The difficulty and realities of controlled Space Flight

[bdewoody]

In some ways I believe that Star Trek, Star Wars, BSG, Stargate and others have misguided a lot of interested but uneducated space enthusiasts in their concept of the realities of space flight. Relatively small ships with no provision for fuel capacity and manuverability like that of aircraft operating in an atmosphere. We have grown so used to seeing the "ease" of space flight as depicted on the silver screen some of us lose sight of what we are really capable of. Everything we have built up to now are in actuality just space gliders with minimal ability to alter trajectory. All our manuvers up to now are balistic trajectories moving from one gravity well to another. We can't just go from one place to another without carefully using the gravity wells of nearby planets and moons. The vast amounts of fuel that would be required to manuver independantly prohibit anything else. We need some space TV and movies that more accurately reflect the true nature of space flight so the everyday enthusiast will better understand what we are facing.

 

[orionrider]

Apollo XIII is a good example. When the explosion occurred, they were halfway to the Moon, but it was impossible for them to just stop and come back. They had to use the Moon to turn around and fling back to Earth.

The planned 2026 encounter with an asteroid will be the first time a manned spacecraft does actually stop and reverse course in deep space. In fact, it will be the first time people leave Earth orbit!
Just that single stunt will request international cooperation, a huge budget and the most powerful spacecraft ever built :idea:

 

[bdewoody]

I think more powerful than we are capable of and therefore a total waste of time and money that can better be spent on more worthy projects. No means of propulsion that exists or is in planning has that much power. There is that spiral, more power, more fuel, more mass which in turn requires more power etc, etc, etc.

 

[orionrider]

more powerful than we are capable of

Not quite. And actually, there IS already a rocket able to orbit the required 200 tons of propellant for the voyage. All components have even been flight tested... Much cheaper than designing from scratch, just reactivate the production line from the blueprints, and voilà... And if you assemble the parts on your side of the pond you can legally print 'Made in USA' on the label

But even using this behemoth, assembling a 1,000 ton 4-man Mars ship or a small Moon base would take 5 launches :shock:

http://www.k26.com/buran/Info/Hercules/vulkan.html
http://en.wikipedia.org/wiki/Energia

 

[bdewoody]

The moon or Mars is one thing and I guess the rocket you are writing about could get a crew there and back. The topic of discussion is a vehicle to get a manned crew to an asteroid and back without having to wait a year or more until it is in the right position again. That means a spacecraft that can manuver on its own without gravity assists to get to the desired asteroid then alter course to match speed and direction with said asteroid and then after a short visit again change speed and direction to return to earth. We have nothing capable of such drastic manuvering.

 

[DarkenedOne]

In some ways I believe that Star Trek, Star Wars, BSG, Stargate and others have misguided a lot of interested but uneducated space enthusiasts in their concept of the realities of space flight. Relatively small ships with no provision for fuel capacity and manuverability like that of aircraft operating in an atmosphere. We have grown so used to seeing the "ease" of space flight as depicted on the silver screen some of us lose sight of what we are really capable of. Everything we have built up to now are in actuality just space gliders with minimal ability to alter trajectory. All our manuvers up to now are balistic trajectories moving from one gravity well to another. We can't just go from one place to another without carefully using the gravity wells of nearby planets and moons. The vast amounts of fuel that would be required to manuver independantly prohibit anything else. We need some space TV and movies that more accurately reflect the true nature of space flight so the everyday enthusiast will better understand what we are facing.

There are a number of technologies that you see in those Scifi movies that we are really no where near possessing. These include faster-than-light drives, teleportion, and artificial gravity without centrifugal force. The fundamental physics of these things in particular are currently beyond our understanding. We cannot even be sure if they are even possible.

The problem with the technology we use now for propulsion at least for human mission particularly chemical rockets is that they have way to low a specific impulse to be economically efficient for space flight. With a specific impulse that maxs out at 400 seconds it takes a huge amount of fuel just to do the most basic orbital maneuvers. For example, to go to lunar orbit from LEO it would require something like 2/3 of the mass of your spaceship be fuel. Honestly using chemical rockets for space flight is like using compressed air to drive your car. You need a huge amount of it to go anywhere.

In the shows that you mentioned they explain that they use some type of nuclear plasma drive. The physics of this type of propulsion is fairly well understood and building such drives is well within our near term capability. We have a great understanding of nuclear power. We understand that nuclear fuel has an energy density almost a million times greater than chemical. We are also developing a decent understanding of ion and plasma propulsion. Similar technologies have been well tested in deep space probes and commercial satellites. Current ion propulsion drives for deep space probes are capable of specific impulses around 5000 seconds. That is over 10 times greater. Combining the two technologies in a human sized ship has been on peoples minds for a long time now. However the people with the money and motivation, NASA, simple to not have the vision to make such spaceships a reality.

 

[bdewoody]

I agree about an ION or plasma rocket motor being the solution to true independent space flight. Such a motor would have to be built or at least assembled in space. Another possibility is the construction of such motors on the moon where the escape velocity is much lower than earth.

I believe though that an ION or plasma propulsion system capable of making space flight independent from using the gravity wells of various solar system objects requires thrust much greater than anyone is capable of producing at this time.