Pretorian28715

KSP Calculations Spreadsheet [inDev]

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Hi Everyone,

I've been working on a spread sheet in Excel, for various calculations relating to KSP.

This is firstly, to learn more about the Physics and Math involved in KSP [and Space flight in general], and secondly, because I was thinking of starting a Barebones Career, as in only adding parts and planets in terms of mods and not anything like KER or Mechjeb, and possible doing IVA only's. [not sure if I'm that confidant with my KSP skills yet though :D].

 

So far I have: -

  • Hohmann Transfer
  • Bi-Elliptic Transfer
  • Interplanetary Transfer
  • Satellite Minimum Altitude
  • Satellite Transfer/Phasing Orbit
  • Rocket Equation (REq) deltaV - available 
  • REq - Total Mass for required deltaV 
  • REq - deltaV remaining  [WIP]
  • TWR 

 

To Add

  • I have just started on the Rocket Equation [it's giving me a Headache already and I've not started to turn it around yet] [Ok now starting to turn it around, headache still coming]

 

Questions to everyone: -

Would anybody else want a copy?

What else should I try to add?

What format should I distribute in? If even wanted.

[i'll add others as they come up]

 

Anyone who is interested please post so I know it will be wanted.

First draft - some sheets are WIP

https://drive.google.com/file/d/0B8rJGx3hp3uJUTFPQWNhWE5Xb28/view?usp=drivesdk

Updates: -

Sheet added 

References and/or inspiration: -

Link1 - Interplanetary How-To Guide by @Kosmo-not
Link2 - and the PDF version of @Kosmo-not's Guide provided by @Nexus24680
Link3 - Special Thanks to @OhioBob and his Website
Link4 - Inspired by @Nexus24680's Orbital Calculator
Link5 - Orbits calculator spreadsheet By @Gaarst
TBC - Satellite Minimum Orbit Calculator By TBC
TBC - Satellite Orbit and 'Spacing' Calculator By TBC
Link8 - Interplanetary Trajectories with Low TRW (and No Math) By @Brainlord Mesomorph [Testing Needed]
Link9 - The "reverse rocket equation" explained By @GoSlash27 [some Tabs WIP]

 

If anyone knows who or what thread(s) the Satellite stuff come from, 'cos for the life of me I can not find them again?

Edited by Pretorian28715
Update

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Pretorian,

 I don't need a copy, but a couple suggestions: You don't need to reverse the rocket equation to find remaining DV. So long as you know the current mass of your ship, the amount of fuel available, and the Isp of your engine, you can calculate that directly.

 If you carry your "total mass" calculator a little farther, you can get it to design you a stage.

 Finally, I'd suggest adding a burn time calculator.

 

 Best,
-Slashy

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55 minutes ago, GoSlash27 said:

Pretorian,

 I don't need a copy, but a couple suggestions: You don't need to reverse the rocket equation to find remaining DV. So long as you know the current mass of your ship, the amount of fuel available, and the Isp of your engine, you can calculate that directly.

 If you carry your "total mass" calculator a little farther, you can get it to design you a stage.

 Finally, I'd suggest adding a burn time calculator.

 

 Best,
-Slashy

Thanks, I was just adding a few things that would be useful in the event I did a caveman or caveman evolved career.

I was also trying to make the sheets independent of each other, but still working on some of them, this is afterall WIP. 

The whole exercise is also so I can learn the math etc... involved. But thanks for the feedback. Need to give references for work I've used to help me too. Any other help is appreciated too.

Edited by Pretorian28715

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Awesome work!

This is 1000x better than mine

Just a couple questions:

Can you make a RSS (Real Solar System) version?

Is it customizable?

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3 hours ago, Nexus24680 said:

Awesome work!

This is 1000x better than mine

Just a couple questions:

Can you make a RSS (Real Solar System) version?

Is it customizable?

Yes fully customisable just change the data in 'Kerbal' as all other Sheets pull from this. It just means that the data has to be entered first.

