets.com/ for commercial kits for making really fancy pressurized water rockets, even 3-stage rockets! You can get many many uses out of a bottle.
In Larry Niven's Known Space books, rockets are launched from earth using some kind of super-compressed material encased in tanks made of some unobtanium, a vastly improved version of those water rockets.
4gotunameagain 2 days ago [-]
Only one way to find out !
vvchvb 2 days ago [-]
I think so:
1. It's only a drop out two of alcohol
2. Carbonated drinks are at a very high pressure already.
I could, if I wasn't feeling lazy right now, do the math to compare the two pressures. Its easy stuff - two drops of alcohol combusted + assumption all the combustion products are ideal gases vs Henry's law for CO2. This last one will require looking up how much co2 is dissolved in the product, but thats not too hard.
But, like the other commentator pointed out.... there's only one way to find out.
rkagerer 2 days ago [-]
Could a 3D printed nozzle of some sort improve its characteristics?
hermitcrab 2 days ago [-]
Almost certainly. But it might need to be printed out of something with moderate heat resistance.
desertmonad 2 days ago [-]
Mentos and cocacola or maybe vinegar & baking soda variant could be safer.
I'm sure kids would have fun with this.
Loved launching bugs(unharmed) in my nova payloader as a kid :-)
k7sune 2 days ago [-]
Humm the next logical step would be to pressurize the rocket before igniting it. Or maybe to add some water in the bottle to increase the propelled mass. They just need a way to ignite the alcohol fume from the top……
neuroelectron 2 days ago [-]
I would think the next logical step would be pressurizing a stainless steel thermos with liquid methane and mating it to a 3d printed copper prototype manifold and turbine pump.
nealabq 2 days ago [-]
Could you do this with dry corn starch? Shake it up in the bottle and light it before the dust settles.
pbhjpbhj 1 days ago [-]
A common science demo in UK used to be exploding a cloud of custard powder - ostensibly powdered sugar and cornstarch.
I'm not sure that corn starch would stay as a fine powder long enough for that to work.
However, if you have a long cardboard tube:
* place the tube vertically with an ignition source at the bottom (small candle perhaps)
* pour fine powder in the top (may need a step ladder if the tube is tall enough)
* satisfying whoosh
Don't look down the tube as you are doing it and don't do it indoors, obvs!
huhtenberg 2 days ago [-]
I wonder if adding a static charge to the dust would help it to stay airborne longer.
DeathArrow 2 days ago [-]
Can't we just have reusable space ships with engines that burn some kind of fuel and we just replenish that fuel?
It seems a waste to use rockets and replace the whole rocket or most parts of it after each flight.
Sharlin 2 days ago [-]
Heard about the Space Shuttle? Or the SpaceX Falcon 9?
The reason it hasn’t been done in scale before SpaceX is that reusability is a hard problem to solve and it is/was more economical to use expendable launch vehicles than to develop recoverable and refurbishable stages.
You might also like to read about single-stage-to-orbit (SSTO) which is something of a pipe dream. The rocket equation is a bitch.
The shuttle was a re-usable ship, the rockets used to get it into space were not reusable.
skissane 2 days ago [-]
That’s not true… both the RS-25 SSMEs and the SRBs were reused - however, the extent of refurbishment required between flights was so extensive, time-consuming and expensive, that it erased much of the benefits of reusability
usrusr 2 days ago [-]
The SRBs were collected from the sea for reused and the upper stage was reused after landing horizontally. The only thing not reused was the upper stage drop tank. That single use drop tank was rather big, true, but not a rocket, not a rocket at all.
The Soviet lookalike did use a single use rocket as its second stage, with the reusable part just being an orbiter.
Sharlin 2 days ago [-]
Interestingly, the Buran’s Energyia launch vehicle could possibly have been made reusable exactly because the tank and the engines were one unit. At the expense of payload capacity, of course. And anyway the Soviets were confused about the whole shuttle concept because it didn't seem to make economical sense, reusable booster or not – but they assumed the Americans knew something they didn't.
usrusr 2 days ago [-]
How would Energyia become reusable? Tail landing? Is there more to this, something specific that would make Energyia a candidate for tail landing other than just "if F9 can do it, in theory every liquid fueled rocket could do it"?
all the concepts i've seen were horizontal landing mostly with fold-out wings
usrusr 1 days ago [-]
Wow, that's ... ambitious. I'd imagine the extra mass to make an energyia-size tank+engines able to land horizontally to be enormous. It's not just wings (plus folding mechanism, if you believe that's worth saving a bit of drag on the way up) but also landing gear plus all the structural strengthening required.
