Long-term Laythe - Part 25

Further Flashback

In Part 24 there was a flashback to the launchings of the R.A.P.I.E.R. powered spaceplane, the R.A.P.I.E.R. powered SSTO rocket, and the Airdale plane toward Laythe. Before we get to those payloads arriving at Jool, I'll mention the single ship that was sent out in the next transfer window that came up after those three payloads were sent (transfer windows from Kerbin to Jool occur about every 115 days).

Below we see the Laythe ShoreLab being launched on a Reusable Rocket. The ShoreLab is a jet-hopper/floating-laboratory designed to study the sea bottoms offshore from Dansen Island. Unlike Kerbin, where you can see some interesting things through the water, the surface of Laythe's seas are not transparent (at least not with the video settings I use), but this ship will allow our explorers to peek beneath the surface (but not actually navigate around under the sea). This is also the first ship I've built using the cupola module, which will serve here as our glass-bottom boat.

To push the ShoreLab to Laythe, the boys at KSC decided to use Laythe Tug 3, which had returned earlier from Laythe and was sitting in Kerbin orbit. It only had standard docking ports, but this was a relatively light payload. Below is the Tug3 Refurbisher mission being launched on a Reusable Rocket (which can lift that payload into orbit without requiring any of the payload's fuel, and leave enough fuel in the sustainer that it can return to KSC). The rear tank will be docked to the bottom of the Tug, and then propellants and monopropellant from the top tank will be transferred to the main tank of the Tug. The top part of the Refurbisher will need to retain less than 15 units of fuel to deorbit and be recovered via parachute at KSC.

Once Tug 3 was refurbished, it was docked to the ShoreLab and was ready to be sent off to Jool. Just this one ship for this transfer window...and not even a double-Tug-train.

Tug 3 with the ShoreLab was sent off with a standard two-burn escape maneuver. The rear tank was expended during the escape burn, and dropped off as the ship left the Kerbin system. The ascending node occurred out beyond the orbit of Dres and took about 78 m/s of delta-V. We'll see the arrival of the ShoreLab at Laythe in a future episode (when the main game file gets to Year 26 Day 89).

Tug Treatments

For Laythe Tugs 4, 6, 7, and 8 that were waiting in Kerbin orbit, I decided just to land them near the KSC so that they could receive some minor improvements (adding Senior docking ports, and removing some unneeded parts). The following pictures show the recovery sequence with pictures of the various Tugs. First, Tug 4 does its retro burn. These Tugs all had enough fuel to target them in to KSC (in one case, just barely). Tug 4 will only need refitting with Senior docking ports.

Below, reentry is demonstrated by Tug 6. These later-model Tugs will need Senior docking ports added, and the removal of all those probe bodies that were included once upon a time for extra torque, but which are no longer needed because a single ASAS unit now provides plenty of torque.

Tug 7 demonstrates the two-stage main deployment of the parachutes. One pair was set to deploy fully at 600 meters, and the second set deployed fully at 500 meters. The resulting deployment shocks were gentle enough to keep the heavy nukes from snapping off.

Tug 8 landed close to Tug 7. All of the Tugs were landed to the west of the Research area of KSC.

Below, all four Tugs are down safely and the refurbishing can begin. Note that the nuclear engines will not be refurbished...the amount of fissile fuel you need to make the nuclear reactors work is much greater than the amount that would be used up in several trips to Jool and back (which each take less that 40 minutes of engine runtime), so the nukes are fine. I envision an unmanned rover/crane coming out to the Tugs to clamp some radiation shields around the nuclear engines (which are radioactively 'hot' because they have been used) to make them safe to handle by the refurb crews in the VAB.

Here's one of the refurbished Tugs as it would appear on top of a Reusable Rocket to be returned to orbit for continued use. Shortly before launch, the radiation shields will be jettisoned (see the animated GIF below). There are a couple girders on the side boosters to bounce the shields off to the sides. This leaves behind the minimal shielding of the engine fairings, and those will be jettisoned when the nuclear engines are ignited at high altitude.

Those Tugs will be used to send more payloads out to Jool later.

