What's your favorite method of space launch or travel? (realistic only please)

[Mr Skeptic]

So there are several ways we could get off this rock, and also several ways to travel somewhere once we do. Which practical method is your favorite?

 

I think for liftoff I would prefer a launch loop for the absurd cheap launch capacity from ground-based electricity. Alternately, a nuclear lightbulb, for its high specific impulse and flexibility. Or Project Orion (no relation to the shuttle of the same name) for the awesomeness factor of being able to lift an entire city, if people didn't mind nuking the atmosphere while sitting on a pile of nukes, and also the only craft I am aware of that could both lift off and travel to another star.

 

For traveling after lift-off, you have additional options. For short range travel I think nuclear lightbulb would be best. For long range travel, Project Daedalus would be the most ideal if possible, or Project Longshot which uses current technology. These would however have to be constructed in orbit.

[SH3RL0CK]

I do like the idea of the space elevator (http://en.wikipedia.org/wiki/Space_elevator) to enter earth orbit. As the saying goes, from here you are half-way to anywhere.

 

Interplanetary, I still favor chemical and ion rockets and/or solar sails (http://en.wikipedia.org/wiki/Solar_sail) as I'm not excited about nukes in space for lots or reasons.

 

Interstellar, I would prefer a solar sail if this could be made workable. But I think it would have to be one of the nuclear proposals you mentioned above.

[insane_alien]

a nuclear drive doesn't necessarily mean a series of nuclear bombs going off (and the only messy ones are ones that derive some power from fission) so the drive system of longshot is fine, it uses inertial confinement to initiate the fusion reaction rather than a fission primary.

 

there are also nuclear thermal rockets which just use a contained reactor to superheat a reactionmass (typically hydrogen). i have also seen a fusion based one which is essentially a leaky tokamak with reactor plasma(sounds star trekkie) vented straight into the nozzle and out into space.

[D H]

"Realistic only" and you guys immediately launch into discussions of a bunch of things that are pipe dreams only? You might want to reword the question.

[insane_alien]

realistic isn't confined to existing tech only, we aren't talking about warp drive or anything just near future technology which is plausible.

[bascule]

My preferred method would be some sort of enormous railgun type of contraption which is able to launch a small projectile containing nanorobots/utility fog.

 

This package could be relatively teensy... thousandths of a gram or less! You could launch it with a giant railgun type of apparatus... maybe thousands of miles long.

 

With such a combination, I don't forsee it being too difficult to get such a package relatively close to light speed, with a rather loose definition of "relatively" (and no pun intended). Half light speed? 75% light speed? It's certainly better than what we could do with a spaceship containing a large and fragile human.

 

Once this little package gets to a suitable destination planet, it can land, and the nanorobots/utility fog can start self-replicating, and building whatever we want on the destination planet, including a "teleporter" machine that can receive a message via radio and build human beings.

[Mr Skeptic]

Yes, I've considered that for the future of space travel. It would be ideal once we develop nanorobots. So far, it seems like it would have to be far into the future. Also, you will need to make your rocket big enough to survive space radiation and collisions with particles. Also, you will be wanting to decelerate so as not to vaporize at the destination.

[Moontanman]

My favorite is the nuclear light bulb rocket already mentioned. It could be used to lift mass of the earth several times as efficiently as a Saturn five moon rocket with no radiation release.

 

http://www.nuclearspace.com/Liberty_ship_menupg.aspx

 

Of course there is always the good old salt water nuclear rocket.

 

http://en.wikipedia.org/wiki/Nuclear_salt-water_rocket

[John Cuthber]

Some of the big problems with space travel are

the provision of energy to give you a meaningful speed through the cosmos

protection from cosmic radiation

provision of gravity (or its equivalent) because our bodies don't do well in zero g.

taking enough people with you to ensure that you can maintain some sort of balanced society.

 

My plan to achieve those goals is to get a really big rock, put it in orbit round a star that's already moving, give it a breathable atmosphere and populate it with a few billion people.

 

Any takers?

[Cap'n Refsmmat]

Where can I sign up?

[One of the Few]

I personally favor Rail Guns or anything involving massive amounts of magnetism, this would only be feasible for interstellar travel as anything that left one on earth would be obliterated. As for inter galactic travel, I own michio kaku's Physics of the impossible, and he describes how massive fusion bombs released through a blast sheid could bring a ship to "nearly" light speed.

[Moontanman]

Hey the salt water nuclear rocket is a continuous atomic bast!

[Inquisitive Stone]

What about an interstellar ramjet:)

[THX-1138]

I was wondering why ramjets hadn't been mentioned yet.

 

One thing I don't like about lightsails is having to deal with the stellar wind. If the wind was solely composed of electrons, or protons and stripped nuclei, you could deal with it by putting a charge on the sail. (In fact, you might get a little boost from the repulsion.) But it's not -- it's composed of both positively and negatively charged particles, which will stick to the sail and cause all sorts of problems.

 

Well away from the star the issue becomes less of a concern -- but the light pressure is lower out there, too.

