If you can read this, either the style sheet didn't load or you have an older browser that doesn't support style sheets. Try clearing your browser cache and refreshing the page.

(SeattlePI)   Okay, folks, that's as far and as long as we can imagine thrusting through space ... So, let's pack it in   (seattlepi.com) divider line 109
    More: Interesting, NASA, jabs  
•       •       •

11601 clicks; posted to Main » on 26 Jun 2013 at 6:10 PM (1 year ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



109 Comments   (+0 »)
   
View Voting Results: Smartest and Funniest

Archived thread
 
2013-06-26 05:08:12 PM
i.imgur.com
"I do believe that he said thrusting."
"You are correct. He then said pack it in."
"Heh."
 
2013-06-26 06:14:22 PM
It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?
 
2013-06-26 06:14:25 PM
/ Approves

netdna.shebudgets.com
 
2013-06-26 06:14:53 PM
FTA: "...can provide 30 million-newton-seconds of total impulse to the spacecraft."

images.sodahead.com
 
2013-06-26 06:15:07 PM
Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.
 
2013-06-26 06:15:12 PM
Get me two of those...
 
2013-06-26 06:15:20 PM
Ahm givin' 'err ahll she's goht cap'n!
 
2013-06-26 06:18:52 PM
One thing not mentioned, or if it was I missed it, did it have to be refueled, or is that on one "tank" or whatever?
 
2013-06-26 06:19:12 PM
upload.wikimedia.org

If only we had two of them...
 
2013-06-26 06:19:44 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


TFA talks about its use for scooting around the solar system, mining asteroids for crystals to make Sinibombs & such.  Doesn't sound like they plan to use it for a straight shot to the next star system right away.
 
2013-06-26 06:20:14 PM
Meh, most of my hard-drives have more hours than that thing.  One of my oldest I still use is sitting at over 67,000 hours and climbing.
 
2013-06-26 06:22:06 PM

UberDave: Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.


That's probably right.  These kind of engines are very low thrust, but very high efficiency.  If I ran the numbers right, that's a specific impulse of nearly 4,000s, which is fantastic.  Conventional rocket engines are in the 300-400s range.
 
2013-06-26 06:22:08 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


It's for constant acceleration. Would you rather inertia carry you slowly or constantly gain velocity so when you cut it off the inertia carries you more quickly?

UberDave: Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.


With such puny thrust, a NEXT-based ion drive would need to run for 10,000 hours - just over a year - to reach a suitable speed for space travel. Dawn, a NASA probe that's powered by previous-generation NSTAR ion thrusters, accelerated from 0 to 60 mph in four days. As a corollary, ion thrusters only work at all because of the near-vacuum of space; if there was any friction at all, like here on Earth, an ion drive would be useless. The good news, though, is that the (eventual) max speed of a spacecraft propelled by an ion drive is in the region of 200,000 miles per hour (321,000 kph).
 
2013-06-26 06:22:22 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


The longer you can accelerate the faster you go.
 
2013-06-26 06:22:23 PM
So, its kind of like you're with a gal and she's like "are you done yet?  I'm tired!"

Hail to my ion thrusters.  Yeah baby...
 
2013-06-26 06:22:31 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


Ion thrusters are ridiculously low thrust.  The only reason you use them is because they're high efficiency (so you can carry less fuel), but you have to fire them up over loooooong time periods to get any kind of actual velocity going.

So five years is probably not completely out of the ballpark, I wouldn't think.  Depends what you're planning to do of course.
 
2013-06-26 06:22:36 PM
It doesn't matter if they test it for five thousand years, this Administration doesn't give a crap about space exploration and we're not going anywhere meaningful for a long, long time.
 
2013-06-26 06:22:47 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


They don't have a hell of a lot of oomph, they are just stupid efficient. So if you want to go really fast with one you have to run it a long time. Fortunately, it can run a long damn time (obviously), and as far as I know it's about the only engine that will.
 
2013-06-26 06:23:14 PM
On 6 October 2007, Dawn turned on its ion engines and has been thrusting itself through the Asteroid Belt.

/Mind you, it did take a year off to take a lot of nice pictures of the asteroid Vesta
 
2013-06-26 06:23:27 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


You can continue increasing speed as you burn fuel.
 
2013-06-26 06:25:01 PM
What they didn't mention in TFA is that they're really shutting down the experiment because the device they used to monitor it can only operate for five years.  That's the problem when you use ionic pentameter.
 
2013-06-26 06:25:23 PM
So, did we find God?
 
2013-06-26 06:25:44 PM
The pelvic thrust will drive you insane.
 
2013-06-26 06:28:08 PM
Grumpy Cat:
So, did we find God?


What does God need with an ion propulsion engine?
 
2013-06-26 06:28:53 PM

dragonchild: What they didn't mention in TFA is that they're really shutting down the experiment because the device they used to monitor it can only operate for five years.  That's the problem when you use ionic pentameter.


Boooooo
 
2013-06-26 06:30:29 PM

dragonchild: What they didn't mention in TFA is that they're really shutting down the experiment because the device they used to monitor it can only operate for five years.  That's the problem when you use ionic pentameter.


userserve-ak.last.fm

//Sees what you did there.
 
