Altaïr
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Questions for Realictis level of difficulty
- Thread starter Catalyst_Kh
- Start date
Altaïr
Space Stig, Master of gravity
Staff member
Head Moderator
Team Kolibri
Modder
TEAM HAWK
Atlas
Deja Vu
Under Pressure
Forum Legend
I finally gave it a try on the realistic mode. Here's my launcher:
That's the same launcher, but with a different payload, this one weighs 98 tons, which is slightly below the maximum capacity. Here's the launch:
When my first stage ends burning, I'm at that point:
Then I reach orbit with a little fuel left, that will be a welcome margin:
From there I burn to the Moon:
Then the Moon insertion:
I finally have 36.44 tons delivered in Moon orbit, alittle below what I estimated I must say, but still largely enough.
Then the Moon part is easy:
With 9.5% of remaining fuel I had a good margin with that module.
Now the return to Earth:
See, I still had 3 quarters of my fuel tank remaining, that was largely enough (an euphemism for "way too much" actually...)
To answer a few things, XenonSpace is right, you shouldn't rely on Titans only to reach orbit. It's justified for the first stage since you need a maximum of thrust at that moment, but once you're in flight at a reasonable speed (3 km/s in my case, but you can set a higher threshold) it's better to switch to the more efficient Frontier engines. They have less thrust but consume less fuel per unit of thrust produced (this is what a higher specific impulse means). You still have to compensate for gravity, but as your speed gets higher you experience less and less that effect, until it cancels out completely when you reach orbital velocity.
I saw you asked for the meaning of delta-V too. Delta-V literally means "velocity difference", this is by how much you can make vary your velocity. To make things simple, for example if you accelerate and raise your speed by 100 m/s, you've spent 100 m/s of delta-V. The delta-V you have at your disposal is mainly affected by the fuel available of course, but also specific impulse, and it's negatively affected by dry mass (everything that isn't fuel).
Otherwise the conception of your lander is pretty good, you make some useful savings there. In this game the question is not only "How to send more", but also "How to do the same thing with less". Optimization is crucial to succeed, especially in realistic mode
That's the same launcher, but with a different payload, this one weighs 98 tons, which is slightly below the maximum capacity. Here's the launch:
When my first stage ends burning, I'm at that point:
Then I reach orbit with a little fuel left, that will be a welcome margin:
From there I burn to the Moon:
Then the Moon insertion:
I finally have 36.44 tons delivered in Moon orbit, alittle below what I estimated I must say, but still largely enough.
Then the Moon part is easy:
With 9.5% of remaining fuel I had a good margin with that module.
Now the return to Earth:
See, I still had 3 quarters of my fuel tank remaining, that was largely enough (an euphemism for "way too much" actually...)
To answer a few things, XenonSpace is right, you shouldn't rely on Titans only to reach orbit. It's justified for the first stage since you need a maximum of thrust at that moment, but once you're in flight at a reasonable speed (3 km/s in my case, but you can set a higher threshold) it's better to switch to the more efficient Frontier engines. They have less thrust but consume less fuel per unit of thrust produced (this is what a higher specific impulse means). You still have to compensate for gravity, but as your speed gets higher you experience less and less that effect, until it cancels out completely when you reach orbital velocity.
I saw you asked for the meaning of delta-V too. Delta-V literally means "velocity difference", this is by how much you can make vary your velocity. To make things simple, for example if you accelerate and raise your speed by 100 m/s, you've spent 100 m/s of delta-V. The delta-V you have at your disposal is mainly affected by the fuel available of course, but also specific impulse, and it's negatively affected by dry mass (everything that isn't fuel).
Otherwise the conception of your lander is pretty good, you make some useful savings there. In this game the question is not only "How to send more", but also "How to do the same thing with less". Optimization is crucial to succeed, especially in realistic mode
If it's just that don't worry, here are a few of my creations:
View attachment 96133 View attachment 96134 View attachment 96135
Your launcher can't be worse than those right?
View attachment 96133 View attachment 96134 View attachment 96135
Your launcher can't be worse than those right?