Sounds suspiciously like one of those projects you propose when you want something finer short term but assume that they never survive to the point where they actually need to deliver?
Sharlin 2 days ago [-]
Not so. The solid rocket boosters were reused, as were the three SSMEs bolted to the orbiter itself. The only part that wasn’t reusable was the external fuel tank because bringing it back intact from almost orbital speeds would’ve been hilariously uneconomical.
That said, refurbishing both the SRBs and the SSMEs after each use was labor-intensive and as such expensive.
inglor_cz 2 days ago [-]
"Refurbishable" would be a better term than "reusable".
Refurbishment of the shuttle orbiter took months and tens of thousands of work hours before it could fly again. It was pretty far from what ordinary people understand under "reuse", though not completely outside the meaning of the word.
snickerbockers 2 days ago [-]
not sure what this has to do with the middle-school science-fair project in the OP, but the whole "reusable shuttles" idea hasn't really panned out that well. The Russian Soyuuz rockets haven't changed much since the 70s and they have an excellent safety record compared to the space shuttles.
numpad0 2 days ago [-]
Earth's gravity is too strong and human energy exploitation isn't large enough to allow for such reusable rockets. The rockets we humans fly look massive and shame to discard, but they're more like liquid fueled balloons than proper spaceships for their scales.
e.g., the Al-Li metal layer of Shuttle ET was 0.1" thick at thinnest points yet those ET were 150ft+ tall. iPhone back covers are thicker than that. Rocketry gears are infuriatingly flimsy relative to their size, but they have to be because that's what it currently takes to fly to space.
If we could build ships on the Moon from Lunar rocks out of a grinder, or if we could build an all-fusion spaceships, we can (relatively)easily have 2m thick radiation shielding, or 8km wide hulls, or anything we want.
But we're not doing it, but are stuck with lox-fuel chemical propulsion, so we can only make them so durable.
> The common soda can, a marvel of mass production, is 94% soda and 6% can by mass. Compare that to the external tank for the Space Shuttle at 96% propellant and thus, 4% structure. The external tank, big enough inside to hold a barn dance, contains cryogenic fluids at 20 degrees above absolute zero (0 Kelvin), pressurized to 60 pounds per square inch, (for a tank this size, such pressure represents a huge amount of stored energy) and can withstand 3gs while pumping out propellant at 1.5 metric tons per second. The level of engineering knowledge behind such a device in our time is every bit as amazing and cutting-edge as the construction of the pyramids was for their time.
MarkusWandel 2 days ago [-]
The (early) Atlas ICBM was even less substantial than a soda can. There used to be one parked on the front lawn of our local science museum. It had to be kept inflated with pressurized air. When the time came to retire it and they let the air out...
In service, of course, the necessary pressure would have been maintained by propellant boil-off.
chipsa 2 days ago [-]
In service, it was pressured with nitrogen, just like it was while not in service. RP-1 is not an especially volatile fuel.
bityard 2 days ago [-]
I don't think NASA is having any problem finding room in their budget for soda bottles.
actionfromafar 2 days ago [-]
This is exactly what the article describes. Only the fuel and oxidant need replacing.
DeathArrow 2 days ago [-]
Yes, I know. I am only asking why we don't do it and why we didn't do it until now.
gus_massa 2 days ago [-]
It's a toy that can go up 50 feet or less. You can't scale it too much. To get to space you need like 100km (x6000) and then a lot of speed sideways to get to orbit.
This model works with a drop of fuel that evaporates and mix with the air. In a real rocket you most inject the fuel and oxygen from the tanks into the very hot and high pressure burning chamber, so you need pumps.
actionfromafar 2 days ago [-]
I think the reason can be the industry incumbents - there just isn't much money to be made with such a simple design, only a nozzle and combined fuel and oxidant tank in PET plastic which can be recycled, no moving parts.
trhway 2 days ago [-]
>Flying model rockets is a relatively safe and inexpensive way for students to learn ...
according to the current laws - it isn't, and may be even more dangerous than walking to the school on your own.