2013-06-26 06:34:38 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


This type of an engine is designed to take advantage of exactly what you mentioned.  Just a few points to correct and inform:

1.  zero G (which doesn't really exist) has nothing to do with your ability to continue at a constant velocity indefinitely, the reason you can do that is due to conservation of momentum ("an object in motion will tend to stay in motion unless something acts upon it")  On Earth the thing that 'acts upon something' is friction due to atmospheric drag, or an object getting in the way (like the Earth itself).  The reason this works in space is due to the lack of an atmosphere and thus effectively no drag.  (In reality, there is some, but it might as well not exist for our purposes so we will just say 'no drag')

2.  These engine don't just work for a long time, they are VERY efficient.   Of course, due to With that in mind, the reason these engines are of interest isn't that you can get something somewhere eventually, but that they can get you there faster because they can convert more energy into thrust for a given amount of fuel.   Take 10kg of rocket fuel, and 10kg of fuel for these engines and these engines will produce more energy from those 10kg than the rocket.  More energy converted into useful thrust = faster (eventually)   It also means you can take advantage of a lot of things which wouldn't happen if you had to wait a long time for your spaceship to arrive at it's destination.   It also means you can have your spaceship go somewhere, and THEN go somewhere else.   With traditional rockets, we mostly just consider it a one way trip.
 
2013-06-26 06:34:57 PM

dragonchild: What they didn't mention in TFA is that they're really shutting down the experiment because the device they used to monitor it can only operate for five years.  That's the problem when you use ionic pentameter.


I'm not sure if this comment is really awesome or really awful...
 
2013-06-26 06:36:44 PM
Quick, somebody Pshop up an "Ionic" tag for this story.
 
2013-06-26 06:37:12 PM
That's an article?

*quote*

"good"
 
2013-06-26 06:37:59 PM

bingethinker: Quick, somebody Pshop up an "Ionic" tag for this story.


I had a greenlight back in the days of yore which used that joke
 
2013-06-26 06:38:11 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


So think about it this way.

You have a car.  It's a fairly pathetic little car with a 1 HP engine.  The good news is that there is no air resistance whatsoever so eventually you can accelerate up to plaid speed, you can go between any point A and any point B by a more or less straight line, and there's no traffic.

You need to get from LA to NYC.  Are you better off accelerating to 25, and holding it there, or accelerating as high as you can get in half the distance, flipping, and then decelerating the rest of the way?
 
2013-06-26 06:38:28 PM

Lochsteppe: Doesn't sound like they plan to use it for a straight shot to the next star system right away.


For actually getting out of the solar system, a gravity assist using Jupiter or (theoretically) a solar flyby is going to impart far more velocity than any possible ion engine.  However, efficient rocketry means we can line up those kinds of slingshots better.
 
2013-06-26 06:39:55 PM

adenosine: dragonchild: What they didn't mention in TFA is that they're really shutting down the experiment because the device they used to monitor it can only operate for five years.  That's the problem when you use ionic pentameter.

I'm not sure if this comment is really awesome or really awful...


Both?
 
2013-06-26 06:40:51 PM

Lawnchair: For actually getting out of the solar system, a gravity assist using Jupiter or (theoretically) a solar flyby is going to impart far more velocity than any possible ion engine.


Uhhh the maximum velocity a gravity boost can impart is the relative velocity between the spacecraft and the gravitational body.  Planets don't move that fast.
 
2013-06-26 06:41:34 PM

UberDave: Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.


Don't forget that acceleration increases as you use up reaction mass. With a 1000Kg starting mass and 230Kg final mass, plugging the numbers into the Rocket Equation yields something more like 333,500 km/s for the final velocity.
 
2013-06-26 06:41:54 PM
Make that between the destination and the gravitational body.
 
2013-06-26 06:47:14 PM
Something smells fishy here.  How do they know how long the next one will run for?  Hmmm?
 
2013-06-26 06:48:18 PM

adenosine: dragonchild: What they didn't mention in TFA is that they're really shutting down the experiment because the device they used to monitor it can only operate for five years.  That's the problem when you use ionic pentameter.

I'm not sure if this comment is really awesome or really awful...


Awfulsome.
 
2013-06-26 06:48:20 PM

JesseL: UberDave: Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.

Don't forget that acceleration increases as you use up reaction mass. With a 1000Kg starting mass and 230Kg final mass, plugging the numbers into the Rocket Equation yields something more like 333,500 km/s for the final velocity.


Can we quit with the km/s? The speed of light called and asked that you all slow down.

METRES per second, guys.

/
 
2013-06-26 06:49:46 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


The thruster provides very very little inertia. It takes a ton of time to get up to speed
 
2013-06-26 06:51:08 PM

ProfessorOhki: With such puny thrust, a NEXT-based ion drive would need to run for 10,000 hours - just over a year - to reach a suitable speed for space travel. Dawn, a NASA probe that's powered by previous-generation NSTAR ion thrusters, accelerated from 0 to 60 mph in four days. As a corollary, ion thrusters only work at all because of the near-vacuum of space; if there was any friction at all, like here on Earth, an ion drive would be useless. The good news, though, is that the (eventual) max speed of a spacecraft propelled by an ion drive is in the region of 200,000 miles per hour (321,000 kph).