Please tell me how it is possible to rotate engine positions only for 15%-20% degrees? Like on your 3rd picture. In rocket editor i was able to make only 0%/90%/180% degrees rotations for any giver object, and nothing else.
Sorry for the late reply, Catalyst_Kh.
The design I was referring to was similar to Altaïr's, specifically about the staging. The core stage has a very low TWR, and need to be assisted by side boosters for a few minutes. After the boosters ran out of fuel, it became a dead weight, and is useless now. This is why we need to dump it using a side separator. At this point the core stage has a high enough TWR to continue the flight.
When your apogee nearly reaches the Kármán line and the core stage is empty, this is where high efficiency second stage comes into play. After second stage separation, it might go slow at first, so I recommend adding a lighter third stage when the second stage has reached it's end of service.
After reaching orbit, navigate to the Moon and start up the fourth stage, a single Frontier would suffice. I generally aim around 5 km above the surface (I'm on mobile without expansion packs), but for safety 10-12 km is good. Do the Apollo style for the best efficiency, and the rest is history.
Note: plan your reentry to skid the atmosphere like this,
avoid to go straight to the ground. This results in higher temperature and lower stability, which could be catastrophic. Opting to use the trajectory shown in the image makes it easier to control and lower the possibility of your capsule burning.
To rotate parts, you could install Part Editor mod or manually edit them in the game files.
The design I was referring to was similar to Altaïr's, specifically about the staging. The core stage has a very low TWR, and need to be assisted by side boosters for a few minutes. After the boosters ran out of fuel, it became a dead weight, and is useless now. This is why we need to dump it using a side separator. At this point the core stage has a high enough TWR to continue the flight.
When your apogee nearly reaches the Kármán line and the core stage is empty, this is where high efficiency second stage comes into play. After second stage separation, it might go slow at first, so I recommend adding a lighter third stage when the second stage has reached it's end of service.
After reaching orbit, navigate to the Moon and start up the fourth stage, a single Frontier would suffice. I generally aim around 5 km above the surface (I'm on mobile without expansion packs), but for safety 10-12 km is good. Do the Apollo style for the best efficiency, and the rest is history.
Note: plan your reentry to skid the atmosphere like this,
avoid to go straight to the ground. This results in higher temperature and lower stability, which could be catastrophic. Opting to use the trajectory shown in the image makes it easier to control and lower the possibility of your capsule burning.
To rotate parts, you could install Part Editor mod or manually edit them in the game files.
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Thank you very much Altaïr and XenonSpace. I understand now the full extent of my huge blunder.
I was taking off from Earth directly to the Moon in one stright line!
That is why i couldn't even reach Moon without two Titans powering the second stage! Even one Titan was not enough (with a reasonable payload). It was unthinkable to expect, that Frontiers can be used, since one Frontier is the whole 4 times weaker, than only one Titan. And i needed 2 Titans, which required 8 Frontiers for replacement, or at least 7.
What a failure of mine! No wonder that i had so much difficulties.
You just try to reach Moon in one stright line from Earth at Realistic level yourself - and you will understand all the grief.
While now i will try to utilize this new strategy, i think i can deliver way much more payload with it, than 50 tons. I will try it and see how much i can.
I understand now that i can simply catapult myself to the moon from Earth orbit, but before today i didn't even realized, that such an efficient strategy exists at all.
I was taking off from Earth directly to the Moon in one stright line!
That is why i couldn't even reach Moon without two Titans powering the second stage! Even one Titan was not enough (with a reasonable payload). It was unthinkable to expect, that Frontiers can be used, since one Frontier is the whole 4 times weaker, than only one Titan. And i needed 2 Titans, which required 8 Frontiers for replacement, or at least 7.
What a failure of mine! No wonder that i had so much difficulties.
You just try to reach Moon in one stright line from Earth at Realistic level yourself - and you will understand all the grief.
While now i will try to utilize this new strategy, i think i can deliver way much more payload with it, than 50 tons. I will try it and see how much i can.
I understand now that i can simply catapult myself to the moon from Earth orbit, but before today i didn't even realized, that such an efficient strategy exists at all.
