Rockhound: I USED TO HAVE A NEIGHBOR THAT TENDED TO SAY STUFF A LOT LIKE THAT WHEN I WAS A KID.
Iceman: WELL, AS LONG AS THEY'RE OVER THERE AND WE'RE OVER HERE, I'M NOT TOO WORRIED.
Frosty: FROSTY CHECKING IN. I'M HEADING BACK WITH A FULL LOAD OF VOLATILES BUT NOTHING SPECIAL. MAN, ALL MY LIFE I'VE WANTED TO GET A CALL FROM ET. AND NOW HE TELLS US TO GO TO HELL? WHAT DID WE EVER DO TO HIM?
Rockhound: HEY, FROST, GOOD TO HEAR FROM YOU. MAYBE OLD ET HAS BEEN PICKING UP OUR TELEVISION BROADCASTS. EVEN I FIND SOME OF THOSE PRETTY OFFENSIVE.
Wiener: WIENER CHECKING IN. MAMA TOLD ME NOT TO ARGUE ABOUT RELIGION, SO I'LL STAY OUT OF IT. I'LL BE FILING A CLAIM WHEN I GET IN. OUT.
Iceman: WE'LL BE LOOKING FOR YOU, KID. DECIDED TO OPEN THAT SANDPAPER FACTORY AND SETTLE DOWN?
Searcher: ANY OF YOU GUYS EVER DO THE CALCULATIONS ON HOW FAR OUT YOU COULD PICK UP A BROADCAST TELEVISION SIGNAL? IT'S PRETTY DISMAL. AT TWENTY LIGHT-YEARS, YOU'D NEED THIS HUGE HIGH-GAIN ANTENNA ABOUT THE SIZE OF A PLANET, AND IT WOULD HAVE TO BE DIRECTED STRAIGHT AT US, SCANNING A BROAD RANGE OF FREQUENCIES. AND YOU STILL PROBABLY COULDN'T EXTRACT ANY INFORMATION FROM THE SIGNAL. WE SETIZENS HAVE BEEN LOOKING FOR A SIGNAL LIKE THAT FOR OVER A CENTURY. EVERY FEW DECADES WE PICK UP A SNIPPET OF SOMETHING THAT LOOKS LIKE A SIGNAL AND THERE'S A LITTLE EXCITEMENT, BUT WE'VE NEVER GOTTEN ANYTHING CLEAR, CONTINUOUS, AND UNAMBIGUOUS. NOT UNTIL THIS SIGNAL CAME BLASTING IN. I'M WONDERING IF MAYBE THEY PICKED UP OUR RADAR PINGS, FROM ALL THE MAPPING WE'VE BEEN DOING OUT HERE.
Iceman: SO HOW COME THIS IS SO STRONG IF OURS WOULD BE SO HARD TO DETECT?
Searcher: BEST GUESS, THEY'VE GOT A HIGH-GAIN ANTENNA THE SIZE OF A PLANET POINTED AT US, AND THEY'RE CRANKING A FEW BILLION WATTS OUT OF IT. AND WE'VE GOT A BUNCH OF DECENT-SIZED DEEP-SPACE ANTENNAS POINTED AT EVERY HABITABLE-LOOKING STAR WITHIN ABOUT SEVENTY LIGHT-YEARS, WITH SOME FAIRLY SOPHISTICATED LISTENING EQUIPMENT ON EACH ONE. WE DON'T KNOW WHAT THEY DETECTED, BUT THERE IS NOT MUCH DOUBT THE MESSAGE IS MEANT FOR US, BECAUSE IT IS DEFINITELY BEING BEAMED STRAIGHT AT US. BIG PART OF MY MISSION IS TO COMPARE SIGNAL STRENGTH HERE TO MEASUREMENTS WE ARE GETTING AT THIS DISTANCE AT RIGHT ANGLES. ITS COMING RIGHT DOWN OUR THROATS HERE IN THE VICINITY OF RENDEZVOUS, STRAIGHT FROM THAT LITTLE YELLOW STAR OVER YONDER, RIGHT TOWARD OUR LITTLE YELLOW STAR, WITH THIS OUTPOST RIGHT ON THE LINE, GIVE OR TAKE A FEW HUNDRED MILLION KILOMETERS.
