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Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by airstrike on Sunday May 31, 2020 @10:58AM (#23369958)
Truly amazing.

> Also, do I even have to say it? Of course those boosters are gonna land! The propulsive landing test program is isolated from the Falcon Heavy program right now, but the two will merge as the success rate for both programs increases.

Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by rrss on Sunday May 31, 2020 @12:15PM (#23370497)
It seems like it would be really hard to land the boosters with no throttle.
Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by jcims on Sunday May 31, 2020 @12:20PM (#23370541)
There's been a few clues that we won't forever be without throttle. IIRC it looked like he was tinkering with a hybrid propellant system. Could also create a flame diverter if he's stuck with solid propellant.
Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by rrss on Sunday May 31, 2020 @02:09PM (#23371349)
I just watched a couple of his videos, and it sounds like he got pretty close to landing with solid propellant ('echo'), but ultimately decided that it was too finicky and ended that project to move onto a liquid biprop rocket.
Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by epaulson on Sunday May 31, 2020 @03:04PM (#23371767)
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?
Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by pmorici on Sunday May 31, 2020 @05:23PM (#23372857)
One of spaceX’s founding engineers was building liquid fueled hobby rocket engines in his friend’s garage before joining spacex

https://en.m.wikipedia.org/wiki/Tom_Mueller

Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by sandworm101 on Sunday May 31, 2020 @03:40PM (#23372052)
>> 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 more useful. They wouldn't need oxidizer.

Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by namibj on Sunday May 31, 2020 @07:56PM (#23374204)
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 can use for the LOX parts. Just use a simple pressurized tank configuration. Small amounts (sub-kg) of LOX only really restrict you from certain surfaces, such as asphalt, due to the risk of LOX spilling into the ground and turning it explosive.

Otherwise it's arguably safer than everything except maybe 30% peroxide/aluminium in a hybrid rocket.

[0]: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/197600...

Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by jcims on Sunday May 31, 2020 @09:52PM (#23374836)
Nitrous oxide is a viable and easily handled oxidizer for hobby engines.
Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by namibj on Sunday May 31, 2020 @11:32PM (#23375265)
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 by chasd00 on Monday June 01, 2020 @10:10AM (#23378623)
yeah Nitrous Oxide is the oxidizer of choice for hobbyists. It gets used in hybrid rockets and there is/was a couple companies making hybrid rockets available for sale.

Making a tank that's light enough to fly but does not turn into a pipe bomb is _one_ of the hard parts. Also, ignition is and fueling is difficult. iirc Tripoli requires remote fill on hybrid rockets and since a lot of these experimental engines are flown in the desert at FAR (https://friendsofamateurrocketry.org/) temp. becomes an issue.

people are doing it though, i mean it's really impressive to see how far amateurs can push things. We may see the first individual reach the Karman Line this September at BALLS if Covid19 doesn't get in the way. A couple of college teams have done it but not just a random guy. Granted, the guy I'm betting on is very well known in the hobby and not "random" at all.

Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by sandworm101 on Monday June 01, 2020 @12:56AM (#23375569)
>> 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 by namibj on Monday June 01, 2020 @03:24AM (#23376081)
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.

Re:A 1/48 scale model of the SpaceX Falcon Heavy rocket by bigiain on Sunday May 31, 2020 @10:47PM (#23375079)
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 by chasd00 on Monday June 01, 2020 @10:03AM (#23378535)
super late to the thread but i hope you read this. I'm in the high power rocketry scene and liquid engines are out there in the amateur world but uncommon.

You don't see many flights though but there's plenty of test footage. I think one main reason for lack of flights is that Tripoli and NAR ( the two main self-governing bodies for high power rocketry ) currently do not insure bi-propellant rockets at their events. Another reason, is configuring the engine for flight is complicated because of the tanks and pressurization required. It seems like most amateurs run out of effort or money once they have a working injector, combustion chamber, and nozzle. The last mile ( tanks and pressurization ) seem to be out of reach mostly.

btw, if anyone has an engine they want to fly I will happily build you an airframe! :)