Wow, he is even is trying to design landable boosters like in the real thing! WTF!
A 1/48 scale model of the SpaceX Falcon Heavy rocket
81–90 of 96 posts
Re: A 1/48 scale model of the SpaceX Falcon Heavy rocket
#82Earlier quoted context omitted.
Majority of engineers with a degree are useless right after graduation. Its a ton of random math that (most) of which you don't use again since you use modeling software. Source: Did Aero Someone doing this as a Amateur can damn well pick up whatever they need to.
> Its a ton of random math that (most) of which you don't use again since you use modeling software. You absolutely need that math because you need to know when the modeling software is giving the wrong answer. You’re supposed to do quick and dirty calc by hand (ok fine I use mathematica) in a simplified system, then you refine with numerical software and compare the two. It’s shockingly easy to get the wrong answer…
Not a mech eng but I've taken several eng classes and do a lot of DIY stuff. I've been designing a swing set/exercise rig for myself in Inventor and using FEA to sanity check my beam sizes for the given loads, just cause why not. Since I already had it parameterized, I wanted to see what load it would take with legs made out of 1.25x5.5 boards, just cause. The sim showed it would take several hundred pounds with almost no lateral deflection. Hmmm.
Anyone who's worked with decking boards knows they are pretty wobbly by themselves. I'm staring at the results, intuitively knowing they're dead wrong. So I model a plain column of one of these boards 16' long and 2000lbs, straight down. Zero side deflection.
Ah, I realized, it doesn't model buckling.
Map != territory.
It's always important to have multiple perspective of inference on a problem.
Re: A 1/48 scale model of the SpaceX Falcon Heavy rocket
#83Earlier quoted context omitted.
>> understood to be fairly safe, is there something equivalent for liquid rockets? No. Lighter fluid can be a reasonable fuel, but the oxidizer is the issue. Either you use liquid oxygen (very cold, explosive, generally dangerous) or something nasty like nitric acid or MMH that will eat your flesh for lunch. Given the altitudes involved, I would suggest that small jet/turbine engines meant for model aircraft would be…
LOX isn't explosive. And LN2 is quite popular/widely used, and of arguably little danger. What I'm not sure about is whether it's safe to get (small amounts of) LOX spilled on your hand (LN2 is safe, my hands still work and the teacher didn't complain in like 2012 (between 2008 and 2015, but I can't guarantee anything tighter)). Yes, LOX is cold. So what? Just look at, say, [0] for information on what materials you c…
Nitrous oxide is a viable and easily handled oxidizer for hobby engines.
Re: A 1/48 scale model of the SpaceX Falcon Heavy rocket
#84Earlier quoted context omitted.
Are liquid engines still in the realm of hobbyists? The estes engines he's using are pretty widely used and understood to be fairly safe, is there something equivalent for liquid rockets?
>> understood to be fairly safe, is there something equivalent for liquid rockets? No. Lighter fluid can be a reasonable fuel, but the oxidizer is the issue. Either you use liquid oxygen (very cold, explosive, generally dangerous) or something nasty like nitric acid or MMH that will eat your flesh for lunch. Given the altitudes involved, I would suggest that small jet/turbine engines meant for model aircraft would be…
About 10-15 years back a friend and his other high powered model rocketry buddies were flying rockets that used nitrous oxide as an oxidiser (and using polypropylene or cardboard as the fuel!)
They were just squirting compressed liquefied N2O in to their motors, but were talking about the possibility of throttling by adding a controllable valve.
Re: A 1/48 scale model of the SpaceX Falcon Heavy rocket
#85Earlier quoted context omitted.
He’s been pretty careful to not do anything illegal (he’s talked about this in a few live-streams), for example not open-sourcing any of his control software and using just local IMU data for in-flight control.
Is this a typically US thing or does this kind of thing risk getting you into trouble elsewhere too? I mean the first thing you'd want to try once you have a "platform" is things like GPS guidance, adding wings & making cruising rockets, trying terrain guidance etc. Isn't the cat out of the bag with this kind of tech already, much like strong crypto was once a non-exportaple technology in the US, but now it isn't? Wh…
Didn't work out great for this guy from New Zealand: http://www.aardvark.co.nz/pjet/cruise.shtml
(Not "go to jail" bad, but "The New Zealand government has moved aggressively to shut down this project -- and by using quite unscrupulous methods which appear to be in breach of the law." type of bad...)
