I can't believe I spent two hours watching this tripe.

[AZRedhawk44]

thousand-AU mission

What's so interesting at 1000 au?

I hear that the sun "lenses" so that incoming light and radiation from the part of the galaxy hidden behind the sun curves back in at around 550 au.  Of course, the Earth orbits the sun giving us a glimpse of radio transmissions hidden behind it as we move around it, so I'm unclear as to what is to be gained by finding the solar lensing focus point.

Given that Voyager 1 is 116 au from the Sun right now, moving at about 38,000 mph and about to exit the Heliosheath (and quite possibly suffer instrumentation failure from the change in the environment and our current unknown capability to maintain radio contact through such a transition), what is it you would like to learn at 1000 au that is so deep into "nothing?"

Don't get me wrong, I applaud the attempt, but I just don't understand the point of sending something to 1000 au if:
1. It's going to take 10+ years for it to get there
2. It's not going to be retrieved
3. It's not going to be manned
4. There's no resource out there to exploit
5. It's not capable of interstellar travel

[AZRedhawk44]

Help me here.

I thought there is no 'top speed' in vacuum?

In other terms, if I accelerated the spacecraft to the point of breaking orbit, wouldn't it keep going at the same speed until it came under the influence of an outside force?

His point is that VASIMIR and similar techs have lower acceleration, but also less infrastructure mass to accelerate and greater fuel utility.

When accelerating (whether VASIMIR, Orion, or chem rocket) you have to accelerate your payload, your fuel and your motor all at the same time.  The Orion pusher-plate is a liability.  That same mass can be spent on more fuel for a gentler source of motive power, that, while it is not capable of vertical orbital insertions, is capable of acceleration to escape orbit or exceed current typical chemical rocket speeds.

Once in space, dealing with a "space truck," a VASIMIR is a more efficient choice than an Orion.  Less nimble, probably.  But greater range and greater top speed.

[birdman]

Help me here.

I thought there is no 'top speed' in vacuum?

In other terms, if I accelerated the spacecraft to the point of breaking orbit, wouldn't it keep going at the same speed until it came under the influence of an outside force?

You are correct, but your time to get to the destination is a function of final velocity--the higher ISP, the longer you can deliver a given amount of thrust for a given amount of propellant (hence, units of seconds--time for one pound of thrust from one pound of propellant).  Orion delivered a significant amount of thrust, but it's ISP was lower than more modern systems--so they get more time at a given thrust, thus higher final velocity, shorter transit.  

[birdman]

What's so interesting at 1000 au?

I hear that the sun "lenses" so that incoming light and radiation from the part of the galaxy hidden behind the sun curves back in at around 550 au.  Of course, the Earth orbits the sun giving us a glimpse of radio transmissions hidden behind it as we move around it, so I'm unclear as to what is to be gained by finding the solar lensing focus point.

Given that Voyager 1 is 116 au from the Sun right now, moving at about 38,000 mph and about to exit the Heliosheath (and quite possibly suffer instrumentation failure from the change in the environment and our current unknown capability to maintain radio contact through such a transition), what is it you would like to learn at 1000 au that is so deep into "nothing?"

Don't get me wrong, I applaud the attempt, but I just don't understand the point of sending something to 1000 au if:
1. It's going to take 10+ years for it to get there
2. It's not going to be retrieved
3. It's not going to be manned
4. There's no resource out there to exploit
5. It's not capable of interstellar travel

It was primarily for ultra-long baseline astronomy.

It's also one step on the way to ultra-long duration missions--first was TAU, then IP, all steps to prove the tech--think mercury/gemini/Apollo type progression.

[AJ Dual]

Honestly, for right now Orion as much as I love the numbers is a political/economic dead-letter. It would take a radical "F-U World" shift in policy to produce such a craft.

VASIMR is nice because the thrust can be tuned for high thrust, and high efficiency/specific impulse. (within reason and the limits of the design) I believe this makes it suitable for "break orbit" at high thrust/low efficiency, and then "cruise" (gaining speed all the way) at low thrust/high efficiency.

An ion engine has incredible efficiency and Isp, but low thrust.

The Saturn V has incredible thrust, but poor efficiency/Isp.

