https://wiki.kerbalspaceprogram.com/api.php?action=feedcontributions&user=Empiro&feedformat=atomKerbal Space Program Wiki - User contributions [en]2024-03-28T09:51:27ZUser contributionsMediaWiki 1.29.0https://wiki.kerbalspaceprogram.com/index.php?title=Tutorial:Advanced_Rocket_Design&diff=95181Tutorial:Advanced Rocket Design2019-07-24T21:56:46Z<p>Empiro: /* Delta-v map */ Correct for latest KSP delta-V to orbit of ~3500.</p>
<hr />
<div>''By Vincent McConnell and Kosmo-not''<br />
<br />
Getting to learn basic rocket science for a space game like Kerbal Space Program can be very important to the success of building rockets that can perform a desired job. In this guide, we will be covering things like calculating the full Delta-V of your ship, explaining how to perform transfer maneuvers, getting Thrust to Weight Ratio, calculating the Peak G-force experienced during a particular burn, also calculating Delta-V needed for a full Hohmann transfer and much more.<br />
<br />
==Delta-V==<br />
<math>\Delta v</math> (change in velocity) is the bread and butter of rocket science. It is probably the most important thing to know about your rocket because it determines what your rocket is capable of achieving. Among the several things we will explain in this basic tutorial, <math>\Delta v</math> is most likely the most useful thing you will apply to Kerbal Space Program while building a rocket. <br />
To find the <math>\Delta v</math> of your rocket for each stage at a time we have to sum up the part masses of every single part of the stage.<br />
<br />
* Total mass: <math>m_\text{total}</math><br />
* Fuel mass: <math>m_\text{fuel}</math><br />
* Dry Mass: <math>m_\text{dry} = m_\text{total} - m_\text{fuel}</math><br />
<br />
The equation only needs the total and dry mass, but as it is easier to get the dry mass by subtracting the fuel mass from the total mass. Of course other combinations like calculating the total mass and measuring the fuel and dry mass are also possible.<br />
<br />
The next important part of this set of calculations is to find your engine's specific impulse. Specific impulse is a measure of how fuel efficient an engine is (the greater the specific impulse, the more fuel efficient it is). For example, the non-vectoring stock engine [[LV-T30 Liquid Fuel Engine|LV-T30]] has a vacuum specific impulse of 300 s. So here, we must apply the [[w:Tsiolkovsky rocket equation|Tsiolkovsky rocket equation]]. More informally known as "The Rocket Equation". <br />
<br />
It states:<br />
:<math>\Delta v = I_{sp}\cdot \ln\left(\frac{m_\text{total}}{m_\text{dry}}\right)</math><br />
If the specific impulse is given in seconds it is necessary to multiply this value by <math>9.82\frac{m}{s^2}</math> (see also [[Terminology#isp|Terminology about I<sub>sp</sub>]]). <br />
<br />
So go ahead and sum up your stage's total mass with fuel. Then, go ahead and sum up the mass minus the fuel (this can be done by just adding up the 'dry mass' where given). Input these into the equation in the place of <math>m_\text{total}</math> and <math>m_\text{dry}</math>. Following is a quick example, where the surface gravity of Earth <math>9.81\frac{m}{s^2}</math> is used:<br />
<br />
[[File:Advanced Rocket Design example.png|thumb|Example rocket]]<br />
<br />
{| class="wikitable"<br />
! colspan="2" | Stage 3 (TMI, Mun lander, Return)<br />
|-<br />
| <math>m_\text{total}</math> || <math>3.72 \text{t}</math><br />
|-<br />
| <math>m_\text{dry}</math> || <math>1.72 \text{t}</math><br />
|-<br />
| <math>I_\text{sp}</math> ||<math>400 \text{s}</math><br />
|-<br />
| <math>\Delta v</math> || <math>3027.0 \frac{m}{s}</math><br />
|-<br />
! colspan="2" | Stage 2 (Kerbin orbit insertion)<br />
|-<br />
| <math>m_\text{total}</math> || <math>7.27 \text{t}</math><br />
|-<br />
| <math>m_\text{dry}</math> || <math>5.27 \text{t}</math><br />
|-<br />
| <math>I_\text{sp}</math> || <math>300 \text{s}</math><br />
|-<br />
| <math>\Delta v</math> || <math>946.8 \frac{m}{s}</math><br />
|-<br />
! colspan="2" | Stage 1 (Ascent):<br />
|-<br />
| <math>m_\text{total}</math> || <math>38.52 \text{t}</math><br />
|-<br />
| <math>m_\text{dry}</math> || <math>14.52 \text{t}</math><br />
|-<br />
| <math>I_\text{sp}</math> || <math>350 \text{s}</math> (estimated due to atmospheric flight)<br />
|-<br />
| <math>\Delta v</math> || <math>3349.9 \frac{m}{s}</math><br />
|-<br />
! colspan="2" | Total<br />
|-<br />
| <math>\Delta v</math> || <math>7544.6 \frac{m}{s}</math><br />
|}<br />
<br />
=== Multiple engines ===<br />
To calculate the I<sub>sp</sub> for multiple engines with different I<sub>sp</sub> values, you need to find total thrust and mass flow:<br />
:<math>I_{sp_{avg}} = \frac{\sum\limits_i^n(thrust_i)}{\sum\limits_i^n(\dot m_i\cdot g_0)} = \frac{\sum\limits_i^n(thrust_i)}{\sum\limits_i^n\left(\frac{thrust_i}{I_{sp_i}}\right)} = \frac {thrust_1 + thrust_2 + \dots + thrust_n}{thrust_1\div I_{sp_1} + thrust_2\div I_{sp_2} + \dots + thrust_n\div I_{sp_n}}</math><br />
<br />
This will give you the correct I<sub>sp</sub> to use for your Δv calculation. If all engines are the same, they act as one engine in this calculation so the sums aren't needed.<br />
<br />
==Calculating transfer maneuvers==<br />
The next part of this tutorial is how to perform a transfer maneuver. This kind of action is called a [[w:Hohmann transfer orbit|Hohmann Transfer]] and it requires two burns at opposite points in an orbit. Adding velocity will boost our apoapsis higher. We would then simply wait until we hit our newly established apoapsis and then add more velocity to boost our periapsis to circularize. Or, we could drop our orbit by subtracting velocity by burning retro-grade.<br />
<br />
We can also apply some <math>\Delta v</math> calculations to find out how much thrust we will need to perform this maneuver. We will break this burn up into impulses. For example purposes, we will start at a 100&nbsp;km orbit and then boost into a 200&nbsp;km orbit. Both circularized. The formula for the first burn is the following:<br />
<br />
<math>\Delta v_1=\sqrt{\frac\mu{r_1+R}}\Bigg(\sqrt{\frac{2(r_2+R)}{r_1+r_2+2R}}-1\Bigg)</math><br />
<br />
This is the formula for the final burn in the transfer:<br />
<br />
<math>\Delta v_2=\sqrt{\frac\mu{r_2+R}}\Bigg(1-\sqrt{\frac{2(r_1+R)}{r_1+r_2+2R}}\Bigg)</math><br />
<br />
Where:<br />
* <math>\mu</math>= Gravitational parameter of parent body (3530.461&nbsp;km³/s² for [[Kerbin]]).<br />
* <math>r_1</math>= The altitude of our first orbit (100&nbsp;km in this case).<br />
* <math>r_2</math>= The altitude of our second orbit (200&nbsp;km in this case).<br />
* <math>R</math>= The radius of parent body (600&nbsp;km in this case).<br />
<br />
This formula will give us our velocity for the burn in km/s (multiply by 1000 to convert it into m/s). <br />
It's important to make sure that you will have the <math>\Delta v</math> in the stage to make this burn. Again, you can do that by using the <math>\Delta v</math> calculations above.<br />
<br />
In our case we get a Δv<sub>1</sub> of 73.65&nbsp;m/s, a Δv<sub>2</sub> of 71.23&nbsp;m/s and a total Δv of 144.88&nbsp;m/s.<br />
<br />
==Calculating fuel flow==<br />
Next, we will explain how to calculate fuel flow in mass to see how much fuel a burn uses up in a specific amount of time. <br />
<br />
If we know the <math>\Delta v</math> needed for the burn and the total mass of the rocket before the burn, we can calculate how much fuel is required to complete the burn.<br />
<br />
First, we calculate the mass of the rocket after the burn is complete. To do this, we use the Tsiolkovsky Rocket Equation, inputting the initial mass and <math>\Delta v</math> of the burn. We can then solve the equation for the final mass (“dry mass”) after the burn. The difference between these two masses will be used to determine the length of time that is needed to complete the burn.<br />
<br />
The equation for mass flow rate of fuel, given I<sub>sp</sub> and thrust, is:<br />
:<math>\dot m = \frac{thrust}{I_{sp}}</math><br />
where <math>\dot m</math> is the mass flow rate of fuel consumed. Again if the specific impulse is given in seconds it needed to multiplied by 9.81&nbsp;m·s⁻² (see also [[Terminology#isp|Terminology about I<sub>sp</sub>]]).<br />
<br />
Dividing the difference between initial mass and final mass for the burn by the mass flow rate of fuel, we can determine how many seconds are required.<br />
<br />
Usually, when the thrust is in kN and the specific impulse is in m/s the result is in Mg/s (= t/s). As the density of the [[liquid fuel]]/[[oxidizer]] mixture is 5 Mg/m³ this gives 1/5&nbsp;m³/s = 2&nbsp;dm³/s (= l/s).<br />
<br />
==Orbital velocity==<br />
Rather easy is the formula to calculate the orbital velocity of an orbit. This assumes circular orbit or the velocity of a specific point in an orbit. For this, we simply do this calculation:<br />