Liftyee 2 days ago [-]
Reading this in the UK, I'm not sure if "walking to school on your own" is supposed to be a safe or unsafe reference point.
I thought that children walking to school is unthinkable in the US because everything is designed for cars and public transit is inadequate/nonexistent. Made worse by endless suburbia stretching for miles. Someone please prove me wrong...
Nextgrid 2 days ago [-]
> children walking to school is unthinkable in the US because everything is designed for cars and public transit is inadequate/nonexistent
The hysteria around it is even worse than any of the actual dangers.
jebarker 2 days ago [-]
I live in the US and my daughter has/will have less than 1 mile to walk to every school she'll ever go to before college. Just an existence proof though!
dhosek 2 days ago [-]
And if she goes to a small residential school, she can keep that up at college. I attended the Claremont colleges where all six campuses (there’s a seventh now) of the schools lay within a one square mile area and if you were silly and only attended classes at your own school, your longest distance between dorm and classroom might be half a mile or so.
Even a sprawling area like Tucson has a public elementary school in each square mile of residential neighborhood. I live in an inner-ring suburb of Chicago (Oak Park) which has 8 elementary schools (plus two middle schools) serving an area of 4.5 square miles. The middle schools require the longest travel distance of about 2.5 miles (taxicab metric). The high school serves a broader region, but that’s fairly typical in the Chicago area but the furthest students travel is about 4 miles (which is a bit less than the commute distance for the most distant students at the high school I attended as a kid one suburb to the south). My own grade school walk was less than half a mile. High school was three miles away for me, and I would get a ride or take the bus in the morning, but often walked home when there was less of a time pressure (sometimes I would walk with friends who lived in the opposite direction from me after school and then back to my own home which made my walk home five miles).
SamBam 2 days ago [-]
Depends very much where you are. In a medium city many/most middle schoolers are walking to school.
boutell 2 days ago [-]
I could say a lot, but I'll just point out that most American school districts provide school bus transportation.
Eduard 2 days ago [-]
> soda bottle
The article never states that the bottle should be made of plastic. Or glass.
fuzzylightbulb 2 days ago [-]
Please go find us a 2 liter soda bottle being sold in the United States in 2025 that is made of glass.
nancyminusone 2 days ago [-]
I don't think a glass bottle would break at this scale, but it would be too heavy to fly
Rendered at 06:09:08 GMT+0000 (Coordinated Universal Time) with Vercel.
There are some fantastic model rocketry competitions for youngsters. There is one running in the UK right now (Google 'UKROC') and equivalent ones in the USA, France and Japan. Plenty of guidance is available and it isn't dangerous if you are sensible. We entered a team into UKROC 2 years running and had an amazing time.
[1]Not for some of the developers, apparently. https://mcvuk.com/development-news/squad-devs-blast-kerbal-s...
Only surpassed by the time I tried to grab a falling soldering iron by the tip this is the source of the worst burn I've ever received. I cannot stress how vicious an ignited alcohol mixture in a container can be.
LOL, I can empathize quite a bit, as someone that has a nasty burn scar on my hand caused by a glob of melted saltpeter and sugar from an accidental ignition of a concoction I was cooking one fourth of July in my youth.
Not sure how we made it through our youth without learning what the inside of a jail cell looked like, but I suppose things were different before 9/11.
That was, indeed, an aspect of the problem I alluded to before. I have made it a few times before, and I was going to use the gas grill outside, but it seemed to be acting up, and I didn't trust it, so I thought it would be "safer" to move inside.
Combine that with me iterating on a few different batches with "improvements", such as lining the bottom of the pan with tinfoil so I could lift it out, and then next making an extra large batch... well multiple lessons were learned that day, including how to deal with insurance companies from some shrewd negotiating from my parents, given most the entire kitchen needed to be replaces and the entire house needed to be scrubbed floor to ceiling.
> Not sure how we made it through our youth without learning what the inside of a jail cell looked like, but I suppose things were different before 9/11.
Ha, probably true, especially since my recipe came from a copy of the anarchist cookbook my older brother happened to have (and I wouldn't be surprised if you happened upon it the same way). It's got a lot of dangerous stuff in it, but honestly, as a tool for sparking curiosity it works pretty well.
Please don't post comments saying that HN is turning into Reddit. It's a semi-noob illusion, as old as the hills.
Rockets are fun. With one remaining eye explain to mummy and daddy how this happened again.
