Ok, so maaaaaybe I might be working on something again.

[Whackjob]

Aaaand the thread's thrown into the basement where it can wither.

[TMS]

^

I think they call it "community management".

[Kerbart]

Aaaand the thread's thrown into the basement where it can wither.

Not really. You had me at "mainsail seperatron"

[GreenWolf]

There's a certain point where a vehicle moves from being a large vehicle to a mobile city. Whackjob's rocket has passed that point and kept going. I'm pretty sure it now qualifies as a small country.

[Jovus]

Aaaand the thread's thrown into the basement man-cave where it can wither get away with more.

FTFY

Off-topic: I've idly wondered what would happen if regex and Whackjob met at a KerbalKon and were left alone in a room together. (Probably they'd just talk about KSP and decide to get beers together, but in my head they're like opposite poles of awesome.)

[Whackjob]

If there were ever a KerbalKon near me and the budget permitted it, I would go.

[LABHOUSE]

Sadly it doesn't matter even if you have an 8 core 6ghz water cooled monster CPU. The game code is the limitation. Whackjob must be a very patient man!

And to those that put his build style down, he is part of a spectrum of build styles. The awesome end.

He is past that, the awsome and patient at become more awsome part.

[GiantTank]

http://forum.kerbalspaceprogram.com/threads/57626-Realistic-Solar-System-Crafts-MEGATHREAD/page45

Well (scroll down a bit, like 4 posts) might be the USSR. However it used PP and various other mods, and i cfg edited the launch clamps to be 100 times normal strength.

Edited March 29, 2015 by GiantTank

[NFUN]

http://forum.kerbalspaceprogram.com/threads/57626-Realistic-Solar-System-Crafts-MEGATHREAD/page45

Well (scroll down a bit, like 4 posts) might be the USSR. However it used PP and various other mods, and i cfg edited the launch clamps to be 100 times normal strength.

Did the VAB break and corrupt several times while making it, did your processor fry, could the explosions of thousands of parts be seen from Jool? If not, you haven't make a Whackjovian craft.

[federicoaa]

http://cloud-4.steamusercontent.com/ugc/710781191332169115/74956944C372858634C73F6A438F2E2228EE17F0/

Now THAT is a seperatron!

Only you could think of using a mainsail as separatron. Well done.

[LABHOUSE]

Sadly it doesn't matter even if you have an 8 core 6ghz water cooled monster CPU. The game code is the limitation. Whackjob must be a very patient man!

And to those that put his build style down, he is part of a spectrum of build styles. The awesome end.

Ksp can only use one core...

[Merinsan]

Aaaand the thread's thrown into the basement where it can wither.

That explains why I had so much trouble finding it!

I still want to see this finished.

Watching the Mun split in half because you didn't slow down enough will be epic!

[NFUN]

Ksp can only use one core...

*6ghz per core.

[Hobbes Novakoff]

As luck would have it Whackjob, strangely there's a challenge up from just a few days ago to do exactly what you're going to do.

[GiantTank]

Did the VAB break and corrupt several times while making it, did your processor fry, could the explosions of thousands of parts be seen from Jool? If not, you haven't make a Whackjovian craft.

I do actually think it caused a really bad bug that made the VAB unresponsive after a couple of minutes and made it so you couldnt launch crafts, build things or anything like that. It even reached into the stock game, and I had to reinstall thr whole game. Im trying it again anyway.

[NFUN]

I do actually think it caused a really bad bug that made the VAB unresponsive after a couple of minutes and made it so you couldnt launch crafts, build things or anything like that. It even reached into the stock game, and I had to reinstall thr whole game. Im trying it again anyway.

Now that's the spirit!

[Whackjob]

I may have to change tactic, here. I might have to... build small. Blech.

I can indeed get a very terrific speed going. But I'm trying for a continuous boost. The big stuff with big engines aren't big in one area: Burn time.

Back to the drawing board. No biggie.

[Frybert]

I may have to change tactic, here. I might have to... build small. Blech.

I can indeed get a very terrific speed going. But I'm trying for a continuous boost. The big stuff with big engines aren't big in one area: Burn time.

Back to the drawing board. No biggie.

I am coming to the same conclusion. All my ships are turning out surprisingly small.

A new challenge for DubyaJay, can you build small?

[GreenWolf]

The thing about boost ships (or torchships, if you prefer) is that not only do they have high thrust, they also have high Isp. Mainsails are lacking in one of those areas.

Whether you like it or not, you might not have a choice when it comes to using nukes (at least for part of it) if you want a boost ship.

