Difference between revisions of "Tutorial: Gravity Assist/zh-cn"

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*'''对应版本:'''0.18.4
 
*'''对应版本:'''0.18.4
  
== How to do it ==
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== 如何进行 ==
  
In this example we will leave from Kerbin to a trajectory to Duna by performing a gravity assist around the Mün. Usually you need to raise your apoapsis to 85 million km to escape from Kerbin. With this method we will just have to get to the Mün orbit (12 million km). This will save you fuel for several hundred m/s of delta-v.
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在这个例子里,我们要离开Kerbin,利用Mün完成引力助推,并进入前往Duna的轨道。通常,你需要把轨道远点高度提升到八千五百万公里才能脱离Kerbin。用这个办法,我们只需要进入Mün轨道(一千两百万公里)就可以。这样可以为你节约相当于几百m/s delta-v的燃料。
  
# Get your ship into a circular Low Kerbin Orbit
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# 飞船进入环Kerbin低圆周轨道;
# Zoom out so you can see the orbit of Kerbin around the sun.
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# 缩小图像直到可以看到Kerbin的公转轨道;
# Arrange for a fly-by with the Mün just like you learned in the "Going to the Mün" ingame tutorial, but arrange for it to happen while the mün is heading into the direction you want to go. In this case we want to get further way from the sun, so do it when the Mün is going in that direction - the moment it intersects the orbit of Kerbin.
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# 按照"Going to the Mün"教程中学到的方法,安排前往Mün的飞掠轨道,需要注意的一点是,应该注意到达Mün时,它正向你需要的方向前进。在本例中,我们需要的是飞离太阳的方向,因此在设计轨道时注意Mün的运行方向 —— 即Mün轨道与Kerbin公转轨道交汇的时刻;
# Accelerate time until you reach the sphere of influence of the Mün
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# 加速时间,直到抵达Mün的引力范围;
# Now plan another course correction maneuver. The maneuver is more effective when you are close, so try to pass the Mün as close as possible without colliding. Your Mün periapsis needs to be behind Mün on Müns trajectory. When you pass in front of Mün, you will lose speed instead of gaining it. Also watch the declination of your trajectory - when it gets too high it will be problematic.
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# 现在规划一次轨道校正机动。因为引力助推离目标天体距离越近效果越明显,所以只要不发生碰撞,离Mün越近越好。你的Mün轨道近点应位于Mün运行方向的后方。如果飞船从前方经过Mün,你会减速而不是加速。同时应注意轨道的倾角 —— 太高就会有问题了;
# Accelerate time until you left the SoI of the Mün.
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# 加速时间,直到离开Mün的引力范围;
# When you check the map you will notice that you are on a much wider orbit than you were before the Mün fly-by (likely with an apoapsis beyond Minmus orbit), but it's not a Kerbin escape trajectory yet. The Mün hasn't yet given you all the speed it can.
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# 观察轨道地图,你会发现飞船现在的轨道比飞掠Mün前变得更长(轨道远点很可能位于Minmus轨道的后方),但它并不是Kerbin的逃逸轨道。你还没有从Mün获得足够的全部速度;
# So perform another correction maneuver which leads you to another close Mün fly-by and again try to pass it as close as possible.
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# 所以,再进行一次轨道校正机动,再度飞掠Mün,并尽可能靠近它飞行;
  
Congratulations, you should now be on an orbit leading you in the general direction of Duna with plenty of fuel left for the return trip. When you want to go back, perform the same trick with Ike.
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祝贺你,你现在会进入一条大致飞向Duna的轨道,而又为返程省下了足够的燃料。如果希望返回Kerbin,你可以利用Ike进行类似的机动。
  
 
== Reverse Gravity assist ==
 
== Reverse Gravity assist ==

Revision as of 04:38, 24 June 2013

引力弹弓效应的极简模型:飞船速度可以得到2倍行星速度的叠加

重力助推是一种非常节约燃料的加速(或减速)机动方式。这种机动就是,当位于天体的引力范围球体之内时,它会对飞船产生一定的牵引力,从而相应为飞船产生加速(或减速)的效果。当你飞离某颗行星,如果它带有卫星,那么我们就可以利用该卫星进行重力加速机动,从而节约大量的燃料。

  • 长度:30分钟
  • 难度:适中
  • 对应版本:0.18.4

如何进行

在这个例子里,我们要离开Kerbin,利用Mün完成引力助推,并进入前往Duna的轨道。通常,你需要把轨道远点高度提升到八千五百万公里才能脱离Kerbin。用这个办法,我们只需要进入Mün轨道(一千两百万公里)就可以。这样可以为你节约相当于几百m/s delta-v的燃料。

  1. 飞船进入环Kerbin低圆周轨道;
  2. 缩小图像直到可以看到Kerbin的公转轨道;
  3. 按照"Going to the Mün"教程中学到的方法,安排前往Mün的飞掠轨道,需要注意的一点是,应该注意到达Mün时,它正向你需要的方向前进。在本例中,我们需要的是飞离太阳的方向,因此在设计轨道时注意Mün的运行方向 —— 即Mün轨道与Kerbin公转轨道交汇的时刻;
  4. 加速时间,直到抵达Mün的引力范围;
  5. 现在规划一次轨道校正机动。因为引力助推离目标天体距离越近效果越明显,所以只要不发生碰撞,离Mün越近越好。你的Mün轨道近点应位于Mün运行方向的后方。如果飞船从前方经过Mün,你会减速而不是加速。同时应注意轨道的倾角 —— 太高就会有问题了;
  6. 加速时间,直到离开Mün的引力范围;
  7. 观察轨道地图,你会发现飞船现在的轨道比飞掠Mün前变得更长(轨道远点很可能位于Minmus轨道的后方),但它并不是Kerbin的逃逸轨道。你还没有从Mün获得足够的全部速度;
  8. 所以,再进行一次轨道校正机动,再度飞掠Mün,并尽可能靠近它飞行;

祝贺你,你现在会进入一条大致飞向Duna的轨道,而又为返程省下了足够的燃料。如果希望返回Kerbin,你可以利用Ike进行类似的机动。

Reverse Gravity assist

Pass in front of a moon to brake and behind a moon to accelerate

Should you enter the Duna-Ike system in a suitable trajectory, you can perform a reverse-gravity-assist to lose speed instead of gaining it. To do so just do an Ike-fly-by. In order to lose speed instead of gaining it, your Ike periapsis needs to be in front of Ike's trajectory instead of behind it.

Powered Gravity assist

To get even more out of a gravity assist, you can perform a powered gravity assist. As you know, accelerating at your periapsis has the greatest effect on your apoapsis. This still applies to your periapsis during a gravity assist. When you accelerate during your fly-by, this fuel is used very efficiently to increase the apoapsis of your final trajectory. This is, however, a very difficult technique, because it is hard to control your final trajectory, even when using a maneuver node.

Using a reverse gravity assist around Tylo to get into a Jool orbit. The necessary course correction required less fuel than getting close enough to Jool for an aerobrake maneuver. It is also much safer than aerobraking.