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Betting on rarity really works well when it comes to levees and hurricanes, building design parameters and earthquakes, etc. I mean, sure, lots of people have died when the really rare events eventually happened, but I'm sure that means that going forward rare things won't actually happen anymore.~

While I think that humanity could survive another event on the level of the Chicxulub impact, I don't think that a larger event is survivable. There are also problems unique to humanity as an increasingly capable technological civilization, including problems that may not even be foreseen. Aside from potential anthropogenic biological and technological threats, there are also hypothetical threats from the outside, with the nasty possible combination of RKVs with the Prisoner's Dilemma.

Protection? Gonna have to go with obscurity.

If aliens can move about the galaxy freely, the ships would have to be large to hold a sustained, reproducing population. That means they can move lots of mass. Hello, asteroid bombardment.

If they can move at greater speeds, then they can do the same with whatever solids they find floating about. Hello, relativistic bombardment.

Scroll down a bit to the excerpt from The Killing Star. http://www.projectrho.com/rocket/rocket3x2.html#rbomb

'course, that's just annihilation. I don't really see the point of conquering. ...unless they think we're pretty tasty but even that seems unlikely.

Something like a Brussard Ramjet?

Bullshit is the opposite of truth. Your last sentence alludes to the real truth, which is 'this is what I want even though it won't happen'. But merely wanting something isn't going to rewrite human nature. That's as much genetic as it is social. Even if we could eliminate the instincts that have put us at the top of the food chain I doubt that it would make us very fit to explore space. Although the reality of space exploration is almost certainly 'apes or angels', I don't think we want to turn ourselves into a herd of ibexes before we leave the cradle on the chance that odds are we won't meet any lions. Even if that chance is astronomically (heh) high, as long as it is possible such self-neutering is irresponsible.

There's a link of the wiki page to this other site: http://www.projectrho.com/rocket/rocket3x2.html#rbomb

An excerpt from the book is there and it is just chilling to read.

I agree. For all the problems of that the space shuttle has (over budget, the bizarre requirement to return satellites from orbit, the constantly shifting requirements during development in the 70s), it was an honest to god space ship. It wasn't a rocket. It had cargo. It had a big crew. It had robot arms. It flew like an airplane. Orion or Ares or whatever they're calling the new rocket and capsule, just seems like a step backwards. We've done rockets. Yes they work. Yes they're cheap and good enough. But damn it, they're not romantic. The CEV isn't the 1960's version of 2010, the the space shuttle was.

Where's my space plane? Where's my single stage to orbit launchers? Damn it. Maybe they're not practical. I don't know. But I do want my space plane, even if at the same time, I've become quite skeptical of the whole idea of manned space exploration. (Robotic exploration on the other hand, I'm a big fan of.)

All this talk about space battles, and no one's linked to the Atomic Rockets page?

Atomic Rocket

Be warned, if you're the sort of person who found this article interesting, you could loose the rest of your day to that site.

As for the analysis itself, I'm surprised that the author didn't say anything about the importance of heat. Not only for how craft get rid of it, but also because the heat sources of energetic rockets and missiles make them very easy to see. If you can see your enemy coming from the other side of the solar system, it changes a lot of things about the upcoming fight.

Airplanes have a constant flow of air to dump heat into. In space, you either need huge surface area (big radar cross section), a big internal store, or low power consumption. But you need big power consumption to move fast and do damage. An internal store will likely be needed for the times when you have to retract your heat spreaders due to enemy fire.

Read the Project Rho stuff (and Attack Vector Tactical) Very smart guys spending a lot of time thinking things out.

It's mentioned in the article comments, but Atomic Rocket is a good place to start, and almost as time-sucking as TV Tropes.

