For Questions That Don't Merit Their Own Thread

[p1t1o]

6 hours ago, Grand Ship Builder said:

Now, how hard is it to get to C in Kerbal Space Program without glitches?

"Get to C"?

[Steel]

11 hours ago, Grand Ship Builder said:

Now, how hard is it to get to C in Kerbal Space Program without glitches?

I'm guessing by "C" you mean the speed of light? Provided you have infinite fuel it's just a matter of waiting long enough. I can't imagine it's possible without infinite fuel without making a ship so huge it melts any computer that comes near it.

EDIT: Scott Manley actually has a video about this very topic: https://www.youtube.com/watch?v=FCXMpWMEc1w

Edited May 23, 2017 by Steel

[p1t1o]

Ooooooh "c" hahahahaha! The capitalisation threw me, the only thing I could think of was he wanted to build boats, and go to "sea" lolol.

Yeah, no, you cant really get to c in KSP. As far as I know, relativistic effects are not modelled. Which is moot because c is like, realllly fast, like super-ridiculous fast. Ludicrous even

Mass ratio for a conventional ship to do this is just insane. If you want to go high relativistic with conventional reaction engines, ship sizes very quickly start reaching just stupid sizes, like solar-system sized, with 1kg of cargo (including the weight of the engines/structure/tankage etc!!!) and start taking millions of years to expend their fuel. But light speed is so fast guys I cant even...

Of course, in reality, the ship would literally need to be of infinite size because relativity.

But at least in that case, a large portion of your ship is at your destination already.

[Spaceception]

1 hour ago, p1t1o said:

But at least in that case, a large portion of your ship is at your destination already.

If your ship is the size of infinity, I doubt a large part is at the destination, more like impossibly tiny in comparison

[sevenperforce]

14 hours ago, Grand Ship Builder said:

Now, how hard is it to get to c in Kerbal Space Program without glitches?

You need an effective fuel fraction of 1:1.193e3161.

No, that's not a typo. 1.193x10³¹⁶¹. That's 11,930 thousand million billion trillion quadrillion quintillion sextillion sextillion septillion octillion nonillion decillion undecillion duodecillion tredecillion quattuordecillion quindecillion centillion centillion centillion centillion centillion centillion centillion centillion centillion times more fuel than payload.

Given that the mass of the Dawn ion engine is a quarter-tonne, you'd need 3e3160 metric tonnes of xenon, not counting the mass of the tanks. To put this in perspective, the mass of the observable universe is roughly 6e49 metric tonnes. If every particle in the observable universe was a massless Dawn ion engine that could consume one trillion universes every nanosecond, and you ran these engines from the Big Bang until the heat death of the universe, you would still need to repeat this process 10⁴⁹³ times before you'd burn through that much xenon.

 

 

[SuperFastJellyfish]

I did this a few years ago with infinite fuel.  I used the least massive probe core, a hammer, an SAS module, and two RTGs(I couldn't get a single one to attach nonoffset).  After it was out of fuel, the thumper had the highest TWR of all the engines back then, as far as I remember.  I let it run for a few days straight(4, I think).  I'll post some pics after work, if you want.

Edit:  Although infinite fuel is a 'glitch', this is as close to as good as you can get, as has been pointed out already.

Edited May 23, 2017 by SuperFastJellyfish
Hammer, not a Thumper.

[sevenperforce]

Not sure if it's considered a glitch, but if you DO get enough speed going, you can always get a nice multiplier by smashing into Jool just right. In reality, there is a maximum gravity assist you can get, but I don't think the game simulates slingshots properly at high speeds.

15 minutes ago, SuperFastJellyfish said:

I did this a few years ago with infinite fuel.  I used the least massive probe core, a thumper, and two RTGs(I couldn't get a single one to attach nonoffset).  After it was out of fuel, the thumper had the highest TWR of all the engines back then, as far as I remember.  I let it run for a few days straight(4, I think).  I'll post some pics after work.

The Mammoth has the highest vacuum TWR of any engine now. I used two of them and turned on infinite propellant and infinite electricity -- lemme see how fast I get to c.

[sevenperforce]

Here's the LV.

Infinite electricity, infinite prop, no heating damage:

Toasty on ascent:

Even toastier in space.