<br />
<math>\sqrt{\frac\mu r}</math><br />
<br />
Where:<br /><br />
<math>\mu</math> = Gravitational Parameter of parent body. (km³/s²)<br /><br />
<math>r</math> = radius of orbit. (km)<br />
<br />
If we input the radius of the orbit in Kilometers, our orbital velocity will come out in Kilometers per second. In a 100&nbsp;km orbit, our radius will be 700&nbsp;km.<br />
Meaning our velocity will be ~2.2458 kilometers per second (km/s), or 2245.8&nbsp;m/s.<br />
<br />
==Delta-v map==<br />
A <math>\Delta v</math> map consists of approximate amounts of <math>\Delta v</math> needed to get from one place (whether it is on the ground or in space) to another. The <math>\Delta v</math> values we have for our <math>\Delta v</math> map are approximate and include a fudge factor (in case we slip up on our piloting). Our map is as follows:<br />
<br />
{|<br />
|Launch to 100&nbsp;km Kerbin orbit: || 3500&nbsp;m/s<br />
|-<br />
|Trans-Munar Injection: || 900&nbsp;m/s<br />
|-<br />
|Landing on the Mun: || 1000&nbsp;m/s<br />
|-<br />
|Launch from Mun and return to Kerbin: || 1000&nbsp;m/s<br />
|-<br />
|Total <math>\Delta v</math>: || 6400&nbsp;m/s<br />
|}<br />
<br />
If we design our rockets to have 6400 total <math>\Delta v</math>, and the acceleration of the launch stages are adequate, we can have confidence that our rocket is able to land on the Mun and return to Kerbin. A rocket with a little less <math>\Delta v</math> can accomplish this goal, but it is less forgiving of less efficient piloting.<br />
<br />
== Calculate the acceleration ==<br />
{{See also|Thrust-to-weight ratio}}<br />
<br />
Calculating the thrust-to-weight ratio is very simple. It is important to know the thrust to weight ratio of your rocket to ensure your rocket will actually liftoff. If your TWR is less than 1, you can bet that you won't make an inch in altitude when starting from the launch pad. The minimum optimal TWR to have for your rocket at launch is 2.2.<br />
<br />
To lift off the rocket's thrust need to exceed the gravitational force. The formula for this is simply the thrust of all of your current stage engines divided by the weight of your ship, fully fuelled.<br />
:<math>F_T > F_G = m \cdot g \implies TWR = \frac{F_T}{F_G} = \frac{F_T}{m \cdot g} > 1</math><br />
To calculate the acceleration simply use [[w:Newton's second law|Newton's second law]]:<br />
:<math>F = m \cdot a = F_T - F_G = F_T - m \cdot g = m \cdot a \implies a = \frac{F_T}{m} - g</math><br />
These calculations only work when counteracting gravity. While coasting on an orbit the gravitational acceleration isn't important and thus the TWR may be below one and still work. The acceleration is at minimum directly after launch when the craft is heavy and at maximum immediately before running out of fuel, when the tanks are dry:<br />
:<math>a_{min} \approx \frac{F_T}{m_{total}} - g</math> and <math> a_{max} \approx \frac{F_T}{m_{dry}} - g</math><br />
The dry mass also includes the fully fuelled upper stages of the craft. To determine the g-force simply divide achieved acceleration by <math>g_0 = 9.81 \frac{m}{s^2}</math>. As the craft is in free fall, the gravitational acceleration isn't felt by the crew so the accelerations appear to be higher for the crew leading to cancelling out the factor g:<br />
:<math>\text{g-force}_{min} \approx \frac{F_T}{m_{total} \cdot g_0}</math> and <math>\text{g-force}_{max} \approx \frac{F_T}{m_{dry} \cdot g_0}</math><br />
<br />
As the weight of the ship depends on the current gravitation (<math>g</math>) the TWR differs between the celestial bodies.<br />
<br />
== Conclusion ==<br />
This guide will hopefully have helped with designing your rockets to allow you to get the job done—whatever it may be—with no test flights first. We hope this guide has been helpful to new and continuing KSP pilots alike.<br />
<br />
[[Category:Tutorials|Advanced Rocket Design]]</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=Kerbodyne_KE-1_%22Mastodon%22_Liquid_Fuel_Engine&diff=95180Kerbodyne KE-1 "Mastodon" Liquid Fuel Engine2019-07-24T04:21:00Z<p>Empiro: /* Usage */</p>
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<div>{{Expansion|mh|small=no}}<br />
{{User:ArnePeirs/created part}}<br />
{{:Kerbodyne KE-1 "Mastodon" Liquid Fuel Engine/Box}}<br />
<br />
== Usage ==<br />
The Mastodon has the second-highest thrust-to-weight ratio of any liquid fuel engine in the game, trailing only the [[LFB_KR-1x2_"Twin-Boar"_Liquid_Fuel_Engine|"Twin-Boar"]], which has the highest after subtracting away the integrated fuel tank. Because the Mastodon can be independently mounted, clusters of this engine are an ideal way to lift extremely heavy payloads.<br />
<br />
== Product description ==<br />
{{Quote|Considered to be the behemoth of rocket technology, this propulsion system is the pinnacle of power.|manufacturer=KD}}<br />
<br />
== Variants ==<br />
As of {{version|1.4.1}} this engine has three models that can be switched in the editor.<br />
<br />
{{multiple image<br />
|align=left<br />
|width=200<br />
|image1=KE-1_Full.png<br />
|alt1=Full variant<br />
|image2=KE-1_Mid.png<br />
|alt2=Mid variant<br />
|image3=KE-1_Bare.png<br />
|alt3=Bare variant<br />
|footer=The different variants of the engine<br />
}}<br />
{{clear|left}}<br />
<br />
== Trivia ==<br />
=== Real-world comparison ===<br />
The engine was inspired by the American [[w:Rocketdyne F-1|F-1 engine]].<br />
<br />
== Changes ==<br />
;[[1.6]]<br />
* Decreased unlock cost from 135000 to 32000<br />
* Decreased cost from 22000 to 8000<br />
* Increased crash tolerance from 6 to 15<br />
* Increased EC generation from 3 to 8<br />
* Improved Isp<br />
;[[1.4.5]]<br />
* Added ModuleTestSubject<br />
;[[1.4.1]]<br />
* Initial Release<br />
<br />
{{Making History parts}}<br />
[[Category:Liquid fuel engines]]</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=Kerbodyne_KE-1_%22Mastodon%22_Liquid_Fuel_Engine&diff=95179Kerbodyne KE-1 "Mastodon" Liquid Fuel Engine2019-07-24T01:13:09Z<p>Empiro: /* Usage */</p>
<hr />
<div>{{Expansion|mh|small=no}}<br />
{{User:ArnePeirs/created part}}<br />
{{:Kerbodyne KE-1 "Mastodon" Liquid Fuel Engine/Box}}<br />
<br />
== Usage ==<br />
The Mastodon has the second-highest thrust-to-weight ratio of any liquid fuel engine in the game, trailing only the [[LFB_KR-1x2_"Twin-Boar"_Liquid_Fuel_Engine|"Twin-Boar"]], which has the highest after subtracting away the integrated fuel tank. Because it can be independently mounted, clusters of this engine are an ideal way to lift extremely heavy payloads.<br />
<br />
== Product description ==<br />
{{Quote|Considered to be the behemoth of rocket technology, this propulsion system is the pinnacle of power.|manufacturer=KD}}<br />
<br />
== Variants ==<br />
As of {{version|1.4.1}} this engine has three models that can be switched in the editor.<br />
<br />
{{multiple image<br />
|align=left<br />
|width=200<br />
|image1=KE-1_Full.png<br />
|alt1=Full variant<br />
|image2=KE-1_Mid.png<br />
|alt2=Mid variant<br />
|image3=KE-1_Bare.png<br />
|alt3=Bare variant<br />
|footer=The different variants of the engine<br />
}}<br />
{{clear|left}}<br />
<br />
== Trivia ==<br />
=== Real-world comparison ===<br />
The engine was inspired by the American [[w:Rocketdyne F-1|F-1 engine]].<br />
<br />
== Changes ==<br />
;[[1.6]]<br />
* Decreased unlock cost from 135000 to 32000<br />
* Decreased cost from 22000 to 8000<br />
* Increased crash tolerance from 6 to 15<br />
* Increased EC generation from 3 to 8<br />
* Improved Isp<br />
;[[1.4.5]]<br />
* Added ModuleTestSubject<br />
;[[1.4.1]]<br />
* Initial Release<br />
<br />
{{Making History parts}}<br />
[[Category:Liquid fuel engines]]</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=Kerbodyne_KE-1_%22Mastodon%22_Liquid_Fuel_Engine&diff=95178Kerbodyne KE-1 "Mastodon" Liquid Fuel Engine2019-07-24T00:51:37Z<p>Empiro: </p>
<hr />
<div>{{Expansion|mh|small=no}}<br />
{{User:ArnePeirs/created part}}<br />
{{:Kerbodyne KE-1 "Mastodon" Liquid Fuel Engine/Box}}<br />
<br />
== Usage ==<br />
The Mastodon has the second-highest thrust-to-weight ratio of any liquid fuel engine in the game, trailing only the [[LFB_KR-1x2_"Twin-Boar"_Liquid_Fuel_Engine|"Twin-Boar"]]. However, it can be independently mounted, making clusters of this engine an ideal way to lift the heaviest payloads.<br />
<br />
== Product description ==<br />
{{Quote|Considered to be the behemoth of rocket technology, this propulsion system is the pinnacle of power.|manufacturer=KD}}<br />
<br />
== Variants ==<br />
As of {{version|1.4.1}} this engine has three models that can be switched in the editor.<br />
<br />
{{multiple image<br />
|align=left<br />
|width=200<br />
|image1=KE-1_Full.png<br />
|alt1=Full variant<br />
|image2=KE-1_Mid.png<br />
|alt2=Mid variant<br />
|image3=KE-1_Bare.png<br />
|alt3=Bare variant<br />
