Venus tour with all parts Recovered.

[Marmilo]

I can get engine ISP.

Bruh...
It's in the engine description...

 

[TtTOtW]

That would be Efficiency. Just plug that in.

 

[Altaïr]

Congrats SFSAbhishek , that's a first one indeed.

For those who are not keen on maths but still want to go into delta-V calculations, I have an interesting tool, the ship design assistant. It's a spreadsheet in which you enter the characteristics of your ship, and it calculates everything for you. I use it a lot myself. Here is the link:

SFS 1.5 - Ship Design Assistant

It's in read-only mode. That's intentional, otherwise several persons could use it at the same time. Please make your own copy to use it.

Here is how to use it:


Firstly, you may only be interested in the upper part. The tables below are used for more specific calculations. You have to fill the grey tables, the blue tables show the results.

Engine configuration:
In the up left corner, you have to specify which engines you use, and how many of each:

It's done that way because the specific impulse is tricky to calculate when you mix several types of engines. The blue table below shows the characteristics of your engine configuration.

There's also a colum labelled "unused". You may want to use that one when you don't use all engines.
That would be the case typically for a starship, that has 3 vacuum engines, and 3 ground engines. Which could be 3 Frontier and 3 Hawk ingame. While navigating in space, you'll only use the Frontier engines. In this case, you would enter "3" in the "Unused" column to tell that you don't use the Hawk engines. The assistant won't take them into account to calculate thrust, fuel consumption and specific impulse, but it will still account for their mass.

Ship specifications:
Then, in the up right corner, you have to specify how much fuel your ship has at its disposal, and the mass of all other parts (anything that is not an engine or a fuel tank):

Then you have everything you want to know in the blue table below, especially the delta-V.

Example:
As an example, the sheet has been filled for this ship:

- Engines: it uses a single Valiant. In the engine table, just enter "1" for the number of Valiant engines, and leave the rest to 0.
- Fuel: 20 tons
- Remaining mass: we have 1 capsule (4 tons), 1 separator (0.4 tons) and 1 parachute (0.4 tons), so that's 4.8 tons.

And that's all!

Note that this is meant to be an assistant, not a full calculator. You can only calculate the characteristics of one stage at once. It's possible to find some more advanced caluculators in this sense (Horus Lupercal has one for example). But it's practical to make a few tweaks while being very simple. ("What if I add an engine? More fuel?"...)

 

[Blazer Ayanami]

You know, I gotta say is not mandatory to use maths to play this game. Some maths always look nice on a complex and well planned mission, but is not mandatory to use them. Hell, I never use maths and still nobody can stop me.

 

[Marmilo]

You know, I gotta say is not mandatory to use maths to play this game. Some maths always look nice on a complex and well planned mission, but is not mandatory to use them. Hell, I never use maths and still nobody can stop me.

I almost never use advanced mathd

 

[Blazer Ayanami]

I almost never use advanced mathd

Yeah, I mean apart from some basic comprehension of what is TWR and ISP, nothing else is really really really mandatory.

 

[Altaïr]

I totally agree, it's absolutely not necessary to play SFS to do some advanced maths.

...

Oh wait, I think I reversed something there!

Joke apart, the rocket equation is still pretty simple. And when you just fill a few boxes you don't even feel like you're doing maths. But everyone can play simply obviously.

How come log to base e is inside the delta V formula

Ooooh I see someone explicitely asking for some ugly maths there

I would have to show you the demonstration to answer precisely, but to make it short, the logarithm comes from an integration. When you integrate the reciprocal function ("f(x) = 1/x"), you get the natural logarithm. That's how you end with that logarithm in the formula.

 

[bobbblair123]

View attachment 53233 View attachment 53234
That would be Efficiency. Just plug that in.

