Difference between revisions of "Tutorial:How to get to Duna"

Revision as of 16:37, 22 December 2012

Duna. If you don't see this at some point during the tutorial, you've probably done it incorrectly.

Traveling to Duna

Duna is Kerbin's second closest neighbor. After a successful landing on Eve, it is likely your next logical step. It perhaps the ideal planet for interplanetary voyages for several reasons:

1. Its close proximity to Kerbin.
2. Its small size and gravity well (comparable to The Mun).
3. Its atmospheric composition is thick enough to support aerobraking, yet also thin enough to permit an ascent back to orbit.
4. Possessing moon similar to Kerbin's, Ike, in addition to several mysterious Easter Egg locations.

With a little bit of luck, skill, and determination, you can successfully land on Duna and return to Kerbin, all in one ship, with ease.

Specifications

• Length: 1-3 hours
• Difficulty: Moderate/Hard
• For version: .17
• Recommended Delta-V: ~7760 m/s
  • ~4700 m/s to orbit around Kerbin
  • ~1060 m/s for interplanetary transfer
  • ~1500 m/s for ascent to orbit.
  • ~500 m/s for return to Kerbin

Additionally, you will need a good understanding of orbital mechanics (see Tutorials section), angles, and a lot of patience.

Steps

Step 1 - Build Your Rocket

An extremely barebones, lightweight interplanetary rocket. Despite having no middle stage it can reach Duna, and return to Kerbin with a little piloting skill.

To perform a successful landing on Duna you will need a large rocket. Unless you are planning to deploy a spaceplane in the Dunan atmosphere (a perfectly viable option), you will need something resembling a highly beefed-up Mun Rocket.

Upper Stage

Balancing this stage is tricky. Largely similar to a Mun lander, with several key differences:

1. With proper parachute rigging, it will require little/no thrust for a landing (though save at least one parachute for Kerbin!)
2. For a return to Kerbin, you MUST touch down with at least 1 large fuel tank and an engine with high specific impulse intact.

The best way to describe something that can get off of Duna, is a ship somewhere between one that can take off from the Mun, and one that can take off from Kerbin. You will need at least 2000ms Delta-V for the orbit and return, you can test this by seeing if your lander is **almost** capable of reaching Kerbin orbit by itself.

Middle Stage

This is the stage that will be doing a lot of the work. It must be capable of getting from Kerbin to Duna, and positioning your lander craft for the terminal descent. It must carry enough fuel for the DeltaV you will need to successfully pull this off.

Lower Stage

This stage should take you at least into Kerbin's orbit if you hope to reach Duna. It will require several large thrusters to lift the interplanetary vehicle itself into orbit, probably assisted by some SRBs. For reference, it should be about 1.5x bigger than what you would need for a 1 way trip to Eve.

Step 2 - Planetary Alignment

While not absolutely essential, the easiest and fastest way to reach Duna from Kerbin is ensuring that they are properly aligned. Otherwise, you may spend a lot of time (possibly years) and fuel drifting until they happen to match up.

To do so, check your map and make sure that Duna is ahead of Kerbin in its orbit around Kerbol.

Look at it like a clock, if Kerbin is at 3 o'clock relative to the Sun, Duna should be at 1:30. Warp until they are in this position relative to each other.

Alternatively, you can visit The Interplanetary Guide and Calculator to calculate your own path.

Step 3 - Launch to Kerbin Orbit

Take off as usual (see Tutorials for how to achieve orbit), only tilt your craft heading east instead of the usual west. Unless you've done your own calculations, try to aim for a circular equatorial orbit spinning counter-clockwise at around 120,000 meters.

Step 4 - Fly from Kerbin to Duna

If have successfully reached your desired orbit around Kerbin, begin your high-velocity burn. Keep an eye on your map, wait until you are at about 5 o'clock around Kerbin (150 degrees), and get your velocity up to approximately 3020 m/s.

It's really important to watch the map while you are accelerating. As you accelerate your Kerbolar orbital path should move to intersect Duna's. If all goes well, there should be a brief moment where you are captured by Duna's gravity well right around the target velocity. Immediately cut your thrust. If you overshoot, just turn the craft around and do a slight retro burn until you are caught again.

This journey should take 70-120 days. While you are traveling around Kerbol, consider tweaking your trajectory until your periapsis around Duna is at the equator, and lower than 100km.

Step 5 - Arriving at Duna

When you enter Duna's sphere of influence you will always be traveling at escape velocity. Begin firing retro until you are in some kind of orbit, after you are caught it doesn't matter how far out you are.

Assuming that you are trying to save fuel we are going to be doing an aerobrake here. As shown on the information page, Duna's atmosphere begins around 40km, so we are going for a periapsis lower than that. A periapsis of 15,000 meters above the surface will aerobrake you into orbit around Duna. Putting it slightly under 10,000 meters should be enough for a landing.

If you are not planning on landing, being a forward burn at the apoapsis (once it has reached the desired altitude) to circularize your orbit.

Step 6 - Land on Duna

Adjust your orbital path to where you would like to land, and continue aerobraking to bleed off that extra velocity. Eventually you will be caught on a terminal descent through the atmosphere. Note that Duna's atmosphere is thinner and smaller, and so is your margin of error. Deploy your chutes around the 5k mark, and lower whatever landing gear you brought with you and fire retrorockets if the chutes aren't slowing you down enough. Ultimately we're going for typically touchdown speed (6-12m/s). Avoid tipping over at all costs, unless you plan on staying.

Congratulations! You've landed on another planet! Walk around, feel the cool, toxic breeze of an afternoon on Duna!

Step 7 - Back to Orbit

Make sure Duna and Kerbin are in the proper alignment. This time, Duna should be at 3 o'clock with respect to Kerbol, and Kerbin itself should be at roughly 5:30. Warp until they are in alignment, do not take off until this has been achieved.

While not nearly as difficult as ascending from Kerbin, you are still negotiating a decent-sized gravity well and an atmosphere. Our goal is to conserve as much fuel for the interplanetary burn as possible. Try to aim for a circular orbit, roughly 70km altitude, around Duna's equator.

Step 8 - Fly from Duna to Kerbin

Thankfully, this step requires less than half as much Delta-V as the trip from Kerbin to Duna. When your orbit is at 10 o'clock around Duna (-120 degrees), begin your burn. Our final velocity is going to be somewhere around 1500 m/s.

When you are captured by Kerbin, tweak your approach as much as you can in advance, we're running on a tight fuel budget here and the sooner you make adjustments the less fuel you will need. If you can get your periapsis within 50km of Kerbin, you will not need to burn for the rest of the trip.

Step 9 - Landing back on Kerbin

Once you are back in Kerbin's SOI, make whatever changes to your approach you want to assuming you still have fuel. Keep your periapsis somewhere below 50km, keep it shallow though for a safe descent.

Jettison your lander stage and go in with just the command module. Hopefully you've saved a parachute or two!

Congratulations! Once you've succeeded at a round trip to Duna, anything is possible.

Ideas

Land on Duna's moon, Ike

Hunt for the various easter eggs on Duna's surface.

Attempt a round trip to Eve (extremely difficult, but not impossible).

Fly to the next one out, Jool (and its moons).

Using the rover mod [1]. reattempt the Mars rover "Curiosity" landing!