Re: 72MJ escape velocity, storage for 5 hours on mains
Justin, Sat Feb 14 2015, 04:43AM

Oh about a warehouse full of super capacitors.

Re: 72MJ escape velocity, storage for 5 hours on mains
Sulaiman, Sat Feb 14 2015, 05:15AM

you could electrolyse water,
less than 1 litre of water electrolysed to hydrogen and oxygen,
remote operation may be a good idea

P.S. a compressed hydrogen & oxygen stoichiometric mixture will self-detonate.

OR

14,400 photo-flash capacitors from disposable cameras?
(e.g. 100 uF @ 316V each)

Re: 72MJ escape velocity, storage for 5 hours on mains
klugesmith, Sat Feb 14 2015, 05:23AM

It would be quite ordinary technology if you put the 1 kg payload on a 735-metric-ton space elevator platform.

Raising the platform 10 meters in 1 hour would store 72 megajoules at a rate of 20 kilowatts.
You could do it with a 27 horsepower motor, plus allowance for losses in gear train or hydraulic pump.

The Subject line in OP does not match the message body,
so it's not really clear what Andy wants to do.

Re: 72MJ escape velocity, storage for 5 hours on mains
Andy, Sat Feb 14 2015, 05:27AM

Water converted to gas, would only need to increase to 7.5 atm, instantly to supply 12km/sec velocity to reach escape velocity .

I was wondering of ways to convert 72MJ into KE to fire something into space.

It doesnt have to invole caps or inductors.

Just brain storming.

Sulaiman
With h and o to stop detention, would have a steel struct inside the chamberto break the shockwave and lower the damaging energy wave.

Kuldsmith
The life long goal is a space eelevator, but you have to start at the bottom :)

Halfdead
Just basing it on money isnt a problem at this stage, but year that will put a halt to it.

Re: 72MJ escape velocity, storage for 5 hours on mains
Patrick, Sat Feb 14 2015, 10:12AM

Im not sure if he means the goal is to push 1kg up to orbit, but "escape velocity" in the title suggests so.
theres this that basically is a solution to the energy supply-coupling-generation problem :

but its not electromagnetic...

it explosively (like RDX) fires a slug down a 90 degree barrel to compress H and O to detonation as previously said (by sulaiman), the the barrel fires at some angle upward.

Re: 72MJ escape velocity, storage for 5 hours on mains
klugesmith, Sat Feb 14 2015, 05:13PM

Good link, Patrick, but read it more closely. That Livermore gun, and other 2-stage hypervelocity guns, use pure hydrogen between the piston and the projectile. The high-pressure, high-temperature transfer fluid needs to be (relatively) low density, thus have a high speed of sound.

The Internet shows that the SHARP gun demonstrated velocities of 3 km/s. I saw smaller ones at Caltech Geological & Planetary Science lab.
A contemporary NASA design gets 1 inch pellets up to 7.5 km/s.

Gerry Bull's vertical HARP gun reached about 2 km/s and launched things into space (i.e. much higher than 100 km).

Conventional Explosively Formed Penetrators can hit around 2 km/s without any gun baggage. I wonder how much HE it takes to release 72 MJ?

Andy, why did you choose a 10 meter acceleration length? Your 1 kg projectile needs to withstand 735 metric tons of force, for acceleration of 735,000 gees. What will it be made of, and what good will it do?

Re: 72MJ escape velocity, storage for 5 hours on mains
Patrick, Sat Feb 14 2015, 08:07PM

thats a good question, thats basically a reasonable volume of propellent or HE for an artillery shell.

YEP, wiki says...

Energy content
See also: TNT equivalent
Cross-sectional view of Oerlikon 20 mm cannon shells (dating from circa 1945) showing color codes for TNT and pentolite fillings

Pentolite is a high explosive used for military and civilian purposes e.g. warheads and booster charges. TNT is reported to contain 2.8 mega joules per kilogram explosive energy.[16] The actual heat of combustion is 14.5 megajoules per kilogram, which requires that some of the carbon in TNT react with atmospheric oxygen, which does not occur in the initial event.[16] The explosive energy utilized by NIST is 4184 J/g (4.184 MJ/kg).[17] The energy density of TNT is used as a reference-point for many other types of explosives, including nuclear weapons, the energy content of which is measured in kilotons (~4.184 terajoules) or megatons (~4.184 peta joules) of TNT equivalent.

For comparison, gunpowder contains 3 megajoules per kilogram, dynamite contains 7.5 megajoules per kilogram, and gasoline contains 47.2 megajoules per kilogram (though gasoline requires an oxidant, so an optimized gasoline and O2 mixture contains 10.4 megajoules per kilogram).

Chemical energy is just all-around easier to assemble and keep than electrical, we keep having this problem as humans. (drones in my case) nothing really allows rapid reliable conversion. Even fuel cells to capacitors would be a difficult scheme to muddle with.

Re: 72MJ escape velocity, storage for 5 hours on mains
BigBad, Sun Feb 15 2015, 10:22PM

Tesla model S seems pretty good at storing energy though.

Dunno what the momentary power of a model S battery would be.