Considering that the nearest solar system to ours is Proxima Centauri, which is 4.2 light years away...

So possibly 200,000mph, light year is 5.87849981 × 1012 miles...

I'd say pack a lunch. Maybe a few books.
 
2013-06-26 06:51:21 PM

opiumpoopy: JesseL: UberDave: Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.

Don't forget that acceleration increases as you use up reaction mass. With a 1000Kg starting mass and 230Kg final mass, plugging the numbers into the Rocket Equation yields something more like 333,500 km/s for the final velocity.

Can we quit with the km/s? The speed of light called and asked that you all slow down.

METRES per second, guys.

/


D'oh. Sorry about that.
 
2013-06-26 06:53:26 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


Not really no. Unless you really want the trip to take the maximum amount of time possible, you thrust for as long as possible for the first half and then reverse thrust for as long as necessary in the second half.
 
2013-06-26 06:57:50 PM
This runtime isn't actually that outlandish.  These types of engines are being put on geosynchronous satellites for station keeping.  GEO sats don't actually stay put exactly where you want them - the earth's gravitational field isn't perfectly uniform, 3rd body perturbations, solar radiation pressure, etc. all combine to mean that you need to regularly fire thrusters to maintain your orbital slot.  The amount of fuel these vehicles can carry to maintain this position is one of the primary limitations on their useful life.

The numbers I've heard indicate that the GEO sats with the ION thrusters fire them for 8 to 12 hours/day.  Combine that with a 15 year expected service life and you see that these engines could possibly exceed this test span - not to mention orbital repositioning burns and enough gas to graveyard it when you're done.
 
2013-06-26 06:59:44 PM

debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?


no
 
2013-06-26 07:00:49 PM

JesseL: opiumpoopy: JesseL: UberDave: Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.

Don't forget that acceleration increases as you use up reaction mass. With a 1000Kg starting mass and 230Kg final mass, plugging the numbers into the Rocket Equation yields something more like 333,500 km/s for the final velocity.

Can we quit with the km/s? The speed of light called and asked that you all slow down.

METRES per second, guys.

/

D'oh. Sorry about that.


No, you used the equation correctly and the proper units are km/s (for that expression of it).

It's just that it's a classical mechanics equation - never meant to be used for velocities that high.  It doesn't know about Einstein, so it happily exceeds the speed of light.
 
2013-06-26 07:01:28 PM

Flatus: It doesn't matter if they test it for five thousand years, this Administration doesn't give a crap about space exploration and we're not going anywhere meaningful for a long, long time.


Are you QA's new alt because everyone has ignored him? or a politics tab troll that got lost?
 
2013-06-26 07:02:31 PM

Cerebral Knievel: Flatus: It doesn't matter if they test it for five thousand years, this Administration doesn't give a crap about space exploration and we're not going anywhere meaningful for a long, long time.

Are you QA's new alt because everyone has ignored him? or a politics tab troll that got lost?


That's not a QA post.  That post implies that it would be worthwhile.
 
2013-06-26 07:02:39 PM
One explination was probably sufficient, but if anyone else would like to explain it again, feel free.

"the reason you can do that is due to conservation of momentum ("an object in motion will tend to stay in motion unless something acts upon it") "

That's what I said, inertia.
 
2013-06-26 07:05:22 PM
I still hold out hope that one day, a plasma-based ion thruster (that can actually operate in an atmosphere), will be efficient and powerful enough to use from the ground-up.
Once we get that, space-travel will be affordable for everyone; unfortunately right now, the engines are so low-thrust that friction in the air eliminates any point.  Also, most ion-engines simply won't work in an atmosphere, you need a vacuum to function.  I understand the magnetoplasmadynamic thruster designs, as well as the VASIMR engines, can actually operate in an atmosphere, but even they generate so little thrust there is no point.

Get this going guys with 100 times the current thrust levels, and space is an hour away in your average family (flying!!) car :)

/ May not actually be possible though.
// Goddamnit reality.
 
2013-06-26 07:06:37 PM
If someone has already mentioned this, i apologize.
Chemical rockets produce a shiat load of force for a short time. A chemical rocket accelerates hard until it reaches escape velocity, then spends most of its time in free-fall.
Ion drives (and the like) produce a very small amount of force, but can maintain it for much longer. Because of the very high exhaust velocity, ion drives can steadily wind up to staggering speeds, but might take several years to do so. An ion drive can't go from a planet's surface into orbit, but it can drive an interplanetary craft.
 
2013-06-26 07:08:30 PM

noitsnot: JesseL: opiumpoopy: JesseL: UberDave: Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.

...

It's just that it's a classical mechanics equation - never meant to be used for velocities that high.  It doesn't know about Einstein, so it happily exceeds the speed of light.


Oops - I goofed.  Your numbers are all crazy too, resulting in your huge velocity (but my point is still valid...)
 
2013-06-26 07:10:16 PM
Wizard Drongo: I still hold out hope that one day, a plasma-based ion thruster (that can actually operate in an atmosphere), will be efficient and powerful enough to use from the ground-up.