On the previous page i was reffering to this new strategy i invented:
1. Sending to another planet from Earth a big canister, like 12x16 fuel tank, which is more than half empty (to be able to deliver it), or even almost empty, with nothing at all, only engine, canister, and the absolute minimum of other required modules.
2. Placing this canister on the comfortable orbit.
4. Sending new rocket from Earth, with Fuel Deliver Guy system, which is smaller and more optimal, with all fuel tanks filled to the maximum, and size of tanks depending on how far another planet is.
5. Refueling our canister at orbit of another planet from by Fuel Delivery Guys.
Something like this below (it is only a sketch, without improvements and consideration, just to illustrate the idea):
One Fuel delivery guy saves horizontal space, other guy saves vertical space, depending on what is more important for the current Launcher model.
6. Now we can send missions to that planet with all the needed stuff taken from Earth. With big ships or shuttles or any multistage landing systems, but taking very little fuel tanks with it, or taking big fuel tanks (because they will be needed later) which are just empty! To save a lot of important weight for everything else, while our mission can refuel many times at the destination point to perform everything we want, and then refuel again before going home.
While for Moon mission steps 3 and 4 are not even needed, we can take a smaller canister in step 1 (which will contain more fuel inside already) or start with step 4 at once and it will be more than enough for refueling our lander on LMO for Moon mission from the very next Launcher.
But now i understand, that i can improve my plan even more - i can add Step 3:
3. Placing Many big canisters right at LEO and filling it full too, then connecting all LEO canister in one huge space gas station. To refuel our outgoing missions on LEO too, before our double catapulting to other planets, which gives the possibility to upload much bigger ships from Earth to LEO, with much bigger payloads, which are barely reaching LEO with empty fuel tanks already.
Where by double catapulting i mean that we capapult our rocket from LEO to Moon, using Earth gravity, with a trajectory to pass very close to Moon's surface from it's behind (behind its vector of movement), but not taking LMO and instead starting to burn engines to maximum acceleration forward, when we will be near Moon, to catapult ourselves second time with huge speed to any other planet we want.
1. Sending to another planet from Earth a big canister, like 12x16 fuel tank, which is more than half empty (to be able to deliver it), or even almost empty, with nothing at all, only engine, canister, and the absolute minimum of other required modules.
2. Placing this canister on the comfortable orbit.
4. Sending new rocket from Earth, with Fuel Deliver Guy system, which is smaller and more optimal, with all fuel tanks filled to the maximum, and size of tanks depending on how far another planet is.
5. Refueling our canister at orbit of another planet from by Fuel Delivery Guys.
Something like this below (it is only a sketch, without improvements and consideration, just to illustrate the idea):
6. Now we can send missions to that planet with all the needed stuff taken from Earth. With big ships or shuttles or any multistage landing systems, but taking very little fuel tanks with it, or taking big fuel tanks (because they will be needed later) which are just empty! To save a lot of important weight for everything else, while our mission can refuel many times at the destination point to perform everything we want, and then refuel again before going home.
While for Moon mission steps 3 and 4 are not even needed, we can take a smaller canister in step 1 (which will contain more fuel inside already) or start with step 4 at once and it will be more than enough for refueling our lander on LMO for Moon mission from the very next Launcher.
But now i understand, that i can improve my plan even more - i can add Step 3:
3. Placing Many big canisters right at LEO and filling it full too, then connecting all LEO canister in one huge space gas station.
To refuel our outgoing missions on LEO too, before our double catapulting to other planets, which gives the possibility to upload much bigger ships from Earth to LEO, with much bigger payloads, which are barely reaching LEO with empty fuel tanks already.Where by double catapulting i mean that we capapult our rocket from LEO to Moon, using Earth gravity, with a trajectory to pass very close to Moon's surface from it's behind (behind its vector of movement), but not taking LMO and instead starting to burn engines to maximum acceleration forward, when we will be near Moon, to catapult ourselves second time with huge speed to any other planet we want.
