[HN Gopher] How to not build a two stage model rocket
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How to not build a two stage model rocket
Author : KMJ-007
Score : 117 points
Date : 2025-04-13 04:00 UTC (19 hours ago)
(HTM) web link (knowone08.gitbook.io)
(TXT) w3m dump (knowone08.gitbook.io)
| gostsamo wrote:
| I hoped for some kind of postmortem to understand what went wrong
| and what was learned from the failure.
| lmm wrote:
| The second and especially third pages have some of that.
| gostsamo wrote:
| oh, it looked like link to another post
| user_7832 wrote:
| Here's the direct link to the 3rd page if anyone wants :
|
| https://knowone08.gitbook.io/vgecrocketry/subsystem-survival...
|
| I'd recommend reading the earlier 2 pages for context though.
| mykowebhn wrote:
| I don't get why it was bad to name the rocket Vanessa.
| tamad wrote:
| I was wondering the same. I'm not in this industry, but perhaps
| rockets are not typically given human names, so it's a joke?
| Also, it's spelled Venessa rather than Vanessa, so maybe it's
| humorous because of the misspelling.
| thedufer wrote:
| I think the author was pointing at the fact that "Venessa"
| looks like a typo.
| quibono wrote:
| I didn't know about OpenRocket! Great that there are open source
| solutions for this stuff
| hermitcrab wrote:
| OpenRocket is great. But it obviously isn't doing a full CFD
| simulation, so take the apogee (max altitude) estimates with a
| pinch of salt. It estimated our apogee about 15% higher than we
| actually got.
| michaelcampbell wrote:
| When I was a kid I was into Estes model rockets and it always
| amazed me the preferred/documented way of glomming the multiple
| stages of engines together was a single strip of scotch tape.
| baking wrote:
| My memory is that two-stage rockets had a few more points of
| failure but were harder to retrieve, so not really worth the
| effort. The Estes engines solved most of the technical
| challenges, but I lived in an area with lots of trees and no
| huge expanses of open space.
| sumanthvepa wrote:
| From the blog post: "Pro tip: just take your time and design the
| O-ring system properly. Trust us -- you don't want to gamble with
| hot gases and bad seals."
|
| I think NASA may have learnt that lesson in '86.
| hermitcrab wrote:
| > Turns out, PVC was never the move. It's lightweight, yes, but
| also has the structural integrity of a soggy biscuit under
| pressure.
|
| I believe that PVC is not considered safe for model rockets, as
| it turns into shrapnel if it ruptures. Happy to be corrected, if
| that isn't right.
| Taniwha wrote:
| so does the steel they replaced it with ductile metals like
| aluminium are required by HPR rocket safety codes
| hermitcrab wrote:
| Yes, you want something that tears (like aluminium) rather
| than fragments.
| hermitcrab wrote:
| Note that making your own fuel is:
|
| a) Very dangerous, if you don't know what you are doing.
|
| b) Illegal without a licence in some countries (such as the UK).
| diggan wrote:
| What's the fun of buying ready made parts and just assembling
| it? At least the authors probably learned something new in the
| process.
|
| Besides, the fuel "hacking" they seem to be doing seems
| relatively simple, isn't it what is commonly called "Rocket
| Candy" or something like that? In that case, it's a fairly
| common propellant made by amateur's. We're on _Hacker_ News
| after all, as long as they 're not hurting other people, if
| it's illegal or not should matter less.
| gosub100 wrote:
| What's the fun of doing a bunch of work but not getting a
| successful launch (best case) or blowing your hand off or
| burning the house down (worst case)?
| mystified5016 wrote:
| For the same reason that it's generally illegal to make your
| own fireworks: you have a pretty good chance of killing
| yourself or more importantly kill someone nearby.
|
| The risk of letting random people blow themselves up is one
| thing, but having innocent bystanders get killed or maimed is
| totally different.
|
| Most fully developed adults agree that putting yourself at
| risk in the pursuit of your hobbies is fine, with limits.
| Putting _others_ in danger who are unaware of the risk to
| life and limb is _not_ acceptable. You, a private citizen,
| simply do not have the right to produce bombs as a hobby
| because of the undue risk to everyone around you.
| diggan wrote:
| So, basically a longer and reworded version of "as long as
| they're not hurting other people"?
| noqc wrote:
| As long as they _can prove that they are not risking_
| hurting other people. Suppose that I fire a gun in a
| randomly chosen direction and don 't hurt anyone, should
| I be allowed to repeat the process?
| hermitcrab wrote:
| It is great that people are going out doing stuff, having fun and
| learning. But this project seems like a disaster in the making.
|
| -Making your own fuel.
|
| -Using inappropriate materials (e.g. PVC)
|
| -Poor storage of motors.
|
| -People are standing quite close to the rocket when it launches.
|
| -There seem to be buildings quite close to the launch in one of
| the videos.
|
| -Night launches. How are you going to get out of the way, if you
| can't see the rocket?
|
| 2 stage rockets are particularly dangerous, because as the second
| stage can launch horizontally or downward if the first stage
| tilts (as shown in one of the videos).