VASIMR has some ability to throttle and modulate it's output to do both as desired.

(ETA) woah, 6 replies, I thought you were busy birdman. 

[seeker_two]

It really comes down to this....if you were an intelligent, technologically-advanced, space-faring species traveling through the cosmos and discovered a backwater, low-tech world whose greatest technological advances are internet porn and APS, would you want to stop here?..... 

[birdman]

Honestly, for right now Orion as much as I love the numbers is a political/economic dead-letter. It would take a radical "F-U World" shift in policy to produce such a craft.

VASIMR is nice because the thrust can be tuned for high thrust, and high efficiency/specific impulse. (within reason and the limits of the design) I believe this makes it suitable for "break orbit" at high thrust/low efficiency, and then "cruise" (gaining speed all the way) at low thrust/high efficiency.

An ion engine has incredible efficiency and Isp, but low thrust.

The Saturn V has incredible thrust, but poor efficiency/Isp.

VASIMR has some ability to throttle and modulate it's output to do both as desired.

(ETA) woah, 6 replies, I thought you were busy birdman. 

I finished up my presentation for this week (design review on a new walk-a-way safe small nuke plant I'm designing for some investors), so I got a few minutes free :)

Yeah, VASIMIR is pretty cool, and with the lightweight solid state RF modules being built for AESA radars, it can be made pretty lightweight...after all, vacuum is easy to get in space, and the field strengths required aren't that hard (cryo is also easy once you are away from earth, just shield the magnets from local heat sources, and keep the sun off them and you don't even need a cryocooler--they use that technique for JWST, and it gets the mirror down to 20K I believe, which is well below the transition temp for high temp superconductors.  With all that, the biggest issue is the power source, and advanced reactor designs are within the ranges you need for most things.  As for fuel, well, technically, it will "burn" anything, but the lower the atomic weight the better.  Liquid hydrogen is a PITA to store for long periods, so ammonia is probably the best choice for extended durations (easily kept as a dense liquid, average atomic weight of the products is 4.25, low Z of nitrogen means low plasma losses, etc)

[Phyphor]

The Fithp from Footfall were the least advanced alien species conqueror I think I've ever heard of in sci-fi.  

Harold Turtledove's World at War series has an even worse species.

[birdman]

Harold Turtledove's World at War series has an even worse species.

Liberals?

[Phyphor]

Help me here.

I thought there is no 'top speed' in vacuum?

In other terms, if I accelerated the spacecraft to the point of breaking orbit, wouldn't it keep going at the same speed until it came under the influence of an outside force?

Actually, c is the top speed of objects in vacuum on this side of the c line, (tachyonic objects are hereby disregarded)
 

[Phyphor]

Liberals?

No, The Race - basically anthropomorphic lizards carrying assault rifles.  Their space fleet could only get up to about .5c and had nukes and such, but the other species they fought were all basically sword bearing barbarians.... their probe found some guy on our world in chain mail carrying a sword so they thought we were the same.  Unfortunately, hundreds of years later, it was WW2 and they came in and decided to try and conquer.

It's a worthwhile read, IMO

[Tallpine]

It really comes down to this....if you were an intelligent, technologically-advanced, space-faring species traveling through the cosmos and discovered a backwater, low-tech world whose greatest technological advances are internet porn and APS, would you want to stop here?..... 

How would we feel if we destroyed an anthill in Africa ?

 

[RocketMan]

This has been an absolutely fascinating read, gentlemen.  APS has got to be one of the premier sites on the web, considering incredible variety of talent that exists here.
By the way, did anyone else that watched the program notice John Ringo was one of the 'experts' that was interviewed?

[AJ Dual]

No, The Race - basically anthropomorphic lizards carrying assault rifles.  Their space fleet could only get up to about .5c and had nukes and such, but the other species they fought were all basically sword bearing barbarians.... their probe found some guy on our world in chain mail carrying a sword so they thought we were the same.  Unfortunately, hundreds of years later, it was WW2 and they came in and decided to try and conquer.

It's a worthwhile read, IMO

It was indeed a good read. The Race was essentially a huge McGuffin/Foil for the way Turtledove wanted to play with WWII, but it largely worked.