I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

Atomic Rockets (index)

Space War: Introduction

Space War: Detection

Space War: Weapons Intro

Space War: Weapons: Conventional

Space War: Weapons: Exotic

Space War: Defenses

Space War: Warship Design

Space War: Strategy and Tactics

I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

Atomic Rockets (index)

Space War: Introduction

Space War: Detection

Space War: Weapons Intro

Space War: Weapons: Conventional

Space War: Weapons: Exotic

Space War: Defenses

Space War: Warship Design

Space War: Strategy and Tactics

I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

Atomic Rockets (index)

Space War: Introduction

Space War: Detection

Space War: Weapons Intro

Space War: Weapons: Conventional

Space War: Weapons: Exotic

Space War: Defenses

Space War: Warship Design

Space War: Strategy and Tactics

I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

Atomic Rockets (index)

Space War: Introduction

Space War: Detection

Space War: Weapons Intro

Space War: Weapons: Conventional

Space War: Weapons: Exotic

Space War: Defenses

Space War: Warship Design

Space War: Strategy and Tactics

I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

Atomic Rockets (index)

Space War: Introduction

Space War: Detection

Space War: Weapons Intro

Space War: Weapons: Conventional

Space War: Weapons: Exotic

Space War: Defenses

Space War: Warship Design

Space War: Strategy and Tactics

I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

Atomic Rockets (index)

Space War: Introduction

Space War: Detection

Space War: Weapons Intro

Space War: Weapons: Conventional

Space War: Weapons: Exotic

Space War: Defenses

Space War: Warship Design

Space War: Strategy and Tactics

I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

Atomic Rockets (index)

Space War: Introduction

Space War: Detection

Space War: Weapons Intro

Space War: Weapons: Conventional

Space War: Weapons: Exotic

Space War: Defenses

Space War: Warship Design

Space War: Strategy and Tactics

I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

Atomic Rockets (index)

Space War: Introduction

Space War: Detection

Space War: Weapons Intro

Space War: Weapons: Conventional

Space War: Weapons: Exotic

Space War: Defenses

Space War: Warship Design

Space War: Strategy and Tactics

I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

Atomic Rockets (index)

Space War: Introduction

Space War: Detection

Space War: Weapons Intro

Space War: Weapons: Conventional

Space War: Weapons: Exotic

Space War: Defenses

Space War: Warship Design

Space War: Strategy and Tactics

I'm not quite sure how all the physics works out, but everything I've read says there's no stealth in hard sci-fi.

Project Rho

Rocket Punk

the failure of radio astronomy to detect signals coming from other civilizations

EM communications are probably not the most advanced method out there, not to mention that the idea that EM signals can travel indefinitely has been debunked. Even if there were signals out there, they probably wouldn't reach us intact. Add to this the 'Apes or Angels' view of development.

the calculations being done by several people, based on evolutionary science and bio-chemistry, of the probability of life forming spontaneously

Based again on a sample size of ONE. That's not science any more than the Drake Equation. Only in the last century or so have we finally figured out roughly how life formed here, once, and even that not completely, and now we want to pretend we can extend that rough understanding to billions or trillions of unexplored environments and unknown conditions? Really? NOT. SCIENCE.

Well, that depends. For more engines, you need: *more power *more cooling *more fuel And you get: *more trust Provided you dont increase the fuel quantity, you will get just more thrust/acceleration from more engines (nice for going throught the radiation belts fast) but the overall journey time could actually be longer(added mass). Basically for any added mass, you need more mass (engines,fuel,power sources) to move it and even more mass if you want to go fast. Of course, when you ignore money, it could be built. But it would looks like a pyramid made of fuel tanks, radiators, reactors and engines with one human in a specesuit sitting in an open cockpit :) BTW, when you ignore also the technical aspect, you get a torchship. You can get from planet to planet in days accelerating at comfortable 1g...but the power requirements are OBSCENE and you would slice a space station in half with your propulsion plume if you are not careful enought :)

There is no free lunch. VASIMR is not radically more efficient than a chemical rocket.