Rockhound: STILL SOUNDS LIKE MY NEIGHBOR. IT SEEMED TO OFFEND HIM THAT WE JUST EXISTED.
Searcher: LATEST UPDATE. THEY DECIDED TO TAKE “LOOK THIS WAY” LITERALLY. THEY CALLED SOME FRIENDS AND PUT A BIG TELESCOPE ON IT, AND THEY SEE A NEW CLASS OF OBJECT THEY CAN'T UNDERSTAND, RIGHT IN THE GLARE OF THAT STAR THE SIGNAL IS COMING FROM. VERY HOT GAMMA RAYS. THEY'RE ASKING TO GET ONE OF THE LARGE DEEP-SPACE ARRAYS TRAINED ON IT TO SEE IF THEY CAN GET A BETTER LOOK. CALL ME PARANOID, BUT I'VE GOT THIS CREEPY FEELING THAT MAYBE ET HAS LAUNCHED SOME KIND OF DOOMSDAY WEAPON. A BIG BALL OF ANTIMATTER MAYBE? IT SOUNDS LIKE IT IS PRETTY FAR OUT, BUT WHO KNOWS? GUYS, I'D LIKE YOU TO BE READY IN CASE THEY ASK US TO DO SOMETHING LIKE SETTING UP TO TAKE MEASUREMENTS OR EVEN MOUNT SOME KIND OF DEFENSE.
Rockhound: COUNT ON ME.
Iceman: RENDEZVOUS 3 STATION IS AT YOUR DISPOSAL.
Violet: VIOLET CHECKING IN. YOU BOYS KNOW I ALWAYS DO WHATEVER I'M ASKED.
Frosty: ANYTHING YOU NEED, ASK.
Crusty: CRUSTY CHECKING IN. I'M PRETTY FAR EAST. YOU HAVE MY COORDINATES IN CASE I'M IN A POSITION TO DO ANYTHING.
Stinky Pete: STINK CHECKING IN. I'M NORTH A COUPLE OF AU. AT YOUR DISPOSAL.
Searcher: I'M TRANSMITTING THE ENCRYPTION KEY FOR THE SETI LEAGUE MESSAGES. I HEREBY MAKE YOU GUYS HONORARY MEMBERS. FEEL FREE TO READ MY MAIL.
* * * *
The core passed thru the Oort cloud nearly three thousand times before it crossed paths with an ancient, pristine, primordial snowball. The icy body was large, sufficiently so to be round and to have formed differentiated layers. It might arguably pass as a Pluto-class dwarf planet by some definitions. It was about to change to a classification all its own.
Neither body was moving especially fast relative to the other, and their feeble gravities accelerated the approach only a little. The collision was gentle by astronomical standards. The core plunged into the snowball virtually dead on, lodging near the center. Displaced ice propagated ahead of the core, and ejected a shower of icy chunks on the opposite side, much as a bullet hitting a ripe melon might eject a spray at the exit wound. The remaining energy of the collision became heat, not a great amount, but to a body used to hovering near absolute zero, it was like being stabbed with a hot poker. Gas spewed from the fissures as the material around the core melted and boiled.
The object froze again within a few millennia, preserving scars that would be unchanged in a billion years.
* * * *
Victor crosschecked the readings from the borebot with those from probes he had dispatched to orbit El Dorado. Despite an unexplained background neutrino noise, he could tell exactly where the core was, and it was a beauty. The ice it was buried in was a bonus, not a nuisance, for, although volatiles were relatively plentiful in the Cloud, the distance between bodies was hardly trivial, and nobody likes to haul water from a distant well. Some miners liked the shielding deep ice provided.
The borebot was nearing the core, grinding through hard ice that now produced odd pieces of rock and metal. He slowed its pace as the sensors indicated that there were only a few meters to go. The sampling instruments displayed a forest of new peaks.
"EDS shows iron, nickel, aluminum, copper, yada, yada, gold, silver, platinum, the works! It's like getting a chemistry set for Christmas. I am so disgustingly rich."
The robot panel beeped and he looked at the display. “Starting to make contact. Okay, stop boring and just clean up with the lasers. Nice and easy."