You found yourselves cheering for the Germans at times, having the best tanks and the aliens had one really nasty moment when one of their larger ships anti-missile systems proved less than effective on a 16"-class artillery shell. Ooops.

Then the Germans reminded you who the Nazis were when they sent out concentration camp survivors to gather up all the uranium/plutonium they could find from the alien ship.

The Race was actually a rather decent occupying power, provided no one fought back. They were certainly better than German or Japanese occupation.

The later books in the 1960's where the aliens have been fought to a standstill, in charge of Poland and a buffer area between the Third Reich and Germany, and have Africa and South America (they like it hot anyway) are confounded by a three way war in China, and the Middle East is getting messy...

The Germans, Americans, and Russians all have nuclear armed space programs facing off with the aliens in a four-way cold war.

Unrealistic in the premise, (even for Sci-Fi) but well executed and thought out in the details like most of his work.

[seeker_two]

How would we feel if we destroyed an anthill in Africa ?

Then again, would you travel all the way to Africa to destroy an anthill?.....


....well, maybe Obama would..... 

[HankB]

. . . You found yourselves cheering for the Germans at times, having the best tanks and the aliens had one really nasty moment when one of their larger ships anti-missile systems proved less than effective on a 16"-class artillery shell. Ooops.

Uhhh . . . Not to nitpick, and it's been a while since I read the books, but I thought the artillery was a bit larger . . . either the "Gustav" or "Dora" railroad gun, that had an 800mm (30.5") shell. IIRC, the standard projectile for these guns weighed about 8 tons . . . 

[AJ Dual]

You're right. I just remember it was a big artillery shell.

[HankB]

Harold Turtledove's World at War series has an even worse species.

What about H.G. Well's Martians? Arrive in giant cannon shells, have a heat ray (laser?) and poison gas, "may have" discovered flight (!) and, well, that's about it.  Well's Martians who were so formidable to a Victorian military would have posed little challenge to a modern mechanized Earth army. (Which is why the ones Tom Cruise & Gene Barry faced in their movies were given impenetrable force fields.)

Or consider Harry Turtledove's "Roxolani" in his short story, The Road Not Taken. Their early discovery of gravity control sent them on a quest to conquer the galaxy, but their weaponry was lacking.

[TommyGunn]

What about H.G. Well's Martians? Arrive in giant cannon shells, have a heat ray (laser?) and poison gas, "may have" discovered flight (!) and, well, that's about it.  Well's Martians who were so formidable to a Victorian military would have posed little challenge to a modern mechanized Earth army. (Which is why the ones Tom Cruise & Gene Barry faced in their movies were given impenetrable force fields.)

Or consider Harry Turtledove's "Roxolani" in his short story, The Road Not Taken. Their early discovery of gravity control sent them on a quest to conquer the galaxy, but their weaponry was lacking.

Give Wells a break, he couldn't possibly have known about phased plasma rifles in the 40 megawatt range in 1899.

[AJ Dual]

H.G. Wells gets tons of extra credit points for even coming up with the idea, and the whole microbe angle was pretty clever/edgy for its day.

I suppose his thinking was that such a dry, cold, and austere world as Mars was relatively sterile. Silly to think now, because with ecosystems as we know them beginning and ending with the microbes, and as the hardiest survivors of all, should mean the Martians knew of the risks, but that was not common knowledge back then.

"Germ theory" as a cause of disease was still relatively new.

Or the lack of bacteria and pathogens could be seen as a symptom of Mars dying and what forced their hand to invade Earth as a last ditch effort to save their race.

Hell, it could STILL happen, even to us, or some other race. For instance, say some race that evolved around a red giant or red dwarf, likes temperatures around the boiling point of water, and has lots of sulfur compounds in their biology. Because of their home star, they see in light from red, into the IR range, and they've never ever imagined that bacteria smaller than 600nm were possible. (Unless they used full spectrum, or blue/green light (like harsh UV to them), or electron microscopes... they couldn't even detect them.)

And the filters on their bio-suits to explore Earth are 1-2 microns. (1000nm)

There's plenty of archea and deep-sea trench, and geothermal spring bacteria that would love to much on them...