Reaching Other Planets
Interplanetary distances are far bigger (orders of magnitude) than those in LEO (low earth orbit) or Moon. Surprisingly for inner planets like Venus or Mars you'll need not much more dV than to reach the moon. Obviously you need respectively bigger LV(Launch vehicle - rocket) capable of putting your ejection module (part of the craft that puts you into trajectory of the target body) and payload to LEO. Short checklist to reach nearest planets :
- Interplanetary communications
- deep space avionics.
- LV capable of 3+ t to LEO or more depending on your payload. (150t plus) It is important to make your payload (probe) as light as possible and to use as efficient engines (ISP, and propellant densities) for last stages as possible to minimize your payload mass. It is good to have some capability to make middle course trajectory corrections (RCS is usually enough).
See the RealAntennas Wiki for help with planning. Make sure to use the highest communications tech level available and upgrade your tracking station if you can. It is not only enough to have a connection though, 1bit/s connection is rather incapable of relaying substantial experiment data. Make sure to have proper bandwidth and power generation capacity to actually transfer experiments data back to Earth.
Open communications menu on your antenna. You can adjust your tech level and transmit power here. Clicking on Antenna planning will show interface that shows how particular setup will behave in selected scenario.
You need to select your vessel antenna that you plan to use, then on the "Peer" list select either ground station (different ground stations have different capabilities) or by clicking on "GroundStation" button you'll have options to choose another vehicle antenna (for relay checking purposes). Then you should specify the distance between antennas. There is preset of prepared distances listed ans bodies in middle section. Selecting one of them will give you min and max distance values on the bottom part. It is important to select proper distance to evaluate ow your comms will work when you arrive. On the bottom you have summary window. You see parameters of selected antennas, then distances you selected (you can alter them if you wish), and finally summary of antenna connectivity and bandwidth available at specified distance. Click "Plan!" button to see results. If there is "(No Connection)" in orange font then you don't have connection at specified distance. You might notice that no connection also appears when you have one sided communications (craft is capable of receiving data but not able to send anything back for example) in that case you'll not be able to control your craft or send data back. Increasing power of transmitter or using antenna with bigger gain might help in that case.
Your probes need to have some source of power to function. Mercury, Venus and Earth are relatively short from the Sun and solar power is somewhat cheap (in weight) for what you get. Mars starts to show decreased power production, and vetting to dwarf planets and Jupiter builds challenge for solar powered crafts, though it is not impossible to do so. Most deep spade probes use RTG to power the craft.
- make sure you have enough power when you reach your target
- use kerbalism window (bottom right in VAB when you have statistics for your probe - look at energy consumption and select target body if using solar)
- adjust for transit times (might be long time) so your power source works effectively when you reach the target.
Highlighted menu shows kerbalism window. Top bar has three settings on top - left is body- in this example Earth, you can select your target body, middle icon resembles solar exposure, and right option allows you to check on target states (different orbits or landed) Mouse over on particular figures will give you short report what consumes / produces particular resource. Make sure you detach your payload from a rocket when you check power usage requirement, otherwise it will be calculated for whole vehicle!
Pro tip: Avionics have built in antenna but those have low gain so depending on your scenario it is better to use them as main antenna in LEO on ejection module to keep control of the craft and disable them on your probe as it is of no use on interplanetary ranges to limit passive power draw. Once you are done with ejection burn you'll be far enough (or soon be) for your directional antenna to become useful so you can separate ejection stage when it is no longer needed.
Transfer window planner helps with selecting proper time and launch from your home body so that final orbit trajectory is going to intersect target body at some point. This is the rainbow colored option in menu (bottom in VAB and right during flight).
Though you can transfer technically at any time it requires a LOT more energy than doing so in proper orbit alignment. It is like taking over another vehicle (for those who drive) it is way easier when other vehicle is breaking and driving slow, than when you drive uphill and other vehicle is accelerating. With rocket big enough you can do anything, but in reality you don't want to :)
You need to:
- Select target body you want to reach
- Put your launch site inclination next to parking orbit height (I use 200km)
- Select orbit height around your target or leave that with whatever value when selecting flyby. (Note that selected orbit is circular orbit at that height, which is usually way more expensive than elliptical orbit. Having this much dV will enable you to do a lot of maneuvers when you arrive so it might come handy if you plan to get low or land on a planet without atmosphere.)
This window shows you multitude of important information. Not only it shows best timing for departure (not Launch!) but also places it so that when you are in orbit that has proper inclination and LAN (I'll show you later how to get there) then you can burn prograde only (most efficient) on selected time to get really good initial trajectory. It also shows you required DV for ejection and insertion burn if selected. If you select "No Insertion Burn" checkbox below Final Orbit field, then you'll get best window for flyby only. It will be probably cheaper (in dV) than for capture , but Insertion burn will be very expensive and impractical.
It is good to create KAC alarm tor your transfer window so you won't miss it and it will contain all necessary information to make that burn.
When launching your craft to Parking orbit, select your required orbit inclination from alarm menu, and fill Launch to LAN on the bottom of ascend guidance menu, so you end in proper orbit. I usually launch an 30min before departure to have some time to plan maneuver and get to parking orbit. When ready engage autopilot which will put you in pretty good spot for ejection burn.
TBD
TBD
Venus will need a lunar-rated heat shield, unless you slow down into an orbit first, but Mars can do fine with an LEO-rated heat shield.
RealChute can be programmed to do calculations for other planets. Note that standard parachutes will be melted on Venus, so you'll have to use Kevlar and open them fairly low, but the thick atmosphere makes slowing down easy. You may not even need parachutes. On Mars, parachutes can be quite useful, but, like in real life, they won't be able to slow your craft all the way to a soft landing. Kevlar may be the material to go with here as well. There are some small throttlable engines you can use, or you can use an engine with an RCS config. If you're very skilled, you can even use a skycrane for style points, though you may run into bugs with the cable.