Halp me, I'm just some noob player :(
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Altaïr
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That's nice Horus Lupercal 
As you're on it I'll let you have a look, but just to give my two cents, I'm generally not keen on mixing several types of engines. There can be good reasons to do it, but keep in mind that each additional engine adds mass, which decreases delta-V (even if on the other hand you can raise your Isp that way).
Specific impulse is a very important parameter to maximize your delta-V, but dry mass is important aswell! That's why using a calculator is useful, because it can calculate all of this for you, so you know if your choice is a good deal or not in the end.
As you're on it I'll let you have a look, but just to give my two cents, I'm generally not keen on mixing several types of engines. There can be good reasons to do it, but keep in mind that each additional engine adds mass, which decreases delta-V (even if on the other hand you can raise your Isp that way).
Specific impulse is a very important parameter to maximize your delta-V, but dry mass is important aswell! That's why using a calculator is useful, because it can calculate all of this for you, so you know if your choice is a good deal or not in the end.
That's nice Horus Lupercal
As you're on it I'll let you have a look, but just to give my two cents, I'm generally not keen on mixing several types of engines. There can be good reasons to do it, but keep in mind that each additional engine adds mass, which decreases delta-V (even if on the other hand you can raise your Isp that way).
Specific impulse is a very important parameter to maximize your delta-V, but dry mass is important aswell! That's why using a calculator is useful, because it can calculate all of this for you, so you know if your choice is a good deal or not in the end.
As you're on it I'll let you have a look, but just to give my two cents, I'm generally not keen on mixing several types of engines. There can be good reasons to do it, but keep in mind that each additional engine adds mass, which decreases delta-V (even if on the other hand you can raise your Isp that way).
Specific impulse is a very important parameter to maximize your delta-V, but dry mass is important aswell! That's why using a calculator is useful, because it can calculate all of this for you, so you know if your choice is a good deal or not in the end.
Pink
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Altaïr
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That's exactly that.
To be precise, delta-V is calculated that way:
DV = g(Earth)×Isp×Ln(1 + fuel_mass/dry_mass)
So when you're on a ballistic trajectory, it's just a matter of Isp and "fuel/dry" ratio indeed.
Now when fighting a gravitational field, TWR is also important (actually that's even more important). Isp is still helpful of course: if an engine has the same thrust than another one but a higher Isp, it means it will consume less fuel. For this, it can be interesting to increase drastically your thrust, even if you lose a few seconds of Isp to do so.
Having a lot of TWR can't really hurt, but as Mooncrasher explained it very well, it can be overkill: you could already get a very good result with less engines. Now in a sandbox mode it won't really hurt you. It would if you were in a carreer mode and if you had to pay for each engine
Regarding the atmosphere, what really hurts is if you reach a high speed in a thick atmosphere (which is more likely to happen with a high TWR indeed, even if this is not directly related). Especially if your rocket isn't aerodynamic. That's another parameter to optimize. If your TWR is too high at a given moment, don't forget you can always reduce it by adjusting your throttle
To be precise, delta-V is calculated that way:
DV = g(Earth)×Isp×Ln(1 + fuel_mass/dry_mass)
So when you're on a ballistic trajectory, it's just a matter of Isp and "fuel/dry" ratio indeed.
Now when fighting a gravitational field, TWR is also important (actually that's even more important). Isp is still helpful of course: if an engine has the same thrust than another one but a higher Isp, it means it will consume less fuel. For this, it can be interesting to increase drastically your thrust, even if you lose a few seconds of Isp to do so.
Having a lot of TWR can't really hurt, but as Mooncrasher explained it very well, it can be overkill: you could already get a very good result with less engines. Now in a sandbox mode it won't really hurt you. It would if you were in a carreer mode and if you had to pay for each engine
Regarding the atmosphere, what really hurts is if you reach a high speed in a thick atmosphere (which is more likely to happen with a high TWR indeed, even if this is not directly related). Especially if your rocket isn't aerodynamic. That's another parameter to optimize. If your TWR is too high at a given moment, don't forget you can always reduce it by adjusting your throttle
Altaïr
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Altaïr
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Here is mine:
https://docs.google.com/spreadsheet...zOEbB5pSJMOjeiR-ES4y0HOzxy8/edit?usp=drivesdk
It's in "read only" mode, but you can make your own copy and work on it from your phone by using google sheets.
