Apollo Landing Tutorial - KSP-RO/RP-1 GitHub Wiki
Designing a Probe to Soft Land on the Moon
You will want to design the craft from the ending goal (the landing) backwards to the launch vehicle. This means you design the lander, then the braking stage, then the TLI stage, then the launch vehicle. At each stage, you want to make sure you have the right amount of dV for the job of the stage.
Between your Landing Stage and Braking Stage, budgeting for around 2800 should give you plenty for safely landing.
1. The Lander
The amount of delta-V on your lander can vary a lot (depending on your braking stage), and so can your design options. If you want to go with a "caveman" landing, you don't even need landing legs. No matter what you decide to do, there are some things that you will need to make sure you have:
- Comms Device
- Power Generation / Storage (30 Days worth for most experiments)
- Enough delta-V
- Good enough TWR (Good goal is at least 2 TWR, the higher the better)
2. The Braking Stage
This stage can also vary a lot. A common approach is to use a high TWR solid rocket (or AJ10 stage) to perform the majority of the braking burn before allowing the lander to finish the final descent and touchdown.
More coming soon!
Apollo-style Landing Guide
Written by SRBuchanan on the RO/RP-1 discord.
1. While in low orbit and opposite the intended landing site, burn retrograde to lower your periapsis
Ideally you want your periapsis to be directly over your landing site and as low as possible while still ensuring your flight path clears the terrain. Bear in mind that 'sea level' on the Moon or other airless bodies is somewhat arbitrary and the actual terrain can be dozens of kilometers higher.
2. Begin your final descent burn when your time to periapsis is half of your total descent stage burn time
While this method isn't pin-point accurate, but it will do for beginners). This guide assumes you've already designed a descent stage. For reference, the Apollo lander had a TWR of 2:1 (local to the Moon, of course) at the start of the descent burn and 2,470 m/s of delta-V in the descent stage.
3. Begin the descent burn pointed retrograde and use pitch, not the throttle, to control your vertical speed
As your orbital speed drops, your vertical speed will climb, and you will counter this by pitching your lander above retrograde. Do not adjust the throttle; keep it maxed for the entirety of this part of the landing. If you begin falling towards the surface too swiftly, pitch up. If you aren't falling fast enough, pitch down. You will have to pitch up more as the descent burn continues.
4. Enter final hover, using the throttle to control descent rate
Continue adjusting pitch to control descent rate until you have shed your orbital velocity and are stationary or traveling at low speed over the surface. Lock the spacecraft to retrograde (ensuring that your reference frame is the surface) and begin to adjust the throttle to control descent rate. Remember that the faster you fall the less fuel you waste, but don't get overzealous and crash. At this point the landing will proceed much like one in stock KSP.
5.Slowly and gently touch down on the surface.
Profit.