A little help if you can.

Rubecula

I was asked by my mates daughter, (nice little thing, very polite... and too clever for a ten year old) a question that I was stuck on answering.

We were talking science to help her with her homework. I may have gone a little too advanced in retrospect, as I was talking about rockets and steam and stuff any way it went something like this:

"So a rocket moves by throwing hot gas out of the back at a high speed"

"And steam does that too doesn't it?"

"Yes thats right that is how steam engines work"

"Can you have a steam powered rocket?"

"Well not with a steam engine, much too heavy"

"Use a big bomb like an atom bomg, that will make the steam very hot."

"Ummmmm."

At this point I changed the subject. Reason being, I was not sure.

Could a rocket be built with an atomic engine that superheated water to make a steam rocket? It would make refuelling easy amongst the icey stuff out there... well maybe I am not sure, but she has me thinking.

Any of you got any ideas about this? Would it work? Would it be cheaper?

Bruthal

The rocket works by the expulsion of the hot rapidly expanding gasses out the back, there is nothing in space for it to push againts but it propels the rocket forward as it pushes against the rocket as it is expelled out the back.

Steam ejecting from the back of any object in space would give it propulsion in the opposite direction, but it probably would not have the same volatility as something like oxygen-hydrogen burning. Interesting though.

Rubecula

Yes it really has me thinking about it. Obviously it woould need a lot of technology, such as a strong pressure vessel to hold in the steam, and putting an atomic power module in space is frowned on a bit. But it seems more and more feasible the more I think of it. At the moment though it is probably easier to use conventional rockets. But who knows what will happen in the future.

Kids, lol they come up with some amazing things don't they?

Bruthal

Yes there probably is potential for different propulsion technology if a vessel is built in space, as getting it up there from the ground needs a large amount of propulsion power in a short time. Once in space it could be accellerated up to speed and it will continue on then.

Kids have some ideas at times alright.

QuimWedge

You are right it all come down to weight. Currently we use chemical rockets to get us into space aka solid rocket boosters. Their power to weight ratio is massive but they are not efficient.

Unless you are will to disregard current safety systems your nuclear reactor is going to be heavier than a conventional rocket which will give you some problems.

Have you thought about ion propulsion? Might be a little sci-fi but it has less moving parts, is much more efficient and will not run out of fuel like a conventional rocket. It works on the same principle; high pressure, high temperature gas is expanded through a nozzle.

Also there was plans in the US to create a rocket which would be propelled by nuclear explosions. Maybe you're mates daughter knows something you don't!
http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

slade_x

Rubecula wrote: »

"So a rocket moves by throwing hot gas out of the back at a high speed"

"And steam does that too doesn't it?"

"Yes thats right that is how steam engines work"

That isnt how a steam engine works, fuel is burned to create the steam to create pressure to drive a mechanical piston. the exhaust from a steam engine isnt a propellant in the conventional engine. thats why the exhaust on a steam train engine is on the top and not on the back

Rubecula wrote: »

"Use a big bomb like an atom bomg, that will make the steam very hot."

"Ummmmm."

At this point I changed the subject. Reason being, I was not sure.

Could a rocket be built with an atomic engine that superheated water to make a steam rocket? It would make refuelling easy amongst the icey stuff out there... well maybe I am not sure, but she has me thinking.

Any of you got any ideas about this? Would it work? Would it be cheaper?

It would not be cheaper from the ground, our current propellants given our level of techonology are currently the cheapest. Steam is not efficient for such a purpose. for starters along with having to have huge amounts of water you would also need fuel to generate the heat to convert it to steam. so instantly your rocket is way too heavy to reach escape velocity with steam as a propellant.

However there are proposals to use steam rockets that release superheated water through a nozzle where it instantly flashes to high velocity steam for interplanetary transport using either nuclear or solar heating as the power source to vaporize the water that could be collected from around the solar system. Although if you are going to harness solar energy you may as well harness it directly with a solar sail as there would be less to go wrong

Rubecula

ROFL yes I know about the steam engine not working quite that way, I was talking to her about Heron's (Of Alexandria) steam engine.:pac:

I think I went into too much details with her, tried not to make same mistake in OP.;)

My fault, my mistake.:o

Good reaing of your post though, thanks for that.

clln

slade_x wrote: »

. Although if you are going to harness solar energy you may as well harness it directly with a solar sail as there would be less to go wrong

Ikaros is still sailing,!

