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Is this a acceptable satellite launch?


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Acceptable by what metric? I mean, if you were trying to place the satellite in any old orbit, then you succeeded. The orbit wasn't planar, though, which might be a failure depending on what the satellite was intended for.

If you were asking about the launch vehicle and profile, then there are all kinds of things you could improve. First off, your ascent profile was way, way off. Flying straight up and then turning sharply over when you reach space is probably the least efficient possible way to get to orbit. What you should do instead is fly what's called a gravity turn. This is where you gradually turn over during the launch, starting the turn at 100 m/s or so, and slowly leaning over during the rest of the launch, so that you reach horizontal just as you're reaching the highest point in your trajectory. This way, you minimize losses due to fighting gravity. There are plenty of resources on the forum on how to do one of these; I've only given a cursory explanation.

The vehicle design also left room for improvement. First off, the Swivel is a terrible upper stage engine. It weighs too much. Its nominal use case is as what's called a sustainer - which is a long-burning central engine that's augmented early in flight by boosters of some sort. For your use case, the Terrier would have been a better choice. Second, the Kickbacks were not a good choice for booster. They're too large and powerful for the core stage you had. See how you shot off the pad? Your thrust-to-weight ratio must have been close to 2, when it really should have been nearer to 1.3 or 1.4. You lost a fair amount of delta-V to fighting the atmosphere. Third, you didn't give yourself any good sources of control authority with either your boosters or your first liquid stage - neither the Kickbacks nor the Reliant you used had any control authority. Either pick engines that do gimbal, add vernier thrusters (Twitch engines work decently well) for attitude control, or add some control surfaces. Fourth, your second liquid stage was nearly as big as your first liquid stage. Typically, you want the second stage to be substantially smaller than the first stage - at most half as large, and nominally somewhere around a quarter as large.

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I agree with @IncongruousGoat. Launching straight up and then turning once you reach space is one of the least efficient ways of getting to orbit, although it is the simplest to visualize especially for people who know nothing about orbital mechanics. This is how I introduce my friends to the concept of orbits sometimes. A more efficient way is to slowly turn on the way up so you're not fighting gravity the whole time (although this concept is a bit weird it works). It takes some practice but not much.

3 things about your launch vehicle, also stated earlier. One, it's somewhat inefficient - you generally want to have your stages smaller as you go. You should consider a more vacuum optimized engine like the LV-909 for the second stage. Two, things you should add for quality of life - fins on the first stage to aid in control, and struts so your boosters aren't flopping around so much. Third, for this sort of mission, even without modification, your launch vehicle looks pretty overpowered. You had half a tank of fuel left in orbit, more than that even. Extra margin is a good thing to have, but I'm guessing that you could probably use that same rocket to put that same satellite in orbit of the Mun. If you fixed the ascent profile and optimized it a bit, it could probably put the satellite around Duna or Eve given a big enough antenna. If you want to shrink the vehicle to the point where it can just accomplish the mission, make the top stage an FL-T200 and an LV-909 and keep the first stage as is. Drop the boosters entirely (but remember fins). If you pilot properly this should work.

Lastly I think you couldn't control the second stage because it was out of battery power.

 

I know this appears negative, but you appear to be relatively new to the game, in which case you're doing fantastic for someone so new - it is rocket science, after all! :)

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  • 3 weeks later...
On 8/24/2018 at 1:45 AM, IncongruousGoat said:

Acceptable by what metric? I mean, if you were trying to place the satellite in any old orbit, then you succeeded. The orbit wasn't planar, though, which might be a failure depending on what the satellite was intended for.

If you were asking about the launch vehicle and profile, then there are all kinds of things you could improve. First off, your ascent profile was way, way off. Flying straight up and then turning sharply over when you reach space is probably the least efficient possible way to get to orbit. What you should do instead is fly what's called a gravity turn. This is where you gradually turn over during the launch, starting the turn at 100 m/s or so, and slowly leaning over during the rest of the launch, so that you reach horizontal just as you're reaching the highest point in your trajectory. This way, you minimize losses due to fighting gravity. There are plenty of resources on the forum on how to do one of these; I've only given a cursory explanation.