|footer=The different variants of the engine<br />
}}<br />
{{clear|left}}<br />
<br />
== Trivia ==<br />
=== Real-world comparison ===<br />
The engine was inspired by the American [[w:Rocketdyne F-1|F-1 engine]].<br />
<br />
== Changes ==<br />
;[[1.6]]<br />
* Decreased unlock cost from 135000 to 32000<br />
* Decreased cost from 22000 to 8000<br />
* Increased crash tolerance from 6 to 15<br />
* Increased EC generation from 3 to 8<br />
* Improved Isp<br />
;[[1.4.5]]<br />
* Added ModuleTestSubject<br />
;[[1.4.1]]<br />
* Initial Release<br />
<br />
{{Making History parts}}<br />
[[Category:Liquid fuel engines]]</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=KV-3_%27Pomegranate%27_Reentry_Module&diff=95176KV-3 'Pomegranate' Reentry Module2019-07-23T02:36:53Z<p>Empiro: /* Usage */</p>
<hr />
<div>{{Expansion|mh|small=no}}<br />
{{:KV-3 'Pomegranate' Reentry Module/Box}}<br />
<br />
The '''KV-3 'Pomegranate' Reentry Module''' is a [[Command Module]] housing three [[Kerbal]] crew members during their mission. It has a rounded shape, similar to a pomegranate or [[Stayputnik]].<br />
<br />
== Usage ==<br />
Generally placed at the top of the rocket, the KV-3 Pomegranate provides basic command module functionality.<br />
<br />
It features a 0.625 m [[radial size]] node on top, typically used for parts like the [[Mk16 Parachute]], [[Docking|docking ports]], [[service bay]]s, or [[SAS]] modules. On the bottom, it has a 1.25m radial node. As the node is part of the heatshield, it includes a "free" decoupler. This decoupler does not take up any additional mass, but can only be fired if the pod is attached to something else.<br />
<br />
Notably unlike the previous pods, the KV-3 has a small integrated heatshield, no [[monopropellant]], and ''no reaction wheels''. The last one requires extra care in craft design, else a mission could be curtailed or lost due to limited control options. It is lighter than the other 3-kerbal pods.<br />
<br />
Note that the heatshield is not designed for re-entry from interplanetary speeds.<br />
<br />
== Product description ==<br />
{{Quote|Many little Kerbals inside this one. Couldn't fit more.|manufacturer=Probodobodyne}}<br />
<br />
== Trivia ==<br />
* The part's CFG file suggests that this capsule was originally named "Tato".<br />
<br />
=== Real-world comparison ===<br />
The KV-3 was inspired by the [[w:Voskhod (spacecraft)|Voskhod]] (3 person variant).<br />
<br />
== Changes ==<br />
;[[1.4.1]]<br />
* Initial Release<br />
<br />
{{Making History parts}}<br />
[[Category:Command modules]]</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=KV-2_%E2%80%98Pea%E2%80%99_Reentry_Module&diff=95175KV-2 ‘Pea’ Reentry Module2019-07-23T02:36:43Z<p>Empiro: /* Usage */</p>
<hr />
<div>{{Expansion|mh|small=no}}<br />
{{:KV-2_‘Pea’_Reentry_Module/Box}}<br />
<br />
The '''KV-2 ‘Pea’ Reentry Module''' is a [[Command Module]] housing two [[Kerbal]] crew members during their mission. It has a rounded shape, similar to a pea or [[Stayputnik]].<br />
<br />
== Usage ==<br />
Generally placed at the top of the rocket, the KV-2 Pea provides basic command module functionality.<br />
<br />
It features a 0.625 m [[radial size]] node on top, typically used for parts like the [[Mk16 Parachute]], [[Docking|docking ports]], [[service bay]]s, or [[SAS]] modules. On the bottom, it has a 1.25m radial node. As the node is part of the heatshield, it includes a "free" decoupler. This decoupler does not take up any additional mass, but can only be fired if the pod is attached to something else.<br />
<br />
Notably unlike the previous pods, the KV-2 has a small integrated heatshield, no [[monopropellant]], and ''no reaction wheels''. The last one requires extra care in craft design, else a mission could be curtailed or lost due to limited control options. It is lighter than the other 2-kerbal pods, with the exception of the [[Munar Excursion Module]].<br />
<br />
Note that the heatshield is not designed for re-entry from interplanetary speeds.<br />
<br />
== Product description ==<br />
{{Quote|Two little green Kerbals like peas in a Pea Pod. The engineers managed to fit an extra Kerbal in the same space!|manufacturer=Probodobodyne}}<br />
<br />
== Trivia ==<br />
* The part's CFG file suggests that this capsule was originally named "Onion".<br />
<br />
=== Real-world comparison ===<br />
The KV-2 was inspired by the [[w:Voskhod (spacecraft)|Voskhod]] (2 person variant).<br />
<br />
== Changes ==<br />
;[[1.4.1]]<br />
* Initial Release<br />
<br />
{{Making History parts}}<br />
[[Category:Command modules]]</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=KV-1_%27Onion%27_Reentry_Module&diff=95174KV-1 'Onion' Reentry Module2019-07-23T02:36:18Z<p>Empiro: /* Usage */</p>
<hr />
<div>{{Expansion|mh|small=no}}<br />
{{:KV-1 'Onion' Reentry Module/Box}}<br />
<br />
The '''KV-1 'Onion' Reentry Module''' is a [[Command Module]] housing one [[Kerbal]] crew member during their mission. It has a rounded shape, similar to an onion or [[Stayputnik]].<br />
<br />
== Usage ==<br />
Generally placed at the top of the rocket, the KV-1 Onion provides basic command module functionality.<br />
<br />
It features a 0.625 m [[radial size]] node on top, typically used for parts like the [[Mk16 Parachute]], [[Docking|docking ports]], [[service bay]]s, or [[SAS]] modules. On the bottom, it has a 1.25m radial node. As the node is part of the heatshield, it includes a "free" decoupler. This decoupler does not take up any additional mass, but can only be fired if the pod is attached to something else.<br />
<br />
Notably unlike the previous pods, the KV-1 has a small integrated heatshield, no [[monopropellant]], and ''no reaction wheels''. The last one requires extra care in craft design, else a mission could be curtailed or lost due to limited control options. Against the the Mk1 pod specifically, it is comparable in cost (590 funds vs 588 with all resources removed), can handle somewhat higher temperatures (both in general rating, and the aforementioned heatshield), has a slightly lower impact tolerance (12 vs 14 m/s), and is and marginally lighter (0.75 vs 0.8 tonnes without resources).<br />
<br />
Note that the heatshield is not designed for re-entry from interplanetary speeds.<br />
<br />
== Product description ==<br />
{{Quote|The design bureau cried when the finance department cried “that’s your lot!”|manufacturer=Probodobodyne}}<br />
<br />
== Trivia ==<br />
* The part's CFG file suggests that this capsule was originally named "Shallot".<br />
<br />
=== Real-world comparison ===<br />
The KV-1 was inspired by the [[w:Vostok (spacecraft)|Vostok]].<br />
<br />
== Changes ==<br />
;[[1.4.1]]<br />
* Initial Release<br />
<br />
{{Making History parts}}<br />
[[Category:Command modules]]</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=Tutorial:_How_to_Get_into_Orbit&diff=79737Tutorial: How to Get into Orbit2017-12-04T02:42:00Z<p>Empiro: /* Rocket tumbles or goes out of control */</p>
<hr />
<div>{{Caution|<br />
*The instructions listed almost invariably fail for larger [[Rocket]]s, since it assumes a very small [[rocket|Rocket]] with good maneuvering.<br />
}}<br />
This tutorial describes a simple launch profile to get a vehicle to [[Orbit]] over [[Kerbin]], and back again.<br />
<br />
==Specifications==<br />
*'''Length:''' 15–20 minutes<br />
*'''Difficulty:''' Harder than a suborbital flight, easier than an orbital intercept.<br />
*'''Skills needed:''' Seat of the pants<br />
*'''For version:''' 1.0.2<br />
<br />
==Rocket Design==<br />
[[File:Cheapest Kerbin Orbit Rocket Tut.png|thumb|right|180px|Rocket assembled and ready to launch. [[TT18-A Launch Stability Enhancer]]s optional. 0.25]]<br />
The rocket should preferably be liquid fueled with at least two stages. An example of a simple manned orbiter:<br />
<br />
*[[Command Pod Mk1]]<br />
*[[Mk16 Parachute]]<br />
*[[Heat_Shield_(1.25m)]]<br />
*[[TR-18A Stack Decoupler]]<br />
*[[FL-T400 Fuel Tank]]<br />
*[[LV-909 Liquid Fuel Engine]]<br />
*Another [[TR-18A Stack Decoupler]]<br />
*[[FL-T800 Fuel Tank]]<br />
*[[LV-T30 Liquid Fuel Engine]]<br />
<br />
In order to make sure the staging sequence is correct, see our guide on [[Tutorial:Game_Manual#Rocket_Staging|Rocket Staging]].<br />
<br />
==Steps to Orbit and Back==<br />
<br />
===Launch Preparation===<br />
<br />
# Set thrust to maximum by hitting Z.<br />
# Toggle on [[SAS]] by hitting T.<br />
# Hit M to go to [[Map View]]. Tilt the view so that you're looking straight down [[Kerbin]]'s North pole, which will give a clear view of the trajectory arc towards the East and the [[Apoapsis]] label.<br />
# Switch back to the normal viewmode by hitting M to enjoy the [[launch|Launch]] spectacle.<br />
<br />
===Accelerate to 100 m/s===<br />
<br />
