Halp me, I'm just some noob player :(

[Roosterbooster]

The "IRONY"

 

[Roosterbooster]

Also think of orbits: A simple way to think is "We are going so fast that when we fall we go off of the edge" or somewhat.

Ah, too bad... But even when being good at maths, it's still better to first understand how it works in practice.

We can still explain a particular equation if you wish, but as equations are not especially popular I didn't really think it was worth it to make a thread for that.
And some phenomenons can be understood in a way simpler way with experience: the gravitational slingshot is a good example for this. The maths behind that are painful, but in practice it's a similar phenomenon to shooting a ball at a moving truck

 

[Horus Lupercal]

Anyway @Horus Lupercal, what if you make a guide on landing and making an orbit on the Galilean Moons, especially Europa?

This should help...

Mission 2: 'Apollo' Moon Landing.

Next up on Basics FM, a return moon landing.

In this one, I'm going to concentrate on the specifics of this mission from orbit onwards

• Selecting a target body
• Transfer windows
• Trans-Lunar Injection (TLI) burns
• Encounters
• Achieving Lunar Orbit
• Powered Landings
• Take Off from the Moon to LLO (Low Lunar Orbit)
• Trans-Earth Injection (TEI)
• Aerobraking
• Atmosphere Entry and parachute landings
• Mission Recovery

Europa has a very similar gravity and orbit speed to the moon, and is also airless to boot so the above explanation post applies. It's just a bit harder to get there (a Dv cost of 3419m/s for a direct burn from LEO to Low Europa Orbit without any gravity assists) because of the distances involved but once you're there, it's quite easy.
Europa is quite flat as well so landing is pretty easy compared to the other moons around Jupiter.

 

[Horus Lupercal]

Also think of orbits: A simple way to think is "We are going so fast that when we fall we go off of the edge" or somewhat.

Orbit
Everything in the solar system is attracted to everything else. This force is gravity. And I mean everything. Your chair, the bolt holding your bed together, the girl you like at school. All of these things exert a force, pulling you towards them and vice versa.
You just don't notice, because the force is almost negligible unless the objects are massive.
Objects like a planet, for example...
Earth is so big that it drags everything towards it and doesn't like letting go. So whenever something is launched away from it, it will always try and fall back towards it in an arc. Now, an orbit is essentially an arc so big that it misses Earth completely and keeps going around in a circle. It's still falling towards Earth, but never hits it.
How this happens is that object is moving so quickly that gravity hasn't got time to make it strike the ground before it goes off the side of the world. This speed is called escape velocity and varies from place to place.

 

[Roosterbooster]

"the girl you like at school"

 

[Pink]

This should help...




Europa has a very similar gravity and orbit speed to the moon, and is also airless to boot so the above explanation post applies. It's just a bit harder to get there (a Dv cost of 3419m/s for a direct burn from LEO to Low Europa Orbit without any gravity assists) because of the distances involved but once you're there, it's quite easy.
Europa is quite flat as well so landing is pretty easy compared to the other moons around Jupiter.

It's worth pointing out the default moon gravity settings...
All values m/s^2
Earth: 9.8 / 9.8
Luna: 1.42 / 1.62
Io: 4.32 / 1.8
Europa: 2.32 / 1.314
Ganymede: 5.84 / 1.428
Callisto: 4.24 / 1.235
First value is SFS, second is real life.
As you can see, Jupiter's moons have very high gravity in SFS. Europa is still the second easiest though (after Luna).

 

[A guy who likes sfs]

It’s finaly the weekend. And I see this fortress of words. Guess it’s back to Friday...

(But this is WAY better than the language block at school, I actually learned for a change)

 

[A guy who likes sfs]

It's worth pointing out the default moon gravity settings...
All values m/s^2
Earth: 9.8 / 9.8
Luna: 1.42 / 1.62
Io: 4.32 / 1.8
Europa: 2.32 / 1.314
Ganymede: 5.84 / 1.428
Callisto: 4.24 / 1.235
First value is SFS, second is real life.
As you can see, Jupiter's moons have very high gravity in SFS. Europa is still the second easiest though (after Luna).