I think you'll be waiting a long time but fortunately scramjet/ramjet design is getting to the point where relatively efficient ground to orbit vehicles are probably not far off and from orbit you're halfway to anywhere
 
2013-06-26 07:11:00 PM

debug: One explination was probably sufficient, but if anyone else would like to explain it again, feel free.


They don't have a hell of a lot of oomph, they are just stupid efficient. So if you want to go really fast with one you have to run it a long time. Fortunately, it can run a long damn time (obviously), and as far as I know it's about the only engine that will.
 
2013-06-26 07:11:43 PM
Sounds like this would be the perfect engine to put in a spacecraft that would be launched by a mag-lev track. It actually seems like a perfect solution.
 
2013-06-26 07:12:42 PM
a.abcnews.go.com
"I've never seen anything like her. And ion propulsion at that. They could teach us a thing or two."

/hot ions, hot series and hot link.
 
2013-06-26 07:12:55 PM
30 million-newton-seconds

So what's that in pounds per square week?
 
2013-06-26 07:14:17 PM

Bob Down: 30 million-newton-seconds

So what's that in pounds per square week?


40 rods/hogshead
 
2013-06-26 07:19:16 PM
Be careful of your Furman derivation, especially if you're traveling several siriometers.
 
2013-06-26 07:22:07 PM

ProfessorOhki: The good news, though, is that the (eventual) max speed of a spacecraft propelled by an ion drive is in the region of 200,000 miles per hour (321,000 kph).



picturescrazy: debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?

You can continue increasing speed as you burn fuel.


That's all well and good, but if ProfessorOhki's numbers are right... how the heck would you be able to maneuver at that speed and what kind of craft would you need to avoid exploding from an impact with even debris the size of a pebble at that speed?
 
2013-06-26 07:25:00 PM

noitsnot: noitsnot: JesseL: opiumpoopy: JesseL: UberDave: Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.

...

It's just that it's a classical mechanics equation - never meant to be used for velocities that high.  It doesn't know about Einstein, so it happily exceeds the speed of light.

Oops - I goofed.  Your numbers are all crazy too, resulting in your huge velocity (but my point is still valid...)


Getting the numbers to embed in the URL correctly is a little awkward there. I tried again and got 212,869km/s.

/off to try to solve the relativistic rocket equation
 
2013-06-26 07:28:31 PM

JesseL: With a 1000Kg starting mass and 230Kg final mass, plugging the numbers into the Rocket Equation yields something more like 333,500 km/s for the final velocity.


That's faster than the speed of light.

You may have misplaced a decimal or something.
 
2013-06-26 07:29:33 PM

Ishkur: JesseL: With a 1000Kg starting mass and 230Kg final mass, plugging the numbers into the Rocket Equation yields something more like 333,500 km/s for the final velocity.

That's faster than the speed of light.

You may have misplaced a decimal or something.


He forget to carry the 1
 
2013-06-26 07:29:47 PM
I've got 5 bucks that says the light barrier will be as inconsequential as the sound barrier.
 
2013-06-26 07:30:25 PM
Plugging the numbers in myself, I arrive at the surprising result of 278.4 kittens/blender
 
2013-06-26 07:31:19 PM

DubtodaIll: Sounds like this would be the perfect engine to put in a spacecraft that would be launched by a mag-lev track. It actually seems like a perfect solution.


Unless you can get it over escape velocity with a mag-lev track (and keep it from burning up in the atmosphere at that velocity), I don't think it would have the acceleration to round out its orbit before it falls back to Earth.

/everything I know about orbital mechanics I learned from playing Kerbal Space Program
 
2013-06-26 07:31:55 PM

Ishkur: JesseL: With a 1000Kg starting mass and 230Kg final mass, plugging the numbers into the Rocket Equation yields something more like 333,500 km/s for the final velocity.

That's faster than the speed of light.

You may have misplaced a decimal or something.


As mentioned, it's a classical equation as applied to relativistic velocities.   It's going to be inaccurate because the equation doesn't know that c is the speed limit and that mass and energy (and therefore achievable velocity) all behave in odd ways near the limit.
 
2013-06-26 07:34:31 PM

JesseL: DubtodaIll: Sounds like this would be the perfect engine to put in a spacecraft that would be launched by a mag-lev track. It actually seems like a perfect solution.

Unless you can get it over escape velocity with a mag-lev track (and keep it from burning up in the atmosphere at that velocity), I don't think it would have the acceleration to round out its orbit before it falls back to Earth.

/everything I know about orbital mechanics I learned from playing Kerbal Space Program


Build a track long enough and theoretically there's almost no limit to the speed you can reach, escape velocity would be easily attainable. The article didn't mention what kind if fuel the ion engine use but I'm just guessing its considerably lighter than rocket fuel which is why it would be optimal for the mag lev track. Also, if you can get a ship in to the atmosphere at bear escape velocity, you can get one out just make a more substantial blast shield.
 
2013-06-26 07:37:02 PM

The All-Powerful Atheismo: Cerebral Knievel: Flatus: It doesn't matter if they test it for five thousand years, this Administration doesn't give a crap about space exploration and we're not going anywhere meaningful for a long, long time.

