The Hundred Gram Mission (11 page)

"But when you tank up, do you wonder about how much weight, the gas
itself
adds?"

"What? No!"

"Exactly. What goes into your tank weighs so little, you don’t even consider it. But what if you needed to drive across to the East Coast, and there were no gas or charging stations on the way. You’d have to take all your gas with you. Maybe get a trailer with some tanks."

"Okay. Sorry, I still don't see your point."

Henrikson smiled. "Doesn’t the trailer add weight? Are you getting the same mileage, pulling all that fuel, behind you? Aren’t you using more gas, just to pull along gas?"

Sam was no fool.  "So a nuclear Pathfinder would be burdened with its own fuel?"

"A
fission or fusion
Pathfinder would be burdened. The mission would be possible, Mr. Snyder. It just wouldn’t be practical. The ship would be a monster, and I don’t want to design a monster anymore than anyone else will want to pay for one. What is practical, is using antimatter."

Spektorov cleared his throat. All eyes went to him.

"Doctor, isn't antimatter fuel a 100% efficient? Cause I've been looking through your group’s notes, and it seems you guys can't decide."

"Yes, most people think it's 100% efficient. It is when an electron meets its own anti-particle, the positron. But, this is not the case with all antimatter. For example, when an antiproton meets a proton. Then, only part of that system becomes energy. The rest, becomes other particles.
[xx]
"

"So we want the first case? 100% conversion into energy?" asked Sam.

"No. Full conversion is a bad idea, because energy isn’t the same thing as thrust.  We want better efficiency from the fuel, sure. But we also need something coming out the exhaust for the ship to push against. 

"With total conversion, you just get gamma rays. They’re high energy and go in all directions. You can’t really deflect them either –not practically. And if you did, the ship would soak most of it, as heat."
[xxi]

"So let me review here," said Spektorov. "Fission and fusion can do the job, but are too inefficient. Antimatter can too, but is
too
efficient?"

"Essentially. However, different engine designs give different results. We simply need an engine that balances efficiency and thrust."

"Is there such a design?" asked Spektorov.

"As a matter of fact, yes. Remember I said with protons-antiprotons, you get mostly particles?"

"Sure," lied Sam.

"That’s what the ‘beamed core’ design
[xxii]
uses. The collisions create charged particles, among others. A powerful magnetic field pushes the opposite, charged particles, out as exhaust.  These particles leave at close to light speed. The process is ten times more fuel efficient than fusion."

He pulled up a new slide of an engine diagram. Colored field lines and moving arrows showed flow. "Gentlemen, this is the beamed core rocket. The best efficiency
and
the best thrust, for the Pathfinder mission."

The other scientists and engineers smiled, as did Henrikson. Someone started to clap, but stopped when no one joined.

Sam made a face.

"
Really
? I’m not impressed. You want us to fund an engine that’s never been made? With a fuel that needs explaining?"

The team lost their smiles. 

"Why are you bothering with fuel at all?" Sam continued. "You could just use a light sail. Build and operate a laser beaming station near the sun. It could run for a few months and then you’re done. Light sail tech already exists, and it's getting cheaper. Just yesterday Mitsubishi announced they’ll be putting up a commercial beaming station."

"Mr Snyder, you
have
done your reading," Henrikson smiled and nodded appreciatively. "But how big do you think a light sail would need to be to get to Alpha Centauri?"

"I don’t know. Big?"

"Huuuge?" ventured Spektorov.

"Certainly. Let’s say the a probe that weighs a metric ton. Now, a tenth of light speed is the fastest we can safely go.  Faster, and collisions with interstellar dust and gas become too dangerous. At this speed it’s a forty year trip. With me so far?"

"Go on."

"That sail would have to be four kilometers in diameter. The beaming station’s output would have to be sixty five gigawatts.
[xxiii]
Gigawatts
, Mr. Snyder. And that’s just a flyby, it wouldn’t stop."

"It can't?"

"Not without another beaming station at Alpha Centauri, to slow it down.  Well, it is possible to slow it down, using only a laser from Earth. But the sail would need to split into two. And your energy needs would go into the hundreds of terawatts. Thousands if you want to send a bigger mission. The world uses about 20 terawatts, a year.
[xxiv]
"

"You worked out those numbers?" asked Sam.

"No, but I’ve done my reading too, Mr. Snyder. These are Robert Forward’s numbers from back in the 1980s. People have been trying to solve these problems a lot longer than we have. You are correct, light sailing is an old and mature technology. Also, the engineering is much simpler than what we’re proposing."

"If it's still somehow simpler, then isn't it the way to go?" asked Spektorov.

"The problem is the time window. A beamed core rocket needs a window long enough to get underway. That's it. After that, politics becomes irrelevant. The rocket will arrive, whether or not Earth cares.   With light sailing though, long term support is critical. Someone needs to flip the switch on the second station, forty years later. Someone needs to
build
the second station. Will they succeed? The second laser could destroy countries. Do you think it's existence would be tolerated? We can’t guarantee that. No one can. That’s why we ruled it out."

"So is that it, then?" asked Spektorov. "We need to build a beamed core rocket?"

"
Later
. We need make antimatter first, specifically antiprotons."

"And how do we do that?" asked Spektorov.

"There are all kinds of ways, all of them terrible. We even considered harvesting antiprotons from the magnetospheres of gas giants.
[xxv]
What we kept coming back to, were particle accelerators."

"Like CERN?" asked Spektorov.

"Yes. They create antimatter as a byproduct. Not much though: CERN will produce a gram – in a hundred billion years. However, an accelerator can be custom-built to produce more antiprotons. For best results, we want to smash heavy metal ions –Lead, Thorium, ideally Uranium."