Great! Glad I caught you Marmilo and TtTOtW. ( One day I hope you tell me what that stands for) so a kolibri (in space, relative velocity irrelevant) with an Isp of 260 with say 4 tons fuel 5.5 tons total with tank and engine gives me how much ∆v to play with? My understanding specific just means divided by weight (as apposed to mass)

 

[Marmilo]

One day I hope you tell me what that stands for

In space propulsion or smth like that.

 

[TtTOtW]

SPecific Impulse, but the French version that puts the I in front.

 

[Horus Lupercal]

TtTOtW. ( One day I hope you tell me what that stands for)

Think nocturnal cartoon lab mice

a kolibri (in space, relative velocity irrelevant) with an Isp of 260 with say 4 tons fuel 5.5 tons total with tank and engine gives me how much ∆v to play with?

Grab a decent calculator and input the numbers you've just given into the formula shown above.

9.8 * 260 * LN(5.5/1.5) = ΔV (in this case, 1437 and a bit m/s)

That is the sum total of how much that rocket can change its velocity.

 

[bobbblair123]

Congrats SFSAbhishek , that's a first one indeed.

For those who are not keen on maths but still want to go into delta-V calculations, I have an interesting tool, the ship design assistant. It's a spreadsheet in which you enter the characteristics of your ship, and it calculates everything for you. I use it a lot myself. Here is the link:

SFS 1.5 - Ship Design Assistant

It's in read-only mode. That's intentional, otherwise several persons could use it at the same time. Please make your own copy to use it.

Here is how to use it:
View attachment 53237

Firstly, you may only be interested in the upper part. The tables below are used for more specific calculations. You have to fill the grey tables, the blue tables show the results.

Engine configuration:
In the up left corner, you have to specify which engines you use, and how many of each:
View attachment 53238
It's done that way because the specific impulse is tricky to calculate when you mix several types of engines. The blue table below shows the characteristics of your engine configuration.

There's also a colum labelled "unused". You may want to use that one when you don't use all engines.
That would be the case typically for a starship, that has 3 vacuum engines, and 3 ground engines. Which could be 3 Frontier and 3 Hawk ingame. While navigating in space, you'll only use the Frontier engines. In this case, you would enter "3" in the "Unused" column to tell that you don't use the Hawk engines. The assistant won't take them into account to calculate thrust, fuel consumption and specific impulse, but it will still account for their mass.

Ship specifications:
Then, in the up right corner, you have to specify how much fuel your ship has at its disposal, and the mass of all other parts (anything that is not an engine or a fuel tank):
View attachment 53239
Then you have everything you want to know in the blue table below, especially the delta-V.

Example:
As an example, the sheet has been filled for this ship:
View attachment 53240
- Engines: it uses a single Valiant. In the engine table, just enter "1" for the number of Valiant engines, and leave the rest to 0.
- Fuel: 20 tons
- Remaining mass: we have 1 capsule (4 tons), 1 separator (0.4 tons) and 1 parachute (0.4 tons), so that's 4.8 tons.

And that's all!

Note that this is meant to be an assistant, not a full calculator. You can only calculate the characteristics of one stage at once. It's possible to find some more advanced caluculators in this sense (Horus Lupercal has one for example). But it's practical to make a few tweaks while being very simple. ("What if I add an engine? More fuel?"...)

Ship design asst require a spreadsheet app to use?

 

[TtTOtW]

Great! Glad I caught you Marmilo and TtTOtW. ( One day I hope you tell me what that stands for) so a kolibri (in space, relative velocity irrelevant) with an Isp of 260 with say 4 tons fuel 5.5 tons total with tank and engine gives me how much ∆v to play with? My understanding specific just means divided by weight (as apposed to mass)

Remember your probe. That's 3t. Kolibri, 0.5t. 5t fuel tank, 5t (0.5t tank, 4.5t fuel). So full mass: 8.5t. Empty, 4t.

9.8×260×ln(8.5/4)=1920.61m/s.

 

[TtTOtW]

Ship design asst require a spreadsheet app to use?