We also did some messing around with coke/butane rockets. These could easily knock teeth out and I made my son wear his full face cycling helmet before handling them.
Model rockets with solid fuel motors obviously require an even greater level of respect.
I've never been hurt by an actual rocket motor, but I thought I lost a finger with the woosh rocket that exploded. . . Luckily just a cut and some burns and not on my face.
Once the motor is ignited, nothing will put it out. Not even immersion in water.
The motors are not made to NASA standard and don't always do the expected thing.
Model rockets with solid fuel motors can go 1000s of feet. If they come down in one piece without a parachute (which does happen). You don't want to be under it.
They can set fire to dry ground. I've seen it happen.
None of the above are an issue if you are being sensible, following guidelines and paying attention.
Also: a bad fuel mixture will clog your nozzle with "solid combustion residue", as we called it with my friend, leading to the infamous rapid unplanned disassembly (the motor will promptly explode), so if you value your life and not being in prison, never ever use metal containers for it. Thin PVC pipe dangerous enough in case of RUD, but is much less likely to kill you.
(Obviously, I too somehow survived childhood unharmed...)
I survived my childhood unscarred, somehow.
I also seem to recall a type of toy vehicle that was propelled by some compressed gas as it slid, suspended along a horizontal wire/string, but I'm drawing a blank regarding the type of propellant right now. It seemed safe enough to use indoors, especially considering the constrained pathway.
I loved water rockets as a kid and I also enjoyed actual model rocketry, except they seemed too hazardous for me to find a launch area where bystanders felt completely safe. Model rocketry is sometimes 90% modeling, and 10% launching them. Estes can make some really precious designs that fly horribly but look great in a Plexiglas cube on your shelf.
I lost most of the ones I built due to poor launch conditions, and while I chose deserted school campuses during vacation or weekends, I didn't make any friends with security patrols there!
The stoichiometric AFR for isopropanol is 10.4:1 according to the sources I found. For 1g of fuel you need 10.4g of air which at SSL[1] corresponds to around 8.5L. One drop of fuel does consume several liters of air to burn. The volume difference is really that huge --- and the higher the AFR, the bigger the difference; gasoline engines are around 14.7:1, and diesels go much higher when idling or under light load.
Relatedly, fuel economy expressed as an area: http://theskepticalzone.com/wp/weirdly-fuel-efficiency-can-b...
[1] https://en.wikipedia.org/wiki/Standard_sea-level_conditions
I've heard of using ordinary rubber party balloons for this.
https://patents.google.com/patent/US3733309A/en
The patent says they are good to 100 psi for regular operation and people pump them up to 2x that when they shoot them up as rockets.
It's fun to make a "chemical pressure bomb" out of that kind of bottle, the classiest way to do that is to use liquid nitrogen, the second classiest way is to put in a pellet of dry ice, if you have no class at all you put in some aluminum foil and either a strong acid ("The Works" drain cleaner) or a strong base (Lye/Sodium Hydroxide) which in either case will evolve hydrogen. [1]
The dry ice version goes off in 30-45 minutes if you put in just the pellet, if you add some hot water it works like a hand grenade and will explode less than a minute, cold water is intermediate. These are dangerous at point blank range
https://www.youtube.com/watch?v=ZygYNfAKjNs
but in my experience harmless 10 feet away. [2] [3] When I was in college my friends and I made a bunch of them and threw them into a vacant lot at night and thought 30 minutes later that we'd failed, but soon we heard a series of loud explosions which caused the neighbors to call the police. The cops drove by and shined a spotlight into the area and we were worried that the last one would go off when he was there but it exploded just after he drove off.
See also https://en.wikipedia.org/wiki/Boiling_liquid_expanding_vapor...
[1] ... and spray dangerous chemicals. Don't do it.
[2] had one blow the bottom out of a small plastic waste basket though and read a report which I couldn't find this time about a high school chemistry teacher who tried this in class and it blew up in a student's hand, blinding him
[3] usually the bottle is torn up such that most of the plastic is in one big piece with jagged edges, today people would worry about microplastic generation
I don't imagine ANY plastic bottle survives too many lift-offs.
In Larry Niven's Known Space books, rockets are launched from earth using some kind of super-compressed material encased in tanks made of some unobtanium, a vastly improved version of those water rockets.