What about the terrestrial planets?

 

[Altaïr]

What about the terrestrial planets?

They are very close to the real world gravity. I don't remember exactly the numbers, but there's practically no difference.

 

[Blazer Ayanami]

I've got your Dv as 2530m/s. Don't worry about that though, its just my calculator works out ISP itself rather than relying on the tooltip which is wrong.

But, nope, you're not going crazy or looking at things wrong.

It's generally accepted that it takes upwards of 2800-3000m/s of Dv to achieve LEO purely because of (as Danny puts it) drag and its effects on launch, despite it only needing about 1667m/s to make a circle at 30km.
We're (as in, the actual great minds on the forum) still trying to figure out how to calculate the exact Dv cost to break the atmosphere but the sheer amount of variables make it very complex without using simulations and at the minute its just a case of best guess and experience

Well, I hope those calculations are finished shortly, cause I made a rocket with a dV of 2975 m/s and I thought It was enough to reach LEO... Then *Boom!*
Couldn't pass 1100 m/s....

Expectation vs Reality

 

[Blazer Ayanami]

By the way, do I really need to do all those complex calculations to find ISP of a mix stage?

....Or can I just find the average by adding all the ISP's and dividing by the number of engines?

 

[A guy who likes sfs]

They are very close to the real world gravity. I don't remember exactly the numbers, but there's practically no difference.

Ok, thnx for tellin tho

 

[Horus Lupercal]

Well, I hope those calculations are finished shortly, cause I made a rocket with a dV of 2975 m/s and I thought It was enough to reach LEO... Then *Boom!*
Couldn't pass 1100 m/s....

Expectation vs Reality

Ha, good luck with that. Even the Great and Powerful Oz (Altair) won't go near it because of the sheer number of things that need to be taken into account to make it accurate. Especially in the case of how turd drag is in game.

By the way, do I really need to do all those complex calculations to find ISP of a mix stage?

Yes, yes you do. That way pointed out above is actually the easy way. The other way is even more complex...

1. you need the exhaust velocity of an engine. To work this out, you multiply thrust by fuel consumption.
2. Then, you multiply that, by g (9.8) to get an individual engine ISP
3. Do that for all engines
4. Now, for each individual engine, divide its force by its own ISP. Do this for all of the engines and add the totals together. Then take the combined total of all the thrust your engines create and divide that by the all the totals you've just worked out.

....Or can I just find the average by adding all the ISP's and dividing by the number of engines?

Lets try it...

• Hawk. Individual ISP = 250.741 x 2 = 501.482
• Broadsword. ISP = 281.492
  • Total = 782.974
• Divide 782.974 / 3 = 260.9913333333333 seconds

Answer from earlier on = 254.86 seconds.

It's ok, I once thought the same as well until Space Stig showed me to the path of Redemption...

 

[Blazer Ayanami]

Ha, good luck with that. Even the Great and Powerful Oz (Altair) won't go near it because of the sheer number of things that need to be taken into account to make it accurate. Especially in the case of how turd drag is in game.



Yes, yes you do. That way pointed out above is actually the easy way. The other way is even more complex...

1. you need the exhaust velocity of an engine. To work this out, you multiply thrust by fuel consumption.
2. Then, you multiply that, by g (9.8) to get an individual engine ISP
3. Do that for all engines
4. Now, for each individual engine, divide its force by its own ISP. Do this for all of the engines and add the totals together. Then take the combined total of all the thrust your engines create and divide that by the all the totals you've just worked out.

Lets try it...

• Hawk. Individual ISP = 250.741 x 2 = 501.482
• Broadsword. ISP = 281.492
  • Total = 782.974
• Divide 782.974 / 3 = 260.9913333333333 seconds

Answer from earlier on = 254.86 seconds.

It's ok, I once thought the same as well until Space Stig showed me to the path of Redemption...