Solar escape was reached within the first 2 minutes. This is after I let it run a bit longer.

Looks like the maximum acceleration is 266.3 m/s², so I'd need to run it for just over 32 days. 

EDIT: Actually, upon review, an empty Separatron has a far higher TWR than a Mammoth, so lemme rebuild it real quick.

Edited May 23, 2017 by sevenperforce

[SuperFastJellyfish]

I found my old post from 2013.   11 days MET, but I had it running at 4x warp the whole way there.

Edited May 23, 2017 by SuperFastJellyfish

[sevenperforce]

With a bunch of Separatrons, I can boost my acceleration up to 1,270.1 m/s²; with artful use of 4x warp, this will get me to c in about 16.4 hours. Ignore the "max acceleration" shown; that is adding its spin rate, which is rather prodigious at this point.

[Aghanim]

On 5/23/2017 at 8:55 AM, Grand Ship Builder said:

Now, how hard is it to get to C in Kerbal Space Program without glitches?

In stock KSP? Really hard, even with infinite fuel cheat turned on.

In modded KSP? Pretty easy, use KSP Interstellar warp drive with a fusion reactor or antimatter reactor to power it off, and set it to 1c. Feel free to overclock it to 500c or more

Disclaimer: Warp drive may violate conservation of energy, law of physics, and/or destroy the universe

Question: If a particle travelling faster than the local speed of light in water creates Cherenkov radiation, will a warp ship travelling faster than vacuum speed of light creates Cherenkov radiation too?

Edited May 27, 2017 by Aghanim

[sevenperforce]

1 hour ago, Aghanim said:

Question: If a particle travelling faster than the local speed of light in water creates Cherenkov radiation, will a warp ship travelling faster than vacuum speed of light creates Cherenkov radiation too?

No. A ship in warp is not moving at all; rather, the space around it is moving. Moreover, Cherenkov radiation is the result of interactions with the local medium; a vacuum has no medium and so there is nothing to interact with.

[Grand Ship Builder]

Would, hybrid rockets (for mostly, well, rockets), L.A.C.E. (for mostly spaceplanes) engines, and tripropellant engines (for both) be feasible in Kerbal Space Program?

 

[raxo2222]

How fast interstellar spaceship could travel until cosmic microwave background gets blueshifted enough to heat/irradiate it?

How would blueshifted into visible range microwave background look?

[Steel]

15 minutes ago, Grand Ship Builder said:

Would, hybrid rockets (for mostly, well, rockets), L.A.C.E. (for mostly spaceplanes) engines, and tripropellant engines (for both) be feasible in Kerbal Space Program?

 

Anything is feasible in KSP!

On a slightly more serious note: you would't really notice the difference between a normal liquid rocket and a hybrid in KSP, except maybe slightly lower ISP.  The same goes for tripropellant engines too, you'd get slightly better ISP numbers and have an extra fuel type to look at, but other than that there would be no fundamental differences. I'm not familiar with what L.A.C.E. is so I can't really comment

7 minutes ago, raxo2222 said:

How fast interstellar spaceship could travel until cosmic microwave background gets blueshifted enough to heat/irradiate it?

How would blueshifted into visible range microwave background look?

To answer the second part, it would just look like the entire sky was glowing pretty uniformly I think. The fluctuations in the CMBR are so small that the eye would almost certainly not be able to tell the difference from one point to the next.

Edited May 29, 2017 by Steel

[Grand Ship Builder]

1 minute ago, Steel said:

Anything is feasible in KSP!

On a slightly more serious note: you would't really notice the difference between a normal liquid rocket and a hybrid in KSP, except maybe slightly lower ISP.  The same goes for tripropellant engines too, you'd get slightly better ISP numbers and have an extra fuel type to look at, but other than that there would be no fundamental differences. I'm not familiar with what L.A.C.E. is so I can't really comment

L.A.C.E. stands for Liquid Air Cycle Engine, in which they take the air from the atmosphere, cool it down way colder than a precooler, and then turn it into liquid oxygen. This greatly reduces the lift-off weight needed, though technically you're making your craft heavier as it goes up instead of lighter.

[raxo2222]

6 minutes ago, Steel said:

Anything is feasible in KSP!