Are you QA's new alt because everyone has ignored him? or a politics tab troll that got lost?

That's not a QA post.  That post implies that it would be worthwhile.


thanks.. just wanted to make sure...

also... for the sake of snark,,,

They turned it off!?
DAMN YOU OBAMA!!!!
 
2013-06-26 07:37:17 PM

DubtodaIll: JesseL: DubtodaIll: Sounds like this would be the perfect engine to put in a spacecraft that would be launched by a mag-lev track. It actually seems like a perfect solution.

Unless you can get it over escape velocity with a mag-lev track (and keep it from burning up in the atmosphere at that velocity), I don't think it would have the acceleration to round out its orbit before it falls back to Earth.

/everything I know about orbital mechanics I learned from playing Kerbal Space Program

Build a track long enough and theoretically there's almost no limit to the speed you can reach, escape velocity would be easily attainable. The article didn't mention what kind if fuel the ion engine use but I'm just guessing its considerably lighter than rocket fuel which is why it would be optimal for the mag lev track. Also, if you can get a ship in to the atmosphere at bear escape velocity, you can get one out just make a more substantial blast shield.


Bear escape velocity is approx. 37 mph.
 
2013-06-26 07:41:11 PM
So the Ion engine in Kerbal Space Program is modeled fairly close to reality after all.

It has a 4200sI with a thrust of 0.5kN. It takes forever to get up to a decent km/s but it's far and away the most efficient engine in that game. I mainly use it on probes but it's also helpful as a secondary engine on some of the longer manned missions that I've tried. KSP is a great game by the way if you love anything about space and space travel like I do. It's probably the closest you'll ever come to being like NASA without actually being in NASA itself. If you like gaming I'd suggest trying it out.
 
2013-06-26 07:43:20 PM

JesseL: UberDave: Someone do the math.  I'm hastily (and probably incorrectly) getting 30,000 k/s for that thrust and run time given 1000kg in mass (770 for fuel plus me rounding it up).  I thought it would be way faster.

Don't forget that acceleration increases as you use up reaction mass. With a 1000Kg starting mass and 230Kg final mass, plugging the numbers into the Rocket Equation yields something more like 333,500 km/s for the final velocity.


That's faster than light.  I declare your calculations invalid.
 
2013-06-26 07:46:58 PM

DubtodaIll: Build a track long enough and theoretically there's almost no limit to the speed you can reach, escape velocity would be easily attainable.


You'd need to run the track in a vacuum tunnel all the way to the upper atmosphere, because hitting denser air at 11.2km/s (or faster to compensate for the frictional loss) will probably do very bad things to your craft. We had the Stardust reenter at 12.4km/s, but it got to decelerate in the upper atmosphere and was going much slower by the time it got to denser air.

DubtodaIll: The article didn't mention what kind if fuel the ion engine use but I'm just guessing its considerably lighter than rocket fuel which is why it would be optimal for the mag lev track.


Ion engines are powered by electricity (from whatever source you like) and typically use Xenon as reaction mass.
 
2013-06-26 07:47:05 PM

DubtodaIll: The article didn't mention what kind if fuel the ion engine use


Yes it did. It was in the caption under the pic though. It uses Xenon gas and after 5 years had used only 770kg. Pretty efficient if you ask me.
 
2013-06-26 07:56:49 PM

JesseL: DubtodaIll: Build a track long enough and theoretically there's almost no limit to the speed you can reach, escape velocity would be easily attainable.

You'd need to run the track in a vacuum tunnel all the way to the upper atmosphere, because hitting denser air at 11.2km/s (or faster to compensate for the frictional loss) will probably do very bad things to your craft. We had the Stardust reenter at 12.4km/s, but it got to decelerate in the upper atmosphere and was going much slower by the time it got to denser air.

DubtodaIll: The article didn't mention what kind if fuel the ion engine use but I'm just guessing its considerably lighter than rocket fuel which is why it would be optimal for the mag lev track.

Ion engines are powered by electricity (from whatever source you like) and typically use Xenon as reaction mass.


This is just brain cloud science, but seems like you could use the electromagnetic field of the track to create a pocket around the craft. Something like the principle with submarine launched trident missiles, they don't actually get wet because of the pocket of air created by the launch process. So if you could get a conductive gas (like mercury or something) an envelope the craft during the launch sequence, it could possible absorb most of the friction when exiting the maglev.
 
2013-06-26 07:59:38 PM

Voiceofreason01: Wizard Drongo: I still hold out hope that one day, a plasma-based ion thruster (that can actually operate in an atmosphere), will be efficient and powerful enough to use from the ground-up.

I think you'll be waiting a long time but fortunately scramjet/ramjet design is getting to the point where relatively efficient ground to orbit vehicles are probably not far off and from orbit you're halfway to anywhere


Well, I did recently read an MIT paper showing there's the possibility that the old "lifter" design of popular "fringe" science fame may actually have some potential...I'm not very literate on electrodynamics and plasma-based propulsion, but it occurs to me, if you mated the "lifter" to a convention plasma engine...I mean, the lifter creates a nice steady "breeze" of ionised gas (mostly nitrogen I recall), pump that into your VASIMR engine...plasmarise it, heat it up and accelerate it a lot more, and you're gonna increase the thrust...those lifters can barely lift themselves without a power source, and the VASIMR engine produces a few N, tops, but the lifter itself can do a few N, the vasimr a few N, then refine refine refine...
You don't need an wicked fast engine, just one that can overcome drag and a bit more...