The borebot finished exposing the metallic core, then backed off to allow the surface to be imaged. Victor studied the image proudly, his eyes glancing to the piece in his hand for comparison. The texture was amazingly similar. The shape ... His eyes focused on one spot of the borebot's field of view, and he leaned closer to be sure. He traced his finger around one feature of the image.
"Borebot two, zoom image to the indicated area. Scan holographically. Okay, now cut a forty centimeter core at the indicated position, depth ten centimeters, and transport it to the surface."
He held the piece in his hand up at arm's length, and compared it again to the image. “Can't be. That would just be too weird for words."
* * * *
Searcher: ALL NET ALERT! THE LATEST TRANSLATION IS IN. “CORRUPTION OF CREATION, ABOMINATION OF THE WORD, LOOK THIS WAY. THE HYDROGEN SUCKING LIGHT-CHASER COMES. SEE YOUR DAMNATION APPROACH, UNSTOPPABLE. YOU ARE TO BE CONSUMED IN THE FIRE OF YOUR OWN STAR. OUR OBLIGATION TO WARN IS FULFILLED. PREPARE TO DIE.” THE SETI LEAGUE SAYS THEY ARE NOW CHECKING WITH EVERYONE THEY KNOW TO SEE IF “HYDROGEN-SUCKING LIGHT-CHASER” MIGHT MEAN A BUSSARD RAMJET.
Violet: SO YOU WERE RIGHT. THEY DID LAUNCH SOMETHING AT US. DO YOU SUPPOSE THEY CAN ACTUALLY TARGET EARTH FROM THAT FAR AWAY?
Iceman: OH, NICE. THEY'RE GENOCIDAL MANIACS, BUT AT LEAST THEY'RE ETHICAL!
Rockhound: WHAT'S THIS ABOUT A BUSSARD RAMJET? I THOUGHT THOSE WERE JUST SCIENCE FICTION GADGETS. AND I THINK I ALSO READ THAT THE IDEA WOULD NOT WORK. SOMETHING ABOUT EXCESSIVE DRAG.
Searcher: NEGATIVE, ROCKDOG. ACCORDING TO MY DATABASE, THE IDEA WAS PUBLISHED BY DR. ROBERT W. BUSSARD IN 1960, IN A SCIENTIFIC JOURNAL CALLED Astronautica Acta. BACK IN THE LAST MILLENNIUM, THERE WERE A FEW PAPERS ON FLAWED DESIGNS THAT COULDN'T WORK, BUT THERE IS STILL SERIOUS WORK GOING ON IN THE FIELD. GIVE ME A MINUTE TO READ THIS.
Rockhound: I LIKE YOUR ANTIMATTER IDEA BETTER.
Searcher: ROCK, THE LATER STUDIES DETERMINED THAT THE DRAG OBJECTION CAN BE OVERCOME IF THE ENGINE DOES NOT ACTUALLY BRING THE HYDROGEN UP TO SHIP SPEED. A WORKABLE VERSION WOULD USE RELATIVISTIC FLOW DYNAMICS TO COMPRESS THE FUEL EXTERNAL TO THE SHIP AND CAUSE IGNITION, SOMETHING LIKE A SCRAMJET
.
Rockhound: SO WHY HAVEN'T WE BUILT ONE?
Searcher: WE STILL DON'T KNOW HOW TO BUILD A REACTOR THAT FUSES ORDINARY HYDROGEN TO PRODUCE USEFUL ENERGY.
Iceman: WHAT ARE WE LOOKING FOR AND HOW DO WE STOP IT?
Rockhound: WHAT ABOUT ANTIMATTER? WOULDN'T AN ANTIMATTER ROCKET ALSO “CHASE LIGHT"?
Searcher: I'VE GOT ANOTHER MESSAGE COMING IN. ROCK, AN ANTIMATTER ROCKET STILL OBEYS THE ROCKET EQUATION. TO APPROACH LIGHT SPEED AS CLOSELY AS A RAMJET CAN, THE FUEL TO PAYLOAD MASS RATIO WOULD HAVE TO BE PHENOMENAL, AND THE PROJECTILE WOULD BE A FEATHERWEIGHT BY THE END OF THE FLIGHT. A RAMJET WOULDN'T LOSE MASS; IN FACT RELATIVITY SAYS IT gains MASS. MAYBE A LOT OF IT. BUT THERE'S ALSO A HYBRID DESIGN, ONE THAT USES ANTIMATTER FUEL BUT SCOOPS UP HYDROGEN TO REACT AGAINST IT AND SERVE AS REACTION MASS.