|
| I think they are being irresponsible with the safety of
| themselves and anyone nearby. I would strongly recommend they
| learn a bit of safe practices and make a single stage rocket that
| works reliably, before even attempting 2 stage.
| sumanthvepa wrote:
| As opposed to the way SpaceX does it?
|
| Let huge rockets blow up over active airspace?
|
| This looks like a bunch of college kids building small little
| rockets. I'm probably taking a much bigger risk walking on the
| street, where I live in India.
|
| It's a little risky. But do the stuff far enough away from
| people and they'll be fine.
| pfdietz wrote:
| SpaceX's rockets launch with downrange areas carefully
| considered; launches have been aborted because of boats
| wandering into these areas.
| cratermoon wrote:
| Twice now Starship has exploded over the Gulf of Mexico and
| caused massive and dangerous disruptions to commercial
| passenger air travel. Flights were delayed and some
| diverted because of fuel limitations.
| hermitcrab wrote:
| I get the impression that SpaceX's attitude is that it is
| cheaper to learn by blowing stuff up, than it is to
| meticulously plan everything (as NASA is famous for).
| However, SpaceX don't have to pay for the externalities
| (such as disrupted air travel). I don't see SpaceX
| attitude changing now that Musk seems to be running[1] a
| sizeable chunk of the US government.
|
| [1] into the ground.
| JumpCrisscross wrote:
| > _Starship has exploded over the Gulf of Mexico and
| caused massive and dangerous disruptions to commercial
| passenger air travel_
|
| Disruptive, yes. Dangerous, no. (They're disruptive
| because the planes avoid the debris field. Launches are
| also scheduled such that no plane should be pinned down
| by debris.)
|
| I'd also note that, apart from two deaths in 2014,
| SpaceX's track record with human lives is pristine.
| hermitcrab wrote:
| >It's a little risky.
|
| Everything in life involves risks. And there are cultural
| differences in attitude to risk. But some of these risks are
| quite unnecessary.
|
| Also, I would consider making your own fuel (without
| sufficient expertise), as more than 'a little risky'.
| Especially if they move on to bigger rockets.
| foobarian wrote:
| > making your own fuel (without sufficient expertise), as
| more than 'a little risky'
|
| It seems like just the classic smoke bomb recipe with KNO3
| and sugar. I would be comfortable preparing this even
| indoors, let alone outside.
| SoftTalker wrote:
| My friends and I made far riskier stuff as teens based on
| our high school chemistry knowledge. It was fun but in
| retrospect not particularly safe.
| 0_____0 wrote:
| I get the sense that the team represented here are going it
| alone e.g. there aren't amateur rocketry organizations around
| that they can work with and gain knowledge and working
| practices from.
|
| Maybe someone on here who is in amateur rocketry can reach out
| and forge some connections between their group and more
| established ones? That's the true beauty of the Internet,
| right?
| cge wrote:
| Yes, for context: this appears to be a group at Vishwakarma
| Government Engineering College in Ahmedabad, India. A quick
| search suggest that there might not really be any regulation
| or much of a community for model rocketry in India in
| general.
| ryzvonusef wrote:
| reminds me of the BPS Space youtube channel, he makes rockets
| too:
|
| https://www.youtube.com/@BPSspace
|
| https://bps.space/pages/about
| gosub100 wrote:
| That guy is amazing in not just his accomplishments but his
| determination and resolve over the year (And I'm surprised the
| authorities haven't shut him down over ITAR type regulations).
| mavamaarten wrote:
| Except that he launches them from a proper launching site
| whilst hiding in a bunker/shelter, rather than standing around
| the thing in flip flops.
| karmicthreat wrote:
| https://www.youtube.com/bpsspace Does some pretty informative
| work with amateur rockets.
| magicalhippo wrote:
| If you want to build a two-stage _water_ rocket, Air Command
| Rockets has detailed build series over on YouTube[1], from simple
| soda bottle setups to a custom rocket that they got[2] to over
| 1600m (5000 ft).
|
| That's air and water propelling a rocket a mile up!
|
| [1]: https://www.youtube.com/@AirCommandRockets
|
| [2]: https://www.youtube.com/watch?v=GCaiK3Zqs4M
| clbrmbr wrote:
| I had a lot of fun building rockets in a similar way as a kid. We
| also tried PVC but discovered that it fails in a dangerous way,
| after which we used only copper. I had fun programming a PIC16 in
| assembler to read from the accelerometer and fire the home made
| igniters of black powder, nitrocellulose laquer, and nichrome
| wire.
| polishdude20 wrote:
| A few years back I built a dual stage model rocket using regular
| rocket motors:
|
| https://youtu.be/zPtFv-cwcfQ?si=mjy6hg9YPARpTkRV
| sandworm101 wrote:
| I would be warry about doing this, no matter what country you are
| in. Using commercial motors is one thing, baking your own very
| much another. There is a very fine line between cooking up some
| rocket propellant and operating a bomb factory. Imagine getting
| discovered with a few pounds of homemade explosives and box of
| electronics. I wouldn't want to have that conversation with the
| police.
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(page generated 2025-04-13 23:01 UTC)