BDB Apollo Program

[septemberWaves]

BDB recently updated their Apollo and Saturn parts, and they're extremely good so I wanted to show them off with some mission reports.

First up, a hypothetical Apollo Block 1 launch on a Saturn I rocket. In reality no Apollo spacecraft were launched on Saturn I in favour of using Saturn IB with its increased payload capacity, but originally Apollo would've launched on the Saturn I.

The crew arm is retracted several minutes before launch, as it will need to be out of the way in the event of a pad abort that requires the command module to be pulled away from the vehicle.

Liftoff.

Stage separation, and jettison of the launch escape tower. A launch abort after the first stage has no need for the high thrust of the launch escape system.

The Apollo spacecraft most people are familiar with is the Block 2 spacecraft. The Block 1 lacks a docking port, as it was never meant to fly with the lunar module.

The burn time of the S-IV stage is extremely long. The engines have low thrust but high specific impulse, as is typical for upper stage cryogenic engines.

Spacecraft deployment once in orbit. The S-IV stage has built-in separation motors that will help to de-orbit it.

The spacecraft remains in orbit for several hours.

Ignition of the service propulsion system to de-orbit the spacecraft.

Service module jettison in preparation for re-entry. The re-entry trajectory used is rather steep to simulate thermal loads of a lunar re-entry.

The Apollo spacecraft has its center of mass offset during re-entry. This allows it to take advantage of atmospheric lift to adjust or extend the re-entry trajectory.

Following re-entry, the parachute cover and nose cone is jettisoned.

Drogue chute deployment.

Main chute deployment.

I was unable to take a screenshot of the spacecraft post-splashdown due to a strange game bug that caused the spacecraft to bounce chaotically on contact with water, annihilating the heat shield and forcing me to use several cheats to recover the capsule.

[septemberWaves]

The first crewed Apollo spacecraft that launched successfully were Block 2 spacecraft, launched atop the upgraded Saturn IB rocket.

Ignition. The first stage engine layout is the same as on the Saturn I: a cluster of eight H1 engines, only the outer four of which are capable of gimballing.

Liftoff.

The main change to the first stage from the Saturn I is that the first stage of the Saturn IB has different fins. I don't know what the purpose of this change is, but presumably it improves the aerodynamic properties of the vehicle.

Stage separation.

The S-IVB stage is a new addition to the Saturn IB. It carries much more fuel than the S-IV, and is powered by a single J-2 engine rather than six clustered RL10 engines. The version of the S-IVB used on the Saturn IB rocket uses simple RCS thrusters which lack prograde ullage thrusters, as an S-IB launch will never need to ignite the second stage more than once (and the first ignition is ullaged by separation motors).

The Apollo spacecraft, in its familiar Block 2 configuration with a docking probe. It is mounted atop the Spacecraft LM Adapter (SLA), though this payload module remains empty on Saturn IB flights save for containing the Apollo service propulsion system.

Spacecraft deployment once in orbit. The Saturn IB is able to place the Apollo spacecraft in a wider range of orbits than the S-I due to the improved payload capacity allowed by the S-IVB stage.

A quick EVA to show off the EVA light.

De-orbiting.

[septemberWaves]

Before the lunar landings, there were several test flights of the spacecraft, including of the entire Saturn V stack.

Five powerful F-1 engines (with excellent Waterfall plumes) propel the Saturn V rocket. This particular flight is only going to Earth orbit, like Apollo 4 and 6, which were uncrewed test flights of the vehicle and went to a highly elliptical orbit to test the heat shield at lunar re-entry speeds.

First stage cutoff and separation, second stage ignition. The S-II stage ullage motors are attached to a cylindrical structural component, which is jettisoned shortly after the ullage motors burn out to reduce mass. Ullage motors are necessary on the real rocket to stabilize propellant for the five J-2 engines that power the second stage, as the rocket motors push the propellant to the bottom of the tank (or push the bottom of the tank to the propellant;  either way works thanks to relativity). Gravity fulfils this function on the launch pad for the first stage.

The launch escape system, from what I have read, was typically jettisoned 20 to 30 seconds after second stage ignition. A launch abort beyond this point would have no need for the launch escape system due to the much lower thrust-to-weight ratio of all remaining stages.

Apollo 6 experienced two engine failures on the S-II, as well as an engine failure of the S-IVB. I haven't been able to find out which specific engines failed on the second stage, but testing with BDB Saturn indicates that it is still stable with any combination of two engine failures on the S-II.

As I said, this mission isn't going beyond Earth orbit. But we'll be seeing more of the Saturn V later.