If you do, can you send me a copy, then I can add an RSS-DataBase tab too.

And Thank you :D.

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4 hours ago, Pretorian28715 said:

Yes fully customisable just change the data in 'Kerbal' as all other Sheets pull from this. It just means that the data has to be entered first.

If you do, can you send me a copy, then I can add an RSS-DataBase tab too.

And Thank you :D.

Hmmm

I find it a little bit complex.

I'm working with another game which uses 2d orbital mechanics and doesn't need things like inclination, etc.

Could you make a simplified version for 2d orbital mechanics?

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1 hour ago, Nexus24680 said:

Hmmm

I find it a little bit complex.

I'm working with another game which uses 2d orbital mechanics and doesn't need things like inclination, etc.

Could you make a simplified version for 2d orbital mechanics?

I haven't started on adding the Inclinations/plane changes in yet [need to get my head around it first], although it is planned for a future Sheet, in principle you can just ignore it.

Also I am making a few changes to the whole Spreadsheet, to make it more intuitive [hopefully]. I shall add some instructions to the OP too.

 

@GoSlash27, sorry forgot to mention earlier, it is for general perusal, or use by whom ever see's fit.

I mentioned you and the others as I feel that as I drew inspiration or outright 'stole' from you; you should be given well deserved credit, especially in your case as I knew you could throw Algebra at the equation, but was not sure how to approach it and your thread has given me a starting point. On a side note will you be expanding the Reverse Rocket Equation thread? [oh and why Lister?]

 

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Can you isolate these formulas for me? 

And explain them?

• Ejection Angle

• Ejection Velocity

• Interplanetary Hohmann Transfer Delta-V

Please.

Like putting them on a different excel file with all the variables and the formulas.

Thanks in advance.

:)

Edited by Nexus24680

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3 hours ago, Pretorian28715 said:

I haven't started on adding the Inclinations/plane changes in yet [need to get my head around it first], although it is planned for a future Sheet, in principle you can just ignore it.

Also I am making a few changes to the whole Spreadsheet, to make it more intuitive [hopefully]. I shall add some instructions to the OP too.

 

@GoSlash27, sorry forgot to mention earlier, it is for general perusal, or use by whom ever see's fit.

I mentioned you and the others as I feel that as I drew inspiration or outright 'stole' from you; you should be given well deserved credit, especially in your case as I knew you could throw Algebra at the equation, but was not sure how to approach it and your thread has given me a starting point. On a side note will you be expanding the Reverse Rocket Equation thread? [oh and why Lister?]

 

Pretorian,

 Don't worry about "stealing" anything you get from me or anyone else. We put these things out there because we *want* others to make use of it and expand upon it.

 As for my further expansions on the reverse rocket equation... I don't know. I'm not playing much KSP these days. If you wish to explore that territory, you have my blessing.

 Why Lister: I kinda identify with him. I don't take any of this terribly seriously and look vaguely like him. Plus, I'm a Red Dwarf fan.

Best,
-Slashy

 

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8 hours ago, GoSlash27 said:

Pretorian,

 Don't worry about "stealing" anything you get from me or anyone else. We put these things out there because we *want* others to make use of it and expand upon it.

 As for my further expansions on the reverse rocket equation... I don't know. I'm not playing much KSP these days. If you wish to explore that territory, you have my blessing.

 Why Lister: I kinda identify with him. I don't take any of this terribly seriously and look vaguely like him. Plus, I'm a Red Dwarf fan.

Best,
-Slashy

 

Which is why I have made this available too. Share the learning, but I got into the habit of referencing so it gets included, also means that whomever uses this can look at the material and if they so choose can delve deeper into it. Kinda like I am now really.

I would appreciate it if you did continue the thread too or do you any materials you refer to?

Now there is an idea for a thread, sources.

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2 hours ago, Nexus24680 said:

I wrote something up there

That comes from Kosmo-not's Interplanetary really but I'm on mobile at the mo, so when I get to my pc again them yes I can.

