Spaceships of the Future: Visions of Interstellar Starship Travel

Originally posted by stumason

Originally posted by TopsyTurvyOne
how did the apollo rockets adjust course for the moon in the vacuum
of space after performing this initial evasive manoevre?

Er, with it's engines?

Here is a nice little image of the various stages of an Apollo launch.

edit on 1/7/13 by stumason because: (no reason given)

how do you eject a gas into a vacuum and expect work to be done?
gasses cannot exist in areas of zero pressure.

the trajectory indicated in your link doesn't seem to take a path that
avoids the worst of the vast and impenetrable van allen belt as represented
by the colourful representation from my last post.

reply to post by TopsyTurvyOne

how do you eject a gas into a vacuum and expect work to be done?
gasses cannot exist in areas of zero pressure.

It doesn't push against the vacuum of space, it pushes against it's own fuel. And a vacuum isn't entirely empty to begin with, no real vacuum exists, just very low pressure.

reply to post by TopsyTurvyOne


May I suggest reading some basic information about how rockets work:

Rockets

That picture is not an exact representation (it even says so on the diagram) - it is an approximation to give an idea of the trajectory used.

Originally posted by HauntWok
reply to post by TopsyTurvyOne

 

how do you eject a gas into a vacuum and expect work to be done?
gasses cannot exist in areas of zero pressure.

It doesn't push against the vacuum of space, it pushes against it's own fuel. And a vacuum isn't entirely empty to begin with, no real vacuum exists, just very low pressure.

how can anything move by pushing against itself? the micro-second that gas meets the
vacuum it is instantly exhausted and dispelled into the void. no work can be done.
space cannot be a very low pressure zone. to all intents and purposes it is a complete vacuum
with zero pressure. gasses cannot exist at zero pressure.

Originally posted by TopsyTurvyOne
how can anything move by pushing against itself? the micro-second that gas meets the
vacuum it is instantly exhausted and dispelled into the void. no work can be done.
space cannot be a very low pressure zone. to all intents and purposes it is a complete vacuum
with zero pressure. gasses cannot exist at zero pressure.

Are we really going to do this? Have you even read the link into basic rocketry I gave you?

Put it this way, when you push against a wall, you go in the opposite direction don't you? Or when you release the neck of a balloon, what happens? You are, I hope, aware of Newtons 3rd law?

Basically, the exhaust gases from the rocket shooting out in one direction cause an equal and opposite force, pushing the spacecraft forward. Basic stuff, man.

Originally posted by stumason
reply to post by TopsyTurvyOne

 

May I suggest reading some basic information about how rockets work:

Rockets

That picture is not an exact representation (it even says so on the diagram) - it is an approximation to give an idea of the trajectory used.

i know how they say rockets work in a vacuum, but it doesn't make sense to me.

have NASA produced any accurate representations encorporating the apollo trajectories
taken and their to scale relationships to the van allen belt and the moon?
that might give us a better idea.

reply to post by zazzafrazz


Not to be rude or anything, but that isn't NASA's or any Space exploration's program real craft, those are just show crafts. The real crafts are the ones that can go the speed of GRAVITY.

Plus they have already mastered the use of a MHD drive and been using it since the 1950s. Everything else is a show, ma'am.

reply to post by FreedomCommander


No one said it was real a craft?

They are conceptual illustrations of crafts, as per the first paragraph in the OP.

Originally posted by stumason

Originally posted by TopsyTurvyOne
how can anything move by pushing against itself? the micro-second that gas meets the
vacuum it is instantly exhausted and dispelled into the void. no work can be done.
space cannot be a very low pressure zone. to all intents and purposes it is a complete vacuum
with zero pressure. gasses cannot exist at zero pressure.

Are we really going to do this? Have you even read the link into basic rocketry I gave you?

Put it this way, when you push against a wall, you go in the opposite direction don't you? Or when you release the neck of a balloon, what happens? You are, I hope, aware of Newtons 3rd law?

Basically, the exhaust gases from the rocket shooting out in one direction cause an equal and opposite force, pushing the spacecraft forward. Basic stuff, man.

we need to get back to basics.
when i push against a wall, there is a wall to push back.
when you release the neck of a balloon, there is an atmosphere to push back.
in a vacuum there is nothing to push back.
a thing cannot push against itself to achieve motion.

from your link:

Principle of operation
Rocket engines produce part of their thrust due to unopposed pressure on the combustion chamberRocket engines produce thrust by the expulsion of a high-speed fluid exhaust. This fluid is nearly always a gas which is created by high pressure (10-200 bar) combustion of solid or liquid propellants, consisting of fuel and oxidiser components, within a combustion chamber.

The fluid exhaust is then passed through a supersonic propelling nozzle which uses heat energy of the gas to accelerate the exhaust to very high speed, and the reaction to this pushes the engine in the opposite direction.

In rocket engines, high temperatures and pressures are highly desirable for good performance as this permits a longer nozzle to be fitted to the engine, which gives higher exhaust speeds, as well as giving better thermodynamic efficiency.

-there cannot be any reaction in a vacuum which is void, and where gasses cannot exist
due to zero pressure.