1. It's only a drop out two of alcohol
2. Carbonated drinks are at a very high pressure already.
I could, if I wasn't feeling lazy right now, do the math to compare the two pressures. Its easy stuff - two drops of alcohol combusted + assumption all the combustion products are ideal gases vs Henry's law for CO2. This last one will require looking up how much co2 is dissolved in the product, but thats not too hard.
But, like the other commentator pointed out.... there's only one way to find out.
https://youtu.be/aGBT5pwxThU?si=ay9fm_ZaYImIeNK8 is similar to how it was done.
However, if you have a long cardboard tube:
* place the tube vertically with an ignition source at the bottom (small candle perhaps)
* pour fine powder in the top (may need a step ladder if the tube is tall enough)
* satisfying whoosh
Don't look down the tube as you are doing it and don't do it indoors, obvs!
It seems a waste to use rockets and replace the whole rocket or most parts of it after each flight.
The reason it hasn’t been done in scale before SpaceX is that reusability is a hard problem to solve and it is/was more economical to use expendable launch vehicles than to develop recoverable and refurbishable stages.
You might also like to read about single-stage-to-orbit (SSTO) which is something of a pipe dream. The rocket equation is a bitch.
https://en.wikipedia.org/wiki/Single-stage-to-orbit
The Soviet lookalike did use a single use rocket as its second stage, with the reusable part just being an orbiter.
Sounds suspiciously like one of those projects you propose when you want something finer short term but assume that they never survive to the point where they actually need to deliver?
That said, refurbishing both the SRBs and the SSMEs after each use was labor-intensive and as such expensive.
Refurbishment of the shuttle orbiter took months and tens of thousands of work hours before it could fly again. It was pretty far from what ordinary people understand under "reuse", though not completely outside the meaning of the word.
e.g., the Al-Li metal layer of Shuttle ET was 0.1" thick at thinnest points yet those ET were 150ft+ tall. iPhone back covers are thicker than that. Rocketry gears are infuriatingly flimsy relative to their size, but they have to be because that's what it currently takes to fly to space.
If we could build ships on the Moon from Lunar rocks out of a grinder, or if we could build an all-fusion spaceships, we can (relatively)easily have 2m thick radiation shielding, or 8km wide hulls, or anything we want.
But we're not doing it, but are stuck with lox-fuel chemical propulsion, so we can only make them so durable.
> The common soda can, a marvel of mass production, is 94% soda and 6% can by mass. Compare that to the external tank for the Space Shuttle at 96% propellant and thus, 4% structure. The external tank, big enough inside to hold a barn dance, contains cryogenic fluids at 20 degrees above absolute zero (0 Kelvin), pressurized to 60 pounds per square inch, (for a tank this size, such pressure represents a huge amount of stored energy) and can withstand 3gs while pumping out propellant at 1.5 metric tons per second. The level of engineering knowledge behind such a device in our time is every bit as amazing and cutting-edge as the construction of the pyramids was for their time.
https://ottawacitizen.com/news/local-news/museum-shrugs-as-a...
In service, of course, the necessary pressure would have been maintained by propellant boil-off.
This model works with a drop of fuel that evaporates and mix with the air. In a real rocket you most inject the fuel and oxygen from the tanks into the very hot and high pressure burning chamber, so you need pumps.
according to the current laws - it isn't, and may be even more dangerous than walking to the school on your own.
I thought that children walking to school is unthinkable in the US because everything is designed for cars and public transit is inadequate/nonexistent. Made worse by endless suburbia stretching for miles. Someone please prove me wrong...
The hysteria around it is even worse than any of the actual dangers.
Even a sprawling area like Tucson has a public elementary school in each square mile of residential neighborhood. I live in an inner-ring suburb of Chicago (Oak Park) which has 8 elementary schools (plus two middle schools) serving an area of 4.5 square miles. The middle schools require the longest travel distance of about 2.5 miles (taxicab metric). The high school serves a broader region, but that’s fairly typical in the Chicago area but the furthest students travel is about 4 miles (which is a bit less than the commute distance for the most distant students at the high school I attended as a kid one suburb to the south). My own grade school walk was less than half a mile. High school was three miles away for me, and I would get a ride or take the bus in the morning, but often walked home when there was less of a time pressure (sometimes I would walk with friends who lived in the opposite direction from me after school and then back to my own home which made my walk home five miles).
The article never states that the bottle should be made of plastic. Or glass.