Yes. Yes it is. It's a very efficient Ion drive.

http://www.projectrho.com/rocket/rocket3c2.html

This particular VASIMR is an improvement because it can handle more power... more than solar panels could provide. It will require a nuclear powersource -- a fission plant, or a very very powerful RTG.

Solar panels can potentially provide the entire output of the sun in relevent wavelengths / the efficency of the solar panel... though to do that, it would need to encompass the sun.

I suspect the most likely power would be a nuclear battery (thermo-couples powered by the heat of radioactive decay), but there are many options.

But if you are willing to heft a fission plant into orbit, then you could just use it as a conventional nuclear rocket (i.e. superheated steam)

You don't get the same speed out of that reaction mass, so you don't have the same efficiency.

I wrote: For Isp here

Ahem. What I meant to write was:

For Isp < 2.55e8 (ie 85% of the speed of light) this is actually unattainable (the mass of the non-fuel portions of the ship would need to be negative).

There's a handy table of Isp for some thruster technologies, both real and proposed, here.

You do realize it is "FICTION". Fiction is not necessarily suppose to be scientific. The purpose of Sci-Fi in my opinion is to deal with issues of the day in a format where people won't necessarily reject it out right. Many issues are dealt with and warnings are issued. Lucas screwed up the Star Wars universe with the newest trilogy in my opinion to warn against blind trust in Government, the pitfall of hubris and other things that were pertinent at the time and ring true throughout time. I don't appreciate the poor screenplay or crapping writing, but I understand what he was trying to say.

I won't even bother to do anything more than copy-paste this:

This silly opinion implies that the word "fiction" nullifies the word "science." Since it is "fiction", and fiction is by definition "not true", then we can make "not true" any and all science that gets in the way, right?

Hogwash. By the same logic, the term "detective fiction" gives the author license to totally ignore standard procedures and techniques used by detectives, the term "military fiction" allows the author to totally ignore military tactics and strategy, and the term "historical fiction" allows the author to totally ignore the relevant history.

Imagine a historical fiction novel where Napoleon at Waterloo defeated the knights of the Round Table by using the Enola Gay to drop an atom bomb. It's OK because it is "fiction", right?

This non-argument is the favorite of science fiction fans who like all the zipping spaceships and ray guns but who actually know practically nothing about real science. And who cannot be bothered to go learn.

What good is identifying the asteroid that will kill us all?

Do you have the same attitude when crossing the street?

Why exactly are we going to the moon again? As a launch platform for mars? How about we use that other launch platform we have.. you know, earth.

The same reason we don't use your mom as a launch platform, because of the enormous gravity well.

Surface to Orbit

Orbit to ground bombing (AKA "Rods from God") has been explored by the science fiction writer Jerry Pournelle. Project Thor is just a concept for now but it seems like it would work at least in theory. Here are a couple pictures, pic 1, pic 2, and a second article The Rods from God .

This is probably one of the few threads where this meme is on topic. To put this in perspective we are probably the native american indians greeting the european explorers. And we know how well that turned out for them.

That's assuming they're more advanced than us. But if they're more advanced then us, than in all likelyhood it wouldn't be like indians meeting europeans at all! If we're exceptionally lucky it'd be like our present day society meeting the cro-magnum.

Sir Arthur C. Clarke made a famous observation about space explorers discovering aliens. If one considers the millions of years of pre-history, and the rapid technological advancement occurring now, if you apply that to a hypothetical alien race, one can figure the probabilities of how advanced the explorers will find them. The conclusion is "we will find apes or angels, but not men."

Why? Consider the history of Planet Earth. Let the height of the Empire State building represent the 5 billion year life of Terra. The height of a one-foot ruler perched on top would represent the million years of Man's existence. The thickness of a dime will represent the ten thousand years of Man's civilization. And the thickness of a postage stamp will represent the 300 years of Man's technological civilization. An unknown portion above represents "pre-Singularity Man", the period up to the point where mankind hits the Singularity/evolves into a higher form/turns into angels. Say another dime. Above that would be another Empire State building, representing the latter 5 billion years of Terra's lifespan.

If you picked a millimeter of this tower at random, what would you most likely hit? One of the Empire State buildings, of course.

http://www.projectrho.com/rocket/rocket3aa.html#apesorangels

Seriously.

Remember all those underground nuclear bomb tests that were all the rage?

Now you can direct your anger toward the stars!

Other people have suggested textbooks, classes, government websites and boring stuff like that, so I'll skip those and suggest something fun instead: The Project Rho Atomic Rocket page which has all kinds of cool hard-science stuff for hard-science fiction writers, all about atomic-powered rocketry and related subjects.

The chapter titled "Atomic Radiation" contains all the basic facts and figures you need to figure this stuff out, and lays out all the principles of shielding and exposure in a nifty, easy-to-understand format.
  ('Cause it's important to know how effective your Space Captain's trusty gamma ray blaster is at 100 meters.)

"Exploding a series of bombs under the rocket" actually works. It's called Project Orion, and you feasibly could send city-sized ships to Saturn with it. Later proposals used conventional explosives for the first blast, so there would be little fallout. Unfortunately, the thing's illegal (by the Partial Test Ban Treaty of 1963). The fallout would also kill ten people (globally) per launch, on average.

So that leaves internal engines. Yes, it's possible to make a nuclear rocket. It can either be solid core, liquid core, or gas core.

Solid core is your basic nuclear reactor mounted to a rocket. Heat the reactor up, pass hydrogen (or some other gas) through it, it heats up and goes faster out the other end. The problem is abrasion, and there's also a temperature limitation - if you run it too hot, the reactor melts and that's no good. The temperature limitation means that the rocket's limited to about 1000 seconds of specific impulse.

A liquid core reactor takes that lemon and makes lemonade. The reactor can't melt because it's already molten. With some sophistication, it's possible to make the reactor stable (spinning the mass in some way; I know too little about the details). Put hydrogen in one end, get superheated hydrogen out the other. But now that hydrogen drags with it some uranium too, and you get fallout galore.

The gas core rocket exists in two forms. The open gas core reactor is like the liquid core reactor, except now the uranium is gaseous. Even more uranium mixes with the hydrogen. This leads us to the closed gas core reactor, where the nuclear inferno is trapped inside a "light bulb" of quartz, which is almost transparent to the blackbody radiation in the temperature range in question. Still, that reintroduces temperature limits, but they're far more generous than solid core limits. Hydrogen (or the propellant, whatever it is) is introduced so that it flows on the outside of the quartz, gathering heat and speeding up.

According to this nuclear engine page, closed gas core reactors have specific impulse ranges of 1500 to 3000 seconds, and open gas core reactors have specific impulse ranges of 1800 to 7000s. In contrast, the Space Shuttle has a specific impulse of 450 seconds, and a jet about 2000 seconds. Note that I've only mentioned high-thrust engines; it's possible to make ion engines with extremely high specific impulse, but they'll be no good getting you to orbit, and it takes forever to accelerate in space using such engines.

Don't forget to add a few on the front of the ship as well, less you forget the The Kzinti Lesson: http://www.projectrho.com/rocket/rocket3x.html

No, mirrors will not work. The weapon will use internally a wide beam that is just barely under the intensity level that will damage the weapon's internal mirrors. At the barrel, the focusing mirror will focus the wide beam down to a searing pin-point on the hapless target. The focused beam will be more than intense enough to defeat any mirror the target might be wearing. I have some notes here: http://www.projectrho.com/rocket/rocket3l.html#laserpistol

Me too, old boom boom, AKA "Project orion" http://www.projectrho.com/rocket/orion3.gif, is just too much of an "OMFG they want to do WHAT!" to be forgotten.

http://www.astronautix.com/lvs/orion.htm

Hmmm, you're correct. The Atomic Rockets site shows that while a VASMIR can generate up to 400 Newtons in "low gear", it doesn't have a thrust to weight ratio even close to 1. Darn. I was hoping for a cool "Buck Rogers" style craft. In my excitement I forgot to check the thrust numbers.

So, any spacecraft using this method requires "a nuclear reactor, a VASMIR engine, a large amount (50-75% of the whole thing) of reaction mass, wings" and some means of getting it to orbit.

I do think I mentioned that space travel using our current level of technology bites...

Try this Atomic Rocket website for some more information on this type of engine outside of Wikipedia. What's interesting about this type of engine is that it's capable of trading thrust (what you want to liftoff) for Specific Impulse (what you want in orbit to get best reaction mass efficiency).

This is a pretty good site for information on all types of potential/possible/theoretical propulsion systems, and what it would take to do "real" solar system space travel. That being said, space travel (even within the bounds of just our solar system) via our current level of technology bites.

As someone else noted, this type of propulsion requires about 10MW of electrical energy to function. That energy is not provided by the propulsion system. Something else has to provide it in a compact, dense and energetic form- namely a nuclear reactor onboard the craft. That's why this type of engine shows up at the "Atomic Rocket" website, even though the engine itself doesn't use any nuclear reactions. Some people might not appreciate that the exhaust is not radioactive, as the power plant is just used for electricity.

Unlike a chemical rocket, a spacecraft using this engine would be able to get to orbit with some payload, and would not resemble "a disintegrating totem pole" getting there. Unfortunately, it also requires a nuclear reactor, a VASMIR engine, a large amount (50-75% of the whole thing) of reaction mass, and probably, wings.

Try this Atomic Rocket website for some more information on this type of engine outside of Wikipedia. What's interesting about this type of engine is that it's capable of trading thrust (what you want to liftoff) for Specific Impulse (what you want in orbit to get best reaction mass efficiency).

This is a pretty good site for information on all types of potential/possible/theoretical propulsion systems, and what it would take to do "real" solar system space travel. That being said, space travel (even within the bounds of just our solar system) via our current level of technology bites.

As someone else noted, this type of propulsion requires about 10MW of electrical energy to function. That energy is not provided by the propulsion system. Something else has to provide it in a compact, dense and energetic form- namely a nuclear reactor onboard the craft. That's why this type of engine shows up at the "Atomic Rocket" website, even though the engine itself doesn't use any nuclear reactions. Some people might not appreciate that the exhaust is not radioactive, as the power plant is just used for electricity.

Unlike a chemical rocket, a spacecraft using this engine would be able to get to orbit with some payload, and would not resemble "a disintegrating totem pole" getting there. Unfortunately, it also requires a nuclear reactor, a VASMIR engine, a large amount (50-75% of the whole thing) of reaction mass, and probably, wings.

A proton-proton fusion drive has an exhaust velocity of 12% c, so a proton-proton fusion Bussard Ramjet would have a maximum speed of 12% c. You may remember that a spacecraft with a mass ratio that equals e (that is, 2.71828...) will have a total deltaV is exactly equal to the exhaust velocity. So if a conventional fusion rocket with a mass ratio of 3 or more has a better deltaV than a Bussard Ramjet, what's the point of using a ramjet?

From here

Thomas Rigby told me this:

I remember reading a Popular Science article on the new features of the DD(X) project, one of which is the railgun. According to the article the railgun would fire a 40 pound projectile (about 18.2 kg) with a Mach 8 muzzle velocity and Mach 7 velocity at the target. A quick calculation (setting speed of sound a 343 m/s):

KE = ½ (18.2 kg) (2401 m/s)^2 = 52.46 MJ

KE = ½ (18.2 kg) (2744 m/s)^2 = 68.52 MJ

Which compares much more favorably as a weapon system. Derived values can easily be obtain close to these numbers

We'll take the average range, 225 nmi, for the calculations. Of course we can't just convert 225 straight to meters, since a nautical mile is a bit over 15% longer than a standard mile (about 6076 feet). After converting to miles we can go to meters (or go straight from nmi to meters, if your calculator has a bunch of built-in conversion factors):

1nmi = 1.151mi

225nmi (1.151nmi / mi) = 258.975mi

1mi = 1.609km = 1609m

x = (258.975mi) (1609m / mi) = 416690.775m

Real Value: 416700 m

Dividing by the time (6 min / 360 sec):

Vx = 416700m / 360s = 1157.5 m/s

Which s a far more appropriate velocity for a kinetic kill weapon. However, this is only part of the velocity. The railgun fires in a parabolic arc, getting almost 95 miles up. Assuming the Earth is flat, and the projectile is launched and lands at the same height, this part of the velocity component is easy to calculate. In theory the projectile reaches its maximum height half way through the journey, or at 3 min - 180 s. We can put this into the gravity-displacement equation to determine the speed. A height of 95 miles (500,000 feet) is about 152400 m.

h = -4.9t2 + vt -> v = (h / t) + 4.9t

Vy = (152400m / 180s) + (4.9 m/s2)(180s) = 1728.67 m/s

Now we can combine the two velocity components to determine the actual velocity, by Pythagorean Theorem.

VT = sqrt(1157.5^2 + 1728.67^2) = 2080.41 m/s

Which is much closer to the Mach 7 value that the Navy claims the projectile hits at. Using this value to calculate the kinetic energy:

KE = ½ (18.2 kg) (2080 m/s)^2 approximately 39 MJ

I have some excerpts from The Killing Star here.

First, it's "would HAVE", not "would of."

Second, I was replying to the notion (at least how I interpreted it) that we shouldn't bother with spaceflight until we get a bunch of new, more economical equipment. I was trying to get across that newer, better things don't come along just by sitting there and waiting for them. If you want an improvement, you're going to have to work at it and get experience. Paper studies don't translate into experience or hardware without a whole lot of elbow grease.

Third, it depends on how you define "rocket" as to whether they've reached their potential or not. If you mean the standard chemical rocket, the technology is about as efficient as it gets. If you start throwing in nuclear stuff, it gets more interesting. A nuclear thermal rocket (where a nuclear core heats propellant that then gets expelled) can reach twice the exhaust velocity of a high-end LOX/LH2 engine (like the shuttle's SSME). An overview of the more advanced propulsion concepts is here: http://www.projectrho.com/rocket/rocket3c2.html It gives a good summary of a bunch of concepts that are at least physically possible, though maybe not currently feasible or within our technology level.

Hohmann transfers are used because feeble chemical propulsion cannot produce the delta V required for a quicker transfer orbit.

Atomic Rockets

At the other end of the spectrum of transfer orbits are Brachistochrone trajectories. When the propulsion system becomes powerful enough to produce delta Vs higher than about 10 km/sec, you can treat the planets as being essentially stationary, that is, they will not move appreciably in the short time required for transit.

Hohmann transfers are used because feeble chemical propulsion cannot produce the delta V required for a quicker transfer orbit.

Atomic Rockets

At the other end of the spectrum of transfer orbits are Brachistochrone trajectories. When the propulsion system becomes powerful enough to produce delta Vs higher than about 10 km/sec, you can treat the planets as being essentially stationary, that is, they will not move appreciably in the short time required for transit.

This is NOT a HELL (high-energy laser lift) craft being blasted with a ground-based laser to create shockwaves, this is a photon drive like Niven uses in the Man-Kzin Wars books from time to time.
http://www.projectrho.com/rocket/rocket3c2.html#photon
Downside: "In other words, one lousy Newton of thrust takes three hundred freaking megawatts!!"
Until we're willing to shoot a nuke plant into space with a crew on the other side of a shadow shield and some damn big radiators... not gonna fly. Once we are willing, this baby's gonna fly.

Remember the Kzinti Lesson

a Reaction drive's efficiency as a weapon is directly proportional to it's effectiveness as a drive.

"is Margaret Thatcher modelling it?"

Who cares! Skin-tight space suits on fit, smart astronaut women?

That's every slashdotter's dream!

Bring on the skin-tight space suits Barbarella!!!

Dammit, if I would have known skin-tight spacesuits were really coming I would have studied Astro Physics and went for Airforce ROTC instead of comp sci :(

It's all discussed in the context of various real life and sci-fi gubs but if you go to about halfway down this page there's a pretty good analysis of the use of lasers as weapons.

The basic conclusion seems to be that the laser must be pulsed at a fairly specific frequency in order to do damage, and that some rather nice adaptive optics are needed to focus the beam on the target before it would work at all. The reason for the pulses is that each one would cause a small steam explosion tearing a relativly large hole, with sufficient time between each for the steam and debris to disperse

A large part of the problem with making effective man-portable laser weapons seems to be powering them, then again the laser rifle mentioned in the summery is not exactly lightweight

A lot of the Reagan/Bush Star Wars plans called for powering space lasers with nukes.

http://www.projectrho.com/rocket/

If I could force every Hollywood writer to spend a few hours reading before they scripted another line of "sci-fi", this is where I would send them all.

while staying within the bounds (albeit loosely) of "possible" scientific reality.

Yes, Heinlein really cared about his science ... and particularly his engineering and orbital mechanics. He actually did the orbital mechanics calculations whenever he mentioned specific figures in a story. (I.E. if he said "We burned at 1.3G for 5 seconds to insert into a station-keeping orbit" it generally meant he had actually done that math.)

However, nearly all of his stories depend on "torchships": ships with nuclear drive engines that have a combination of high thrust and high specific impulse that is extremely unlikely in the real world. The closest thing that has been proposed is Zubrin's Nuclear Salt-water Rocket which uses an aqueous solution of plutonium or uranium salt as both fuel and reaction mass, expelling this radioactive mixture out the back -- and a lot of physicists aren't even sure the NSWR could really work. It does have the charming feature of completely ruining the landscape underneath the launch site, which matches Heinlein's torchships pretty well.

There's a fantastic discussion of all this at a website called The Atomic Rocket, which collects in one place all the useful scientific information about space travel and ship design for anyone who is writing fiction or designing games.

For my money, it's the best damn geek site in the history of the web by a clear margin. (Though you have to be an old-school geek who thinks space is even cooler than computers.) Every few months I get sucked in and read the whole thing over again (and it's huge).

while staying within the bounds (albeit loosely) of "possible" scientific reality.

Yes, Heinlein really cared about his science ... and particularly his engineering and orbital mechanics. He actually did the orbital mechanics calculations whenever he mentioned specific figures in a story. (I.E. if he said "We burned at 1.3G for 5 seconds to insert into a station-keeping orbit" it generally meant he had actually done that math.)

However, nearly all of his stories depend on "torchships": ships with nuclear drive engines that have a combination of high thrust and high specific impulse that is extremely unlikely in the real world. The closest thing that has been proposed is Zubrin's Nuclear Salt-water Rocket which uses an aqueous solution of plutonium or uranium salt as both fuel and reaction mass, expelling this radioactive mixture out the back -- and a lot of physicists aren't even sure the NSWR could really work. It does have the charming feature of completely ruining the landscape underneath the launch site, which matches Heinlein's torchships pretty well.

There's a fantastic discussion of all this at a website called The Atomic Rocket, which collects in one place all the useful scientific information about space travel and ship design for anyone who is writing fiction or designing games.

For my money, it's the best damn geek site in the history of the web by a clear margin. (Though you have to be an old-school geek who thinks space is even cooler than computers.) Every few months I get sucked in and read the whole thing over again (and it's huge).