-the higher exhaust speeds necessary for the rocket to function are instantaneously
reduced to zero the micro-second they 'hit' the vacuum.

reply to post by TopsyTurvyOne

-there cannot be any reaction in a vacuum which is void, and where gasses cannot exist due to zero pressure.

Stars and some planets are made of gas.
Those bodies are in space.
Gasses can definitely exist in space.

-the higher exhaust speeds necessary for the rocket to function are instantaneously reduced to zero the micro-second they 'hit' the vacuum.

Things in space do not lose their mass. A force acting on a mass always produces a reaction. Newton said so.

For every action, there is an equal and opposite reaction. -Newton

For every action... Newton is categorical about this.
So there.

Originally posted by TopsyTurvyOne
we need to get back to basics.
when i push against a wall, there is a wall to push back.

Which is analogous to the exhaust gases of a rocket pushing upon themselves...

Originally posted by TopsyTurvyOne
when you release the neck of a balloon, there is an atmosphere to push back.

Actually, in a balloon, there is a fair amount of the exhaust gas pushing on itself as much as any surrounding atmosphere. The balloon would do the same in a vacuum.

Originally posted by TopsyTurvyOne
in a vacuum there is nothing to push back.
a thing cannot push against itself to achieve motion.

Yes, there is. There is the gases expelled by the rocket motor.

Originally posted by TopsyTurvyOne
-there cannot be any reaction in a vacuum which is void, and where gasses cannot exist
due to zero pressure.

The gases don't instantly lose their pressure the moment they are expelled from the rocket.

Originally posted by TopsyTurvyOne
-the higher exhaust speeds necessary for the rocket to function are instantaneously
reduced to zero the micro-second they 'hit' the vacuum.

No, they are not. You are basing your reasoning on false assumptions. I suggest you illuminate yourself

reply to post by zazzafrazz


Hate to be a party crasher but we can't even get inland desalination plants for clean water. We can't even even accomplish a cleanup in isle Fukushima. What is the point of visiting Mars when we can't even take care of our problems here. What a gigantic waste of time. Sad.

These are all fantasy

reply to post by autoprotolysis


I see no reason why it is a waste of time, if anything this will ensure the survival of the species.

As for your examples, you can have an inland desalination plant, but I fail to see why you would. How much saltwater is inland that you would require one? They also use up a lot of elastic trickery. Fukishima was a freak accident and it matters not how advanced you think you are, sometimes stuff happens. Would you have us confined to this rock until we have solved all the Universes mysteries?

Originally posted by LevelEleven
These are all fantasy

I don't know about the others, but Skylon is very real.

Maybe your next post might contain more than a single line of irrelevance?

reply to post by TopsyTurvyOne


When a gas expands inside the cone it pushes the rocket. Thrust doesn't come from pushing against atmosphere. Wow, our schools suck.

Originally posted by ZeroReady
reply to post by TopsyTurvyOne

 

-there cannot be any reaction in a vacuum which is void, and where gasses cannot exist due to zero pressure.

Stars and some planets are made of gas.
Those bodies are in space.
Gasses can definitely exist in space.

i didn't say gasses cannot exist in space, but they cannot exist in a vacuum.

-the higher exhaust speeds necessary for the rocket to function are instantaneously reduced to zero the micro-second they 'hit' the vacuum.

Things in space do not lose their mass. A force acting on a mass always produces a reaction. Newton said so.

i don't think newton was talking about gasses in a vacuum where gasses cannot exists
due to zero pressure. (see boyles law)

For every action, there is an equal and opposite reaction. -Newton

For every action... Newton is categorical about this.
So there.

and if there can be no action, there is no reaction.

Originally posted by TopsyTurvyOne

i didn't say gasses cannot exist in space, but they cannot exist in a vacuum.

they do exist in a vacuum.. this is why there is never truly a perfect vacuum.. it only appears to be a vacuum because the vacuum is infinitely larger than the amount of particles we are introducing by expelling gases.

and if there is no action, there is no reaction.

there is an action.. the air inside a balloon is stationary, when expelled through the hole is it moving very fast.

the air in the ballon has gone from stationary to moving.. this means an acceleration has been in effect. F=MA indicates that an acceleration is the result of an unequal force. and all forces have equal and opposite reactions.. since nothing is holding the ballon in place, it will move in the opposite direction the air is escaping.

the same principal is with rockets.

I don't think these will ever work beyond a handful of probes sent to near by stars. The energy and engineering challenges of a relativistic vehicle (v→c) are just too great to ever overcome.

Instead of building interstellar ships that would bankrupt Earth many times over just to reach other habitable planets, why don't we focus our efforts on massive space stations like O'neil cylinder, Bernal Sphere, and a Stanford Torus? They are many times more feasible and cheaper as they don't require the resources of an entire planet to be exhausted. Much more realistic than living in a relatively small ship that will more than 200 years to get to the nearest habitable planet.

If space colonization is ever to become a reality, then we need to let of this excessive emphasis on planetary bodies. Space stations are clearly the way to go.

reply to post by Diablos


YUP. These are a fantasy.