The vehicle design also left room for improvement. First off, the Swivel is a terrible upper stage engine. It weighs too much. Its nominal use case is as what's called a sustainer - which is a long-burning central engine that's augmented early in flight by boosters of some sort. For your use case, the Terrier would have been a better choice. Second, the Kickbacks were not a good choice for booster. They're too large and powerful for the core stage you had. See how you shot off the pad? Your thrust-to-weight ratio must have been close to 2, when it really should have been nearer to 1.3 or 1.4. You lost a fair amount of delta-V to fighting the atmosphere. Third, you didn't give yourself any good sources of control authority with either your boosters or your first liquid stage - neither the Kickbacks nor the Reliant you used had any control authority. Either pick engines that do gimbal, add vernier thrusters (Twitch engines work decently well) for attitude control, or add some control surfaces. Fourth, your second liquid stage was nearly as big as your first liquid stage. Typically, you want the second stage to be substantially smaller than the first stage - at most half as large, and nominally somewhere around a quarter as large.

Thanks a lot i will be looking foward to these improvments

On 8/24/2018 at 4:53 AM, insert_name said:

I would reccomend adding batteries to the upper stage, you probably lost control because it ran out of power

The batteries where there but hidden

On 8/24/2018 at 3:53 AM, Ultimate Steve said:

I agree with @IncongruousGoat. Launching straight up and then turning once you reach space is one of the least efficient ways of getting to orbit, although it is the simplest to visualize especially for people who know nothing about orbital mechanics. This is how I introduce my friends to the concept of orbits sometimes. A more efficient way is to slowly turn on the way up so you're not fighting gravity the whole time (although this concept is a bit weird it works). It takes some practice but not much.

3 things about your launch vehicle, also stated earlier. One, it's somewhat inefficient - you generally want to have your stages smaller as you go. You should consider a more vacuum optimized engine like the LV-909 for the second stage. Two, things you should add for quality of life - fins on the first stage to aid in control, and struts so your boosters aren't flopping around so much. Third, for this sort of mission, even without modification, your launch vehicle looks pretty overpowered. You had half a tank of fuel left in orbit, more than that even. Extra margin is a good thing to have, but I'm guessing that you could probably use that same rocket to put that same satellite in orbit of the Mun. If you fixed the ascent profile and optimized it a bit, it could probably put the satellite around Duna or Eve given a big enough antenna. If you want to shrink the vehicle to the point where it can just accomplish the mission, make the top stage an FL-T200 and an LV-909 and keep the first stage as is. Drop the boosters entirely (but remember fins). If you pilot properly this should work.

Lastly I think you couldn't control the second stage because it was out of battery power.

 

I know this appears negative, but you appear to be relatively new to the game, in which case you're doing fantastic for someone so new - it is rocket science, after all! :)

 

On 8/24/2018 at 1:45 AM, IncongruousGoat said:

Acceptable by what metric? I mean, if you were trying to place the satellite in any old orbit, then you succeeded. The orbit wasn't planar, though, which might be a failure depending on what the satellite was intended for.

If you were asking about the launch vehicle and profile, then there are all kinds of things you could improve. First off, your ascent profile was way, way off. Flying straight up and then turning sharply over when you reach space is probably the least efficient possible way to get to orbit. What you should do instead is fly what's called a gravity turn. This is where you gradually turn over during the launch, starting the turn at 100 m/s or so, and slowly leaning over during the rest of the launch, so that you reach horizontal just as you're reaching the highest point in your trajectory. This way, you minimize losses due to fighting gravity. There are plenty of resources on the forum on how to do one of these; I've only given a cursory explanation.

The vehicle design also left room for improvement. First off, the Swivel is a terrible upper stage engine. It weighs too much. Its nominal use case is as what's called a sustainer - which is a long-burning central engine that's augmented early in flight by boosters of some sort. For your use case, the Terrier would have been a better choice. Second, the Kickbacks were not a good choice for booster. They're too large and powerful for the core stage you had. See how you shot off the pad? Your thrust-to-weight ratio must have been close to 2, when it really should have been nearer to 1.3 or 1.4. You lost a fair amount of delta-V to fighting the atmosphere. Third, you didn't give yourself any good sources of control authority with either your boosters or your first liquid stage - neither the Kickbacks nor the Reliant you used had any control authority. Either pick engines that do gimbal, add vernier thrusters (Twitch engines work decently well) for attitude control, or add some control surfaces. Fourth, your second liquid stage was nearly as big as your first liquid stage. Typically, you want the second stage to be substantially smaller than the first stage - at most half as large, and nominally somewhere around a quarter as large.

Thanks for the reply guys, its very helpfull. I fly straight up as its the fastest way to get to space, and if I went as you said using the G turn method i would end up scared as my rocket would end up melting up from air friction.

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