Train Traffic

Now we get back to the three trains (double-Tugs with double-payloads, one of which is just extra fuel) that are arriving at the Jool system. Tain #1 did not reach the ascending node of its transfer orbit until it was within Jool's sphere of influence, but Train #3 and Train #2 required plane-shift maneuvers enroute. Because these occurred close to Jool, they only required about 51 m/s of delta-V. This expended the propellants in the rearmost tanks of Train #2, and they were dropped after the burn.

I decided to take the easy route and target all three trains straight to Laythe (rather than do an aerocapture at Jool first). Train #3 and #2 were both targeted very close to Jool back when they left Kerbin, so those orbits were just tweaked a bit until they got Laythe encounters, as seen below, with Train #3 swinging past Jool to a farside encounter and Train #2 encountering Laythe on the way in. Both of these trajectories resulted in intercept velocities of around 5,000 meters per second, leading to hot aerocaptures.

For comparison, Train #1 was targeted (after entering Jool's SOI) to approach Laythe close to tangentially to its orbit. This resulted in an intercept velocity of only 2973 m/s, much less than the other two trains. Changing the radial component of the targeting burn moves the trajectory closer or further from Jool to get the correct intercept with Laythe, and changing the prograde/retrograde component allows you to adjust where Laythe will be in its orbit when the ship arrives (and adjusting the normal component allows you to determine the inclination of the resulting Laythe orbit).

Below, Train #1 came in tangentially and experienced only a few G's and rather anemic flames during aerocapture. Very nice!

After a burn to correct orbital inclination (which expended the rearmost tanks, which were then dropped), and a burn to adjust periapsis for an additional aerobraking pass, and a burn to circularize, the R.A.P.I.E.R. spaceplane and NAMOR 21 payload were safely in low equatorial orbit with nearly three full big tanks of fuel in the double-Tugs.

Below, Train #2 with the R.A.P.I.E.R. SSTO rocket arrived for a flaming hot aerocapture, experiencing up to 8.5 G's of deceleration. After the usual maneuvers, it was also safely in low orbit.

Train #3 swung around close to Jool for a farside encounter with Laythe that was also of the hot 8.5 G variety.

After a plane shift and some orbital tweaks, Train #3 was also in a low equatorial orbit with three nearly-full big tanks in the Tugs (it retained its rearmost tanks, now empty). Such fine deliveries...I should work for FedEx.

Payload Presents

Time to deliver the toys! First down, the R.A.P.I.E.R. spaceplane.

Aldner: "OK, Little Buddy, I'm going to let you fly the spaceplane down under remote control because I'll be the one piloting it for its first flight back to orbit."
Nelemy: "Cool, Dude! Have you chosen a name for it yet?"
Aldner: "It will be named Raptor."
Nelemy: "Um... Rapier Aerospace Plane To Orbit...um...'Round?"
Aldner: "No. Just Raptor."
Nelemy: "Cool."
Aldner: "Let me undock that Saddlebag Deorbiter...we won't be using that."
Nelemy: "Don't we want to land with maximum fuel?"
Aldner: "Maybe later...but I want to do a direct comparison with the performance of the Ladyhawk flight I made, and we didn't use a Deorbiter bringing it down...so we'll let Raptor use its own fuel to deorbit. OK...the Saddlebags are off of the Raptor's docking port...decouple the Raptor from the NAMOR's docking port, and I'll re-dock the Saddlebag Deorbiter to the NAMOR."

Note that the structural plate, girder, and decoupler that held the Raptor to the ship was decoupled along with the Raptor (to free up the top port of the NAMOR), but unlike when the Ladyhawk was deorbited (carrying this junk with it to be jettisoned after retro burn), the Raptor will need to separate the junk before it can use its R.A.P.I.E.R. engine...so that junk will remain in orbit.

Below, Nelemy fired the R.A.P.I.E.R. engine (in closed cycle mode) to deorbit the Raptor (with the Tugs visible in the upper-left).

Rather than waste fuel changing the inclination in orbit, Nelemy used the cross-range capability of the Raptor during entry and in the lower atmosphere to move the ship one degree north to Fido Bay.