Well, thanks for the answer .
Another question: I'm using mix first stages with 4 frontiers and 4 titans... If, during the ascent, I shut down the titans in pairs, im actually increasing ISP and dV, right?

 

[Horus Lupercal]

Well, thanks for the answer .
Another question: I'm using mix first stages with 4 frontiers and 4 titans... If, during the ascent, I shut down the titans in pairs, im actually increasing ISP and dV, right?

Yes you are. Its a good idea to do it as long as your TWR is sufficient to maintain acceleration when you shut down the Titans. Especially as they'll be generating about 4/5ths of your overall thrust

 

[Altaïr]

Ha, good luck with that. Even the Great and Powerful Oz (Altair) won't go near it because of the sheer number of things that need to be taken into account to make it accurate. Especially in the case of how turd drag is in game.



Yes, yes you do. That way pointed out above is actually the easy way. The other way is even more complex...

1. you need the exhaust velocity of an engine. To work this out, you multiply thrust by fuel consumption.
2. Then, you multiply that, by g (9.8) to get an individual engine ISP
3. Do that for all engines
4. Now, for each individual engine, divide its force by its own ISP. Do this for all of the engines and add the totals together. Then take the combined total of all the thrust your engines create and divide that by the all the totals you've just worked out.

Lets try it...

• Hawk. Individual ISP = 250.741 x 2 = 501.482
• Broadsword. ISP = 281.492
  • Total = 782.974
• Divide 782.974 / 3 = 260.9913333333333 seconds

Answer from earlier on = 254.86 seconds.

It's ok, I once thought the same as well until Space Stig showed me to the path of Redemption...

I was about to answer, you were faster than me
On my side, I didn't even realize about the simpler formula you found recently (global thrust / g × global consumption), so in the end you also taught me something

If you prefer The Blazer , our spreadsheets can do this calculation for you!

 

[Horus Lupercal]

I was about to answer, you were faster than me
On my side, I didn't even realize about the simpler formula you found recently (global thrust / g × global consumption), so in the end you also taught me something

If you prefer The Blazer , our spreadsheets can do this calculation for you!

Actually dude, you taught me that as well when we (you) were working out the new ISP from the tooltips cos the thrust was wrong.

I just experimented to see if it worked over more than one engine (cos why not) and it happened to give me the exact answer as the long way of doing it. I'm still using both methods in different sides of my spreadsheet just in case..

 

[Blazer Ayanami]

Wow, thanks Horus Lupercal and Altaïr.

If you prefer The Blazer , our spreadsheets can do this calculation for you!

Thanks a lot for the offer Altaïr but I really prefer to do the calculations myself
I just started to learn about rocket maths about 1 or 2 months ago. All I've done before that, all I did in 1.35 with base game parts I did thanks to trial and error. Remember I needed 54 attempts to make a Venus Return Ship? Well, I still like to learn that way: If you fail, try again. If you have a doubt, ask.

I hope you understand

 

[Wᴏʟꜰʀᴀᴍ]

Wow, thanks Horus Lupercal and Altaïr.


Thanks a lot for the offer Altaïr but I really prefer to do the calculations myself
I just started to learn about rocket maths about 1 or 2 months ago. All I've done before that, all I did in 1.35 with base game parts I did thanks to trial and error. Remember I needed 54 attempts to make a Venus Return Ship? Well, I still like to learn that way: If you fail, try again. If you have a doubt, ask.

I hope you understand

Now I remember the reason why I wanted to learn the equations, it was because I wanted to design a vehicle that's capable of going to Venus and back. I tried to do it earlier this week but my escape vehicle in Venus wasn't able to create its orbit ( I made sure that it was aerodynamic so that it can go through its thick atmosphere but the problem seems to be connected to its delta v, now I'm here, trying to learn it)

 

[Horus Lupercal]

Now I remember the reason why I wanted to learn the equations, it was because I wanted to design a vehicle that's capable of going to Venus and back. I tried to do it earlier this week but my escape vehicle in Venus wasn't able to create its orbit ( I made sure that it was aerodynamic so that it can go through its thick atmosphere but the problem seems to be connected to its delta v, now I'm here, trying to learn it)

Yeah, venus is a real stinker of a location to get back from. I would treat a Venus trip like a take off from Earth. It's gravity is almost as high, it's atmosphere is thicker and the speed needed to hit orbit is almost as fast. It's probably a harder take off because it exposes aerodynamic in-balances in your builds like no other place in the system.

