Sillychris

Carbon nanotubes are just barely strong enough, but what about spider silk? I'd be down with camping out in an elevator car for 2 weeks.

What about a zero stage to orbit space elevator?

That's a fine looking rocket. Around the age of 21 I gave up on rocket recovery and just started building them to explode.

The moon is a gold mine for high energy particle physics. Cosmic rays have been known to get as high as 10^20 eV which is 20-40 million times more powerful than the LHC. We can't observe them directly on Earth, but we do have many arrays set up to measure the shower of secondary particles. Still, it would be nice to get some more direct measurements. Anyway, landing a detector array on the moon will likely spring particle physics ahead faster than anything we currently have. Also, it's cheaper than building the LHC.

mmk, that poked me in the right direction. I think I have my final answer ready: Boiling point is related to vapor pressure which is related to atmospheric pressure. Since the vapor pressure can never get below zero, the boiling point can never get below the vacuum boiling point.

This is a really good idea. My suggestion would be to store the rotor energy on a flywheel which can later be dumped into spinning the rotors on final landing. Only downside is complexity.

That's good news. Can you supply me with a simple argument for why "negative pressure" should not lower the boiling point of a liquid past the vacuum boiling point? I'm doing my senior research project presentation on friday and I don't want to stumble on this if someone asks me.

Yeah I get that by definition of pressure it's not formally pressure, but for mathy purposes it behaves as though it's negative pressure. Here are some papers exploiting the concept: Pless, I. A. & Plano, R. J. (1956). Negative pressure isopentane bubble chamber. Rev. Sci. Intsr, 27(11), 935-937 Hahn, B. (1961). The fracture of liquids under stree due to ionizing particles. Il Nuovo Cimento, 22(3)

So, if you spin the hell out of a liquid you can generate strong negative pressures in the center. It's fairly common knowledge that boiling points of liquids reduce with pressure. What I am wondering is the behaviour of this trend below 0 pressure. Does the boiling point reach a minimum, or does it continue to decrease with decreasing pressure?

Any momentum gain from the xenon striking the solar sail would be eliminated by the xenon exiting the engine port. You could turn the ion engine around and use it to propel you in addition to the solar sail, though.

Velocity, these are some really good suggestions. I particularly like your idea of a mechanical switch that works when the rocket leaves the barrel. I don't know why I was getting tunnel vision over the pressure activated switch. I could do a spring loaded rocker style switch at the rear. As soon as the rocket leaves the barrel, the switch would be free to expand and therefore trigger. I like your photodiode idea, too. Only problem with that is it might be tricky to arm before inserting. I could also go super ultra simple and have a fishing wire pull out an insulator when the rocket is x feet away... maybe that's what I'll do for proof of concept... This community never fails to impress me when I ask for help brainstorming.

I am both daring and stupid. I really want one of those things now.

The swingset is kind of anchored to the earth... And the swinger is kind of anchored to the swingset...

I should also point out that initial testing of dry dowel rockets is extremely promising. They were puncturing 4 layers of corrugated cardboard and shown to be stable in parabolic flight. When an engine is added, that will obviously affect the center of mass and it may affect my fin placement... but probably not. A rocket engine is not sufficienty different in density from wood to affect the design very much. You're obviously wondering how I place fins? Super simple. Rubber arrow fins glued to a portion of the dowel which has been sanded down. When the rocket escapes the barrel, the fins pop out. This also has the added benefit of moving the center of mass forward a bit.

Your advice is wise, and I already have those details covered. I'm fairly experienced with rocketry and deploying it in non-conventional ways. The only piece missing from my design is a method to close an electrical switch when pulling the trigger. I don't want anything connected to the paintball gun. I want an independent cartridge that can be primed, dropped down the barrel, and then fired at your leisure. What I need is a method for the co2 pressure to close a switch. I was wondering if anything out there exists already so I wouldn't have to fabricate it from scratch. If you guys are curious of my application plans, I want to use this to deploy ropes to out of reach targets. And before everyone tells me rocket exhaust melts rope, don't worry. The lead line would be sacrificial and used strictly to hoist the actual rope.

Of course it's not a good idea! That's why I'm doing it. The electrical igniters take a a tiny bit of time (maybe half a second) to ignite the engine. That way the rocket will be clear of the barrel when it ignites. Ideally, I'd like the ignition battery to be at the base of the rocket. That way it rides with the rocket until ignition occurs.

I have some 68 caliber dowel which fits a paintball gun very well. The plan is to fit some of this dowel as a rocket and fire it from the paintball gun... because Canada's cold. The thing I haven't come up with is how to ignite the engine upon firing. I'd like to utilize the firing pressure to close an electric switch. Ideas?

The probe would have to leave a transmitter at the surface and unspool a wire as it descended.

What if we made the bombs a little smaller... and out of D-T pellets?

In a nutshell, you're forgetting about the initial momentum of the propellant. A rocket whipping forward at 1000 m/s is full of propellant whipping forward at 1000 m/s. It's here that you get the extra momentum to reverse.

What if the problem is the other guy? Like what if the other guy is sitting on my face and won't get off?

Albert Einstein. Cosmological constant, anyone?

4:20 pm Seattle time, April 20th

What kind of superpowers would a meat based shark possess?

I think the real concern is the feasibility of waterskiing on these lakes.