Also look to the right in each sheet you should see equations and keys

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12 hours ago, Pretorian28715 said:

Which is why I have made this available too. Share the learning, but I got into the habit of referencing so it gets included, also means that whomever uses this can look at the material and if they so choose can delve deeper into it. Kinda like I am now really.

I would appreciate it if you did continue the thread too or do you any materials you refer to?

Now there is an idea for a thread, sources.

Pretorian,

 That's a pretty ancient thread now. It was all just the rocket equation and algebra, so no references.

Is there something you'd like me to elaborate on or explain in further detail?

Best,
-Slashy

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On 7/10/2017 at 0:26 PM, GoSlash27 said:

If you carry your "total mass" calculator a little farther, you can get it to design you a stage.

 Finally, I'd suggest adding a burn time calculator.

 

 Best,
-Slashy

This first please, about total mass a little further. I think I know what you mean, but if you can clarify.

Thanks

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5 hours ago, Pretorian28715 said:

This first please, about total mass a little further. I think I know what you mean, but if you can clarify.

Thanks

Pretorian,

 First, we generate a "model" of our rocket. One in which the payload is determined by the DV and engine characteristics.

 Using the REq in it's most basic form, you can generate a wet-to-dry ratio (Rwd) for any desired ⌂V. Rwd=e(⌂V/9.81Isp)
Converting Rwd to fuel fraction (Ff) will yield how much of your total mass needs to be fuel. Ff=Rwd/(Rwd-1)
Using your fuel tank's full-to-empty ratio (Rfe) (generally 9), you know how much of your total mass needs to be tanks; your tank fraction (Ft). Ft= Ff/Rfe

Now we have to determine how much total mass our model comprises, which is how much mass our engine can accelerate at our desired rate. This is based on our thrust, desired minimum acceleration, and local conditions.

For a vacuum engine, it's Mtotal=T/ga where Mtotal is total mass in tonnes, T is thrust in kiloNewtons, g is local surface g in m/sec, and a is minimum acceleration in gees.

For an atmospheric engine, thrust needs to be scaled with atmospheric pressure. Since thrust scales linearly with Isp, it's a matter of finding your engine's Isp by pressure, then scaling the thrust.

Now to finishing our model. Our fuel and tanks are currently fractions rather than masses, so let's fix that by multiplying them by total mass. Mf=Ff*Mtotal and Mtank=Ft*Mtotal

Our model rocket's mass is fuel+tanks+engine+payload, and we wish to find our payload, so Mpyld=Mtotal-Mfuel-Mtanks.

This model shows the payload a single engine could move at our desired mission parameters, and is scalable to our desired payload. Doubling the rocket would give us double the payload, and so on. We have gone through all this in order to find out how many engines we need for our stage.

Neng=desired payload/model payload. Since there is no such thing as a fractional engine, this needs to round up to the next integer.

 Now we plug this into the REq from the old thread and proceed as described there.

Best,
-Slashy

 

 

Edited by GoSlash27

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1 hour ago, GoSlash27 said:

(to be continued)

Did you do something like this in the Thread, and this is where I want to take the Tab any way.

So I can take a given Payload, where I want to go, use the DeltaV map add a %age for lee-way and then have it work out what would be needed to get said Payload there and back if required.

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5 minutes ago, Pretorian28715 said:

Did you do something like this in the Thread, and this is where I want to take the Tab any way.

So I can take a given Payload, where I want to go, use the DeltaV map add a %age for lee-way and then have it work out what would be needed to get said Payload there and back if required.

The old way didn't incorporate thrust requirements, and I only passively mentioned this new process. Yes, in the end you can plug in your mission requirements (payload, ⌂V, minimum acceleration, reference body, and atmospheric pressure) and it will spit out a recipe for the stage, stage mass, and (if you want) total cost. If you apply this to all engines simultaneously, it will allow you to compare the results and choose the best option.

