Face to Face with The Tyranny

[Streetwind]

12 minutes ago, Xyphos said:

if piloted correctly, it can take 1 (un)lucky kerbal to a foreign star.

If you read the first post, you will discover why this design is not useful for GarrisonChisholm's purposes...

Edited July 9, 2016 by Streetwind

[Xyphos]

2 minutes ago, Streetwind said:

If you read the first post,

I did read, care to elaborate? I'm not very good at taking hints, you have to be clear and concise when communicating.

Edited July 9, 2016 by Xyphos

[Streetwind]

Well, he is trying to reach a star that is incredibly far away, and describes that if he had a hypothetical vessel with 300,000 m/s of dV, he could shorten the flight so much that he would need "only" a few IRL days at maximum timewarp.

Your vessel has 4,250 m/s in low Kerbin orbit. That is enough to achieve solar escape, but whether or not the remaining 1,500 m/s would be enough to raise AP to the target system is questionable (I have never actually used Extrasolar, so I don't know offhand what is needed). But let's assume it is enough. You are now in a Hohmann transfer to a destination that would take a few RL days of timewarping to reach in a high energy transfer with two hundred times the exit velocity.

In other words, you are now looking at more than half a year of leaving your computer running 24/7 at maximum timewarp. This is why this design is not useful, even assuming it could make it on paper.

[Xyphos]

41 minutes ago, Streetwind said:

you are now looking at more than half a year of leaving your computer running 24/7 at maximum timewarp.

I agree max time warp is too slow even for standard game play, often I let it run for 10 earth-minutes just to get a transfer window.
but the vessel I designed is capable of the task. it's just the games' design that is at fault, not the ship, not the mod.

Edited July 9, 2016 by Xyphos

[Deddly]

8 hours ago, Xyphos said:

...it's just the games' design that is at fault, not the ship, not the mod.

I think the point that @Streetwind is making is that OP is specifically looking for a stock way around that limitation by making the craft go very, very fast. That's why your craft won't help in this case.

[Xyphos]

1 hour ago, Deddly said:

looking for a stock way around that limitation

build a lightweight upper stage powered by a few vectors, enable the infinite fuel cheat.
other than that, nope. if he wants to reach a mod system, he needs mod parts. may I suggest using the Alcubierre Drive?

[septemberWaves]

I have noticed a huge problem with this discussion. Accelerating a craft to c in the Kerbol system is one thing, but even if you were to achieve that, you'd then have to decelerate again once you reach Valentine. Which means that, unless you're happy with a light-speed flyby after several IRL days of timewarp, you really should just download a warp drive.

[Xyphos]

45 minutes ago, eloquentJane said:

you'd then have to decelerate again

(de)acceleration can be done via gravity assists.
it's just the game's time warp feature is too slow for them to work.
looks like it's warp-drive time for this guy.

[wumpus]

On thing I'd recommend doing before tying up the computer for a week or so trying to get to some distant star is to try hyperediting (or manually editing a save) yourself up to 100km/s or whatever delta-v your goal is.  While the kraken is mostly dead, this is exactly the type of thing that can awaken it.

While the forum often uses "the kraken" for any ship killing bug, the specific bug by that name was traced to [single precision] floating point uncertainty when the ship was moving so fast that it was lost due to single precision uncertainty (presumably parts overlapping or similar).  While it was slain by moving the center of reference to center on the spacecraft (and thus gaining maximum precision), a 100k+m/s spacecraft will be wildly attempting to escape that center of reference.  While I don't expect it to awaken the kraken, I'd still want to test it before committing to such a course.

That is not dead which can eternal lie,
And with strange aeons even death may die.

Edited July 10, 2016 by wumpus
s/is/it

[Archgeek]

I'm actually working on a little something for this right now.  Up to about 91.3km/s for 157 tonnes so far, with nearly 9km/s in the final stage, plus a pair of RTGs for trickle charge to help slow down for capture.  I've even made concessions to TWR, throwing away gigantors and engines like some sort of crazy, though it's not easy keeping the gains for more than a couple of stages, and the extra solar panels and structural shenanigans make things get a bit heavy.  The total burn time's a little under 2 days, though, at 41.28 hours.