Re: 72MJ escape velocity, storage for 5 hours on mains
klugesmith, Mon Feb 16 2015, 04:48AM

The dual-engine Model S P85D claims 691 horsepower (515 kW). Much less than twice the single-engine rating, so maybe we are seeing a battery power limit. The car is faster than a Dodge Viper SRT10, but too heavy to beat a Lamborghini LP570-4 Super Trofeo Stradale.
Compared to the 306 MJ battery capacity, that power level is what RC modelers would call a 6C discharge rate.

Andy needs his 72 MJ in less than 2 milliseconds, in fact a "2 million C" discharge rate.
Too fast for chemical batteries or ultracapacitors, but ordinary for HV pulse capacitors as at NIF.


from

Re: 72MJ escape velocity, storage for 5 hours on mains
Andy, Mon Feb 16 2015, 05:14AM

Kludgesmith
The ten meter was more vertical size practically, one km might be doable from a hill thought, it needs electrical components and not sure what gees they can handle etcs.

Would say 20,000 g, plus a E motor from a model rocket.

Re: 72MJ escape velocity, storage for 5 hours on mains
Dédé!, Tue Feb 17 2015, 01:36PM

The new EMALS (Electromagnetic Aircraft Launch System) for the new Gerald R. Ford Class super Carriers stores the energy needed kinetically on 4 disk alternators. Each rotor can store over 100MJ of energy and can be recharged in 45 seconds.

Re: 72MJ escape velocity, storage for 5 hours on mains
BigBad, Wed Feb 18 2015, 02:55AM

This is a spam launcher.

Spam launchers bore me.

Launch loops are the only way to go.

Re: 72MJ escape velocity, storage for 5 hours on mains
2Spoons, Wed Feb 18 2015, 09:43PM

I just want to point out that your 72MJ assumes 100% energy transfer from storage medium into kinetic energy in the projectile. Good luck with that.

Re: 72MJ escape velocity, storage for 5 hours on mains
Andy, Thu Feb 19 2015, 02:13AM

Actualy 88% eff, you shoul check the facts first, which would normaly involve asking the OP about details.

Re: 72MJ escape velocity, storage for 5 hours on mains
2Spoons, Thu Feb 19 2015, 02:34AM

Your first post "...store 72MJ..." and " ... 1kg payload"
Your second post " ...12km/s"
1/2MV^2 gives 72MJ in your projectile.
That's 100% transfer.
Facts checked.

I think 88% is pretty optimistic too. Where did you get that figure from?

Re: 72MJ escape velocity, storage for 5 hours on mains
Dédé!, Thu Feb 19 2015, 07:50PM


escape velocity is 11.2km/s. .5*1*11200^2/(72*10^6)*100=~87%


That idea of a launch loop is pretty interesting. I weigh about 50kg, so with a launch loop it would cost about $150 to reach outer space. That's a hell of a lot less than, let's say, $200000!

Re: 72MJ escape velocity, storage for 5 hours on mains
klugesmith, Thu Feb 19 2015, 10:23PM

Trouble with launch loops is, the cost is just as hypothetical as the technology. STS (Space Shuttle) was originally promoted as getting marginal cost down to $20M (1972) per flight. Total program cost ended up at more than $1.5B (2010) per flight. $200M per astronaut ride. So Soyuz round-trip ticket is a good deal at $50M. Safer, too. (Of course STS did most of the heavy lifting for ISS, and lots of other stuff teh Soyuz couldn't dream of.)

Some net energy values and applications:
1 MJ/kg -- lift to 100 km (Suborbital space tourism).
1.8 MJ/kg -- lift to 179 km (HARP cannon altitude record for 84 kg projectile, in 1966, using a few $1K of consumables).
30 MJ/kg -- LEO at 7.8 km/s, not counting the lift. The target market for launch loops.
63 MJ/kg -- escape from Earth gravity, 11.2 km/s at sea level.

Re: 72MJ escape velocity, storage for 5 hours on mains
Patrick, Fri Feb 20 2015, 08:49PM

The $20M dollar theoretical operation was so bogus as to be outrageous. ( I wonder if you could even get Ammonium perchlorate for those boosters at 20M$)

In any case, the STS for regular access to space was a disaster, thats why we Americans have gone back to apollo/soyuz method. Any of the heavy lift - high orbit launches like Hubble (which were few and far between) could have been launched with custom rockets cheaper than the excess capability of the Shuttles unused over 20+ years of launches.

The shuttles cost a lot for each launch, and there was alot of capability that couldnt be used to its full potential. In space endeavors, efficiency is important due to high cost and danger.

Modularity is important but its got to be done right.

Re: 72MJ escape velocity, storage for 5 hours on mains
BigBad, Sat Feb 21 2015, 12:59PM

They actually more or less succeeded, for flights above the minimum number, the cost did come down to about that, inflation adjusted. Those extra flights were much cheaper.

Of course they didn't launch 50 flights a year, so it was a bit of a pyrrhic victory.
That's the average. There#s a difference between marginal and average.
I think the payload wouldn't be just you, so you'd need about a tonne of life support/reentry as well so it would be more like $3000 and even that is very optimistic.