Best,
-Slashy

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5 hours ago, Pretorian28715 said:

Did you do something like this in the Thread, and this is where I want to take the Tab any way.

So I can take a given Payload, where I want to go, use the DeltaV map add a %age for lee-way and then have it work out what would be needed to get said Payload there and back if required.

 

On 7/10/2017 at 9:09 PM, Nexus24680 said:

Can you isolate these formulas for me? 

And explain them?

• Ejection Angle

• Ejection Velocity

• Interplanetary Hohmann Transfer Delta-V

Please.

Like putting them on a different excel file with all the variables and the formulas.

Thanks in advance.

:)

What I meant here is that I can't find them on your file.

Can you point me where they are?

 

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4 minutes ago, Nexus24680 said:

 

What I meant here is that I can't find them on your file.

Can you point me where they are?

 

I should be able to have a look in an hour or 2.

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4 hours ago, Nexus24680 said:

 

What I meant here is that I can't find them on your file.

Can you point me where they are?

 

JLOXaIz.png

This is the Interplanetary Tab on the spreadsheet. Most will only be interested in the columns B through H, this is the area for the actual calculation Columns J & L are the Equations and Key respectively. All Tabs are set up the same with the Bi-Elliptic Tab below.

FBZCClD.png

Hope this helps, but any other questions please let me know.:)

Edited by Pretorian28715

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Awesome, thanks.

Now what I don't get is that I can't find the DV1 of the Interplanetary Hohmann Transfer.

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10 hours ago, Nexus24680 said:

Awesome, thanks.

Now what I don't get is that I can't find the DV1 of the Interplanetary Hohmann Transfer.

This is in Cell D30 for the manoeuvre burn for the value, and Cells J22 & J23 for the Equations.

Also Cells F21 & G21 for the Sun Orbital DeltaV differences, for the values, and J19 & J20 for the Equations.

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Another question

How do you calculate LO Altitude, Semi-Sync Altitude and Sync Altitude?

And how do you convert it to Real Solar System?

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On 13/07/2017 at 4:54 PM, Nexus24680 said:

Another question

How do you calculate LO Altitude, Semi-Sync Altitude and Sync Altitude?

And how do you convert it to Real Solar System?

LO altitude would be equivalent to LEO [ in RL generally 120Km up to 1000Km], Sync Alt is equivalent to GEO [or KEO], and the Semi-Sync is MEO.

In Stock this means that the Orbital Period is the same as the rotational period of the planet being orbited, so 6 Hrs for Kerbin [KEO] or 24 Hrs for Earth for [GEO]

And for the Semi-Sync it will be half that, so Kerbin 3 Hrs and 12 Hrs for Earth.

These are available in the Satellite Orbit Calculator [SatOrbitCalc], in Cells D6, E6 & F6 you can enter Hours, Minutes and Seconds respectively. Also Cell D3 pulls the Rotational Period from the Kerbal Tab [Note soon to be re-named System]

 

Equation: -

This is calculated based on the Rotational Period of the Body

Sync Orbital Altitude = ( ( ( ( µ * (Po)^2 ) / ( 4 * PI()^2 ) )^(1/3) ) - RB) / 1000

Where: -

µ = GM = Gravitational Parameter of Body e.g. Kerbin =  3.53160E+12

Po = Period of Orbit Required = Rotational Period of Body in Seconds e.g. Kerbin = 6Hrs = 360Mins = 21600 Sec

PI() = π = 3.14159

RB = Radius of Body e.g. Kerbin = 600,000m

This will give you the Altitude above Kerbin's Surface of the KEO. If you want the Semi-Sync orbit just divide Po by 2.

 

And I agree with @GoSlash27 we need a better way to display Equations.

Edited by Pretorian28715
typo

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@GoSlash27I have a quick question for you. Firstly how good is your Excel?

Do you know if it is possible to refer to another Excel file by %Folder%\KSP-Calc\KSP_Calc.xls

Where %Folder% tells the OS/Excel to look in the root folder, kind of how KSP looks in GameData for mods?

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