[Majorjim!]

Ksp can only use one core...

KSP is a multi-threaded game. The issue is the fact that the physics pipeline only uses one core..

- - - Updated - - -

*6ghz per core.

It's not that simple sadly.

[NFUN]

KSP is a multi-threaded game. The issue is the fact that the physics pipeline only uses one core..

- - - Updated - - -

It's not that simple sadly.

Ok, fine. 12 ghz per core. Happy?

[Majorjim!]

Ok, fine. 12 ghz per core. Happy?

LOL, as this will smash every other game in the face, then yes. I am very happy indeed.

[Jovus]

A question and a suggestion for the man of the thread.

Suggestion: if you're interested, instead of shortest time from pad to landing, do the shortest time from LEO to landing. That'll allow you to build big and use big engines, because you don't need the starting TWR to get to space. (Use Hyperedit to get it up there; I shudder to think of orbital construction of one of your monstrosities.)

Question: Instead of your strut-truss-strut-tank system, have you tried a hybrid of cross-struts and cross-fuel-lines? I'm curious, because fuel lines are supposed to flex, and in fact have a much higher breaking tolerance in practice than struts because of it.

[GreenWolf]

Okay, so I went and did the math on this. (Using my existing rocket performance calculation spreadsheets and the equations for Brachistochrone transfers provided by Atomic Rockets.) I'll be calculating a thirty minute one-way trip from Kerbin to the Mün using a Brachistochrone transfer (accelerate halfway there, then flip around and decelerate the other half of the way). I'm not doing a round trip since a Mün to Kerbin trip can accelerate the whole way and use the atmosphere to slow down.

The Brachistochrone equation is:

T = 2 * sqrt(D/A)

Where:

T is transit time is seconds

D is distance in meters

A is acceleration in meters per second per second

For a thirty minute one-way trip to the Mün, our time is 1800 seconds. The Mün has a perfectly circular orbit of 12000000 meters. However, it is 200000 meters in radius, and Kerbin is 600000 meters in radius, so our actual distance (assuming a perfectly spherical Mün [and cow]) is 11200000 meters. So we have:

1800 = 2 * sqrt(11200000/A)

(Divide both sides by 2.)

900 = sqrt(11200000/A)

(Square both sides.)

810000 = 11200000/A

(Multiply by A)

810000 * A = 11200000

(Divide both sides by 810000.)

A = 13.827

So our one way torchship to the Mün needs to accelerate at about one and a half gees.

What's the delta-v?

To find that, we need to use this equation:

Delta-v = 2 * sqrt(D * A)

Same terms as above. Delta-v is delta-v (the snozberries taste like snozberries!)

So we plug in our mumbers from above:

Delta-v = 2 * sqrt(11200000 *13.827)

Delta-v = 2 * sqrt(154862400)

Delta-v = 2 * 12444.372

Delta-v = 24888.744

So to do a one-way trip to the Mün in thirty minutes, our rocket will need to have almost 25 km/s of delta-v, and be capable of accelerating at one and a half gees. This only gets worse when you add in the delta-v for the trip back (which could actually be done faster since you can accelerate the whole way, which also means your trip to the Mün can take more the 30 minutes if you want to do an hour round trip). This also doesn't take into account losses from atmospheric drag, or time lost while turning around to decelerate or spent on the Mün after landing. But I think it's safe to say that your boostship will need upwards of 40 km/s of delta-v.

I'll be calculating the mass ratio (and estimated size) of the 25 km/s, thirty minute to the Mün ship in a later post.

TL;DR: Much rocket, such delta-v.

Edit: Second round of number crunching

Okay, I decided to take a stab at calculating the delta-v needed for a complete, one-hour round trip between Kerbin and the Mün. The math for this is similar to the last one, so I'll stick it inside spoilers so you can skip it if you want.

First, some starting assumptions. I'm assuming that you want to make a one-hour round trip (this was stated in OP, so not a huge assumption.) I'm also assuming that you will be thrusting the entire time (again, stated in OP.) Now we get to some "spherical cow" assumptions.

I am assuming that the Mün and Kerbin are both perfectly spherical (they aren't). I'm also assuming that you can turn around and begin decelerating instantly (doubtful), and that you will spend zero time between Münar touchdown and liftoff (also doubtful). I'm also assuming that you can fly perfectly, and that you begin the deceleration burn at exactly the right moment (again, doubtful). I also assume that Kerbin's atmosphere will decelerate you instantly when you hit sea level (slightly less doubtful).