But for completing my noob strategy experiment and leave it behind i did made one last test flight:
I used my previous rocket from the picture on the 1st page and again took off with direct stright line pass from Earth to Moon, with no LEO, but i only replaced Moon lander on my Launcher for this model:
I went in direct line from Earth ground to Moon ground, landed safely, though a lof of fuel was spent for slowing down before moon, since the approach verctor was direct to the center of the moon.
Then i took off from moon ground and went to Earth and landed safely with a lot of extra fuel left before Earth.
So it looks like Cresign was right - there is no noticeable difference in efficiency between direct landing on the Moon by straght line without LMO and correct Apollo style with LMO, as long as Moon complex is correct model and efficient enough.
But making Apollo style was much more fun, i enjoyed it a lot - thank you all once again. And if i didn't burn too much fuel on catching my LMO canister for refueling - i would have extra fuel near Earth too.
And now i understand, that i don't even need to slow down before Earth at all, if i take correct approach vector, like slicing the atmosphere at 20 km +- without going lower, thus i don't need powerful engine in the stage which is coming home.
While before I thought i need to take LEO first before landing home - and Kolibri is just not powerful enough for that.
I used my previous rocket from the picture on the 1st page and again took off with direct stright line pass from Earth to Moon, with no LEO, but i only replaced Moon lander on my Launcher for this model:
I went in direct line from Earth ground to Moon ground, landed safely, though a lof of fuel was spent for slowing down before moon, since the approach verctor was direct to the center of the moon.
Then i took off from moon ground and went to Earth and landed safely with a lot of extra fuel left before Earth.
So it looks like Cresign was right - there is no noticeable difference in efficiency between direct landing on the Moon by straght line without LMO and correct Apollo style with LMO, as long as Moon complex is correct model and efficient enough.
But making Apollo style was much more fun, i enjoyed it a lot - thank you all once again. And if i didn't burn too much fuel on catching my LMO canister for refueling - i would have extra fuel near Earth too.
And now i understand, that i don't even need to slow down before Earth at all, if i take correct approach vector, like slicing the atmosphere at 20 km +- without going lower, thus i don't need powerful engine in the stage which is coming home.
While before I thought i need to take LEO first before landing home - and Kolibri is just not powerful enough for that.
Also i have a question, is this plan below is correct and worth pursuing?
I want to make a huge Launcher, which will fill "all squares" in blueprint, but i will have a lot of empty fuel tanks in it, so it could take off with only 7 Titans at the bottom.
Then i will go with this launcher to LEO and refuel it on LEO from my big LEO Gas Station, and only then i perform double catapult action to another planet. In such a way i think i can bring around 100 tons of payload to any other planet in each go.
I want to make a huge Launcher, which will fill "all squares" in blueprint, but i will have a lot of empty fuel tanks in it, so it could take off with only 7 Titans at the bottom.
Then i will go with this launcher to LEO and refuel it on LEO from my big LEO Gas Station, and only then i perform double catapult action to another planet. In such a way i think i can bring around 100 tons of payload to any other planet in each go.
One more question: what is best Earth to LEO trajectory?
I mean at which height en route to LEO what angle to Earth i should have? Is there any tables for that? Or some formula? To use less fuel to reach LEO, but taking into consideration, that i also need to escape high-density atmosphere in a faster way (thus taking of starts directly 90° upwards).
I mean at which height en route to LEO what angle to Earth i should have? Is there any tables for that? Or some formula? To use less fuel to reach LEO, but taking into consideration, that i also need to escape high-density atmosphere in a faster way (thus taking of starts directly 90° upwards).
I mean, for example, if i go stright up 90° from Earth ground until i see that my peak ballistic altitude will be 110 km above ground and then i will "instantly" change my rocket to lie 1° for example (almost flat horizontally), to start gaining horizontal speed too, would it be good trajectory?
Or changing angle of velocity somewhat gradually would be more efficient?
What would be best direction of LEO after launch? Clockwise or counterclockwise at the game map image? To be able to more efficiently catapult to Moon from LEO.
Or changing angle of velocity somewhat gradually would be more efficient?
What would be best direction of LEO after launch? Clockwise or counterclockwise at the game map image? To be able to more efficiently catapult to Moon from LEO.
