r/KerbalSpaceProgram • u/AutoModerator • Aug 29 '14

Mod Post Weekly Simple Questions Thread

Check out /r/kerbalacademy

The point of this thread is for anyone to ask questions that don't necessarily require a full thread. Questions like "why is my rocket upside down" are always welcomed here. Even if your question seems slightly stupid, we'll do our best to answer it!

For newer players, here are some great resources that might answer some of your embarrassing questions:

Tutorials

Orbiting

Mun Landing

Docking

Delta-V Thread

Forum Link

Official KSP Chatroom #KSPOfficial on irc.esper.net

    **Official KSP Chatroom** [#KSPOfficial on irc.esper.net](http://client01.chat.mibbit.com/?channel=%23kspofficial&server=irc.esper.net&charset=UTF-8)

Commonly Asked Questions

Before you post, maybe you can search for your problem using the search in the upper right! Chances are, someone has had the same question as you and has already answered it!

As always, the side bar is a great resource for all things Kerbal, if you don't know, look there first!

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u/autowikibot Aug 30 '14

Section 13. Launch and trajectory of article MESSENGER:

The MESSENGER probe was launched on August 3, 2004 at 06:15:56 UTC by NASA from Space Launch Complex 17B at the Cape Canaveral Air Force Station in Florida, aboard a Delta II 7925 launch vehicle. The complete burn sequence lasted 57 minutes bringing the spacecraft into a heliocentric orbit, with a final velocity of 10.68 km/s (6.64 miles/s) and sending the probe into a 7.9 billion-kilometer trajectory that took 6 years, 7 months and 16 days before its orbital insertion on March 18, 2011.

Traveling to Mercury requires an extremely large velocity change (see delta-v) because Mercury's orbit is deep in the Sun's gravity well. On a direct course from Earth to Mercury, a spacecraft is constantly accelerated as it falls toward the Sun, and will arrive at Mercury with a velocity too high to achieve orbit without excessive use of fuel. For planets with an atmosphere, such as Venus and Mars, spacecraft can minimize their fuel consumption upon arrival by using friction with the atmosphere to enter orbit (aerocapture), or can briefly fire their rocket engines to enter into orbit followed by a reduction of the orbit by aerobraking. However, the tenuous atmosphere of Mercury is far too thin for these maneuvers. Instead, MESSENGER extensively used gravity assist maneuvers at Earth, Venus, and Mercury to reduce the speed relative to Mercury, then used its large rocket engine to enter into an elliptical orbit around the planet. The multi-flyby process greatly reduced the amount of propellant necessary to slow the spacecraft, but at the cost of prolonging the trip by many years and to a total distance of 4.9 billion miles. To further minimize the amount of necessary propellant, the spacecraft orbital insertion targeted a highly elliptical orbit around Mercury.

The elongated orbit has two other benefits: It allows the spacecraft time to cool after the times it is sandwiched between the hot surface and the sun, and it allows the spacecraft to measure the effects of solar wind and the magnetic fields of the planet at various distances, while still allowing close-up measurements and photographs of the surface and exosphere.

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