[[Launch]] by hitting the space bar and keep the rocket pointed straight up until the vehicle's speed is 100 m/s. Use the [[Navball]] to keep the [[Navball#Level_indicator|level indicator]] centered on the blue hemisphere. <br />
<br />
===Pitch 10 degrees East===<br />
<br />
When the rocket's speed reaches 100 m/s, start a gravity turn by pressing the D key until the rocket is pitched 10 degrees towards the East. The heading ("HDG") on the Navball should now be 90 degrees.<br />
<br />
While the rocket accelerates, gravity will bend the trajectory downwards. On the Navball this can be observed as the [[Navball#Prograde_and_retrograde|Prograde marker]] dropping further down. Follow it by keeping the level indicator within the circle of the prograde marker at all times especially while in the lower atmosphere, but at about 30km the reaction wheels should be able to compensate. If craft nears the apoapsis too fast, which can be seen in a dropping time to apoapsis, it might be necessary to point “above” the prograde marker, away from the brown half.<br />
<br />
===Stage===<br />
<br />
The fuel of the first stage will run out before 20km altitude. Hit the space bar to discard it and to activate the second stage. Continue to accelerate at full throttle.<br />
<br />
Hit M to switch to map view. Click the Navball toggle at the bottom of the screen to make it visible again. Continue to watch the Navball and steer the rocket to keep it aligned it with prograde.<br />
<br />
===Get apoapsis above 70 km===<br />
<br />
In map view, hover the mouse over the "AP" label on the highest point of the trajectory to monitor the apoapsis height; cut off the engine with X when it reaches 70&nbsp;km (70,000 meters).<br />
<br />
Let the rocket coast towards apoapsis after cutting off the engine.<br />
<br />
===Get periapsis above 70 km===<br />
<br />
As the rocket approaches apoapsis, orient it once more to align with the prograde marker. At 30 seconds before apoapsis, reignite the engine at full throttle with Z. The apoapsis will begin to shift ahead; aim to keep it roughly the same amount of time ahead by throttling up or down with Shift and Control.<br />
<br />
The projected trajectory will begin to widen until the PE label appears on the other side of the planet. A stable orbit will be reached when both apoapsis and periapsis are above 70&nbsp;km. <br />
<br />
===De-orbiting===<br />
Wait until the craft is at apoapsis and orient it for a de-orbit burn by aligning the level indicator on the navball with the chartreuse yellow [[Navball#Prograde_and_retrograde|retrograde marker]]. Now burn until the periapsis is around 30&nbsp;km. Discard the engine and fuel tank by staging, leaving only the command pod with its heat shield and parachute.<br />
<br />
If fuel is scarce, any periapsis below 70&nbsp;km will eventually result in de-orbiting. However, it may take many passes through the atmosphere before the vehicle finally slows down enough.<br />
<br />
===Re-entry===<br />
During re-entry into the atmosphere, the capsule will heat up and lose speed. Keep the level indicator aligned with the retrograde marker to let the heat shield take the brunt of the heat.<br />
<br />
Wait until the capsule's speed drops below 200 m/s, and deploy the parachute.<br />
<br />
==Common problems and solutions==<br />
<br />
===Rocket tumbles or goes out of control===<br />
The most common problem of new players is their rockets going out of control while in the atmosphere. There are multiple causes and slightly different solutions. First, make sure that SAS is on.<br />
<br />
If that doesn't work, then the cause is often a lack of control surfaces and aerodynamics. You will want to place something like the [[AV-R8_Winglet|AV-R8 Winglet]] at the bottom of your rocket. This gives it both stability and control. Using an engine that has a gimbal, such as the [[LV-T45_%22Swivel%22_Liquid_Fuel_Engine|LV-T45]] will also give you more control.<br />
<br />
Another common cause is aggressive piloting. When pitching over or making other corrections, it is important to make small adjustments. Always keep your nose close to the green prograde marker. In other words, make a small adjustment, wait until you're moving in the same direction as your nose is pointing, and then make another small adjustment.<br />
<br />
The final common cause is travelling too quickly while in the lower atmosphere. This causes more aerodynamic pressure on your craft, which may overwhelm the control provided by winglets and engines. If you see flames during ascent, this is a likely cause. The best way to solve this is not to lower your throttle, but instead to add more fuel. The extra fuel also gives you more room to recover from mistakes.<br />
<br />
{{Tutorials}}</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=Tutorial:_How_to_Get_into_Orbit&diff=79736Tutorial: How to Get into Orbit2017-12-04T02:12:09Z<p>Empiro: /* Rocket tumbles or goes out of control */</p>
<hr />
<div>{{Caution|<br />
*The instructions listed almost invariably fail for larger [[Rocket]]s, since it assumes a very small [[rocket|Rocket]] with good maneuvering.<br />
}}<br />
This tutorial describes a simple launch profile to get a vehicle to [[Orbit]] over [[Kerbin]], and back again.<br />
<br />
==Specifications==<br />
*'''Length:''' 15–20 minutes<br />
*'''Difficulty:''' Harder than a suborbital flight, easier than an orbital intercept.<br />
*'''Skills needed:''' Seat of the pants<br />
*'''For version:''' 1.0.2<br />
<br />
==Rocket Design==<br />
[[File:Cheapest Kerbin Orbit Rocket Tut.png|thumb|right|180px|Rocket assembled and ready to launch. [[TT18-A Launch Stability Enhancer]]s optional. 0.25]]<br />
The rocket should preferably be liquid fueled with at least two stages. An example of a simple manned orbiter:<br />
<br />
*[[Command Pod Mk1]]<br />
*[[Mk16 Parachute]]<br />
*[[Heat_Shield_(1.25m)]]<br />
*[[TR-18A Stack Decoupler]]<br />
*[[FL-T400 Fuel Tank]]<br />
*[[LV-909 Liquid Fuel Engine]]<br />
*Another [[TR-18A Stack Decoupler]]<br />
*[[FL-T800 Fuel Tank]]<br />
*[[LV-T30 Liquid Fuel Engine]]<br />
<br />
In order to make sure the staging sequence is correct, see our guide on [[Tutorial:Game_Manual#Rocket_Staging|Rocket Staging]].<br />
<br />
==Steps to Orbit and Back==<br />
<br />
===Launch Preparation===<br />
<br />
# Set thrust to maximum by hitting Z.<br />
# Toggle on [[SAS]] by hitting T.<br />
# Hit M to go to [[Map View]]. Tilt the view so that you're looking straight down [[Kerbin]]'s North pole, which will give a clear view of the trajectory arc towards the East and the [[Apoapsis]] label.<br />
# Switch back to the normal viewmode by hitting M to enjoy the [[launch|Launch]] spectacle.<br />
<br />
===Accelerate to 100 m/s===<br />
<br />
[[Launch]] by hitting the space bar and keep the rocket pointed straight up until the vehicle's speed is 100 m/s. Use the [[Navball]] to keep the [[Navball#Level_indicator|level indicator]] centered on the blue hemisphere. <br />
<br />
===Pitch 10 degrees East===<br />
<br />
When the rocket's speed reaches 100 m/s, start a gravity turn by pressing the D key until the rocket is pitched 10 degrees towards the East. The heading ("HDG") on the Navball should now be 90 degrees.<br />
<br />
While the rocket accelerates, gravity will bend the trajectory downwards. On the Navball this can be observed as the [[Navball#Prograde_and_retrograde|Prograde marker]] dropping further down. Follow it by keeping the level indicator within the circle of the prograde marker at all times especially while in the lower atmosphere, but at about 30km the reaction wheels should be able to compensate. If craft nears the apoapsis too fast, which can be seen in a dropping time to apoapsis, it might be necessary to point “above” the prograde marker, away from the brown half.<br />
<br />
===Stage===<br />
<br />
The fuel of the first stage will run out before 20km altitude. Hit the space bar to discard it and to activate the second stage. Continue to accelerate at full throttle.<br />
<br />
Hit M to switch to map view. Click the Navball toggle at the bottom of the screen to make it visible again. Continue to watch the Navball and steer the rocket to keep it aligned it with prograde.<br />
<br />
===Get apoapsis above 70 km===<br />
<br />
In map view, hover the mouse over the "AP" label on the highest point of the trajectory to monitor the apoapsis height; cut off the engine with X when it reaches 70&nbsp;km (70,000 meters).<br />
<br />
Let the rocket coast towards apoapsis after cutting off the engine.<br />
<br />
===Get periapsis above 70 km===<br />
<br />
As the rocket approaches apoapsis, orient it once more to align with the prograde marker. At 30 seconds before apoapsis, reignite the engine at full throttle with Z. The apoapsis will begin to shift ahead; aim to keep it roughly the same amount of time ahead by throttling up or down with Shift and Control.<br />
<br />