Rockhound: THERE YOU GO; MAYBE WE'RE BOTH RIGHT. BESIDES, WITH ANTIMATTER, IT DOESN'T MATTER IF IT IS GOING FAST, IT'S JUST BAD NEWS IF IT TOUCHES YOU.
Searcher: OKAY, THE NEW MESSAGE IS IN. THE ABSTRACT SAYS THEY HAVE CONFIRMED THAT THE SPECTRUM OF THE NEW OBJECT IS CONSISTENT WITH BROADBAND THERMAL EMISSIONS, IONIZED HYDROGEN, AND ELECTRON/ POSITRON ANNIHILATION, BLUESHIFTED TO 0.992 C.
Rockhound: I HATE TO SAY I TOLD YOU SO, BUT SEE, ANTIMATTER! IF WE CAN SEE IT, WE SHOULD BE ABLE TO STOP IT. ANY CHUNK OF MATTER WOULD DO THE JOB.
Searcher: POSITRONS DON'T NECESSARILY MEAN IT'S AN ANTIMATTER PROJECTILE. PROTON-PROTON FUSION WOULD HAVE TO BE THE FIRST STEP IN USING PLAIN HYDROGEN FOR PROPULSION, ASSUMING THEY USE FUSION AT ALL. MOST OF THE USEFUL ENERGY FROM P-P FUSION IS FROM A POSITRON THAT IS EMITTED WHEN ONE PROTON CHANGES TO A NEUTRON. AND READ MY TRANSMISSION AGAIN ... THAT'S 99.2% OF THE SPEED OF LIGHT! I THINK THAT THING IS AN INTERSTELLAR RAMJET. AND I'M NOT SURE WE can STOP IT. GIVE ME A MINUTE OR TWO TO DO SOME NUMBER CRUNCHING.
Rockhound: YOU CRUNCH, I'LL CATCH UP ON MY RAMJET READING.
Searcher: YEAH, JUST AS I FEARED. LET'S SAY WE CAN SEE THIS AS A TINY SPECK AT ONE LIGHT-YEAR AWAY. AT THAT SPEED, IT WOULD BE LESS THAN THREE DAYS BEHIND THE LIGHT. IT IS A LOT CLOSER THAN IT APPEARS. A lot! I DON'T THINK THERE WOULD BE TIME TO REACT. DAMNATION, THIS INFORMATION IS AT LEAST 3.3 DAYS OLD DUE TO THE TRANSMISSION TIME. WE'RE CLOSER TO THIS THING THAN EARTH, BUT WE'RE WORKING ON OLD DATA.
Iceman: HOW FAR AWAY ARE THEY SEEING IT WITH THAT BIG TELESCOPE?
Rockhound: IS THAT THE TELESCOPE THEY'VE BEEN USING TO SPOT EARTH-SIZED PLANETS AROUND STARS?
Searcher: THEY DON'T HAVE A DISTANCE YET, BUT IF IT REALLY IS GOING THAT FAST, IT WILL APPEAR TO GET BRIGHT FAST. MAYBE WE DON'T NEED A TELESCOPE WITH A 10-KILOMETER APERTURE ANY MORE. EVERYBODY, YOU KNOW THE STAR WE'RE GETTING THE TRANSMISSION FROM. PUT YOUR TELESCOPES ON IT AND SEE IF YOU SPOT SOMETHING THAT SHOULDN'T BE THERE. I KNOW ALL YOU PROSPECTORS HAVE FANCY SPECTROMETERS. CAN ANY OF YOU PICK UP HOT GAMMAS?
Iceman: THE STATION CAN. I KNOW WIENER'S SHIP HAS A GAMMA SCOPE, TOO, BECAUSE I INSTALLED IT MYSELF. I'M ON IT.
Frosty: I HAVE IT ON MINE.
Violet: I HAVE THAT CAPABILITY. I'LL HAVE A LOOK.