I mean, stop me if I'm totally farked retarded here, but say, by dint of a novel power-source (here's the crux of every electrical engine...we'll say fission, but maybe one day, fusion), with ion-based engines, you can raise your craft above gravity.  Not by much in the atmosphere, but enough to go up.  Say you can achieve 50kph.

So go up for 3 hours.  You're at 150km, you're now above the Kármán line.  You're in space.  Your engines are vastly more efficient than jets or rockets (as seen in that paper), so fuel isn't a problem, and your trusty reactor (or Mr. Fusion, whatever) is powering the whole shebang.

Now you're outa the atmosphere, so your engine goes into a more conventional xenon or argon-based propulsion and pump you up to orbital velocity.  Doesn't need to be a fast process, you're running from the reactor here...
So what if it takes 3 days to achieve stable orbit? If your engines are capable of low, but steady thrust, and that thrust is enough to put you, your engines, your reactor and your airframe, into the air, albeit slowly, you can put ANYTHING up in orbit, for virtually sod all.
 
2013-06-26 08:04:38 PM

dragonchild: What they didn't mention in TFA is that they're really shutting down the experiment because the device they used to monitor it can only operate for five years.  That's the problem when you use ionic pentameter.


www.trilobite.org
 
2013-06-26 08:09:18 PM

Wizard Drongo: Voiceofreason01: Wizard Drongo: I still hold out hope that one day, a plasma-based ion thruster (that can actually operate in an atmosphere), will be efficient and powerful enough to use from the ground-up.

I think you'll be waiting a long time but fortunately scramjet/ramjet design is getting to the point where relatively efficient ground to orbit vehicles are probably not far off and from orbit you're halfway to anywhere

Well, I did recently read an MIT paper showing there's the possibility that the old "lifter" design of popular "fringe" science fame may actually have some potential...I'm not very literate on electrodynamics and plasma-based propulsion, but it occurs to me, if you mated the "lifter" to a convention plasma engine...I mean, the lifter creates a nice steady "breeze" of ionised gas (mostly nitrogen I recall), pump that into your VASIMR engine...plasmarise it, heat it up and accelerate it a lot more, and you're gonna increase the thrust...those lifters can barely lift themselves without a power source, and the VASIMR engine produces a few N, tops, but the lifter itself can do a few N, the vasimr a few N, then refine refine refine...
You don't need an wicked fast engine, just one that can overcome drag and a bit more...


I mean, stop me if I'm totally farked retarded here, but say, by dint of a novel power-source (here's the crux of every electrical engine...we'll say fission, but maybe one day, fusion), with ion-based engines, you can raise your craft above gravity.  Not by much in the atmosphere, but enough to go up.  Say you can achieve 50kph.

So go up for 3 hours.  You're at 150km, you're now above the Kármán line.  You're in space.  Your engines are vastly more efficient than jets or rockets (as seen in that paper), so fuel isn't a problem, and your trusty reactor (or Mr. Fusion, whatever) is powering the whole shebang.

Now you're outa the atmosphere, so your engine goes into a more conventional xenon or argon-based propulsion and pump you up ...


Unfortunately, ion engines are nowhere close to offering a thrust/weight ratio >1. Without that it doesn't matter how efficient they are for purposes of getting from the edge of space and into orbit.
 
2013-06-26 08:11:26 PM

DubtodaIll: I've got 5 bucks that says the light barrier will be as inconsequential as the sound barrier.


I would find it absolutely trippy if the pseudo-design of the Star Trek warp drive ends up being the way for FTL travel.  Stupidly large superconducting magnets generating a "More Powerful Than God" magnetic field that gets pulsed down the length of the warp nacelles causing space to warp and drag the rest of the spaceframe with it.

/More Powerful than God - Many thousands or millions of Teslas.
//It'll happen, no matter how many times Quantum Apostrophe drags his wormy ass across the space threads.
 
2013-06-26 08:16:45 PM

Cerebral Knievel: Flatus: It doesn't matter if they test it for five thousand years, this Administration doesn't give a crap about space exploration and we're not going anywhere meaningful for a long, long time.

Are you QA's new alt because everyone has ignored him? or a politics tab troll that got lost?


He does have a point. Space Science is not really high on the budget right now, sadly.

Maybe if we, you know, brought some people home from overseas and refocused some money.

Speaking of, Where IS Quantum Apostrophe? Maybe he got abducted by aliens and elvis?
 
2013-06-26 08:27:56 PM

hardinparamedic: Cerebral Knievel: Flatus: It doesn't matter if they test it for five thousand years, this Administration doesn't give a crap about space exploration and we're not going anywhere meaningful for a long, long time.

Are you QA's new alt because everyone has ignored him? or a politics tab troll that got lost?

He does have a point. Space Science is not really high on the budget right now, sadly.