Yes

 

[bobbblair123]

Remember your probe. That's 3t. Kolibri, 0.5t. 5t fuel tank, 5t (0.5t tank, 4.5t fuel). So full mass: 8.5t. Empty, 4t.

9.8×260×ln(8.5/4)=1920.61m/s.

And your using escape velocity (9.8) why? And yes for the purposes of SFS I did forget a controller/probe. I got Mf and Me. The fuel versus Mf were arbitrary but you are correct to keep the numbers real

 

[bobbblair123]

Yes

✓ thank you

 

[TtTOtW]

9.8 is Earth gravity. It standardises ths calculation instead of having to part calculate differently for each different body.

 

[bobbblair123]

9.8 is Earth gravity. It standardises ths calculation instead of having to part calculate differently for each different body.

Ah. g0 (gravitational acceleration constant.) x Isp (Impulse specific) x In (Mf÷Me) = ∆v. The blankity blank specific is immaterial. A perfect case of just enough knowledge. Reading too many google articles. Now to go plug in some numbers and crash a few rockets

 

[Altaïr]

Ship design asst require a spreadsheet app to use?

You can just use Google Sheets (if you play under Android...), it's what I use, it does the job...

And your using escape velocity (9.8) why? And yes for the purposes of SFS I did forget a controller/probe. I got Mf and Me. The fuel versus Mf were arbitrary but you are correct to keep the numbers real

There's a long story behind that, but to make it short, the authentic rocket equation is:
Delta-V = Ve × ln(Mf/Me)

Ve is the exhaust speed. A greater exhaust speed is more interesting because it generates more impulse with the same fuel consumption. That's why it's considered more efficient.

However, because the americans don't have the same unit system (imperial vs metric) than the rest of the World, this gave a different result for them. That's why specific impulse was created, and for a rocket it is defined as Isp = Ve/g. Note that it's not the exact definition, but let's keep things simple...

The advantage of specific impulse is that it's measured in seconds, so it doesn't depend on the unit system in which it's expressed, as the second is standard in both imperial and metric systems.

Also, to prevent a common confusion, the "g" in the rocket equation is to be understood as "g on Earth". You don't have to consider the gravity of the Moon to calculate a rocket's performance on the Moon. That "g" is always 9.8 m/s^2, no matter what happens.

 

[James Brown]

Now the euler e’s problem won’t left my brain unless I think of it

 

[bobbblair123]

You can just use Google Sheets (if you play under Android...), it's what I use, it does the job...


There's a long story behind that, but to make it short, the authentic rocket equation is:
Delta-V = Ve × ln(Mf/Me)

Ve is the exhaust speed. A greater exhaust speed is more interesting because it generates more impulse with the same fuel consumption. That's why it's considered more efficient.

However, because the americans don't have the same unit system (imperial vs metric) than the rest of the World, this gave a different result for them. That's why specific impulse was created, and for a rocket it is defined as Isp = Ve/g. Note that it's not the exact definition, but let's keep things simple...

The advantage of specific impulse is that it's measured in seconds, so it doesn't depend on the unit system in which it's expressed, as the second is standard in both imperial and metric systems.

Also, to prevent a common confusion, the "g" in the rocket equation is to be understood as "g on Earth". You don't have to consider the gravity of the Moon to calculate a rocket's performance on the Moon. That "g" is always 9.8 m/s^2, no matter what happens.

NASA.gov has a handy sheet for various formulas with explanations for the variables and alternative calculations. Not a huge fan of anything google. Basically bloatware with spyware added.

 

[bobbblair123]

In space propulsion or smth like that.

I meant TtTOtW. I thought Isp meant internet service provider. That's what comes up when you google it.

 

[bobbblair123]

So is there a list of useful and important ones? I've never used them for any mission

 

[TtTOtW]

I meant TtTOtW

Ever watched cartoons?

 

[Pink]

Now the euler e’s problem won’t left my brain unless I think of it

You don't need it for dV.
It's as simple as pie once you do it a few times.