Rockhound: MINE'S BROKEN BUT I THINK I CAN FIX IT. SEARCHER, IF THE RAMJET IS ACCELERATING FOR THE WHOLE FLIGHT, THAT MEANS IT ISN'T GOING AT A CONSTANT SPEED FOR THAT WHOLE LAST LIGHT-YEAR. IT WOULD ACTUALLY BE GOING FASTER NOW. THERE WOULD BE LESS TIME THAN YOU THINK.
Searcher: I HOPE YOU'RE WRONG, ROCK, BUT YOU'RE ALMOST CERTAINLY RIGHT, AND WE BETTER PLAN THE FASTEST RESPONSE WE CAN SCRAPE TOGETHER. WE GOTTA GET A HEAD START ON THE DATA. I'VE BEEN LOOKING AT MY DATABASE, AND HERE'S WHAT I FIND. THIS JUST NUMBS MY MIND. BUSSARD'S OWN ANALYSIS OF THE RAMJET CONCEPT SAID IT WOULD PROBABLY MAX OUT AT ABOUT 99.9999% OF LIGHT SPEED. CAN YOU GET YOUR MINDS AROUND THAT NUMBER? LET'S BET THAT IS WHAT IT WILL BE DOING WHEN IT GETS HERE. HE ALSO DID A SPECULATION THAT A REALLY BIG RAMJET, AT THAT SPEED, COULD BE USED TO TRIGGER AN EXPLOSION OF A star, NOT JUST A PLANET. LET ME READ PAST THE ABSTRACT.
Stinky Pete: STINK CHECKING IN. I GOT TELESCOPES FROM LONG WAVE IR TO HOT GAMMA. THE GAMMA'S ONLY A HALF-METER APERTURE THOUGH.
Iceman: ANYBODY HEAR FROM WIENER? HE'S THE ONLY ONE WHO HASN'T CHECKED IN. HIS GAMMA SCOPE IS A POINT-EIGHT METER WITH A REALLY GOOD DETECTOR.
Frosty: I GOT A HOT GAMMA PINPOINT ON MY SCOPE ABOUT WHERE WE'RE LOOKING. REALLY DOWN IN THE NOISE AND NOT GOOD ENOUGH FOR A SPECTRUM YET. WHAT WAVELENGTHS WOULD WE SEE?
Violet: I THINK I JUST SPOTTED IT. VERY FAINT. I WOULDN'T HAVE NOTICED IT IF SOMEBODY DID NOT TELL ME IT WAS THERE. DO WE HAVE A TRAJECTORY YET?
Searcher: I'M SPEED-READING. HOPE I DON'T MISS ANYTHING IMPORTANT. BUSSARD'S SPECULATION WAS THAT AT FULL SPEED, THE RAMJET WOULD HAVE WHAT HE CALLED A FOUR-DIMENSIONAL TIME-ABLATION SHIELD. WHAT THAT MEANS IS BASICALLY THAT TIME IS MOVING SO SLOWLY ON THE RAMJET THAT IT DOESN'T EVEN KNOW IT HAS HIT A STAR UNTIL IT HAS PENETRATED ALMOST TO THE CORE, TO ABOUT 0.02 OF THE STAR'S RADIUS FROM THE CENTER. THE SHIP HAS ESSENTIALLY BEEN CONVERTING ENERGY INTO EQUIVALENT MASS EVER SINCE IT STARTED APPROACHING THE SPEED OF LIGHT, SO THE ENERGY RELEASED WHEN IT FINALLY VAPORIZES IS STUPENDOUS. STARS WORK BECAUSE THEY HAVE VERY STABLE STEADY-STATE COMPRESSION FORCES BALANCED AGAINST RADIATION PRESSURE WORKING ON THEIR CORES, WHERE THE FUSION IS ACTUALLY TAKING PLACE. AN EXPLOSION OF THIS MAGNITUDE TOTALLY SCREWS UP THIS BALANCE. BUSSARD CALCULATED THE EFFECT OF THE RAMJET EXPLODING WOULD BE TO OVERHEAT A LARGE LOCAL AREA OF THE CORE, WHICH WOULD ESSENTIALLY UNDERGO SOMETHING LIKE A SUPERNOVA IMPLOSION. THAT, IN TURN, BLOWS UP THE STAR. A WEAPON LIKE THAT WOULDN'T JUST KILL EARTH, IT WOULD KILL EVERYTHING IN THE WHOLE SOLAR SYSTEM! DAMN, THESE GUYS MUST REALLY HATE US.