The projected trajectory will begin to widen until the PE label appears on the other side of the planet. A stable orbit will be reached when both apoapsis and periapsis are above 70&nbsp;km. <br />
<br />
===De-orbiting===<br />
Wait until the craft is at apoapsis and orient it for a de-orbit burn by aligning the level indicator on the navball with the chartreuse yellow [[Navball#Prograde_and_retrograde|retrograde marker]]. Now burn until the periapsis is around 30&nbsp;km. Discard the engine and fuel tank by staging, leaving only the command pod with its heat shield and parachute.<br />
<br />
If fuel is scarce, any periapsis below 70&nbsp;km will eventually result in de-orbiting. However, it may take many passes through the atmosphere before the vehicle finally slows down enough.<br />
<br />
===Re-entry===<br />
During re-entry into the atmosphere, the capsule will heat up and lose speed. Keep the level indicator aligned with the retrograde marker to let the heat shield take the brunt of the heat.<br />
<br />
Wait until the capsule's speed drops below 200 m/s, and deploy the parachute.<br />
<br />
==Common problems and solutions==<br />
<br />
===Rocket tumbles or goes out of control===<br />
The most common problem of new players is their rockets going out of control while in the atmosphere. There are multiple causes and slightly different solutions. First, make sure that SAS is on.<br />
<br />
If that doesn't work, then the cause is often a lack of control surfaces and aerodynamics. You will want to place something like the [[AV-R8_Winglet|AV-R8 Winglet]] at the bottom of your rocket. This gives it both stability and control. Using an engine that has a gimbal, such as the [[LV-T45_%22Swivel%22_Liquid_Fuel_Engine|LV-T45]] will also give you more control.<br />
<br />
Another common cause is aggressive piloting. When pitching over or making other corrections, it is important to make small adjustments. Always keep your nose close to the green prograde marker. In other words, make a small adjustment, wait until you're moving in the same direction as your nose is pointing, and then make another small adjustment.<br />
<br />
The final common cause is travelling too quickly while in the lower atmosphere. This causes more aerodynamic pressure on your craft, which may overwhelm the control provided by winglets and engines. If you see flames during ascent, this is a likely cause. The best way to solve this is not to lower your throttle, but instead to add more fuel. The extra fuel also give you more room to recover from mistakes.<br />
<br />
{{Tutorials}}</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=Tutorial:_How_to_Get_into_Orbit&diff=79735Tutorial: How to Get into Orbit2017-12-04T02:11:28Z<p>Empiro: </p>
<hr />
<div>{{Caution|<br />
*The instructions listed almost invariably fail for larger [[Rocket]]s, since it assumes a very small [[rocket|Rocket]] with good maneuvering.<br />
}}<br />
This tutorial describes a simple launch profile to get a vehicle to [[Orbit]] over [[Kerbin]], and back again.<br />
<br />
==Specifications==<br />
*'''Length:''' 15–20 minutes<br />
*'''Difficulty:''' Harder than a suborbital flight, easier than an orbital intercept.<br />
*'''Skills needed:''' Seat of the pants<br />
*'''For version:''' 1.0.2<br />
<br />
==Rocket Design==<br />
[[File:Cheapest Kerbin Orbit Rocket Tut.png|thumb|right|180px|Rocket assembled and ready to launch. [[TT18-A Launch Stability Enhancer]]s optional. 0.25]]<br />
The rocket should preferably be liquid fueled with at least two stages. An example of a simple manned orbiter:<br />
<br />
*[[Command Pod Mk1]]<br />
*[[Mk16 Parachute]]<br />
*[[Heat_Shield_(1.25m)]]<br />
*[[TR-18A Stack Decoupler]]<br />
*[[FL-T400 Fuel Tank]]<br />
*[[LV-909 Liquid Fuel Engine]]<br />
*Another [[TR-18A Stack Decoupler]]<br />
*[[FL-T800 Fuel Tank]]<br />
*[[LV-T30 Liquid Fuel Engine]]<br />
<br />
In order to make sure the staging sequence is correct, see our guide on [[Tutorial:Game_Manual#Rocket_Staging|Rocket Staging]].<br />
<br />
==Steps to Orbit and Back==<br />
<br />
===Launch Preparation===<br />
<br />
# Set thrust to maximum by hitting Z.<br />
# Toggle on [[SAS]] by hitting T.<br />
# Hit M to go to [[Map View]]. Tilt the view so that you're looking straight down [[Kerbin]]'s North pole, which will give a clear view of the trajectory arc towards the East and the [[Apoapsis]] label.<br />
# Switch back to the normal viewmode by hitting M to enjoy the [[launch|Launch]] spectacle.<br />
<br />
===Accelerate to 100 m/s===<br />
<br />
[[Launch]] by hitting the space bar and keep the rocket pointed straight up until the vehicle's speed is 100 m/s. Use the [[Navball]] to keep the [[Navball#Level_indicator|level indicator]] centered on the blue hemisphere. <br />
<br />
===Pitch 10 degrees East===<br />
<br />
When the rocket's speed reaches 100 m/s, start a gravity turn by pressing the D key until the rocket is pitched 10 degrees towards the East. The heading ("HDG") on the Navball should now be 90 degrees.<br />
<br />
While the rocket accelerates, gravity will bend the trajectory downwards. On the Navball this can be observed as the [[Navball#Prograde_and_retrograde|Prograde marker]] dropping further down. Follow it by keeping the level indicator within the circle of the prograde marker at all times especially while in the lower atmosphere, but at about 30km the reaction wheels should be able to compensate. If craft nears the apoapsis too fast, which can be seen in a dropping time to apoapsis, it might be necessary to point “above” the prograde marker, away from the brown half.<br />
<br />
===Stage===<br />
<br />
The fuel of the first stage will run out before 20km altitude. Hit the space bar to discard it and to activate the second stage. Continue to accelerate at full throttle.<br />
<br />
Hit M to switch to map view. Click the Navball toggle at the bottom of the screen to make it visible again. Continue to watch the Navball and steer the rocket to keep it aligned it with prograde.<br />
<br />
===Get apoapsis above 70 km===<br />
<br />
In map view, hover the mouse over the "AP" label on the highest point of the trajectory to monitor the apoapsis height; cut off the engine with X when it reaches 70&nbsp;km (70,000 meters).<br />
<br />
Let the rocket coast towards apoapsis after cutting off the engine.<br />
<br />
===Get periapsis above 70 km===<br />
<br />
As the rocket approaches apoapsis, orient it once more to align with the prograde marker. At 30 seconds before apoapsis, reignite the engine at full throttle with Z. The apoapsis will begin to shift ahead; aim to keep it roughly the same amount of time ahead by throttling up or down with Shift and Control.<br />
<br />
The projected trajectory will begin to widen until the PE label appears on the other side of the planet. A stable orbit will be reached when both apoapsis and periapsis are above 70&nbsp;km. <br />
<br />
===De-orbiting===<br />
Wait until the craft is at apoapsis and orient it for a de-orbit burn by aligning the level indicator on the navball with the chartreuse yellow [[Navball#Prograde_and_retrograde|retrograde marker]]. Now burn until the periapsis is around 30&nbsp;km. Discard the engine and fuel tank by staging, leaving only the command pod with its heat shield and parachute.<br />
<br />
If fuel is scarce, any periapsis below 70&nbsp;km will eventually result in de-orbiting. However, it may take many passes through the atmosphere before the vehicle finally slows down enough.<br />
<br />
===Re-entry===<br />
During re-entry into the atmosphere, the capsule will heat up and lose speed. Keep the level indicator aligned with the retrograde marker to let the heat shield take the brunt of the heat.<br />
<br />
Wait until the capsule's speed drops below 200 m/s, and deploy the parachute.<br />
<br />
==Common problems and solutions==<br />
<br />
===Rocket tumbles or goes out of control===<br />
The most common problem of new players is their rockets going out of control while in the atmosphere. There are multiple causes and slightly different solutions. First, make sure that SAS is on.<br />
<br />
If that doesn't work, then often the cause lack of control surfaces and aerodynamics. You will want to place something like the [[AV-R8_Winglet|AV-R8 Winglet]] at the bottom of your rocket. This gives it both stability and control. Using an engine that has a gimbal, such as the [[LV-T45_%22Swivel%22_Liquid_Fuel_Engine|LV-T45]] will also give you more control.<br />
<br />
Another common cause is aggressive piloting. When pitching over or making other corrections, it is important to make small adjustments. Always keep your nose close to the green prograde marker. In other words, make a small adjustment, wait until you're moving in the same direction as your nose is pointing, and then make another small adjustment.<br />
<br />
