Light speed and the Kraken. A tragedy.

[Sabactus]

Well today I wanted to see if I could attain an appreciable factors of the speed of light and also test to see if the Kraken is still lurking. Bastards still alive. Hit 35,500 m/s and the ship suddenly decided that it was a good time to start doing cartwheels. He\'s going to have to be tamed before we can even consider interplanetary voyages much less interstellar.

[sal_vager]

HarvesteR mentioned he might have solved this but the fix was too late to go in 0.14.3, might be in .4 but we\'ll have to wait and see.

I think his fix limited your top speed and when you reached it, the universe would move instead, and you wouldn\'t notice anything weird.

[Kosmo-not]

Were you operating at 2x time compression? Funky things can happen when you do (like the SAS not keeping up).

Also, why is light speed mentioned in the title?

[Sabactus]

Were you operating at 2x time compression? Funky things can happen when you do (like the SAS not keeping up).

Also, why is light speed mentioned in the title?

I was under 2x and was using MechJab be keep me on prograde. He keeps up pretty well it just gets to a point where the RCS blocks can\'t put out enough power to counteract the induced wobble.

And I meantioned light speed cause that is my goal or at least an appreciable fraction of it

HarvesteR mentioned he might have solved this but the fix was too late to go in 0.14.3, might be in .4 but we\'ll have to wait and see.

I think his fix limited your top speed and when you reached it, the universe would move instead, and you wouldn\'t notice anything weird.

When you say the universe moving around the ship it sounds like warp drive >.<

[sjwt]

You need to check this topic out!

http://kerbalspaceprogram.com/forum/index.php?topic=8069.0

[silent_prtoagonist]

He\'s going to have to be tamed before we can even consider interplanetary voyages much less interstellar.

I\'m not sure why people keep saying that the space kraken is a problem for interplanetary travel. The kraken only comes into play at speeds much higher than what you\'d experience on interplanetary trips. Currently reaching solar escape velocity is quite easy, and once you\'ve done that you can obviously make it to any superior planet. Inferior planets might take be a bit more of a problem, if there was one very very close to kerbol you might reach an absolute speed high enough to anger the kraken near perihelion, but that\'s an extreme case.

[Sabactus]

I\'m not sure why people keep saying that the space kraken is a problem for interplanetary travel. The kraken only comes into play at speeds much higher than what you\'d experience on interplanetary trips. Currently reaching solar escape velocity is quite easy, and once you\'ve done that you can obviously make it to any superior planet. Inferior planets might take be a bit more of a problem, if there was one very very close to kerbol you might reach an absolute speed high enough to anger the kraken near perihelion, but that\'s an extreme case.

High speeds are necessary.

For illustration lets consider this. Lets say you get a craft up to 1,000,000 m/s (as the game is now this is dicey at best) that 1,000 km/s. Earths closest approach to Mars is 56,000,000 km. The average distance is 225,000,000 km. So, assuming closest approach, it will take you 56,000 seconds or 933 minutes or ~39days to reach Mars at its closest approach. At average it climbs to ~156 days. Not inconceivable but remember 1,000,000 m/s is very unstable currently.

Now for interplanetary. Light speed is 299,792,458 m/s. Alpha Centauri is 4.24 light years away. 1% C is ~2,997,924 m/s. At that speed it would take 424 years to reach the nearest star. We need speeds of like .7 C to make it remotely conceivable. Not taking accelerating time into account even at that speed it would take over 6 years to get there, not including relativistic effects.

[Kosmo-not]

You don\'t need to achieve escape velocity of the sun to accomplish interplanetary travel. That\'s overkill. It would be like going to the Mun while more than passing the escape velocity of Kerbin.

[PakledHostage]

High speeds are necessary.

For illustration lets consider this. Lets say you get a craft up to 1,000,000 m/s (as the game is now this is dicey at best) that 1,000 km/s. Earths closest approach to Mars is 56,000,000 km. The average distance is 225,000,000 km. So, assuming closest approach, it will take you 56,000 seconds or 933 minutes or ~39days to reach Mars at its closest approach. At average it climbs to ~156 days. Not inconceivable but remember 1,000,000 m/s is very unstable currently.