First, our trajectory to the Mün. This is a Brachistochrone transfer, like we looked at in the last post. This time, though, we'll try to do our Kerbin to the Mün part of the trip in 40 minutes, while the Mün to Kerbin leg will be 20 minutes.

Here's the math for the Brachistochrone, for those of you following along at home:

2400 = 2 * sqrt(11200000/A)

1200 = sqrt(11200000/A)

1440000 = 11200000/A

1440000 * A = 11200000

A = 11200000/1440000

A = 7.777 m/s^2 (approximately 0.8 gees)

Now for the delta-v:

Dv = 2 * sqrt(11200000 * 7.777)

Dv = 2 * sqrt(87102400)

Dv = 2 * 9332.866

Dv = 18665.733

Not bad. It's better than the first 30 minute ship. But we still need the return ship.

The math for this is actually easier than the Brachistochrone, since we don't need to worry about slowing down.

A = D/T^2

So:

A = (11200000)/(1200^2)

A = 11200000/1440000

A = 11200000/1440000

A = 7.777

Hey, wait, that's the same acceleration as our Kerbin to Mün ship which made the distance in twice the time! That's because the previous one only accelerated half of the way, before turning around to decelerate. The return ship can accelerate the entire way, then use Kerbin's atmosphere to slow down.

So what's our delta-v? This one's another simple one.

Dv = A * T

Acceleration multiplied by time is velocity, and since our initial velocity is zero, our delta-v is just our final velocity (before aerocrushing aerobraking.)

Dv = 7.777 * 1200

Dv = 9333.333

Hey, that's not too bad! When you combine it with the delta-v from the Kerbin to Mün ship, our total delta-v is 28000 m/s! That's far less than what I expected based off of the numbers for the 30 minute ship. So obviously, doing the first leg of the trip (relatively) slowly, and then doing the return trip quickly is better than doing them both the same speed.

But we're missing a few things.

You may have noticed that our acceleration is only 0.8 gees. This is bad. This isn't enough to take off from Kerbin. So we need higher acceleration. But not for the entire trip. Only until we hit Kerbin escape velocity. (You could probably drop your acceleration sooner, but you'd have losses due to gravity.)

The wiki informs us that Kerbin escape velocity is 3431 m/s. Round up and call it an even 3500.

What about losses due to atmospheric drag?

I have no idea. My completely unscientific estimate is that you'll need around 2000 m/s of extra delta-v to escape the atmosphere.

So 30000 m/s of delta-v. Tack on another couple thousand as a safety margin. The first 5000 m/s or so of this need to be done at an acceleration greater than 9.81 m/s^2 (I'm adding in the losses due to drag to the boost stage.) Once you hit escape velocity, you can drop your acceleration to 7.777 m/s^2.

How big is this rocket?

Assuming a specific impulse of 360 seconds (the Isp of the Mainsail), and that our delta-v budget is 32000 m/s, the rocket will have a mass ratio of 8613.18. This is a rocket that is over 99.98% propellant by mass. Yikes.

What if we try nukes? With an ISP of 800, our mass ratio can only improve.

According to my spreadsheets, this gives a mass ratio of 59, or 98.3% propellant by mass. That's a bit better.

What about ions? With their ISP of 4200 seconds, we get a mass ratio of 2.17, or 54% propellant by mass. Hey, that's not bad!

Unfortunately, ion engines are not an option for our torchship, since their thrust is too low for our acceleration needs.

So how do we manage to attain such ridiculous mass ratios?

We cheat the rocket equation.

With staging.

Lots of staging.

To figure out the mass ratio of a multi-stage rocket, you take the mass ratios of all of the individual stages, and you multiply them.

Yes, I said multiply.

For a mass ratio of 8613.18, assuming each of our individual stages has a mass ratio of 9 (88.88% propellant by mass), we'd need to have more than four stages but less than 5. These are, of course, massive stages.

All of the above math was done with some pretty big assumptions in mind, so take it with a Gilly-sized grain of salt. In reality, said rocket might need more or less delta-v depending on landing site, atmospheric drag, piloting skills, and design. Assuming that asparagus staging is used, your number of stages will almost certainly be more than 5. But it should give you an idea of the size of the rocket required.

I have no idea what a thirty minutes round trip would look like. I can run the numbers if anyone wants me too, but I think it's safe to assume that the final numbers will be drastically larger than an hour round trip.

TL;DR: 32000 m/s of delta-v, lots of staging.

Edited March 30, 2015 by GreenWolf
Update

[NFUN]

"These are, of course, massive stages."

Good...