Semi-OT: A General Tech Question Thread for me :)

[Slick]

some SI prefixes:

Code:

---

Factor Name  Symbol 

10E24  yotta Y 

10E21  zetta Z 

10E18  exa   E 

10E15  peta  P 

10E12  tera  T 

10E9   giga  G 

10E6   mega  M 

10E3   kilo  k 

10E2   hecto h 

10E1   deka  da 

 

10E-1  deci  d 

10E-2  centi c 

10E-3  milli m 

10E-6  micro µ 

10E-9  nano  n 

10E-12 pico  p 

10E-15 femto f 

10E-18 atto  a 

10E-21 zepto z 

10E-24 yocto y  

---

so to answer your question, a terawatt is 1000 gigawatts; or 1,000,000,000,000 watts (12 zeros).

edit: typo

[dogscoff]

Many of your questions (and many more) are answered a tthe excellent http://www.projectrho.com/rocket/index.html - which basically looks at the physical limitations of engineering (as they are currently understood) and applies them to all the essential aspects of spacecraft design. It's an invaluable read for any aspiring scifi author who hopes to write with a degree of scientific credibility.

There is a section there headed "artificial gravity" that answers your latest question quote neatly, as well as frequent references to power requirements in the propulsion and weaponry sections.

[douglas]

Starhawk said:
Question 2:

Okay so we all see on Star Trek and Bab 5 and yadda yadda that Artificial gravity is the ultimate sign of the advanced uber race well I have a question regarding this.

As we have seen in such things as Babylon 5 Earth Alliance and Nexus: The Jupiter Incident rotating sections is the poor mans way of getting gravity on a starship, so my question is this why if it is as simple as a rotating section does the US not crank out space ships with rotating sections?

First, artificial gravity is only really useful for manned spacecraft, and the most important reason for sending people into space nowadays is so that they can perform experiments in zero g. Having the whole ship rotate would make those experiments possible only at the center of the ship, and having just a section of it rotate would cost extra. Also, and perhaps most important, the rotating section would have to be BIG in order to avoid seriously disorienting the astronauts. If you've ever been in a centrifuge and looked away from the center, you'll know what I mean. The human perception system does not handle that kind of rotation very well.

El_Phil said:
What on earth do you want gravity for? It will massively increase the cost and complexity of said ship and remove the only reason for doing research in space, zero gravity. Other than that a space lab is just really expensive and not as good normal.

Nothing except artificial gravity can prevent muscles from atrophying and bones from weakening during extended stays in space. Even with highly rigorous exercise regimens, astronauts that stay in space for months, or maybe even weeks, aren't even able to stand up on their own when they return to Earth. The whole human maintenance cycle evolved around the assumption of gravity always being present, and the human body has a distinct tendency to deteriorate in long term weightlessness.

[Slick]

As we have seen in such things as Babylon 5 Earth Alliance and Nexus: The Jupiter Incident rotating sections is the poor mans way of getting gravity on a starship, so my question is this why if it is as simple as a rotating section does the US not crank out space ships with rotating sections?

Not entirely sure but here are some reasons I can imagine:

- the "zero g" environment is preferred for lots of things:
-- some experiments are specifically designed for zero g. Yes, you could place them at the exact center of the craft, but true zero g only exists at a point.
-- making the robotic arms and mechanical things requires much less power/strength. If there were centripital forces needed to be overcome, in practical terms, this means more weight=more money=less payload for other things.
-- reorienting the ship/craft takes less thrust. To overcome gyroscopic forces created by rotation requires more fuel =costlier, less payload, etc.

- the "gravity" will decrease to zero at the center; making it somewhat cumbersome to manage placement of things. (see 2001: Space Odessy for a pretty realistic portrayal)

- in order to simulate earthlike gravity, either the rotational speed or the radius must be increased. But in general the size of the ship/station would need to be larger to make "gravity" somewhat uniform; =costlier, etc.



Perhaps if humans were to undertake a long space journey there would be another solution to simulate artificial gravity. Picture this: A large spacecraft with a huge funnel "scoop" in the front. The scoop would catch residual hydrogen to use as fuel and accelerate at 1g toward the destination. This way the crew lives under 1g all the time. At the halfway point, the crew section and the engine (not the scoop) is rotated 180 degrees and the ship is decelerated at 1 g for the remaining half of the trip. The crew still sees 1g toward their feet during the second half of the trip. I just thought of this, so there are probably a million things that make this just as impractical. (edit: like exceeding the speed of light in a short time...)

[douglas]

Slick said:
Perhaps if humans were to undertake a long space journey there would be another solution to simulate artificial gravity. Picture this: A large spacecraft with a huge funnel "scoop" in the front. The scoop would catch residual hydrogen to use as fuel and accelerate at 1g toward the destination. This way the crew lives under 1g all the time. At the halfway point, the crew section and the engine (not the scoop) is rotated 180 degrees and the ship is decelerated at 1 g for the remaining half of the trip. The crew still sees 1g toward their feet during the second half of the trip. I just thought of this, so there are probably a million things that make this just as impractical. (edit: like exceeding the speed of light in a short time...)

Constant acceleration at 1 g is the perfect solution - if you can find enough fuel. Trying this over any significant distance (astronomically speaking) would require a truly colossal amount of fuel if you carry it all with you, and your collection array would have to be incredibly large to gather enough on the way. Interstellar matter density is typically on the order of 1 atom per cubic meter IIRC.

[Suicide Junkie]

Slick said:
(edit: like exceeding the speed of light in a short time...)

Not to worry, though.

Relativistic time dilation and length contraction will ensure you reach your destination (regardless of if it's a finite distance or not) before that happens.

[Slick]

Crunched a few numbers:

At 1g, you could accelerate for 353.8 days and still not reach the speed of light (barely).

During that time, you would travel 2.85 E12 miles (yes, Starhawk, that's teramiles )

So if you would start decelerating at 1g at the halfway point, you could travel ~5.7 E12 miles (just under 1 light-year) in 2 years.

[Renegade 13]

Not bad at all.

[Starhawk]

Hey thanks for that link I've always been a fan of space ships and the like (as you can probobly tell lol) so that web site will probobly keep me entertained for hours

One reason I've asked some of these questions is because the first book of the Icaran series (hopefully I can write a series I have a plan for 3 books) would cover their earliest days of space travel within the Sol system and I was considering ships with rotating sections toward the aft section of the ship for the sleeping quarters and the like while the duty stations were all in zero g.

I've also heard people saying that within my lifetime we'll probobly see the earliest stages of Space based colonization and therefore military expansion (early infantry security forces and primitive space warships) from the Super Powers, I don't know if this is at all true but it could be very interesting (and probobly somewhat scary) to see it come true.

[Hunpecked]

Slick writes: "At 1g, you could accelerate for 353.8 days and still not reach the speed of light (barely)."

In a Newtonian universe, yes. In our relativistic universe, however, the ship's speed can asymptotically approach c, the speed of light, but never reach it. Meanwhile the ship's mass increases, its length decreases, and time slows down for the ship and its crew. For an entertaining look at relativistic space travel I recommend Poul Anderson's 1970 novel "Tau Zero".