The only plus side to the place is landing is so easy.

 

[Altaïr]

Wow, thanks Horus Lupercal and Altaïr.


Thanks a lot for the offer Altaïr but I really prefer to do the calculations myself
I just started to learn about rocket maths about 1 or 2 months ago. All I've done before that, all I did in 1.35 with base game parts I did thanks to trial and error. Remember I needed 54 attempts to make a Venus Return Ship? Well, I still like to learn that way: If you fail, try again. If you have a doubt, ask.

I hope you understand

Of course, that's a very good way to figure out things by yourself

Now I remember the reason why I wanted to learn the equations, it was because I wanted to design a vehicle that's capable of going to Venus and back. I tried to do it earlier this week but my escape vehicle in Venus wasn't able to create its orbit ( I made sure that it was aerodynamic so that it can go through its thick atmosphere but the problem seems to be connected to its delta v, now I'm here, trying to learn it)

Ah, the aerodynamics problem. One of the most painful in SFS. I've made a thread about this a while ago:
https://jmnet.one/sfs/forum/index.php?threads/aerodynamics-in-sfs.2115/
The aerodynamics in SFS are really weird, but at least, you can test if a rocket is aerodynamic or not. If you manage to make it sharp enough, Venus is not that hard in the end.

Here are a few tips to make a ship aerodynamic:
- RCS and structures are aerodynamics killers. Avoid them as much as possible.
- Don't rely on fairings, they generate no drag at all by themselves, but they don't protect anything either (at least under version 1.4.06)
- avoid separators at all cost, they are bugged and generate a ton of drag, no matter how you place them. If you want a multi-stage rocket, use docking ports instead:

- side separators are ok, though they generate a little drag, but at a reasonable level.
- Don't try to put a ton of engines to fight drag, you will lose that battle. Firstly, each engine generates its own drag, and secondly, at some point you'll waste fuel. If your TWR ratio is bigger than 2, then consider you are feeding drag more than you accelerate, and you'd better lower your throttle in that case.

For more informations about parts and their aerodynamic properties, I listed that in a chart. You'll find it in that post:
https://jmnet.one/sfs/forum/index.php?threads/aerodynamics-in-sfs.2115/page-3#post-37917

 

[Wᴏʟꜰʀᴀᴍ]

Does a rocket with large TWR (like 4) wastes more delta v than an another rocket with lower TWR, given that the throttle is at maximum? For example, a rocket with 1.4 TWR has a delta v of 2000 m/s but it lost 500 m/s due to the drag while a rocket with 4 TWR which has a delta v of 3000 m/s lost 750 m/s. Is that accurate?

 

[Pink]

Something like that.
The most effective speed to launch through the soupy low atmosphere to minimise losses due to drag is at "terminal velocity".
As you get higher (10-15km in SFS)?, the air is thinner and doesn't produce as much drag, so you should accelerate faster.
If you start with a TWR of say, 1.3, you will rise slowly through the low atmosphere, which is good, and by the time you get to 15km, you've burnt off enough fuel that your rocket is lighter and accelerates much faster, which is also desired.

Also, assuming a crazy TWR like 4, by the time you burn low on fuel, you will be accelerating so fast that everything inside the rocket would be pressed into soup in real life, which is bad.

 

[Wᴏʟꜰʀᴀᴍ]

Horus Lupercal, look! I did everything right. Calculating the ISP, TWR, and the delta v. I'm beginning to understand things

 

[Pink]

Well done!

(It's crazy how a game like this can make anyone do maths for recreation. )