On a slightly more serious note: you would't really notice the difference between a normal liquid rocket and a hybrid in KSP, except maybe slightly lower ISP.  The same goes for tripropellant engines too, you'd get slightly better ISP numbers and have an extra fuel type to look at, but other than that there would be no fundamental differences. I'm not familiar with what L.A.C.E. is so I can't really comment

To answer the second part, it would just look like the entire sky was glowing pretty uniformly I think. The fluctuations in the CMBR are so small that the eye would almost certainly not be able to tell the difference from one point to the next.

Im interested in angular size of that spot - would be it large as moon? Or small as lets say any star?

Special relativity says that light gets concentrated around spot in direction where are we travelling to.

Would be it bright as sun? Or bit darker like moon?

I bet at first it would glow like red moon and then shine like blue star when accelerating.

Edited May 29, 2017 by raxo2222

[Steel]

15 minutes ago, raxo2222 said:

Im interested in angular size of that spot - would be it large as moon? Or small as lets say any star?

Special relativity says that light gets concentrated around spot in direction where are we travelling to.

Would be it bright as sun? Or bit darker like moon?

I bet at first it would glow like red moon and then shine like blue star when accelerating.

I think you'd actually have to run some numbers to get an answer, my off-the-cuff knowledge runs out at this point!

EDIT:

@raxo2222 I've just worked out roughly how fast you'd need to go to shift the CMBR (wavelength approx. 1mm) to visible (I picked 500 nm for no real reason). The answer: 0.9999995 c

Edited May 29, 2017 by Steel

[sevenperforce]

19 hours ago, raxo2222 said:

Im interested in angular size of that spot - would be it large as moon? Or small as lets say any star?

Special relativity says that light gets concentrated around spot in direction where are we travelling to.

Would be it bright as sun? Or bit darker like moon?

I bet at first it would glow like red moon and then shine like blue star when accelerating.

The whole prograde half of the sky would glow, but it would be brightest and bluest in the center while fading continuously to red and then to black at the terminator. There would be no defined edge.

19 hours ago, Grand Ship Builder said:

Would, hybrid rockets (for mostly, well, rockets), L.A.C.E. (for mostly spaceplanes) engines, and tripropellant engines (for both) be feasible in Kerbal Space Program?

As Steel said, you can mod anything you want; it just depends on how true-to-life you want to make it. The stock engines in KSP aren't very true-to-life, after all.

A realistic hybrid rocket would be less like a traditional liquid-fueled rocket and more like a restartable solid booster, perhaps with a limited throttle range. Ideally, it would use oxidizer as a resource but not liquid fuel, and once it was expended it would not be refuelable (unlike a liquid rocket, where you can transfer fuel from another ship).

With LACE, again, it depends on how realistic you want it to be. The real-life LACE concept is very problematic; it takes ridiculous amounts of liquid hydrogen to liquify air (so much that you end up just dumping hot hydrogen overboard instead of burning it), and the mechanism to separate the LOX from the liquid nitrogen is heavy. You also run into the reverse rocket equation problem; if you're collecting remass and oxidizer on your way up, your net thrust is the difference between total thrust and the momentum you are losing as you collect air. The faster you're going, the more momentum you lose with every kilogram of air you collect. For KSP, however, one could envision a modified engine precooler that takes liquid fuel as a resource and generated oxidizer; that plus a RAPIER would basically be LACE.

Since KSP only has one liquid fuel type, a triprop engine isn't very easy to pull together. You'd have to mod to create new fuel types. Short of that, you could simply have an engine with a tweakable that can gain thrust in exchange for sacrificing specific impulse (or vice versa); that's basically how a triprop engine works in practice. Another solution would be to have an liquid engine that consumes monopropellant in addition to liquid fuel and oxidizer to increase thrust while losing isp. Since the monoprop in KSP is basically hydrazine, and a triprop engine could conceivably burn hydrazine in addition to hydrocarbon and LOX, that might be a good way to do it without making things overly complicated.

 

[magnemoe]

On 30.5.2017 at 5:07 PM, sevenperforce said:

The whole prograde half of the sky would glow, but it would be brightest and bluest in the center while fading continuously to red and then to black at the terminator. There would be no defined edge.