Rockhound: DAMN BUSSARD TO HELL FOR DREAMING THAT THING UP!
Searcher: ROCK, JUST A GUESS, BUT I'D BE WILLING TO BET GOOD MONEY THAT BUSSARD NEVER VISITED THE STAR SYSTEM THAT LAUNCHED THIS THING. IF NOBODY HAD DREAMED UP THIS IDEA, HOW WOULD WE EVER REALIZE WHAT THAT THING WAS AND MAYBE HAVE A CHANCE TO STOP IT? AND FURTHERMORE, IT TURNS OUT HE'S THE GUY WHO INVENTED THE P-B11 POLYWELL REACTOR THAT RUNS YOUR SHIP, AND WE MIGHT NOT EVEN BE UP HERE WITH A CHANCE TO DO ANYTHING IF NOT FOR HIM. ICE, YOU ASKED HOW TO STOP IT? BUSSARD FIGURED A 200-KM ASTEROID IN THE PATH OF THE THING OUGHT TO DO THE TRICK, IF YOU COULD INTERCEPT IT FAR ENOUGH OUT. THAT SHOULD DESTROY THE SHIP ITSELF, ALTHOUGH I SUSPECT THE FRAG COMING OFF THE COLLISION WOULD NOT BE TOO PEACHY TO BE AROUND.
Iceman: ASTEROIDS ARE IN SHORT SUPPLY OUT HERE, SEARCHER. WOULD AN ICE BALL OF EQUIVALENT MASS DO THE JOB? THE TROUBLE IS, THERE ARE ABSOLUTELY NO MASS DRIVERS OUT HERE LIKE THEY USE TO MOVE ASTEROIDS WITH. LET'S SEE, AN ASTEROID LIKE THAT WOULD BE, SAY, 5 X 1018 KILOGRAMS. SO, LET'S SAY WE HAVE 24 HOURS, FROM A STANDING START, YEAH, WE MIGHT MOVE A BODY OF THAT MASS ABOUT HALF ITS DIAMETER IF WE REDLINED THE REACTORS AND PUMPED REACTION MASS FROM THE BODY ITSELF.
Searcher: I'M HAVING A BRAIN FART GUYS. HONESTLY, I JUST PASSED GAS AND IT GAVE ME A WILD IDEA. AN INTERSTELLAR RAMJET IS DESIGNED TO COLLECT INTERSTELLAR HYDROGEN, AT SOMETHING LIKE MAYBE ONE ATOM PER CUBIC CENTIMETER, RIGHT? AND HYDROGEN IS ACTUALLY A PRETTY PATHETIC FUSION FUEL. IT IS HARD TO LIGHT OFF, IT'S THE REACTION RATE LIMITER IN STARS, AND IT ONLY PRODUCES ABOUT 1 MEV OF USEABLE ENERGY FROM THAT POSITRON. THE SAME SHOULD BE TRUE OF THE RAMJET. THE DEUTERIUM-DEUTERIUM FUSION CHAIN MAKES ABOUT 27 TIMES THAT, AND IT LIGHTS OFF A HELL OF A LOT EASIER! WE'VE GOT DEUTERIUM, AND WE CAN MOVE IT RELATIVELY QUICKLY. SO ANYBODY HERE UP TO CALCULATING WHAT WOULD HAPPEN WHEN YOU PUT A HUNDRED TONS OF DEUTERIUM, AND MAYBE SOME HELIUM-3 FOR GOOD MEASURE, AT MAYBE A MILLION TIMES THE DENSITY OF INTERSTELLAR HYDROGEN, IN THE PATH OF A MACHINE DESIGNED TO EAT AND BURN INTERSTELLAR HYDROGEN?
Iceman: SO YOUR HOPE IS THAT THE COLLECTION SYSTEM WILL DIRECT THAT SLUG OF FUEL INTO THE SHIP ITSELF, AND SET IT OFF? YOU'RE PROBABLY OVERSTATING THE YIELD A LITTLE SEARCHER. I SUSPECT ONLY THE FIRST STEP IN THE CHAIN WILL OCCUR. THE PROMPT D-D REACTION WOULD ONLY PRODUCE ABOUT THE ENERGY OF ... 2000 MEGATONS OF TNT. YEAH, THAT MIGHT JUST DO THE TRICK. IT WOULD BE LIKE DUMPING A LITER OF LIQUID NITROGLYCERINE INTO THE AIR INTAKE OF AN INTERNAL COMBUSTION ENGINE, TIMES TWO TRILLION OR SO.