[Archgeek]

Here we go, the fully stock XenonBreeze Extra-Solar Explorer variant A, 100.3km/s in an 11-stage 247.5 tonne, 457 part package, with a total burn time of 53 hour burn time, under 3 real days:

I've included reaction wheels and more engines than I was comfortable with to make the thing practical(ish).  The A variant here matches the mass ratio of the final stage as best it can.  However, that's not enough.  My spreadsheet's geared up for 41 stages, not 11, so I'm going to rig up a B variant that starts the fuel pod with a single 700 tank, then matches mass ratio with that.  'Should result in a generally more even stage progression.

Oh, and @GarrisonChisholm: here's the .craft file with its sails furled if you're quite interested: https://dl.dropboxusercontent.com/u/59091477/Monstrosities/XenonBreeze Extra-Solar Explorer - a.craft

Panels are on action group 1.

Edited July 11, 2016 by Archgeek
Forgot craft link

[GarrisonChisholm]

On 7/9/2016 at 3:09 PM, eloquentJane said:

I have noticed a huge problem with this discussion. Accelerating a craft to c in the Kerbol system is one thing, but even if you were to achieve that, you'd then have to decelerate again once you reach Valentine. Which means that, unless you're happy with a light-speed flyby after several IRL days of timewarp, you really should just download a warp drive.

In fact (good morning everyone!), I would be content with a fly-by, or even an intercept.  That would be the fantastic achievement.  Without the Near Future mod I recognize a return trip would not be feasible. 

Just to send a probe "that way".  The intercept its would be the issue though as it stands.  For those of you who play with the Near Future Tech mod or Warp Drive, if you draw a maneuver node out from Kerbin orbit, does it reach all the way to the distant star?  I'll get a screen shot of mine, but the "line of travel" just stops at about twice Plock's distance.  I'm going to be making my first attempt on almost blind luck.

[GarrisonChisholm]

On 7/9/2016 at 4:51 PM, wumpus said:

On thing I'd recommend doing before tying up the computer for a week or so trying to get to some distant star is to try hyperediting (or manually editing a save) yourself up to 100km/s or whatever delta-v your goal is.  While the kraken is mostly dead, this is exactly the type of thing that can awaken it.

While the forum often uses "the kraken" for any ship killing bug, the specific bug by that name was traced to [single precision] floating point uncertainty when the ship was moving so fast that it was lost due to single precision uncertainty (presumably parts overlapping or similar).  While it was slain by moving the center of reference to center on the spacecraft (and thus gaining maximum precision), a 100k+m/s spacecraft will be wildly attempting to escape that center of reference.  While I don't expect it to awaken the kraken, I'd still want to test it before committing to such a course.

That is not dead which can eternal lie,
And with strange aeons even death may die.

This is an excellent point, and a fantastic idea.  I will indeed test this!

[GarrisonChisholm]

19 hours ago, Archgeek said:

Here we go, the fully stock XenonBreeze Extra-Solar Explorer variant A, 100.3km/s in an 11-stage 247.5 tonne, 457 part package, with a total burn time of 53 hour burn time, under 3 real days:

I've included reaction wheels and more engines than I was comfortable with to make the thing practical(ish).  The A variant here matches the mass ratio of the final stage as best it can.  However, that's not enough.  My spreadsheet's geared up for 41 stages, not 11, so I'm going to rig up a B variant that starts the fuel pod with a single 700 tank, then matches mass ratio with that.  'Should result in a generally more even stage progression.

Oh, and @GarrisonChisholm: here's the .craft file with its sails furled if you're quite interested: https://dl.dropboxusercontent.com/u/59091477/Monstrosities/XenonBreeze Extra-Solar Explorer - a.craft

Panels are on action group 1.

Wow.  I'm near speechless-  too cool!  It will be tried!  You and your heirs will be buried under heaps of thanks.

I'm also impressed by the mass.  I'm sure my attempt would have been 10x that, given I could only get to 55k dV on ~ 800 tons.

Edited July 11, 2016 by GarrisonChisholm

[Snark]

Incidentally, to anyone who has ever built a seriously-high-dV ship by using ion engines and lotsa-lotsa drop tanks:

After you complete a burn and have gone through however many dozen stages... try switching to map view and turn on the debris display.