Nelemy: "Annnnnd.....touchdown, Dude!"
Aldner: "See how close you can park it to the Ladyhawk, pointing southeast."
Nelemy: "Sure thing. Huh. This new nose wheel steering doesn't seem to be working all that well."
Aldner: "Is it activated?"
Nelemy: "Yeah, Dude."
Aldner: "Ah...you can't steer it with the yaw control, you need to use the rover turn-controls."
Nelemy: "Oh. Whoa! Too sharp. OK, coming around now. Big wide arc. I can turn sharper if I use opposite roll to keep it from wanting to roll over."
Aldner: "You're going to overshoot."
Nelemy: "Close enough. Lined up perfectly. Wheels stop. Your ride is delivered, Dude!"

Next, Kurt brought down the R.A.P.I.E.R. SSTO rocket via remote control. All those glowing-hot R.A.P.I.E.R. engine nozzles look awesome after the retro-burn cutoff. He named it 'RASSTO' for "Rapier Accelerated Single Stage To Orbit," and it is properly pronounced as if Scooby-Doo was saying it.

Not much to control during entry, other than to decide when to pop out the reefed chutes. Two chutes mounted low on the main fuel tank are set to open fully at 600 meters, followed by the other six chutes mounted high on the Hitchhiker Module set to open fully at 500 meters.

With all of the parachutes fully open, the almost-fully-fueled RASSTO still descends at 9.4 m/s, which would damage the new landing gear. So Kurt cut in the engines again just before touchdown to reduce the speed to a few meters per second. This was done with the engines still in closed-cycle mode (rather than air-breathing mode) because it's easier that way (although doing it the trickier way in air-breathing mode would take less fuel...and might not be as difficult as trying to land on jet engines alone would be, because the parachutes have slowed the ship down so there is more time to react to the spool-up/spool-down lag time).

Below, the RASSTO is safely down about 630 meters from the original crew-transfer SSTO rocket. After landing, the RASSTO had a little under 91% of its liquid fuel left, and its oxidizer tanks were filled to a little over 84% of their capacity. The difference in those percentages is because the small side tanks were tweaked to hold less than 100% of their oxidizer capacity, because the ship will use more fuel than oxidizer during ascent because the R.A.P.I.E.R. engines will initially boost the ship in air-breathing mode. It will be interesting to see how well it does returning to orbit (but Kurt better remember to repack the chutes).

Last down, the 3-kerbal version of the BirdDog, which Thompbles brought down via remote control. Below, the retro burn (the Tug Train in the background still has a GasStation attached, which can be landed later).

Nelemy: "So what are you going to call our new BirdDog Airliner? You should call it AirDoggie, Dude."
Thompbles: "I'm naming it Airedale. On course after retro burn. Decoupling the retro pack now."

The Airedale came through the entry flames on automatic, then Thompbles jettisoned the rover-wheel heat shields.

The Airedale was coming in to the Laythe Base area at over 8,500 meters...

Nelemy: "Dude, you're coming in high!"
Aldner: "You'll need to pass over and circle back around."
Thompbles: "Not necessarily..."

Instead, Thompbles rolled the Airedale upside down, then "pulled up" to put it into a dive straight down for about 4,000 meters. Then he rolled it back 180 degrees around and pulled up, leveling the plane off at less than 1,000 meters altitude...which put the plane right in position for a standard landing approach.

Nelemy: "Dude! Airliners don't fly like that."
Aldner: "With a maneuver like that, I expected to see you dropping flares and chaff."
Thompbles: "I couldn't find the buttons for flares and chaff."
Nelemy: "Dude, you're a lot braver than I am trusting that you could do that pull-up without the plane flipping out in pitch!"
Thompbles: "You should try this out in the simulator. This bird has three pods worth of torque authority...it can fly at much higher angles of attack than the BirdDogs without flipping out."
Aldner: "Um...you're going to land a couple kilometers long compared to we usually do."
Thompbles: "I know. That's because I'm going to bring it over here to us at Base 2 during the rollout."

Thompbles drove the Airedale over to Base 2 and parked it next to Aldner's BirdDog 1. See the image below to compare the two planes. As mentioned before, the Airedale uses the exact same basic structure as the BirdDog (same placement of fuselage, wings, gear, docking port, etc.) so that it will be able to use the same GasStations.

Next episode: Playing with the new toys.