One more thing. I downloaded these mod files and put it in \Spaceflight Simulator\Mods\ folder:
Then i launched the game, game showed processing these files, and now i can see this picture if i press "Mod Loader" button in main game menu:
Looks like everything is working fine.
When i entered rocket editor in game i can see this new window, which was not there before:
But i still can't find anywhere, how to make components to rotate to any other positions besides 0°/ 90° / 180° /270°.
How to do that?
Then i launched the game, game showed processing these files, and now i can see this picture if i press "Mod Loader" button in main game menu:
Looks like everything is working fine.
When i entered rocket editor in game i can see this new window, which was not there before:
But i still can't find anywhere, how to make components to rotate to any other positions besides 0°/ 90° / 180° /270°.
How to do that?
Maybe you can tell at least what is best altitude above the ground to start rotation towards LEO direction.
And i still can't make up any type of calculation, which would answer, from what LEO direction vector it is easier to catapult to moon and beyond - from clockwise LEO or from counterclockwise LEO (if looking at the Earth in game map).
And i still can't make up any type of calculation, which would answer, from what LEO direction vector it is easier to catapult to moon and beyond - from clockwise LEO or from counterclockwise LEO (if looking at the Earth in game map).
Maybe some simple instructions do exist, like at X1 kilometers above ground start turning to the side from vertical, at X2 altitude you should have 45°, at X3 altitude 20°. Something like that. While between Xn values we can gradually rotate freely - it will make little difference. Or just a formula for calculating it in excel.
I'll try to answer your questions as best as I can, because I'm not an expert.
What you're describing is gravity assist, the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft, typically to save propellant and reduce expense [Wikipedia]. That could work but I don't think it will give that much of an advantage in terms of delta-v. For more information, take a look on Altaïr's excellent guide about it.
Yes, you should escape the denser atmosphere first with little to no change of your rocket's angle until you're 2 km up. Then, gradually change the angle by around <1° per second. Almost like Altaïr's trajectory. Going straight up and doing a gravity turn once you reached Kármán line is very inefficient, you'll risk falling back to the atmosphere before you can even reach orbit.
What you're describing is gravity assist, the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft, typically to save propellant and reduce expense [Wikipedia]. That could work but I don't think it will give that much of an advantage in terms of delta-v. For more information, take a look on Altaïr's excellent guide about it.
Yes, you should escape the denser atmosphere first with little to no change of your rocket's angle until you're 2 km up. Then, gradually change the angle by around <1° per second. Almost like Altaïr's trajectory. Going straight up and doing a gravity turn once you reached Kármán line is very inefficient, you'll risk falling back to the atmosphere before you can even reach orbit.
Thank you guys.
With correct double slingshot from LEO i was able to bring almost 82 tons to the LMO, which included 4th deliver stage from launcher itself with 20+ tons of fuel left in it, which could be spent for slowing down near Moon. Thus i could bring a lunar complex of 78 tons weight instead of 58.2 tons complex (which was installed at this Launch), if i moved those 20 tons from last delivery stage to the moon complex itself.
But i could bring more than 82 tons total if i were using correct "pitch changing plan" after taking off to LEO. This time i used something very inefficient. For example, i started turning only at 20 km altitude in this launch. If i would start changing pitch after 2 km already, as you all do, maybe i could bring 83+ total tons.
Please suggest, what else i can improve in my rocket model.
Especially this question: I found a way to measure/calculate exactly the size of 3rd and 4th stages, but i can't find a way, how to measure amount of fuel in 1st and 2nd stages. I mean, should i move fuel tanks from 2nd stage to 1st or from 1st to 2nd? In order to reach the optimal altitude and speed when to detach 1st stage. I can't find a way how to calculate when it will be.
I want to finish with my Launcher, improve it now and then focus on other things, so i could comfortably use this Launcher to launch any missions all over Solar system.
Plus i want to build even greater model later, which will have only 7 Titans at 1st stage and thus ALL space in Blueprint rectangle will be used with fuel tanks and big payload at the top. For launching missions with more than 100 tons of weight. With maybe some Jupiter shuttle or who knows what comes to mind later.