Re: A 1/48 scale model of the SpaceX Falcon Heavy rocket
#86Earlier quoted context omitted.
In a just world, he would have 1/48th of Elon’s fame/fortune too.
Unfortunately, sending 1/48 of an astronaut into orbit is not as valuable.
At around $3k per kilo to orbit, I'd bet he'd be _very_ happy with the $6k or so 1/48th of a ~100kg astronaut+spacesuit would mean per launch!
He ain't getting anywhere near orbit using Estes motors though... Not even 1/48th of the way to orbit I'd guess...
(Hmmm, spaceflight.com's pricing page says they'll send a 3U 5kg cubesat payload to LEO for $295,000... That's I guess pretty close to "1/24th of an astronaut to orbit"? Minus the ~10,000% surcharge for "manrated" though, I'm guessing.)
Re: A 1/48 scale model of the SpaceX Falcon Heavy rocket
#87Earlier quoted context omitted.
LOX isn't explosive. And LN2 is quite popular/widely used, and of arguably little danger. What I'm not sure about is whether it's safe to get (small amounts of) LOX spilled on your hand (LN2 is safe, my hands still work and the teacher didn't complain in like 2012 (between 2008 and 2015, but I can't guarantee anything tighter)). Yes, LOX is cold. So what? Just look at, say, [0] for information on what materials you c…
Nitrous oxide is a viable and easily handled oxidizer for hobby engines.
The common steel canisters seem to weight 30g, full (including carton packaging), with 8g payload.
The vacuum ISP of a N2O monopropellant is given on Wikipedia as up to 180s, but the cartridge weight drops that to 48s. One could be chilled with dry ice to a vapor pressure of 2bar, but it's still far from easy to handle when weight is a substantial issue and you want to dynamically control flow, I'd figure.
Re: A 1/48 scale model of the SpaceX Falcon Heavy rocket
#88Qu8k (https://ddeville.com/derek/Qu8k.html) is some impressive amateur rocketry from 2011.
Re: A 1/48 scale model of the SpaceX Falcon Heavy rocket
#89Earlier quoted context omitted.
>> understood to be fairly safe, is there something equivalent for liquid rockets? No. Lighter fluid can be a reasonable fuel, but the oxidizer is the issue. Either you use liquid oxygen (very cold, explosive, generally dangerous) or something nasty like nitric acid or MMH that will eat your flesh for lunch. Given the altitudes involved, I would suggest that small jet/turbine engines meant for model aircraft would be…
LOX isn't explosive. And LN2 is quite popular/widely used, and of arguably little danger. What I'm not sure about is whether it's safe to get (small amounts of) LOX spilled on your hand (LN2 is safe, my hands still work and the teacher didn't complain in like 2012 (between 2008 and 2015, but I can't guarantee anything tighter)). Yes, LOX is cold. So what? Just look at, say, [0] for information on what materials you c…
>> LOX isn't explosive.
Ya, well see what happens when you load it into a model rocket beside some kerosene. Then attach some electronics. Whether oxygen can technically burn or not is moot. There will be fire.
Re: A 1/48 scale model of the SpaceX Falcon Heavy rocket
#90Earlier quoted context omitted.
LOX isn't explosive. And LN2 is quite popular/widely used, and of arguably little danger. What I'm not sure about is whether it's safe to get (small amounts of) LOX spilled on your hand (LN2 is safe, my hands still work and the teacher didn't complain in like 2012 (between 2008 and 2015, but I can't guarantee anything tighter)). Yes, LOX is cold. So what? Just look at, say, [0] for information on what materials you c…
>> LOX isn't explosive. Ya, well see what happens when you load it into a model rocket beside some kerosene. Then attach some electronics. Whether oxygen can technically burn or not is moot. There will be fire.
Except that a hybrid rocket engine burning something like e.g. PMMA is also easy to throttle, and doesn't blow up like a mixed mist cloud of keosene/LOX.
Also, fire != explosion. The former is only hot, the latter has a tendency to throw shrapnel.