The final common cause is travelling too quickly while in the lower atmosphere. This causes more aerodynamic pressure on your craft, which may overwhelm the control provided by winglets and engines. If you see flames during ascent, this is a likely cause. The best way to solve this is not to lower your throttle, but instead to add more fuel. The extra fuel also give you more room to recover from mistakes.<br />
<br />
{{Tutorials}}</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=Tutorial:_How_to_Get_into_Orbit&diff=79734Tutorial: How to Get into Orbit2017-12-04T01:50:50Z<p>Empiro: The 10km, 300 m/s limit no longer applies to current versions of KSP.</p>
<hr />
<div>{{Caution|<br />
*The instructions listed almost invariably fail for larger [[Rocket]]s, since it assumes a very small [[rocket|Rocket]] with good maneuvering.<br />
}}<br />
This tutorial describes a simple launch profile to get a vehicle to [[Orbit]] over [[Kerbin]], and back again.<br />
<br />
==Specifications==<br />
*'''Length:''' 15–20 minutes<br />
*'''Difficulty:''' Harder than a suborbital flight, easier than an orbital intercept.<br />
*'''Skills needed:''' Seat of the pants<br />
*'''For version:''' 1.0.2<br />
<br />
==Rocket Design==<br />
[[File:Cheapest Kerbin Orbit Rocket Tut.png|thumb|right|180px|Rocket assembled and ready to launch. [[TT18-A Launch Stability Enhancer]]s optional. 0.25]]<br />
The rocket should preferably be liquid fueled with at least two stages. An example of a simple manned orbiter:<br />
<br />
*[[Command Pod Mk1]]<br />
*[[Mk16 Parachute]]<br />
*[[Heat_Shield_(1.25m)]]<br />
*[[TR-18A Stack Decoupler]]<br />
*[[FL-T400 Fuel Tank]]<br />
*[[LV-909 Liquid Fuel Engine]]<br />
*Another [[TR-18A Stack Decoupler]]<br />
*[[FL-T800 Fuel Tank]]<br />
*[[LV-T30 Liquid Fuel Engine]]<br />
<br />
In order to make sure the staging sequence is correct, see our guide on [[Tutorial:Game_Manual#Rocket_Staging|Rocket Staging]].<br />
<br />
==Steps to Orbit and Back==<br />
<br />
===Launch Preparation===<br />
<br />
# Set thrust to maximum by hitting Z.<br />
# Toggle on [[SAS]] by hitting T.<br />
# Hit M to go to [[Map View]]. Tilt the view so that you're looking straight down [[Kerbin]]'s North pole, which will give a clear view of the trajectory arc towards the East and the [[Apoapsis]] label.<br />
# Switch back to the normal viewmode by hitting M to enjoy the [[launch|Launch]] spectacle.<br />
<br />
===Accelerate to 100 m/s===<br />
<br />
[[Launch]] by hitting the space bar and keep the rocket pointed straight up until the vehicle's speed is 100 m/s. Use the [[Navball]] to keep the [[Navball#Level_indicator|level indicator]] centered on the blue hemisphere. <br />
<br />
===Pitch 10 degrees East===<br />
<br />
When the rocket's speed reaches 100 m/s, start a gravity turn by pressing the D key until the rocket is pitched 10 degrees towards the East. The heading ("HDG") on the Navball should now be 90 degrees.<br />
<br />
While the rocket accelerates, gravity will bend the trajectory downwards. On the Navball this can be observed as the [[Navball#Prograde_and_retrograde|Prograde marker]] dropping further down. Follow it by keeping the level indicator within the circle of the prograde marker at all times especially while in the lower atmosphere, but at about 30km the reaction wheels should be able to compensate. If craft nears the apoapsis too fast, which can be seen in a dropping time to apoapsis, it might be necessary to point “above” the prograde marker, away from the brown half.<br />
<br />
===Stage===<br />
<br />
The fuel of the first stage will run out before 20km altitude. Hit the space bar to discard it and to activate the second stage. Continue to accelerate at full throttle.<br />
<br />
Hit M to switch to map view. Click the Navball toggle at the bottom of the screen to make it visible again. Continue to watch the Navball and steer the rocket to keep it aligned it with prograde.<br />
<br />
===Get apoapsis above 70 km===<br />
<br />
In map view, hover the mouse over the "AP" label on the highest point of the trajectory to monitor the apoapsis height; cut off the engine with X when it reaches 70&nbsp;km (70,000 meters).<br />
<br />
Let the rocket coast towards apoapsis after cutting off the engine.<br />
<br />
===Get periapsis above 70 km===<br />
<br />
As the rocket approaches apoapsis, orient it once more to align with the prograde marker. At 30 seconds before apoapsis, reignite the engine at full throttle with Z. The apoapsis will begin to shift ahead; aim to keep it roughly the same amount of time ahead by throttling up or down with Shift and Control.<br />
<br />
The projected trajectory will begin to widen until the PE label appears on the other side of the planet. A stable orbit will be reached when both apoapsis and periapsis are above 70&nbsp;km. <br />
<br />
===De-orbiting===<br />
Wait until the craft is at apoapsis and orient it for a de-orbit burn by aligning the level indicator on the navball with the chartreuse yellow [[Navball#Prograde_and_retrograde|retrograde marker]]. Now burn until the periapsis is around 30&nbsp;km. Discard the engine and fuel tank by staging, leaving only the command pod with its heat shield and parachute.<br />
<br />
If fuel is scarce, any periapsis below 70&nbsp;km will eventually result in de-orbiting. However, it may take many passes through the atmosphere before the vehicle finally slows down enough.<br />
<br />
===Re-entry===<br />
During re-entry into the atmosphere, the capsule will heat up and lose speed. Keep the level indicator aligned with the retrograde marker to let the heat shield take the brunt of the heat.<br />
<br />
Wait until the capsule's speed drops below 200 m/s, and deploy the parachute.<br />
<br />
{{Tutorials}}</div>Empirohttps://wiki.kerbalspaceprogram.com/index.php?title=Tutorial:Intermediate_Rocket_Design&diff=79733Tutorial:Intermediate Rocket Design2017-12-04T01:48:27Z<p>Empiro: /* Thrust-weight ratio */</p>
<hr />
<div>{{Dead end|date=April 2014}}<br />
<br />
==Physics==<br />
Before we get into the details, a few physics facts. Namely, center of gravity, point of action and how they matter.<br />
<br />
===Center of gravity===<br />
The [[Center of mass|center of gravity]] is the point in your rocket where it would be in total balance. It's the point where, if the rocket was resting on that point, you could give it a nudge and it would freely follow that nudge without gravity having a say, because left and right, up and down, front and back, they're all equally heavy and perfectly balanced on this single point. That is always one single point in space, and unless you have a very oddly shaped rocket, that point is somewhere inside your rocket. Sadly, this point is usually not the [[Center of thrust|point of action]], i.e. the point where your engines create thrust. If it was, that would be sweet, since we could push the rocket wherever and however we want (ignoring air resistance, of course).<br />
<br />
So the next best thing we can do is to put that point of action "behind" the center of gravity and point its action vector towards the center of gravity. Or, simpler put, put the engine behind the mass and thrust in the other direction.<br />
What sounds obvious at first has some implications. First, your point of action, actually the vector sum of your thrust vectors, for you nitpickers, HAS to be lined up with your center of gravity. In other words, your rocket has to be symmetrical to be stable. You can try that for yourself. Get a broom. Put the endpoint of the handle on your hand, with the brush up, and you will notice that you can balance it. You will also notice two things: First, it's easy to balance it as long as you work hard on it, and it can very easily tilt to one side, and if it does it falls FAST. And second, it's surprisingly more easy to balance the broom with the brush up towards the ceiling rather than having it resing on your hand.<br />
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If you would now put a lot of pressure on that handle, you could thrust that broom upwards without it falling to the side (trust me, it would work). That's basically how our rocket works. Now attach something to the side of the broom and see how this works out for you. If you try to balance the broom the same way, it will fall to the side where you tacked something onto it. Unless you hold it at an angle to the side... looks stupid if it were a rocket, doesn't it? If you would thrust that broom upwards, it would not only fall to that one side, it would actually start to spin around the x-axis and do "loops"... or crash, which is more likely since gravity is playing in this game as well.<br />