Your spent tanks make a great conga line of map icons behind you, gradually spreading out over time if you fast forward a few weeks or months.

Just sayin'. 

(Fond memories of the time when I decided, for reasons not interesting enough to go into, that I needed to get a ship from KSC launch to Eve orbit in under 8 Kerbin days.  Alas, didn't grab screenshots of the debris trail.)

[Archgeek]

11 hours ago, GarrisonChisholm said:

I'm also impressed by the mass.  I'm sure my attempt would have been 10x that, given I could only get to 55k dV on ~ 800 tons.

 

6 hours ago, Snark said:

Incidentally, to anyone who has ever built a seriously-high-dV ship by using ion engines and lotsa-lotsa drop tanks:

After you complete a burn and have gone through however many dozen stages... try switching to map view and turn on the debris display.

Your spent tanks make a great conga line of map icons behind you, gradually spreading out over time if you fast forward a few weeks or months.

Just sayin'. 

It gets worse in both respects:  The B variant, so far, on spreadsheet and mental projection alone, Is up to 101.2km/s in 62 stages for only 166.3 tonnes, with a total burn time of only 52.4 hours.  Also, the thing'll be super noodley if I don't sacrifice some dv for organizational purposes -- there are 31 stages of fuel pod left by the time the spreader plate is dropped, and all but four of them are size zero.  I may have to do a C variant that starts with a bit more than .07 tonnes of xenon at the top of the pod.

61 dumped stages, most of which are going over 20km/s.  Frightful.

[GarrisonChisholm]

9 hours ago, Archgeek said:

 

It gets worse in both respects:  The B variant, so far, on spreadsheet and mental projection alone, Is up to 101.2km/s in 62 stages for only 166.3 tonnes, with a total burn time of only 52.4 hours.  Also, the thing'll be super noodley if I don't sacrifice some dv for organizational purposes -- there are 31 stages of fuel pod left by the time the spreader plate is dropped, and all but four of them are size zero.  I may have to do a C variant that starts with a bit more than .07 tonnes of xenon at the top of the pod.

61 dumped stages, most of which are going over 20km/s.  Frightful.

Hopefully the Kerbals won't find any busy star-lanes in their path for the interstellar grape-shot. 

16 hours ago, Snark said:

(Fond memories of the time when I decided, for reasons not interesting enough to go into, that I needed to get a ship from KSC launch to Eve orbit in under 8 Kerbin days.  Alas, didn't grab screenshots of the debris trail.)

*boggles!*  

The longer I play this game, the more things I learn that I just thought were inconceivable! 

...and I am now pretty sure that that word does not mean what I think it means...

Edited July 12, 2016 by GarrisonChisholm

[Snark]

1 hour ago, GarrisonChisholm said:

*boggles!*  

Aerobraking was... dramatic.

(This was in 0.90, so reentry heat wasn't a thing, but the visual f/x were there.  Hitting Eve's atmosphere at a few dozen km/s was quite a spectacle.  And on the approach, I kept finding myself hitting the comma key, and then realizing again that "no, I'm actually not on timewarp".)

[GarrisonChisholm]

12 hours ago, Archgeek said:

 

It gets worse in both respects:  The B variant, so far, on spreadsheet and mental projection alone, Is up to 101.2km/s in 62 stages for only 166.3 tonnes, with a total burn time of only 52.4 hours.  Also, the thing'll be super noodley if I don't sacrifice some dv for organizational purposes -- there are 31 stages of fuel pod left by the time the spreader plate is dropped, and all but four of them are size zero.  I may have to do a C variant that starts with a bit more than .07 tonnes of xenon at the top of the pod.

61 dumped stages, most of which are going over 20km/s.  Frightful.

Is KER calculating that correctly in the VAB for you?  I find that my ion stages seem to not be accurately displayed.  :\

[Archgeek]

42 minutes ago, GarrisonChisholm said:

Is KER calculating that correctly in the VAB for you?  I find that my ion stages seem to not be accurately displayed.  :\

Not remotely, save for stage zero.  Both Mechjeb and KER are still working on finding a way to deal with [STAGE_PRIORITY] flow, and will display delta-v for drop-tank festival like this as though it were all one stage.  That's why I found myself forced to spreadsheet.