[One of the Few]

While the Railgun is my favorite, honestly the ramjet has the greatest possibility (seeing as it has an infinite specific impulse) with the overall abundance of hydrogen. Also for reconnaissance, if we release nanobots by the trillions all equiped with (for lack of a better term) little pico solar sails. If these all move towards a target it is assured that many will arrive...only to increase their numbers by way of little factories.*

 

*Most of this is explained in Michio Kaku's Physics of the Impossible.

[Dave Cell]

What is the general thought on the space elevator concept? Is it really that far out there?

 

I will start building the giant slingshot now.

[Moontanman]

I'm not so sure a interstellar ramjet is all that realistic, first we cannot control nuclear fusion. control of nuclear fusion has been just a few years away all my life. So far we simply cannot do it. There is also the problem of actually collecting interstellar hydrogen, how do you do it? Most hydrogen atoms in space are neutral, no charge, so a magnetic field has no effect on them. How do you gather up neutral hydrogen? a simple hydrogen fusion reaction with out a working fluid of some sort is not exactly an atomic blast, it would be closer to an ion engine in it's actual thrust. Overcoming the friction of the interstellar medium would be a major problem.

 

http://en.wikipedia.org/wiki/Bussard_ramjet

[CaptainPanic]

Why not use a really big cannon?

In the military, shells and mortars and such are actually becoming "intelligent", meaning that technology exists that will survive a huge acceleration.

The only thing you would need is a much larger cannon, and a longer acceleration (but not necessarily a higher acceleration). Possibly it can simply be powered by pressurized gas, not explosives? I haven't done the math yet, but this seems a simple solution to me... although I can imagine that it's not suited for manned space flight

[SH3RL0CK]

Why not use a really big cannon?

In the military, shells and mortars and such are actually becoming "intelligent", meaning that technology exists that will survive a huge acceleration.

The only thing you would need is a much larger cannon, and a longer acceleration (but not necessarily a higher acceleration). Possibly it can simply be powered by pressurized gas, not explosives? I haven't done the math yet, but this seems a simple solution to me... although I can imagine that it's not suited for manned space flight

 

Well, precedent exists for this idea. The ability to shoot things into near space has actually existed for quite some time. See the WWI weapon: http://en.wikipedia.org/wiki/Paris_gun

 

The Paris Gun was a weapon like no other, but its capabilities are not known with certainty. [2] This is due to the weapon's apparent total destruction by the Germans in the face of the Allied offensive...The projectile reached so high that it was the first human-made object to reach the stratosphere. This virtually eliminated drag from air resistance, allowing the shell to achieve a range of over 130 kilometres (81 mi). The Paris Gun was the largest gun built at the time, but it was surpassed in all respects but range in World War II by the Schwerer Gustav. The unfinished V-3 cannon and Iraqi super gun would have been bigger.

Though the maximum velocity

each shell from the Paris Gun reached a speed of 1,600 metres per second (5,200 ft/s).

= 1.6 km/sec.

 

This is considerably less than required for orbital speed (about 7 km/sec for low earth orbit).

 

http://en.wikipedia.org/wiki/Orbital_velocity#Earth_orbits

 

Could this gun be scaled up by a factor of 4 to 5? I would think there is a reason why rockets and not guns were attempted for the first space flights in the 1950's and 1960's...but I'm not sure these reasons mean a cannon must be impractical.

 

The idea of electronics in the warhead is also not new: http://en.wikipedia.org/wiki/Proximity_fuse

 

But of course there is probably at least an order of magnitude difference between the forces applied to these shells and what would be necessary for a space launch. Again though, I don't see a reason why this couldn't be constructed such that the electronics would survive.

[Mr Skeptic]

They're actually considering a cannon of that sort.

 

http://www-istp.gsfc.nasa.gov/stargaze/SSHARP.htm

[One of the Few]

Yes, a cannon, like the space elevator would mainly be used for cargo i'm guessing. It'd certainly make resupply of the space station alot simpler. But imagine this, in a last ditch effort to save humanity we build a massive rail gun encompassing one half of the moon, and the other half is covered in super efficient photovoltaic cells, all of it escalating dozens of kilometres into the sky. The resulting magnetic acceleration rockets them into the cosmos!

[insane_alien]

Yes, a cannon, like the space elevator would mainly be used for cargo i'm guessing. It'd certainly make resupply of the space station alot simpler. But imagine this, in a last ditch effort to save humanity we build a massive rail gun encompassing one half of the moon, and the other half is covered in super efficient photovoltaic cells, all of it escalating dozens of kilometres into the sky. The resulting magnetic acceleration rockets them into the cosmos!

 

unless of course the half that is covered in PV cells is facing away from the sun.

[One of the Few]

Ugh such a kill joy:D i'm using PV cells as an example really, by the time we have the technology to make something like a hyper rail gun we might have perfected fusion or hell we might still be using fossil feuls.

[insane_alien]

well, if you think about it, all the land you need for a rail gun is a tiny thin strip. it can even circum navigate the moon itself.

 

all you need to do then is cover the rest of the surface with PV panels.

[Moontanman]

Wouldn't centrifugal force become a problem with a rail gun that circumnavigated the moon?