Apollo 5 sent an uncrewed lunar lander to low Earth orbit on a Saturn IB. The purpose of this was to test the spacecraft in space to as much of an extent as was possible in low Earth orbit and without crew.

The mission also provides a good reason to showcase the capped petal fairing for the S-IVB, which is an option for the SLA.

Deployment of the lunar module in low Earth orbit.

Excellent rendition of the lunar module. It's pretty much ideal, the only issue I've encountered with it is that having the flag turned on when using the J-class part switch results in a hovering flag over the open compartment (may be fixed by now, I'll have to check).

Testing the descent engine.

Testing the ascent engine.

There's a couple of things I want to demonstrate with the launch escape system, with an abort test on the Saturn IB. The extreme thrust of the launch escape system makes it difficult to get screenshots of it when it activates, but I did manage to get this one.

The device is also more than just a high-thrust rocket. It also vectors some of the thrust from the rocket motor to control the attitude of the command module and ensure it is safely pulled out of the trajectory of the rocket (I've not managed to figure out if the BDB one actually does this or if it just has fixed asymmetrical thrust for a similar effect). After the solid rocket motor has burned out, control surfaces are deployed to point the capsule retrograde, enabling safe parachute deployment and landing.

[septemberWaves]

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Liftoff of Apollo 11, the first crewed lunar landing.

First stage cutoff and separation.

Second stage ignition. The launch escape system was also prematurely jettisoned at this point due to a minor autostaging error.

Interstage fairing separation following ullage motor burnout.

Second stage cutoff and separation.

Third stage ignition for insertion into a low Earth parking orbit.

Parking orbit achieved successfully.

Following final trajectory calculations, the S-IVB ignites to send the Apollo spacecraft to the Moon.

Apollo missions used a free return trajectory, which allowed the spacecraft to safely return to Earth from a trans-lunar orbit if any emergency on route were to prevent lunar orbit from being achievable. Unfortunately I had a lot of trouble setting up a free return trajectory (most likely due to the n-body influence of Minmus) so I can't demonstrate how one looks, but the idea is that it requires a bit more delta-v and sends the spacecraft to a retrograde orbit of the Moon on a successful mission, or to a direct lunar re-entry on a failed mission.

Once the S-IVB burn is complete, the SLA (Spacecraft Lunar Module Adapter) opens, and the Apollo CSM conducts a series of rotation and translation maneuvers to extract the lunar module.

Final corrections are made with the RCS thrusters while travelling towards the Moon.

At the Moon, the Service Propulsion System ignites to insert the spacecraft into a low lunar orbit. For reasons mentioned previously, the orbit is retrograde, though the incredibly low rotation speed of the Moon means that retrograde orbits make very little difference in the delta-v requirements for landing.

I'd like to point out on this screenshot in particular that the main antenna on the Apollo service module is not static, it rotates on one axis to aim at Earth (or Kerbin, usually).

Low lunar orbit has been successfully achieved.

After the two members of the landing crew transfer into the lunar module, leaving the command module pilot behind, the two spacecraft undock and the lunar module crew prepare for landing.

The Apollo 11 lunar module has successfully touched down.

While on the surface, the crew deploy science experiments, fall over a few times in the low gravity, and of course plant the obligatory flag.

Apollo 11's experiments were limited to things that could be deployed in under 10 minutes, because of the risk that some unforseen circumstances might force an emergency return from the Moon. This experiment package was referred to as Early Apollo Surface Experiments Package (EASEP), and consisted of only the Lunar Ranging Retroreflector (LRRR) and the Passive Seismic Experiment Package (PSEP), as well as the experiment control station and the radioisotope generator required to run the experiments (these last two components were part of every mission).

There's also this passive device, used for colour calibration when examining photographs if I recall correctly.

And of course there's the camera that's been taking these pictures.

Following surface operations, the crew return to the lunar module and lift off from the lunar surface.

I apologize for the part lighting errors in all screenshots beyond this point. I have no idea what caused it but it persisted for the rest of the mission, even after loading quicksaves.

The lunar module has safely returned to lunar orbit.

Following several rendezvous maneuvers, the LM docks with the CSM and the crew transfer back to the command module to return to Earth. The lunar module is left in lunar orbit; by the present day, it's likely that all Apollo lunar modules have now impacted the Moon due to years of cumulative orbital perturbations caused largely by the Moon's uneven distribution of mass.

This is the second time I've done this mission profile and the second time I've accidentally jettisoned the Apollo docking probe instead of undocking it. I'm fairly sure it's normally jettisoned right before re-entry.

Separation of the command and service modules before atmospheric entry.

Unfortunately lighting errors ruined my screenshots beyond this point, but the landing process was nominal, resulting in a complete mission success.