So the first thing to keep in mind is to keep your rocket symmetrical, at least to the point where the center of gravity is always above the combined point of action (if you have more than one engine, you have more than one point of action, which can be summed up to a total point of action and an action vector). In physical terms, that point of action has to be lined up with the center of gravity, with its vector aligned with the hypothetical axis that exists between the cog and the poa. In simpler terms, the point where your rocket would be in balance has to be behind the point where the combined force of the engines pushes, and the engines have to push towards that center of gravity, i.e. their thrust exhaust has to point away from it.<br />
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That also means that "inwards" thrust stabilizes the rocket, as long as the thrust is equal from all sides. It forces the rocket to stay in its current direction, but it also means that you are wasting fuel since you have engines thrusting "against" each other. Think of it as the toe-in of your cars steering wheels.<br />
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===Mass vs. weight===<br />
Your weight is directly related to your mass. Now, strictly speaking, weight is defined as the force on an object due to gravity. But gravity pulls every bit of mass in your rocket with the same force, making acceleration uniform throughout the ship. In space, not spinning and with engines off, there are no other forces actuating, so this is perceived as weightlessness. I'm not sure this is a good analogy, but think of being in a really quiet plane, flying level and at constant speed. You can't tell you're moving. Same thing with gravity, except there you can't tell you're being accelerated.<br />
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What we perceive as weight is caused by other forces, such as drag from an atmosphere, thrust from your engines or (usually) the normal force when landed. Assuming a flat landing area, the normal force matches gravity exactly but in reverse, so you stay at rest. Gravity pulls you down, the normal force is the ground pushing you up. But it doesn't act uniformly on every bit of mass like gravity does, it's just the ground pushing the bottom of the ship, so the force has to be distributed through the ship's structural elements, and that is perceived as weight. Same thing with thrust, or aerodynamic forces.<br />
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But even if you're (feeling) weightless, you're not without mass.<br />
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To cut the theoretical crap short, the more mass you have, the more energy you have to expend to change its speed and direction. The more massive your rocket is, the more fuel you have to spend to make it faster (or slower!). Usually, in this game as well as when you're overweight, physics works against you.<br />
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This also means, that a mass gets "heavier" if you accelerate it faster. More acceleration doesn't increase your mass (unless you're approaching light speed, let's ignore that for now), but the stress (perceived as weight) on the mass increases. That's called g-forces. On Kerbin, you experience 1g. (1g is defined as the acceleration equal to Kerbin's gravity at surface level which is about 9.81&nbsp;m/s², not to be confused with gram).<br />
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How does this affect your rocket? Well, it affects it twofold. First, the more mass you have, the more fuel you have to spend to get that mass up into orbit. Hence "bigger" isn't always "better". We'll get to that in detail later. The other factor is that the faster you accelerate your rocket, the more stress you put on its parts. Some parts are able to sustain that stress. Some are not. It is, in general, easier to build a slowly climbing rocket than one that jumps into orbit at 9g or more, not only because our passengers don't really like having a truck sitting on their chest (which isn't as much an issue so far), mostly the problem now is that the acceleration you put into the rocket stresses the parts that keep it together past their breaking limit. Which means you have to add struts, which add to the mass, which cost you fuel.<br />
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===Thrust-weight ratio===<br />
[[Thrust-to-weight ratio]]<br />
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Basically, it's the result of dividing your thrust (in newtons) by your weight (in kilograms times acceleration, i.e. kg*m/s², so... well, also in newtons). Thrust is what gets you up, weight is what keeps you down. And if thrust > weight, i.e. if your thrust-weight ratio is more than 1, you go up. If thrust < weight, you can put your engines into overdrive and you won't move an inch. For the record, the Saturn V first stage rocket engine had a TWR of 94.1. In other words, it could have lifted itself over 94 times. Beat that!<br />
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What does that mean for our space vehicle? Basically, it means that whatever we put as rockets behind our craft, it has to overcome the total weight of the craft. Which also means that, if you have multiple stages, the upper stages are just dead weight at start. Yes, yes, there are rockets in there and they might have a lot of punch, but they do not add to the thrust at start. Thrust is always only the thrust you ACTUALLY apply, not the thrust your rocket can eventually do in total.<br />
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Note that every rocket engine has a TWR of more than one. By definition. Engines below a TWR of 1 need some kind of aerodynamics on the craft to get it off the ground. The question is, though, whether the dead weight sitting on top of it STILL keeps that equation above 1. The F1's 94.1 TWR doesn't mean that the Apollo craft got shot into orbit at 100g. It means that there was a friggin' HUGE rocket sitting on top of that engine and hence it could barely get the whole behemoth up into an orbit!<br />
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My guess is that Kerbin has a gravity of about 10&nbsp;m/s² (much like earth), meaning that a rocket engine rated at 200 max thrust (like the non-gimballed stock engine) can lift 20 units of mass (or 8 stock liquid fuel tanks). Given that a rocket of 1 stock command center, 7 fuel tanks and 1 engine (totalling a mass of 20.5, 7*2.5+2+1) can't get off the ground but with 6 fuel tanks it can, I'd say that should be about right.<br />
So when building your rocket, always add up the mass of the parts you assembled, multiply by 10, then divide by the thrust of the engines, but ONLY the engines that actually thrust. The more you get out of that, the faster your rocket will climb. Considering that engines seem to overheat more readily if they're operated at the TWR limit, try to get to a TWR of at least 1.7 in your first stage. My Mun rocket has a first stage TWR of 2.2, which is plenty but not overdoing it to the point where the g-forces become unmanageable.<br />
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Also, keep in mind that you will use up fuel as you climb. Your fuel tanks will get emptier with every second your engine fires, making them lighter, meaning, less weight has to be lifted. Plus, gravity decreases with distance squared, which also makes the pull of Kerbin less and less with every inch you climb. Not as much as one would wish, though.<br />
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The most common error that beginner KSP players make is having too much TWR. Having a high TWR decreases overall delta-V, increases drag, and often makes a rocket difficult to control. A TWR of about 1.2-1.4 at launch is all that is needed. When performing maneuvers in space, TWR is even less important, and having a TWR of 0.5 (as calculated from the surface of Kerbin) or less is perfectly acceptable. The easiest way to reduce TWR is to simply add fuel to a stage until the desired TWR is reached.<br />
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==Staging, and when to do it==<br />
Staging usually means tossing dead weight. You jettison spent rocket parts to make your craft lighter. Less mass means less energy required to move the rest of the mass. The obvious choice would now be to stage as much as possible, to carry around as little dead weight as possible. This is not the best strategy, though.<br />
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Staging also means that you have to carry around the weight for the staging equipment and, in case of a liquid fuel set, another liquid engine. A spent stock booster weighs 0.36. The equipment to jettison it weighs 0.4. A spent liquid tank weighs 0.3. The additional engine and the staging equipment to toss it weighs 2.8.<br />