But the trick is, that big part of those fuel banks must be empty at launch, or this rocket will never take off with only 7 Titans.
The plan is to burn fuel only for reaching LEO and bring to LEO huge rocket with empty fuel tanks. Then i will fuel all tanks to full from orbital gas station and then i can do tripple slingshot - double from earth and +1 from moon, to have maximum bossters in velocity in any direction inside solar system.
Also please tell, if my calculations are correct. I calculated, that for moon mission it is best to take clockwise LEO, while for missions to other planets it is much more efficient to take counterclockwise LEO after taking off.
Last question is important since i need to know in which direction on LEO should i build my orbital gas station - i really don't want to build a second one, when i discover that it flies in orbit in wrong direction.
With correct double slingshot from LEO i was able to bring almost 82 tons to the LMO, which included 4th deliver stage from launcher itself with 20+ tons of fuel left in it, which could be spent for slowing down near Moon. Thus i could bring a lunar complex of 78 tons weight instead of 58.2 tons complex (which was installed at this Launch), if i moved those 20 tons from last delivery stage to the moon complex itself.
But i could bring more than 82 tons total if i were using correct "pitch changing plan" after taking off to LEO. This time i used something very inefficient. For example, i started turning only at 20 km altitude in this launch. If i would start changing pitch after 2 km already, as you all do, maybe i could bring 83+ total tons.
Please suggest, what else i can improve in my rocket model.
Especially this question: I found a way to measure/calculate exactly the size of 3rd and 4th stages, but i can't find a way, how to measure amount of fuel in 1st and 2nd stages. I mean, should i move fuel tanks from 2nd stage to 1st or from 1st to 2nd? In order to reach the optimal altitude and speed when to detach 1st stage. I can't find a way how to calculate when it will be.
I want to finish with my Launcher, improve it now and then focus on other things, so i could comfortably use this Launcher to launch any missions all over Solar system.
Plus i want to build even greater model later, which will have only 7 Titans at 1st stage and thus ALL space in Blueprint rectangle will be used with fuel tanks and big payload at the top.
For launching missions with more than 100 tons of weight. With maybe some Jupiter shuttle or who knows what comes to mind later.But the trick is, that big part of those fuel banks must be empty at launch, or this rocket will never take off with only 7 Titans.
The plan is to burn fuel only for reaching LEO and bring to LEO huge rocket with empty fuel tanks. Then i will fuel all tanks to full from orbital gas station and then i can do tripple slingshot - double from earth and +1 from moon, to have maximum bossters in velocity in any direction inside solar system.
Also please tell, if my calculations are correct. I calculated, that for moon mission it is best to take clockwise LEO, while for missions to other planets it is much more efficient to take counterclockwise LEO after taking off.
Last question is important since i need to know in which direction on LEO should i build my orbital gas station - i really don't want to build a second one, when i discover that it flies in orbit in wrong direction.
Second stage with Titans is mandatory because first stage can't move/rotate after taking off, and rotation is needed to grab LEO. Turning instantly overheats main tower and everything explodes. I can do only tiny turns without overheating, which is good enough for low altitude, but after that i need to turn a lot and have to detach 1st stage too early then, when Titans are still needed, thus 2nd stage must have Titans.
I improved my rocket this way:
It gained a little more starting velocity. Since now launcher is spending much more time inside atmosphere and it took only 9 squares of space to make a cap for lunar payload. Reasonable price, much less than previous time.
But with direct straight upwards take off without cap still flies better (faster and higher).
But with direct straight upwards take off without cap still flies better (faster and higher).
By double slingshot from LEO i meant that i accelerate to max right after periapse, but then turn engines off some time later, to make another circle and repeat acceleration after periapse.
Since i spend more time with falling to periapse, than time spent when running away - i grab gravity influence differential as +extra speed for free. It doesn't makes much, but if repeated 3+ times it accumulates some noticeable bonus.
Since i spend more time with falling to periapse, than time spent when running away - i grab gravity influence differential as +extra speed for free. It doesn't makes much, but if repeated 3+ times it accumulates some noticeable bonus.