As Steel said, you can mod anything you want; it just depends on how true-to-life you want to make it. The stock engines in KSP aren't very true-to-life, after all.

A realistic hybrid rocket would be less like a traditional liquid-fueled rocket and more like a restartable solid booster, perhaps with a limited throttle range. Ideally, it would use oxidizer as a resource but not liquid fuel, and once it was expended it would not be refuelable (unlike a liquid rocket, where you can transfer fuel from another ship).

With LACE, again, it depends on how realistic you want it to be. The real-life LACE concept is very problematic; it takes ridiculous amounts of liquid hydrogen to liquify air (so much that you end up just dumping hot hydrogen overboard instead of burning it), and the mechanism to separate the LOX from the liquid nitrogen is heavy. You also run into the reverse rocket equation problem; if you're collecting remass and oxidizer on your way up, your net thrust is the difference between total thrust and the momentum you are losing as you collect air. The faster you're going, the more momentum you lose with every kilogram of air you collect. For KSP, however, one could envision a modified engine precooler that takes liquid fuel as a resource and generated oxidizer; that plus a RAPIER would basically be LACE.

Since KSP only has one liquid fuel type, a triprop engine isn't very easy to pull together. You'd have to mod to create new fuel types. Short of that, you could simply have an engine with a tweakable that can gain thrust in exchange for sacrificing specific impulse (or vice versa); that's basically how a triprop engine works in practice. Another solution would be to have an liquid engine that consumes monopropellant in addition to liquid fuel and oxidizer to increase thrust while losing isp. Since the monoprop in KSP is basically hydrazine, and a triprop engine could conceivably burn hydrazine in addition to hydrocarbon and LOX, that might be a good way to do it without making things overly complicated.

 

Yes, an hybrid rocket in KSP would be just an mix of an solid and liquid fuel engine. It uses the non refuel-able solid fuel and oxidizer. Benefit is restart ability and throttleable.

Yes the thermodynamic of LACE makes little sense, better to bring the LOX up or optionally do an mid air refueling with LOX. Even Sabre use more hydrogen for cooling than the engine need so it has an small ramjet to burn it. 

An oxygen harvesting satellite might be possible. It would need an orbit who dips into the atmosphere, you have an scope who collect air. You would then need to cool it, collect the oxygen, nitrogen can be used as reaction mass or cooling medium, perhaps both. Probably work better as you spend most of your time out of the atmosphere, you would face cooling issues however,  
 

[0111narwhalz]

How can one convert between the Keplerian orbital parameters and a spherical coordinate system? I've found all kinds of stuff on how to convert between spherical, cylindrical, and Cartesian coordinates, but nothing relating to orbital parameters.

[Steel]

2 hours ago, 0111narwhalz said:

How can one convert between the Keplerian orbital parameters and a spherical coordinate system? I've found all kinds of stuff on how to convert between spherical, cylindrical, and Cartesian coordinates, but nothing relating to orbital parameters.

This StackExchange page has the user convert from Keplerian to Cartesian, so you could then convert from that to spherical coordinates. If you wanted to streamline it a bit you could work out the transformation matrices that they're using, combine those with the Cartesian-to-spherical transformation matrices and then do it all in one step.

[0111narwhalz]

Thanks, mate. My search-fu was weak.

[Aghanim]

On 5/30/2017 at 1:45 AM, Grand Ship Builder said:

Would, hybrid rockets (for mostly, well, rockets), L.A.C.E. (for mostly spaceplanes) engines, and tripropellant engines (for both) be feasible in Kerbal Space Program?

 

In modded KSP, KSP Interstellar have aluminium fueled hybrid rocket:  https://github.com/sswelm/KSP-Interstellar-Extended/wiki/HA-1-Aluminum-Hybrid-Rocket

[sevenperforce]

3 hours ago, Aghanim said:

In modded KSP, KSP Interstellar have aluminium fueled hybrid rocket:  https://github.com/sswelm/KSP-Interstellar-Extended/wiki/HA-1-Aluminum-Hybrid-Rocket

Eh, I don't like it. It's not really realistic to mine aluminum to refuel a solid rocket; you can't refuel a solid. Better to have a hybrid rocket full of solid reducer that uses oxidizer from attached tanks as a resource. You can mine for more oxidizer if you want.