Bad things happen when you collide Uranium," said Spektorov.

"Only if you want it to. The colliders would be small – just a hundred meters in diameter. Antimatter production would be massive. As much as a gram a week.
[xxvi]
"

"That doesn’t sound like a lot, Doctor."

The scientists exchanged knowing looks and one giggled. "Mr. Spektorov, one gram of antimatter is an unheard of amount. An amount as powerful as forty
kilotons
of TNT.
[xxvii]
That’s twice what we dropped on Nagasaki. Sun Star Mining would become a nuclear power."

Spektorov and Sam sat up, and looked at each other.

"But is it safe?" asked Sam. 

"Of course not. The nuclear waste produced will be considerable, and deadly. It’s one reason it hasn’t already been done, on Earth."

"How much Uranium would we need?" asked Spektorov. He turned to Sam, "we can talk to the Department of Energy. I know the Secretary."

"You will need far more Uranium than the United States will ever give you, or any country for that matter. Uranium is ideal, though more common elements like Thorium or even Lead will do. It will just take longer, and you will need more accelerators."

"Doctor,
how much
Uranium?"

"Depends on the mission. At a tenth of light speed, and then slowing down," Henrikson made scale balancing motions, "right now, we’re estimating a kilo of antimatter, for every kilo of payload. That will change as we do research and develop the technology. Right now, everything is speculative."

Spektorov looked up, running numbers. Then, the life sagged from his shoulders.

"But we can still get the Uranium, more than enough of it," Henrikson smiled.

"No one will give us the quantities needed, you said it yourself," said Sam.

"That’s because no one has the quantity,
that we already have
."

The wall screen hologram changed to a slowly spinning asteroid.

"This is 2043 QR 3. It is a metal-rich, Near Earth Asteroid. It was visited eight years ago by Sun Star micro probes."

"Why am I only hearing about 2043, now?" asked Spektorov.

"Probably because it’s worthless. 2043 was found to be rich in heavy elements, particularly Uranium.
[xxviii]
No one much cared at the time. The world was switching over to Thorium nuclear and solar power. Uranium was not a growth mineral, on Earth or in space. It still isn't."

"How much Uranium does it have?"

"It’s a piece of failed planet, Mr. Spektorov. It's estimated to be between five to fifteen percent, Uranium."

"I've never heard of anything like this."

"It's like floating, platinum mountains. No one has found those asteroids yet, but statistically, they exist. It is all you will need for not just one mission, but hundreds. And it already belongs to the company."

Sam clapped Spektorov on the back, and they grinned like school boys.

"There are problems, however. While 2043 QR 3 does orbit the Earth, it is a very wide orbit."

"So? Let's move it," said Spektorov. "We've done it before."

"With high ice-content asteroids. 2043 has no ice; we would not be able to mine and make rocket fuel on site. It is has almost no volatiles, so we can't even use lasers to steer by flash-boiled geysers. Moving it closer to Earth will not be cost effective."

"It orbits us, right?" asked Sam. "Why does it matter if it's far away?"

"Protection of the Earth’s magnetosphere," said Spektorov.

"Yes," Henrikson nodded. "Without that, it becomes a very dangerous place to live and work. There are currently no orbitals beyond the Earth's magnetosphere, for just this reason."

"What about underground?" asked Sam. "Just dig a bit."

"Yes, but the asteroid itself is radioactive, Mr. Snyder. But let’s set this aside. Consider how far away 2043 is. From Earth, there isn’t a Sun Star mine you couldn’t reach in three days. 2043 however, will take twenty days by ion drive."

"Ion drives can go a lot faster," said Spektorov.

"An ion drive could get you there in two days, Mr. Spektorov. However, that is not economical. Twenty day assumes a tenth of a pound of thrust. It’s a much more realistic figure. After a three week trip, how long does the engineer stay? It would be too expensive to send him back soon. A year though, would be a good tour. What PhD astronaut would spend a year underground, on hostile 2043? Even if nothing went wrong, they would take a lot of radiation."

"Money talks, we’ll find people."

"Can you find a thousand? Now we’re coming to the biggest problem," Henrikson’s shoulders seemed to sag slightly. "The problem of scale. Let’s say the mission is only half a ton - the mass of a compact car. We would need 500 kilograms of antimatter.
[xxix]
If we built
500
colliders, we would need to run them for five years."

Sam laughed, it was an evil sound. "So this is the big solution you’ve been building up to, all this time? 500 machines smashing Uranium on a distant, hellish, asteroid? For years? "

Mr. Snyder," Henrikson began stiffly, "they can be built more economically than you may think."

"And how is that?"

"By investing in new technology. Von Neumann machines, specifically."

"Are you
fucking nuts?
"

"Sam, settle down!" Spektorov frowned.

"No, no, the best of ESA here wants us all to get arrested for doing banned research, and building a
weapon of mass destruction
."

"Yes, Mr. Snyder. Banned research."

"I’m sorry Doctor, am I missing something here?"

"You are, in fact. Mr. Snyder, we are trying to send an expedition to another star. Immense infrastructure. Technologies that do not exist yet. Unreasonable goals.   Did you not think to expect these things?"

Sam opened his mouth to speak, but Spektorov held up his hand.

"Mr. Spektorov, if you want enough Uranium colliders, you are going to need Von Neumann machines: devices that build more of themselves. You’ll need them at Centauri too, to build the actual colony. How else can you manage given the cost of even the tiniest payload?" he stopped and put on his glasses. "Both of you, please understand this. Nothing about this mission profile, or any other, works without Von Neumann machines.
Nothing
. It's like when we went to Mars. The astronauts had to make air and fuel, in situ. Or as when Amundsen went to the South Pole, living off the land while Scott starved."