Searcher: LET'S HOPE IT'S ENOUG
H. I'M TRYING TO COMPREHEND THE MASS AND ENERGY OF THAT RAMJET. THE DEUTERIUM EXPLOSION MIGHT BE NO MORE THAN A HICCUP IN COMPARISON.
Iceman: YOU MAY BE RIGHT. WE'RE THINKING NEWTONIAN PHYSICS. BUT IN RELATIVITY, F = M.A BECOMES F = g3.M.A. g IS THE LORENZ FACTOR, WHICH AT 0.999999 C IS 707. CUBING IT GIVES 3.536E+08. IT IS OVER 350 million TIMES HARDER TO AFFECT THIS THING'S SPEED THAN IT WOULD BE AT LOW VELOCITY! NO WONDER BUSSARD FIGURED IT WOULD TAKE SUCH A LARGE OBJECT TO KILL THIS THING.
Rockhound: I BELIEVE WE'RE ALL FLYING MARK III EXPLORERS. THE RESCUE POD IS THE WHOLE COCKPIT, COMPUTERS AND ALL. THE SHIP IS BRAINDEAD WITHOUT IT. WE CAN'T SET UP AN UNMANNED MISSION UNLESS WE CAN MAKE IT BACK TO RENDEZVOUS FIRST.
Searcher: THERE'S NO TIME ROCK. AND I THINK IT WOULD TAKE A MONTH TO PROGRAM THESE SHIPS TO DO A RELIABLE AUTOMATED INTERCEPT. ANYBODY GOT ANY QUESTIONS ABOUT THE MATH?
Iceman: TWENTY-ONE BILLION SOULS IN THE INNER SYSTEM, EIGHT OF US OUT HERE. DOESN'T TAKE A ROCKET SCIENTIST TO FIGURE THAT MATH OUT, SEARCHER. I JUST FOUND SOMETHING IN MY DATABASE. IT TURNS OUT THAT AN OUTFIT CALLED DRAPER LABS TOOK A SERIOUS LOOK AT THE RAMJET WEAPON IDEA. THEY CALCULATED THAT THE THING CAN'T TURN WORTH CRAP. IT HAS TO BE LOCKED ONTO ITS FINAL TRAJECTORY FROM SOMEWHERE BETWEEN 1 AND 1.5 PARSECS BEFORE IMPACT. THAT'S A MINIMUM OF 3.3 LIGHT-YEARS. WE'VE GOT THAT GOING FOR US. IF WE CAN DETERMINE ITS TRAJECTORY INSIDE THAT RANGE, WE CAN BET IT WILL STAY ON IT.
Rockhound: SAYS HERE THE SHIP MAY NOT BE A BIG TARGET, BUT IT COLLECTS FUEL BY PROJECTING A FIELD OUT IN FRONT OF IT, SORT OF A FUNNEL. THE WIDER THE FUNNEL, THE MORE AREA IT SWEEPS, THE MORE FUEL IT CAN GATHER. I'M SEEING ALL SORTS OF ESTIMATES FOR THE DIAMETER OF THE FIELD, BUT THIS RAMJET NEEDS TO BE VERY LARGE TO BE A STAR-KILLER. IT NEEDS ABOUT TEN SQUARE KILOMETERS OF SCOOP AREA FOR EVERY TON OF REST MASS OF THE SHIP. LET'S SAY IT IS AS MASSIVE AS AN OLD BATTLESHIP, MAYBE 60,000 TONS, THAT WOULD MAKE THE SCOOP DIAMETER SOMETHING LIKE 860 KILOMETERS. I KNOW THAT'S NOT VERY BIG COMPARED TO DISTANCES OUT HERE, BUT IT'S BETTER THAN HAVING TO HIT SOMETHING THE SIZE OF A SHIP, EVEN A BIG SHIP.
Analog SFF, October 2007 Page 16