IKAROS is a satellite to navigate space, deploying a large solar sail. TradImagine that IKAROS is orbiting the Sun at the same speed and in the same orbit as Earth. If IKAROS speeds up, with its large sail inclined toward the Sun, it will start moving away from the sun, heading outward toward the orbit of Mars. But, if it slows down, it will start falling downward to the Sun and approach to the orbit of Venus.

What is IKAROS' destination?

IKAROS is planned to approach Venus' orbit after a six-month flight. Then, it will travel, relying only on the solar force, until it reaches the far side of the Sun three years after launch. itional satellites always needed fuels wherever their destinations were. The asteroid probe Hayabusa was driven by ion engines, which were energy-saving but still needed fuel called xenon gas.

Flyable without fuel, IKAROS is more than energy saving – it requires no energy. IKAROS can both approach to and recede from the Sun with elaborate use of its solar cells and the pressure of sunlight.

How does IKAROS fly?

Earth makes one revolution a year around the sun. The Earth's orbit around the sun is constant because the centrifugal force produced by the earth's orbital motion and the force of the sun's gravity are balanced. What would happen if Earth slowed down in its orbit? Earth would get closer to the Sun as the centrifugal force weakened. The same dynamics apply to IKAROS.

Not exactly the answer to the the girls question,but is this the type of thing you mean slade-x?
Still needs a lot of propulsion to escape Earth,but a lot less fuel of whatever type to escape gravity.
crafts like these could be launched in much larger numbers as one payload on one launch vehicle as they would not have the weight of fueled probes heading into the Cosmo's,downside being how slow it would be to reach a destination.

food for thought for her anyway!,might get her off your back Rubecula or make her pose even more questions! Lol

hal9000

the US were developing nuclear rockets in the 50-70's under project rover and project NERVA, a few test configurations were fired but none actually flew, wouldnt be crazy about the idea of an in atmosphere explosion though :eek:

glenbrook

That kid is right on the money.

The US funded General Atomics Project Orion from 1958 to 1963. This was design for an interplanetary spaceship weighing up to 10,000 tons powered by by repeated nuclear bombs. The idea is not as crazy as it seems. They calculated that they needed about 800 bombs to reach orbit firing one per second. Once out of Earth's gravity, the ship could zip off to Mars in a month. In theory the design could reach 8-10% light speed, meaning you could reach the nearest stars in a human lifetime. By comparison the fastest spacecraft launched to date (e.g. Voyager 2) will take 40000 years to go the same distance.

The spaceship needed to be huge because nuclear bombs are so powerful, that you need to build it like a standard engineering design, like an ocean liner or a bridge. Current spacecraft are built to be as light as possible and are consequently very delicate. Orion was not going to be like that.

The project died for two reasons. Firstly there were obvious concerns about nuclear fallout and contamination. Secondly, in order to get funding they enlisted the help of the military. The generals were so excited by the idea that they commissioned a military design with the ability to devastate any part of the earth within minutes, a kind of death star. When Kennedy saw this he was horrified and realised that the last thing the earth needed was an arms race in space. It was cancelled in 1963, and killed off with the test ban treaty that prohibits nuclear explosions in space.

Parts of the project are rumored to be still active, and it is all still highly classified. One of the key elements is the ability to mass produce large numbers of nuclear weapons at low cost. That tech needs to stay secret.

The best description I have seen is a BBC4 documentary "To Mars By Atom Bomb", which you might find on the net somewhere.

To come back to the original question. It was not simply enough to explode bombs out the back of the craft for propulsion. There needed to be a source of material to act as plasma to push the craft forward. The obvious choice was water or packed snow.

If a large asteroid is deemed to be heading our way, Orion is currently the only way humanity could reach out and deflect it. Standard chemical rockets just won't do it.

So the nuclear bomb powered steam rocket is a real, feasible concept.
Get that young lady a physics book!

Rubecula

clln wrote: »

Ikaros is still sailing,!



Not exactly the answer to the the girls question,but is this the type of thing you mean slade-x?
Still needs a lot of propulsion to escape Earth,but a lot less fuel of whatever type to escape gravity.
crafts like these could be launched in much larger numbers as one payload on one launch vehicle as they would not have the weight of fueled probes heading into the Cosmo's,downside being how slow it would be to reach a destination.

food for thought for her anyway!,might get her off your back Rubecula or make her pose even more questions! Lol

Next time I will a) keep it simple and Keep off science homework:pac:

Rubecula

glenbrook wrote: »

That kid is right on the money.

So the nuclear bomb powered steam rocket is a real, feasible concept.
Get that young lady a physics book!

LOL the last thing she needs is encouragement, she leaves me feeling thick ROFL All quiet and taking everything you say in then comes out with a blinder.:pac: