Physics of Star Killer Base

If you haven't seen the latest Star Wars ("The Force Awakens", episode 7), stop reading immediately! :)


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Apparently, there has been some griping about the physics of Star Killer Base.

For example, if the planet can't move, and even one shot substantially drains their sun - then you've only got a few shots from your super-weapon (not to mention everyone on the planet will freeze).

Also, if the weapon drains the whole star, then it is really massive overkill (about 12 trillion times according to one site).


There is a much more reasonable explanation!


The photosphere is the region of the Sun which emits visible light.  The key idea is "It [the photosphere] extends into a star's surface until the plasma becomes opaque"

If you strip off the photosphere, then the star will appear opaque i.e. black (at least, until it regenerates).

Ok, so how much energy can you get from the photosphere (we'll assume the Empire, err, First Order, has sufficient tractor beam and shield technology to extract it quickly and safely).


All of my calculations are in a Google Drive spreadsheet.


Final result?  Yes - there's about 1700 times more power than you need to blow up one planet just from fusing the hydrogen in the photosphere into helium (you could get more power by fusing up to iron).


And how rapidly could you fire such a weapon?

I'm not sure of the fluid dynamics, but keep in mind the regions of the photosphere last about 8 minutes (they are upwellings of cooling plasma).  Which implies it might recharge very rapidly indeed!

Crowdsourcing your brainstorming

Back in the days of Mudge, it was easy to brainstorm an idea like industrial applications of black holes.

Now, it's harder.

I figured I would make use of the largest collection of nerds that I know about - Reddit (seeing as how Slashdot has gone down the tubes).

Reddit is divided into groups, and finding the right one can be somewhat of a challenge.

The most direct would be /r/AskScience, since it is really a science question (or, applied science).  But they take a dim view on science fictiony things.

There is also /r/AskScienceFiction, which sounds perfect.  Except, everything there is in role-playing form (it should be /r/AskLARP or something).  There are other more conceptual/design subreddits, but they are all low traffic.

So, I just had to ask my question in a RP fashion, and try and make sense of RP answers.

The answers weren't spectacular.  But I must give credit to /u/Sriad for the best one.  I had thought about using extreme matter compression, but I was thinking of something like a diamond press (which would not be forceful enough).  Treating it more like a fusion bomb makes a lot of sense.

Blackhole Applications

I've been trying to work through some of the implications of constructing and using artificial black holes.

It's particularly interesting, because the numbers are very constrained: either you get a lot of power for a short time (and light mass), or less power for longer time (and high mass).

My latest problem is dealing with increasing power over the lifetime.  A hole which is going to last 20 years, will deliver 66% more power after just 10 years (and things start to get out of hand after that).

I see several possibilities:

1. Design for final power - with longer lasting holes, this isn't too bad.  An 800 year hole (6.7e8 kg) will produce just 10% more power after 100 years.  But with our 20 year hole, you are significantly underpowered (or over-engineered) for most of your usable life.
2. Refit over time - either transplant the hole into a new hull every once in a while, or perform deep reconstruction every few years.  This seems possible, but you need to make sure you don't miss a refit!

This also brings up another issue: disposal (or recharging) of holes.

When a hole hits about 2.28e5 kg, the lifetime is roughly 1 second - that's 2e22 J released in one second (so, Watts).

Basically an enormous bomb (almost 5 million megatons of TNT).

Easy disposal is to chuck the thing into the sun before it gets to this point.  But that needs to be included in the cost - you're building up a lot of energy which you are going to throw away.

"Recharging" would require putting mass back into the hole (which is likely pouring out gigawatts of hard x-rays and gamma rays).  Not an easy task.

Solar Germany

A fascinating post from Ars:

"That has rocketed from an installed capacity of 6GW in 2008 to 25GW in 2011—amounting to half the world's installed solar power, with 7.5GW installed in that year alone."

The article has some interesting data about the bulk price of electricity, but I was startled by these numbers.

I recently heard Germany was going to shut down all their nuclear reactors.  I figured they were on a trend to freeze to death just before the lights go out (I'm pessimistic like that :)

From Wikipedia:

"The installed nuclear power capacity in Germany was 20 GW in 2008 and 21 GW in 2004."

So recent solar panel installations have nearly replaced nuclear.

That is a _lot_ of solar panels.  There are a lot of factors, but there is only about 1 KW/m^2 to work with (and efficiency should cut into that hard).

Or, at least 25 million square meters of panel!

US production from solar? 0.9 GW (2010) - yay us.

Peak Civilization

(a recent article at CNN has got me all depressed)

A few years ago the drumbeat of "peak oil" picked up. Now, it seems to be mostly taken as a given. With the recent Japanese nuclear disaster (among other things), I can't help but think we have reached "peak civilization".

Early science fiction (1900, up to the 60's, even parts of the 70's and 80's) was decidedly optimistic (although not entirely). Mankind was seen as making use of greater and greater stores of energy, and going far. Stories assumed galactic civilization (some took place after many cycles of rise and fall of galactic empires).

At some point, something changed. Perhaps it was the nuclear accidents of the 70's and 80's, or the failure of fusion power. The failure of the space program (which we now see the culmination of, in the last shuttle flights - which will end the American manned space program). Science had promised us the stars, and failed to deliver.

Now, the spectre of global warming is pushing back against greater carbon based energy production. The Fukushima disaster will likely hinder, if not stop nuclear production. Green sources are notoriously inefficient, in terms of land use and construction overhead - they might replace our current production, but growth will be limited.

Science fiction has picked up on this ennui (I don't think it has caused it). Stories of galactic empire are few and far between (John Scalzi is the only current writer I know). Most stories tell of introspective and decadent remnants of humanity, living in dirt (at least, metaphysically, if not physically).

Much of our economy is based on an assumption of growth. It's unclear how we can adapt (we see this in the repeated "bubble" growth and pop cycles). Even population growth is leveling off.

Asimov wrote about computers stretching underneath the whole world (plantary AC). Now, we strive to make computers smaller and less powerful.

It seems we are destined to simply fizzle out. Staring at our belly buttons until the lights go out.

Aerostats

Interesting news article I found in my archives:

"This so-called graphene sealed microchamber is impermeable to even the tiniest airborne molecules, including helium."

Fiction involving nanotechnology often has objects called "aerostats", basically floating machines (usually equipped with fans or jets for movement).

If the balloon wall is impermeable to most atmospheric gases, then the balloon might be able to be "filled" with a vacuum (assuming air pressure won't collapse it). Making it the best lighter-than-air material.

Liberty Ship

I forget where I first saw this... I was poking around on the Internet a couple of years ago, and found a lot of good stuff, this was probably in there. (Related to the Project Rho site, which I've mentioned before).

The Liberty Ship is truly impressive, something for our generation akin to the Saturn 5 rocket. A shame it will probably never be built...

I wanted to run some of the numbers, because I keep getting them jumbled (stupid units):
Mission mass: 2.722e6 kg (6e6 lbs)
Dry+empty mass: 7.258e5 kg (1.6e6 lbs)

The power is given as 80 GW, and the fuel mass flow is 178 kg/s. That translates (via ve = sqrt(2E/m)) to 29,981 m/s exhaust velocity (which matches well with the given 30k). That power sounds high, I will probably examine that in a separate post.

Thrust is ve * fuel mass flow, which yields 5.337e6 N (which roughly corresponds to the given 1.2e6 lbs, if 4.4N=1 lb force - which is what Google implies).

The biggest problem I ran into was finding the right delta v for LEO. Project Rho gives it as 11,180 m/s (before aero and grav drag). Wikipedia gives it as 7.8 km/s without drag (and 1.5-2 km/s drag).

The other problem is the total thrust is very low. With 7 engines, thrust is 37.357e6 N. Dividing that by the loaded weight (mission mass) gives an acceleration of 13.726 m/s^2 (1.4 g's). This will cause a very long lingering in the Earth's gravity well (rockets often use 10 g's for liftoff).

I'm not certain how to calculate the gravity drag. Project Rho gives vd = vo / a, which seems to allow for any velocity. It seems unlikely that any acceleration below 1 g can ever escape, but perhaps I am wrong...

Regardless, this gives us v_drag of 5,575 m/s - which cuts heavily into the given mission dv of 15 km/s (perhaps that is the intent). It is unclear what effect a lifting body has in these figures...

One alternative is to increase the fuel flow (to increase thrust, and decrease linger time). Unfortunately, this cuts into ve. The mass ratio (full mass divided by dry mass) is equal to exp(delta v / exhaust velocity) (that's the natural number, e, to the x power).

So any drop in exhaust velocity has an exponential effect on the mass ratio, which drives up propellant mass, which drives down cargo mass.

You can drive ve back up with engine power, but ve is the square root of power, so half ve must be made up with 4x power...

We're On Pluto

I have been catching up on the newsgroup rec.arts.sf.science. There was an interesting interchange on Project Pluto.

Now, when some people think of Pluto, they think of the ninth planet (yes! a planet! My Very Excellent Mother Just Served Us Nine Pizzas). More, probably think of Mickey Mouse's dog.

Of course, Pluto is the Greek god of Hades/Death/the Underworld. That is probably the inspiration for this thing:

• 75 foot long; 60,000 pound
• nuclear ramjet, cruise missle bus
• 26 nuclear warheads

The second point needs some explaining.

• ramjet - flies by compressing incoming air, this requires a fair amount of air to work at all - end result - it cannot fly slower than the speed of sound (it would be launched using solid rocket boosters, and could never land)
• nuclear - the incoming air is heated by being directly exposed to an unshielded, operating nuclear plant. This means the exhaust is highly radioactive.
• cruise - designed to fly close to the ground (about 1000 feet)
• missle bus - a missle that carries missles (the 26 warheads)

This thing (designed circa 1960!) would follow terrain using pre-constructed radar maps, shattering glass and damaging walls and roofs as it flew to its target - all the time irradiating everything it flew over. It would then pop out a nuke, which would detonate seconds later (Pluto flies just under one mile per second, so it is already miles away). Once it was out of nukes and losing power, it could be crashed into a secondary target (60,000 pounds at Mach 4, plus highly radioactive).

Magnum 360 said: "Thank you very much thats exactly what I was looking for. Wow thats amazing it had the possiablity of staying up in the air for months, to bad the project was stopped."

To which, Mike Ash says: "Too bad the unshielded and unfiltered airborne nuclear reactor with no ability to land after launch was stopped??!!"

This is pretty incredible work (terrain following using vacuum tubes?). Also, the sheer gall of the thing (spewing out radioactive exhaust). Of course, this was the same age which planned to blast a mountain into space using nuclear bombs!

You have to admire their sense of scale and boldness. Today, we are so safety conscious - we'd never do anything approaching this scale. It seems like there should be some middle ground...

Black Hole Catalyzed Total Conversion

That has a nice ring to it. Kind of like "Laser Induced, Gravity Sustained Fusion Reactor".

Weird chain of events: a Slashdot article discussing the physics of space war. Leads me back to Project Rho, re-reading the sections on stealth and heat dissipation. Somehow, I ended up on stardestroyer.net, reading about the Death Star power system (I remember something about the importance of heat dissipation, and how Luke might not have had the impact he thought he did). Someone (maybe there, maybe elsewhere) mentioned the possibility of using black holes to convert matter to energy (this was in the context of a system failure not producing a tremendous boom, at least in comparison to the enormous power output before the failure [the Death Star is assumed to produce more power than Sol - blowing it up could easily wreck a solar system - that is, Yavin or Endor, places the heroes were supposed to be protecting]).

I decided to sit down and actually look at what it would be like to have a black hole around for energy conversion.

The idea is actually pretty simple, you feed matter into a black hole (presumably one already electrically charged so you can keep a handle on it). You then harness the Hawking radiation (HR) for energy.

There are several properties of black holes which make this not entirely unreasonable:

Power output (via HR) is inversely proportional to the square of the mass of the hole.

That means every (log) step down in mass, you go up two steps in the power of your reactor! Smaller holes give more power! It also means the black hole will likely not fail-big, but rather fail-evaporate (giving off a huge amount of energy). A small hole (2e10 kg) would produce about 1e11 W. Making it a little smaller (2e8 kg) would yield 1e15 W (probably too much to get rid of...)

Size is proportional to mass

This has good and bad points. A small hole is really small. 2e10 kg being about 3e-20 m (3e-11 of 1 nm) This means you won't accidentally fall in. But it also means you have to try very hard to get matter into the thing to keep it going.

Lifetime is proportional to mass cubed

This is kind of annoying, but the constants make it ok. A small hole (2e10 kg) would have a lifetime of about 21 million years. It does mean that your initial hole (unless you have a really big accelerator) is going to decay fast.

Actually, with a lifetime like that, it's effectively a battery, with no fuel input. A super small hole (2e6 kg, only two million kilograms!) would have a lifetime of 662 seconds! Definitely a problem, especially considering it is giving off a constant 1e19 W! Don't get burned!

People worrying about the Large Hadron Collider producing black holes shouldn't worry. The energy levels are way too low to produce a hole with any meaningful lifetime. It also means we will need a much larger collider (or better production methods - huge lasers?) to produce commercial black holes.

Steam INNN SPAAACE!

So, I've been thinking about the space elevator, mostly about powering the climbers. Everyone seems to be backing laser power (using ground based lasers to shine on solar panels on the climber).

And, I've been reading Ken Macleod's "Fall Revolution" books, which have "steam launched spaceships". I read them completely out of order, so I never got any details. There is a little in "The Space Fraction".

After looking into it more, I found an excellent source. "Steam" propulsion is somewhat of an exaggeration. The recommended propellants are hydrogen and nitrogen. Water is possible, but not optimal.

But pretty cool, for small scale, high volume launch capacity.

Aluminum + 1000 resources

= Space Elevator! (thank you Civ 4). Of course, if you build in in the city with the Iron Works (excellent Texas barbecue results in double resource output!), it's only 500 resources; a good city can do that in ten or eleven years.

I've been following discussions on building a space elevator for some time now. I was surprised to see CNN discussing it!

There are two primary challenges connected with building a space elevator:

1. The cable (or tether) - Spans 100,000 kilometers from the surface of the earth, up past geosynchronous orbit (the center of mass is at the geosynch point)
   
• This cable need not be one single piece. This is a confusion many people have ("We can't build a carbon nanotube that long!!111eleven!").
• The cable need not be of super materials (100% carbon nanotubes, positronium, etc.) You can make it out of bubble gum, although you'd probably need enough to alter the center of mass of the earth-moon system :)
• Better materials translate into less mass for the initial tether. That means fewer rockets to get all the materials into space.
• Once the initial tether is up, the first cargo can be more tether, to increase the capacity of your elevator (and build new ones).
  
2. The cars (or climbers)
• The tether does not move, instead, the cars pull themselves up or down.
• The climbers are actually the hard problem!
• They must travel the hundred miles or so into the edge of space, and possibly, the 36,000 km to geosync orbit (especially if they are going to be used to add on to the tether).
• It is unlikely we will want to carry enough fuel for a 36,000 km journey (at 200 mph, that's about a five day trip - one way).
• That means we need a means of power distribution to generate power on the ground, and get it to the climbers (most likely lasers and solar panels).
  

The dangers of the space elevator (terrorist attacks on the base, the tether, or the geosync station) are largely exaggerated. Breaking the tether would cause pieces of it to burn up or fall to earth. It is relatively small, and would do little damage. If the base were destroyed, the tether would slowly rise (there is slight pressure up, to keep the tether tight).

The hazard to lower orbiting satellites is more than offset by the increased launch efficiency. (There would need to be a workforce assigned to pushing satellites out of the way, or a way to shift the tether around them - such a shift might even be useful in dodging meteors or terrorist suicide attacks).

The good news is that the space elevator used to be considered a tech level 9 or 10 achievement. It appears, it will be completed easily within the tech 8 time frame.

What is Nuclear Fusion?

Normal matter (stuff) is made up of atoms. These atoms (normally) are made up of protons (positive particles) and neutrons (neutral particles) in a "nucleus", and surrounded by electrons (negative particles). The negative particles repulse other negative particles, while attracting positive particles. The positive particles act in the opposite manner.

In nuclear fusion, very high temperature and pressure are used to squeeze nuclei together. When done to lighter elements (hydrogen - 1 proton, and boron - 5 protons, are favorites), energy is released.

Nuclear fusion holds great potential for cheap, plentiful energy. Hydrogen and boron are very plentiful fuel sources. It is not free from radioactive concerns. Different forms of fusion involve different amounts of radioactive materials (inputs and byproducts). Some are somewhat higher than current fission reactors. Some are less.

The sun is an existence proof for fusion power. There, huge pressure is available due to gravity (the hydrogen is compressed to 150,000 kg/m^3). This allows fusion to occur at a relatively low temperature - 13.6 million degrees. At this temperature, the hydrogen gas becomes "plasma" - the fourth state of matter (after solid, liquid, and gas). In a plasma, the electrons are separated from their nuclei, and the whole thing can be manipulated using electromagnetic fields (very convenient for us).

A typical commercial power planet produces around 1 gigawatt (1 billion watts). Using fusion as the sun does would require 170 billion tons of hydrogen, in a cube-shaped reactor 1 mile on a side (and it would have to sustain the enormous pressure and heat of the sun).

Obviously, some innovation is required to make fusion power work here on Earth. The most promising current projects are:

1. Tokamak - this is the most well funded type of project. A big donut-shaped container, surrounded by magnets, is used to hold the fusion plasma.
2. Laser inertia - powerful lasers push two nuclei together directly. This is how fusion bombs work.
3. Polywell - this design was championed by Robert Bussard (of Bussard ramjet fame). Unfortunately, Dr. Bussard died recently. The project is continuing without him.
   

Tech Level 8 Approaching!

"What do you mean, 'Tech Level 8 approaching?'"

"On a Hawkman rocket cycle. Shall I inform his majesty?"

"Idiot! The emperor would shoot you for interrupting his wedding with this news!"

(with apologies to Flash Gordon)

GURPS uses the concept of tech levels running from 1 to 16. There is a general, societal tech level, but it can also be broken out into categories like power generation, medicine, motive systems, etc. When GURPS was originally written (~1980's) first world nations were described as tech level 7.

So what is predicted for tech level 8?

1. Computers are about 10 time more powerful. The GURPS authors beat themselves up a lot over this. Computers are probably thousands or millions of times more powerful from a frequency/number of transistors point of view. But from a functionality point of view, it's not too bad.
   
2. Human cloning. This one looks on target.
   
3. Prosthetics/Bionics. I think we are close on this one. The war in Iraq has been a big driver just in the last few years. We are getting pretty close to full functionality and look for prosthetics.
4. Robots. I forget the exact capabilities for TL 8. But we are getting pretty good here. Things like humaniform and combat robots are not until TL 9 or 10.
   
5. More efficient in-system space travel. I think the development of ion engines has made this possible. There is also some cool ideas in fission driven (but non-radioactive exhaust) rockets. Unfortunately, I doubt governments will do much innovation. The private sector might have some effect (but would they be allowed to develop a fission rocket?).
   
6. Fusion power. Ahh, fusion power. Always twenty years away. One of the first things I researched on the world wide web (back in 1998). I'll look into this more depth.