[quasarrgames]

On 07/07/2016 at 7:12 PM, GarrisonChisholm said:

 

The first stage sported 17k dV, and I thought "no problem!"  The second stage only lifted it to 25k dV, and I thought "hmm..."  The third stage- well, you know where this is going.  Its not just that successive stages have to be Bigger, its that each stage does less and less *work* per ton.  I know this is what the math says, and I know it has been discussed frequently & intelligently in these forums, but until you come face to face with the diminishing returns of the Equation... its just hard to realize how tyrannical it can be.

That being said, if anyone has a craft-file for something approaching 100,000 dv, I'd love to see it-  if only to pick it apart and have its engineering inform my own decisions.

 

I know how you feel. The Equation hits me right in the face everytime i play with RSS. The biggest problem is the moderating voice in my head that says "It's alright. This rocket should be big enough now." In RSS, if it looks "Big Enough", you won't even get to orbit.

Also, there's a great video by a guy called Turbo Pumped where he uses the sun's gravity to slingshot himself and get another 30,000m/s of speed

Edited July 12, 2016 by quasarrgames

[Kerbart]

This thread is an excellent illustration of the fact that we'll never reach the stars with chemically propelled rockets. Or even rockets in the first place. Light sails and eons of time will have to do the trick, it seems.

[GarrisonChisholm]

1 hour ago, Kerbart said:

This thread is an excellent illustration of the fact that we'll never reach the stars with chemically propelled rockets. Or even rockets in the first place. Light sails and eons of time will have to do the trick, it seems.

I was about to use a "Like" to testify that I agree with your statement, however I could not bring myself to assign the term 'like' to Terran chemical-engined purgatory.  :\  However!  I agree, your statement is correct.  It will take a miraculous breakthrough (incredibly unlikely, but I won't put humanity past it) or a society so stable that eon travel times are not seen as nonsensical.

1 hour ago, quasarrgames said:

Also, there's a great video by a guy called Turbo Pumped where he uses the sun's gravity to slingshot himself and get another 30,000m/s of speed

And yes!  That was the name of the YouTuber (yes?) whose video originally drew me to the realization that if 100k m/sec was possible, studious inquiry might make 300k m/sec plausible (subsequently proven IMplausible).

[Archgeek]

Crapper poopers!  I seem to've mis-apprehended the way [STAGE_PRIORITY] fuel flow works, so my design has less dv than I thought.  It turns out xenon drains from all non-empty tanks the furthest number of decouplers out from the root part that it can, regardless of defined stage order.  Either I've got a bug report to make, or I'll need to redesign the silly things.

Headway's being made with KER's dv calculations, so upon removing the dropped engines and replacing them with equivalent ore tanks, the numbers here should be accurate:

Spoiler

 

[GarrisonChisholm]

Well, I attempted my first high-speed ion craft, but I ended up saving all the ion power for deceleration at journey's end because it was so difficult!  I sent a probe with 25k+ dV of ion power to GregroxMun's END, orbiting at 3.5 billion km.  Using the Kerbin Escape stage and the nuclear Boost Stage I got its speed up to a meager 16.5km sec, but due to the difficulty of the intercept elected to be satisfied with a 31 year intercept, and I'll just try to go into orbit rather than only fly-by.

The effort has informed me of a couple difficulties however.  Firstly, my design (contrary to yours) was horizontally staged, and I encountered a gross oscillation at anything beyond low thrust with the Escape stage.  Secondly, ... is the time.  I can talk about wanting a 100,000 m/sec probe, but that is a Lot of hobby time spent watching fuel tanks empty for accurate staging purposes.  I only burned a nuke last night and I spent over 3 hours on 2 burns- amounting to only about 3km/sec, as more than half the dV in my nuke stage was directed in a Normal or Radial direction so-as to maintain my velocity on my correct intercept.

Lastly, If I successfully plot an intercept of Valentine, as 9.5 Trillion km, "node-massaging" the intercept to maintain the contact but add velocity would be Hellacious!  "30m/sec Prograde, now 40m/sec Radial, now another 30 Pro- oops too far,..."   ...there are a lot more issues than "just" engineering in this endeavor!