I just ran some more numbers to follow up on the How do we get to Mars thread, and you really don\'t need very high speeds. In the example in the post that I just referenced, you only need about 880 m/s at Kerbin\'s SOI to reach a planet orbiting at 1.5 times Kerbin\'s orbital radius. You can achieve that by boosting to just ~3260 m/s at 112 km altitude. By contrast, getting out to the Mun\'s orbital radius from Kerbin orbit requires ~3080 m/s at 110 km altitude. That\'s only about 180 m/s less than you need to get to out to 1.5 times Kerbin\'s orbital radius! (These are post-burn speeds following a 95 second and 80 second burn, respectively, by a 5 mass unit spacecraft powered by a LV-T45 Liquid Fuel Engine.)

The trip would take about twice as long as your ~39 days, but that doesn\'t take very long at 10000x warp.

[sal_vager]

Haven\'t people experienced the kraken at lower speeds though?I thought I read on here that with a large enough ship, you can lose control even inside Kerbins soi.

And what is it that makes your apoapsis jitter so much when it\'s far away? It\'s rounding errors because the engine can\'t handle such big numbers, thats the kraken in a nutshell.

[Kosmo-not]

Haven\'t people experienced the kraken at lower speeds though?I thought I read on here that with a large enough ship, you can lose control even inside Kerbins soi.

I think that may have been me. While orbiting Kerbin, I have had strange forces push my nose away from certain headings. It\'s really annoying when it happens, but at least it doesn\'t happen often.

[sal_vager]

Probably was Kosno-not, I guess whenever I leave my ships and they start to turn a bit, thats the kraken again, it\'s far more noticeable when you fly without ASAS, even if you use warp to cancel any rotation all ships will eventually just start to tumble.

[silent_prtoagonist]

High speeds are necessary.

For illustration lets consider this. Lets say you get a craft up to 1,000,000 m/s (as the game is now this is dicey at best) that 1,000 km/s. Earths closest approach to Mars is 56,000,000 km. The average distance is 225,000,000 km. So, assuming closest approach, it will take you 56,000 seconds or 933 minutes or ~39days to reach Mars at its closest approach. At average it climbs to ~156 days. Not inconceivable but remember 1,000,000 m/s is very unstable currently.

Now for interplanetary. Light speed is 299,792,458 m/s. Alpha Centauri is 4.24 light years away. 1% C is ~2,997,924 m/s. At that speed it would take 424 years to reach the nearest star. We need speeds of like .7 C to make it remotely conceivable. Not taking accelerating time into account even at that speed it would take over 6 years to get there, not including relativistic effects.

That\'s not generally how interplanetary spaceflight works. You don\'t wait for closest approach and then burn straight for Mars. That kind of trajectory is impossible without unrealistic engines (the kind that burn pixie dust and break thermodynamics into a million pieces), and even if you did have such engines it\'d be very inefficient.

Instead you use a hohmann transfer orbit. This is an elliptical solar orbit that leaves Earth on one side of the Sun and meets Mars (or whatever your objective is) on the other. These orbits are very slow, since you have to travel all the way around the Sun, but they\'re generally the most practical trajectory to use. In real life an Earth-Mars hohmann transfer takes about nine months, although the trip time can be shortened by burning a bit more fuel, but using the same basic orbit.

In practice a trip form Kerbin to the next planet out would probably take about 100 Earth-days real time, at absolute speeds in the ballpark of 10-15 km/s. In my experience at least those speeds aren\'t enough to anger the kraken. Nobody said interplanetary travel was going to be quick, that\'s in large part what makes it so difficult, but the answer for KSP is higher time acceleration (or better yet, the click-to-skip system that\'s been mentioned), not higher speeds.

You don\'t need to achieve escape velocity of the sun to accomplish interplanetary travel. That\'s overkill. It would be like going to the Mun while more than passing the escape velocity of Kerbin.

Indeed. I was just using solar escape velocity as a worst-case example. Although it\'s not much overkill. The difference between a munar transfer orbit and Kerbin escape velocity is only a couple hundred m/s. In fact if I\'m not mistaken the Apollo missions actually achieved Earth escape velocity on their way to the Moon, in the interest of getting there in three days instead of the five that a true hohmann transfer would take.