Maybe if we, you know, brought some people home from overseas and refocused some money.

Speaking of, Where IS Quantum Apostrophe? Maybe he got abducted by aliens and elvis?


Oh no.. I get it.. I just had to be snarky... I was originally going to write something along the lines, of nor was it the previous administrations, nor the previous one before that, and nor will it a priority of the next one, or the one after that.

because that is more of a reality that we are dealing with than DERP!!OBAMA!!!!
 
2013-06-26 08:34:22 PM

Elzar: / Approves

[netdna.shebudgets.com image 500x500]


Why the hell did they think that would be something I liked
 
2013-06-26 08:57:40 PM
Just a question for you mathy types: how long would it take for an ion powered craft to reach the voyager probes?
 
2013-06-26 09:07:19 PM
Too bad they used up the world's supply of xenon
/not really
 
2013-06-26 09:10:30 PM

JesseL: /everything I know about orbital mechanics I learned from playing Kerbal Space Program


Same here.
 
2013-06-26 09:15:51 PM
I'm here for the Kerbals.
Leaving dissapointed.
 
2013-06-26 09:42:55 PM

hardinparamedic: Speaking of, Where IS Quantum Apostrophe? Maybe he got abducted by aliens and elvis?


He's probably off worrying about his impending demise and wondering why he can't be immortal like his atoms.
 
2013-06-26 09:43:50 PM
Submitter: Okay, folks, that's as far and as long as we can imagine thrusting through space ...

i.imgur.com
 
2013-06-26 10:32:46 PM

Somacandra: Submitter: Okay, folks, that's as far and as long as we can imagine thrusting through space ...


Psst...check post number uno...
 
2013-06-26 10:55:44 PM

kim jong-un: debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?

This type of an engine is designed to take advantage of exactly what you mentioned.  Just a few points to correct and inform:

1.  zero G (which doesn't really exist) has nothing to do with your ability to continue at a constant velocity indefinitely, the reason you can do that is due to conservation of momentum ("an object in motion will tend to stay in motion unless something acts upon it")  On Earth the thing that 'acts upon something' is friction due to atmospheric drag, or an object getting in the way (like the Earth itself).  The reason this works in space is due to the lack of an atmosphere and thus effectively no drag.  (In reality, there is some, but it might as well not exist for our purposes so we will just say 'no drag')

2.  These engine don't just work for a long time, they are VERY efficient.   Of course, due to With that in mind, the reason these engines are of interest isn't that you can get something somewhere eventually, but that they can get you there faster because they can convert more energy into thrust for a given amount of fuel.   Take 10kg of rocket fuel, and 10kg of fuel for these engines and these engines will produce more energy from those 10kg than the rocket.  More energy converted into useful thrust = faster (eventually)   It also means you can take advantage of a lot of things which wouldn't happen if you had to wait a long time for your spaceship to arrive at it's destination.   It also means you can have your spaceship go somewhere, and THEN go somewhere else.   With traditional rockets, we mostly just consider it a one way trip.


So the short version is it is a turtle vs a rocket is a hare. Got it.
 
2013-06-26 11:16:33 PM

Lochsteppe: debug: It doesn't really seem like that kind of life span would actually be necessary.  Once you're in zero G wouldn't inertia pretty much keep you going?  You would just need thrusters for course changes, right?

TFA talks about its use for scooting around the solar system, mining asteroids for crystals to make Sinibombs & such.  Doesn't sound like they plan to use it for a straight shot to the next star system right away.


Run, coward!!!
 
2013-06-26 11:43:32 PM
I'd just like to point out that they would likely use a combination of engines on this type of craft.  There would probably be traditional thrusters to compliment the fancy ion drive, for maneuverability etc.
 
2013-06-27 12:35:54 AM

Gabrielmot: That's all well and good, but if ProfessorOhki's numbers are right... how the heck would you be able to maneuver at that speed and what kind of craft would you need to avoid exploding from an impact with even debris the size of a pebble at that speed?


Pshaw. Those are engineering problems, it's not rocket science.
 
2013-06-27 12:36:34 AM

Wizard Drongo: Get this going guys with 100 times the current thrust levels, and space is an hour away in your average family (flying!!) car :)


Put 100 of these engines on your family car.
Glad to help.
 
2013-06-27 12:41:01 AM

DubtodaIll: This is just brain cloud science, but seems like you could use the electromagnetic field of the track to create a pocket around the craft. Something like the principle with submarine launched trident missiles, they don't actually get wet because of the pocket of air created by the launch process. So if you could get a conductive gas (like mercury or something) an envelope the craft during the launch sequence, it could possible absorb most of the friction when exiting the maglev.


Electromagnetic fields don't bother most atmospheric gases much. Run a lightning bolt through it and turn it into plasma, and you can do something with it.

Or do use the Bolo tank design. Fire lasers first, to explode the air outward... then fire the payload through the resulting vacuum. First you have to invent those lasers and power sources.
 
2013-06-27 01:47:01 AM
Man, I hope Obama never gets wind of this project. I'd like to see this thing through.
 