It simply uses the delta-V formula above, but automates a lot of painful process.
For example: I calculated fuel mass, dry mass for my ship and its delta-V. I'd like to have a bit more, so I may just add a slightly bigger fuel tank... But this changes fuel mass. Ok, I'll recalculate. Oh no, it also changes dry mass, I forgot! Well I have to recalculate that too.
And what if I change the engine... this changes Isp. Oh but this also changes dry mass!! I have to recalculate everything again!!!
That file is precisely designed to avoid all those things. You can change the engine, add more fuel... It recalculates everything automatically.
https://docs.google.com/spreadsheet...zOEbB5pSJMOjeiR-ES4y0HOzxy8/edit?usp=drivesdk
It's in "read only" mode, but you can make your own copy and work on it from your phone by using google sheets.
It simply uses the delta-V formula above, but automates a lot of painful process.
For example: I calculated fuel mass, dry mass for my ship and its delta-V. I'd like to have a bit more, so I may just add a slightly bigger fuel tank... But this changes fuel mass. Ok, I'll recalculate. Oh no, it also changes dry mass, I forgot! Well I have to recalculate that too.
And what if I change the engine... this changes Isp. Oh but this also changes dry mass!! I have to recalculate everything again!!!
That file is precisely designed to avoid all those things. You can change the engine, add more fuel... It recalculates everything automatically.
Here is mine:
https://docs.google.com/spreadsheet...zOEbB5pSJMOjeiR-ES4y0HOzxy8/edit?usp=drivesdk
It's in "read only" mode, but you can make your own copy and work on it from your phone by using google sheets.
It simply uses the delta-V formula above, but automates a lot of painful process.
For example: I calculated fuel mass, dry mass for my ship and its delta-V. I'd like to have a bit more, so I may just add a slightly bigger fuel tank... But this changes fuel mass. Ok, I'll recalculate. Oh no, it also changes dry mass, I forgot! Well I have to recalculate that too.
And what if I change the engine... this changes Isp. Oh but this also changes dry mass!! I have to recalculate everything again!!!
That file is precisely designed to avoid all those things. You can change the engine, add more fuel... It recalculates everything automatically.
https://docs.google.com/spreadsheet...zOEbB5pSJMOjeiR-ES4y0HOzxy8/edit?usp=drivesdk
It's in "read only" mode, but you can make your own copy and work on it from your phone by using google sheets.
It simply uses the delta-V formula above, but automates a lot of painful process.
For example: I calculated fuel mass, dry mass for my ship and its delta-V. I'd like to have a bit more, so I may just add a slightly bigger fuel tank... But this changes fuel mass. Ok, I'll recalculate. Oh no, it also changes dry mass, I forgot! Well I have to recalculate that too.
And what if I change the engine... this changes Isp. Oh but this also changes dry mass!! I have to recalculate everything again!!!
That file is precisely designed to avoid all those things. You can change the engine, add more fuel... It recalculates everything automatically.
Pink
(Mooncrasher)
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Not quite.
According to my notes:
Thrust(kN)/mass(tons) = acceleration.
This number is how quickly your spacecraft would accelerate with no gravity.
This comes from F=ma.
Acceleration/local gravity = TWR.
Where local gravity is the gravity of whatever object that you want to find TWR for. (In this case, 1.42 for the Moon)
You divide the space acceleration by local gravity, to find what's left over, because that's what TWR is. It's how much thrust you have left over after you account for gravity.
According to my notes:
Thrust(kN)/mass(tons) = acceleration.
This number is how quickly your spacecraft would accelerate with no gravity.
This comes from F=ma.
Acceleration/local gravity = TWR.
Where local gravity is the gravity of whatever object that you want to find TWR for. (In this case, 1.42 for the Moon)
You divide the space acceleration by local gravity, to find what's left over, because that's what TWR is. It's how much thrust you have left over after you account for gravity.