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A compromise has to be found. There is no hard limit to tell when to stage and when not to, what matters is how long you'd have to haul around the dead weight (if it's just a few seconds between the booster's end of life and until the other engine of this stage burns out, just keep the booster attached, it's not worth the extra weight for another set of staging couplers. If it's for the rest of the flight, tossing it pays off easily), whether the spent stage prevents you from firing the next (a lower stage burned up covering an upper stage has to be jettisoned, of course) and what the stage is used for (an upper stage is usually in use longer than a stage to reach orbit that is burning at max power constantly, i.e. a fuel tank in upper stages lasts much, much longer). I find the sweet spot for liquid tanks to be around 4-5 for lower stages and about 2 for upper stages.<br />
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==As much thrust as possible to the bottom==<br />
Also easy to see, the more thrust you apply right from the start, the less dead weight you carry around. It's usually quite pointless to have a lot of thrust further up if you cannot get off the launch pad. On the other hand, as mentioned above, the more thrust you put behind your crate, the more g-force it has to endure and the more you stress your parts. Not to mention the air resistance which is of course worst lower in the atmosphere.<br />
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==draaaaaaag==<br />
While we're at it, drag. I hope I got that one right, it's kinda hard to tell how that part really works. Basically, every part you add has air resistance. Doesn't matter once you're in orbit (and hence satellites rarely look streamlined), but it's a big issue until you hit that magical 70,000 meters. I still have very limited data on how drag really works and what affects what, so far all I can say is that it's there and that you should probably take it into account, i.e. creating insanely wide rockets to cram in a lot of boosters to fire at the same time might be a drag. Literally. Especially if you try to fly such a rocket at high speeds.<br />
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Note: Shape does not matter, only adding drag values (Unless you use Ferram Aerospace Research). This is why asparagus works. (I can't wait for a thousand years into the future, when people will see this and believe it's how asparagus works. Real asparagus)<br />
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==Where do you need the most power?==<br />
That's a simple one again: From ground to orbit. You will NEVER in your flight have to spend as much energy as in that part of your flight. Getting from orbit to the Mun, landing on the Mun, getting back off the moon, flying back to Kerbin and landing there? Easily done with about 1/6th of the fuel spent to get into orbit. I am NOT kidding or exaggerating here. Remember that Saturn V rocket that sent Apollo to the moon? Remember how friggin' huge that thing was? And what a tiny little bit of it actually went to the moon, with the rest being tossed somewhere along the way? Of the total mass of the Saturn V on 2,800,000&nbsp;kg, most of which was fuel, only 120,000&nbsp;kg was used for TLI. It's the same here. You will spend a good 80% of fuel and dump about as much of your rocket before you reach the Mun.<br />
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==Long or wide?==<br />
Preferably neither. Making your rocket longer is about as bad as making it wider. For various reasons. Wide rockets tend to be bottom-heavy (because, usually, they are wide at the bottom, to maximize thrust at liftoff), making them harder to control because they sway easily, and they are prone to out of control rolling if the thrusters on the outer edges are not PERFECTLY aligned (which they are, well, never), due to leverage. Wide rockets usually need quite a bit of SAS to keep from spinning out of control. And they are prone to "flipping", i.e. uncontrollably going upside down because they are easy to tilt and bank. Think of the broom example at the beginning.<br />
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Long rockets are very hard to tilt and bank, making them hard to steer and very sluggish. They also usually suffer from top-heaviness, especially after a good deal of their lower stage fuel is spent, which can result in rockets that are very hard to control and to keep from going "keel-up", i.e. nose-down without a lot of RCS thrust. Long rockets usually need quite a few wings to keep them manageable and responsive. And even then they are very slow to react and need foresightful piloting. They usually keep their direction pretty well as long as they are balanced and there's a lot of thrust applied, but once you bank and tilt them, they can very easily oversteer, especially in horizontal flight with a center of mass that's very close to the top (as it is usually just before your ascent stage is burned up, with a lot of empty and near empty fuel tanks hanging on your tail). Still, I prefer long over wide rockets.<br />
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==So, with all that, what IS now the best design?==<br />
From these tidbits we can puzzle together a few cornerstones that give us a good idea what a GOOD design would be, and what would be a BAD one.<br />
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It's a good idea to put every engine that can actually thrust at launch to work right at launch. Otherwise, they're dead weight that must be hauled upwards before it can be used. If that gives you too much thrust and your rocket starts to fall apart due to excessive G forces, consider putting the throttle to 75% or so. Remember, it is highly inefficient to go faster than 200 meters per second below 10,000 meters. Once your rocket has cleared the thickest portion of the atmosphere you can try bringing the throttle up to full. But if you have a big rocket, it CAN be a very good idea to make the first stage(s) only of solid boosters, they're very light for their push and even with a coupler on them they have a better TWR than liquid engines. Their main drawback, the inability to control their thrust output, doesn't matter for the first 20,000 Meters since you actually just want to get the hell up there. Do not expect too much from that, a full complement of two solid-only stages underneath every single engine of my actual first stage only got me about half a fuel tank. Yes, half a stock fuel tank is all you get for slapping two rows of solid stages under your rocket. The diminishing returns are stunning!<br />
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While solid boosters can be appealing, they prevent you from using the highly efficient "asparagus" stage design. The idea behind the asparagus design is that instead of burning through multiple fuel tanks simultaneously, two fuel tanks stacks are drained at a time. This saves weight because it greatly reduces the fuel mass to tank mass ratio after you have dropped your first two tank stacks. See the thumbnail for details.<br />
[[File:Radial Design Comparison.jpeg|thumbnail|A look at the efficiency of various lower stage designs. All were tested using identical Mechjeb settings, but the amount of fuel necessary to get each design into orbit varies greatly.]]<br />
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With bigger rockets, you'll run into the need to add SAS to keep them manageable. This used to be a paragraph about the differences between ASAS and SAS, but they are now the same thing (with redundant parts). Now you have a set of reaction wheels in each module with a set amount of torque, this can be limited for smaller craft that do not need as much, or increased for larger craft (via spamming SAS modules)<br />
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Your rocket should get thinner as it progresses upwards. From afar, it should look like a teardrop or a very steep pyramid, with multiple radial stages around the bottom stage thinning out to a single top stage. Top-heavy rockets are usually very hard to control, since their center of gravity is far from the point of action. The further away, the bigger the lever, the more wings and other control tidbits you need to keep it upright.<br />
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You need most of your fuel on your way up. Once you're in orbit, even the trans-lunar shot is peanuts compared to the expense to get into an orbit. It's quite ok to create an unwieldy, but powerful lower stage and create a very manageable and precisely controllable stage for upper orbit that has rather little fuel compared to it. Try different designs here, it's alright to have zero control beyond keeping the nose pointed upwards for the first 6,000 or so meters.<br />
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[[Category:Tutorials|Intermediate Rocket Design]]</div>Empiro