2013-06-27 03:03:09 AM
www.showbiz.ie

I would give up if she didn't come after 5 years of thrusting
 
2013-06-27 04:31:47 AM
sphotos-b.xx.fbcdn.net

Twin Ion Engine (TIE)
 
2013-06-27 07:38:49 AM
Eh. Wake me up when NASA gets to this tech level:
img607.imageshack.us
 
2013-06-27 07:47:27 AM

MythDragon: Eh. Wake me up when NASA gets to this tech level:
[img607.imageshack.us image 706x262]


NASA better have the "creative" race attribute or they're farked.
 
2013-06-27 07:49:24 AM

DubtodaIll: I've got 5 bucks that says the light barrier will be as inconsequential as the sound barrier.


I'll take that bet. When they were building aircraft to break the sound barrier, it was known that things can go faster (bullets, meteors, whatever) but not known how to build control surfaces that would work among the shock waves.

Feel free to point me to a link showing where anything with mass has been accelerated past c.
 
2013-06-27 07:51:06 AM

ko_kyi: Feel free to point me to a link showing where anything with mass has been accelerated past c.


I will accept that $5 in the form of cash or a money order
 
2013-06-27 08:13:48 AM

The All-Powerful Atheismo: I will accept that $5 in the form of cash or a money order


Wat
 
2013-06-27 09:11:16 AM

ko_kyi: DubtodaIll: I've got 5 bucks that says the light barrier will be as inconsequential as the sound barrier.

I'll take that bet. When they were building aircraft to break the sound barrier, it was known that things can go faster (bullets, meteors, whatever) but not known how to build control surfaces that would work among the shock waves.

Feel free to point me to a link showing where anything with mass has been accelerated past c.


There isn't any substantial evidence that anything can move faster than light but it's my guess it's because we don't know how to find it.  There was the neutrino incident in Europe where they thought they had evidence of something going faster than light turned out to be a "measuring error."  But they're still debating that.  All of our knowledge currently points to the idea that absolutely nothing can go past the speed of light.  Though we've been wrong before, in fact mostly every time whenever we think there are limits to our capabilities.
 
2013-06-27 09:25:41 AM
farm3.staticflickr.com
 
2013-06-27 09:32:04 AM

DubtodaIll: There isn't any substantial evidence that anything can move faster than light but it's my guess it's because we don't know how to find it.  There was the neutrino incident in Europe where they thought they had evidence of something going faster than light turned out to be a "measuring error."  But they're still debating that.  All of our knowledge currently points to the idea that absolutely nothing can go past the speed of light.  Though we've been wrong before, in fact mostly every time whenever we think there are limits to our capabilities.


The neutrino thing wasnt exactly a measurement error... neutrinos pass through solid objects unobstructed, so what happened was the neutrino burst actually passed through the earth and was detected "faster" than light because the fiber optic signal still had to travel in a curved path around the earth.  They move at the same speed.

Also, a lot of peoples brains interpret the speed of light wrong.  It isnt that "nothing can move faster than light", so much as "light travels at the maximum possible speed".  "Light" isnt the only thing that travels "At the speed of light".
 
2013-06-27 10:06:44 AM

DubtodaIll: There isn't any substantial evidence that anything can move faster than light but it's my guess it's because we don't know how to find it. There was the neutrino incident in Europe where they thought they had evidence of something going faster than light turned out to be a "measuring error." But they're still debating that.


There isn't ANY evidence that anything can move faster than the speed of light; it's a known limitation on how the universe works.  Mass is a function of speed; as speed approaches c, mass approaches infinity.  There is no technological barrier to infinity.  As for the neutrino incident, it was found to be an error.  There's no debate.

I get what you mean in that betting against the tech curve is always bad gamble, but in these cases engineers don't find ways to break the laws of physics; they find ways around them.  Engineering, after all, is a matter of function, not method.  In the 1960s people were imaging we'd have flying cars by this century.  I've seen artist's conceptions of John Doe commuting to work in a suit and hat by hopping into what was basically a streamlined car with rocket engines and wings.  What we have instead is something far more sophisticated, advanced and efficient:  digital telecommunications.  Why bother wasting all that money and time to shuttle someone from point A to point B when you can transfer information over a fiber-optic cable at the speed of light?  THAT'S how you get a technological paradigm shift.  The suits back in the 1960s would never dare dream of a world where a significant percentage of the workforce could generate their output from home; hell, a lot of them are still refusing to wrap their heads around the possibility and mandate commuting to an office.  Preferentially getting excited over the possibility of FTL travel may seem audacious, but it's really just an extrapolation of existing infrastructure.  This work on the ion thruster* is important, but only because few concepts become obsolete entirely.

*huh huh, I said "thrust"
 
2013-06-27 03:44:25 PM

The All-Powerful Atheismo: Ishkur: JesseL: With a 1000Kg starting mass and 230Kg final mass, plugging the numbers into the Rocket Equation yields something more like 333,500 km/s for the final velocity.

That's faster than the speed of light.

You may have misplaced a decimal or something.

He forget to carry the 1


i.imgur.com
 
Displayed 109 of 109 comments

View Voting Results: Smartest and Funniest


This thread is archived, and closed to new comments.

Continue Farking
Submit a Link »






Report