Long-term Laythe - Part 43

Carrying Comsats

Back when Beta 0.90 hit, the OKTO2 probe cores lost the ability to generate any torque at all...and my constellations of communications satellites (which don't actually do anything) around Laythe, Vall, Tylo, Bop, and Pol all lost their ability to orient in space...which makes them do even less. So, first item for today is to take care of getting some refurbishment and replacement comsat equipment headed off to Jool.

The comsats in Laythe orbit have docking ports, so they can be refurbished by adding on a reaction wheel part -- but all the other comsats lack docking ports, so they will eventually need to be replaced. There were only a couple months before the next Kerbin-to-Jool transfer window, so I rolled four d4 to see how many comsats the KSC crew could have ready, and got 9.

Below we see the launch of the comsat payload. Because this payload has roughly half the mass of the typical payloads I send out to Jool, it only required a two-booster version of the Reusable Rocket to get to orbit (despite also carrying a Rockomax X200-32 Fuel Tank that will provide fuel for the trip). You can imagine along with me, the fairing enclosing the payload prior to the nose cone being jettisoned.

We get a closer look at the payload in the next picture as it continues on to orbit. There is a carrier bus (which is also equipped as a comsat) with eight comsats attaced around it. The central spine of the bus ends in a stack of reaction wheels with docking ports which will be used to refurbish the Laythe comsats. Note: The action group that separated the nose cone and fired its sepratrons also deactivated the torque of those reaction wheels...because otherwise the stack waggled around in a rather obscene manner during maneuvers.

After depositing the payload into a roughly 100 km orbit, the Reusable Rocket sustainer separated and returned to KSC for re-use.

To push the payload to Jool, a Tug that had previously been to Jool and back (at least once) was chosen. This Tug was residing in Kerbin orbit attached to the Big Gas Tank, and it was about four-fifths full of fuel that had been taken from the Big Gas Tank and from other ships that had docked there to offload excess fuel. In fact, it had MORE fuel than would be needed, so some was put back into the Big Gas Tank (leaving the Tug's central tank mostly empty) before the Tug was undocked and headed off to rendezvous with the comsat payload.

When the Nuclear Tug rendezvoused with the comsat payload, it first docked its rear end to the comsat payload. Then the Tug separated the X200-32 Fuel Tank from the payload, moved off a little way, flipped 180 degrees, and then re-docked to the comsats using its front docking port.

The fuel from the X200-32 Tank was transferred to the Tug's main tank (leaving the X200-32 almost empty). Then the ship was pointed prograde, and an action group was activated that undocked the X200-32 Tank and fired four canted sepratrons mounted on the tank. The sepratrons gave the X200-32 Tank a big enough kick to deorbit it, in accordance with my No Littering policy.

Because of the low mass of the comsat payload (11.6 tons), the Nuclear Tug would have plenty of fuel to push the payload to Jool even without an additional rear tank attached. The trajectory plotted for Jool transfer is shown below. Jool will be near its node with Kerbin's orbital plane when the ship arrives, so an encounter is showing up even before any plane change maneuver is figured in. (We don't see the trajectory of the returning Grey Havens Express in this plot because that's being handled in a separate copy of the save file.)

The 1,952 m/s burn would take only 12 minutes (as opposed to the nearly 20-minute burn I typically deal with when sending heavier payloads to Jool), so this burn was performed in one step (instead of my usual two). This resulted in the periapsis dropping down below 85 km during the burn, but that was no problem.

The Tug was still firing when the ship passed out of Kerbin's shadow for the back-lit picture below.

The Tug used about 66% of the fuel in its main tank for the Jool transfer burn. The side tanks on the nuclear nacelles were still full, as was the X200-8 Fuel Tank at the base of the payload (the fuel flow through the docking ports had been disabled during the burn).

Whenever I get a transfer trajectory that leads to an encounter (as happened here because Jool was going to be near the node), I always seem to waste lots of time messing with that maneuver, trying to get an acceptable final equatorial orbit...and I'm never happy with the result. It's so much easier to just do the separate plane shift maneuver. Below, we see the plane shift maneuver that I set up (after the ship left Kerbin's SOI) for when the ship approaches Jool -- the node was located just three days before encountering Jool's SOI. Because the plane shift takes place far from Kerbol, it will only require 58.6 m/s of delta-V.

That plane-shift maneuver node also includes the fine-targeting for the Laythe encounter. Below we see the maneuver results, focused on Laythe, coming in for a nearly perfectly tangential encounter. This is important for minimizing the velocity of the encounter and minimizing the heating during aerocapture (which might be an issue by the time this payload reaches Laythe, depending on when KSP 1.0 is released). This targeting is done using Precise Node to tweak the radial and prograde components of the burn to get the desired tangential encounter.

That plane-shift burn, of course, is not going to happen for another 295 days, but the maneuver node is stored with the ship so it will be ready when the time comes (and I set an alarm in Kerbal Alarm Clock to remind me). Did I ever mention how happy I was when Squad made the change that allowed future maneuver nodes to be stored with the ship? Because it's very handy.


Heroic Homecoming

I'm going to skip ahead here and take care of the Old Crew's return to Kerbin. There are a couple other Kerbin-to-Jool transfer windows that will occur during this phase, and I'll go back to them as needed in my timey-whimey ways if I decide there is anything else I want to send out to the New Crew on Laythe during that time (but they already have most everything I could think of to send them).

When we left our Old Crew, heading home in the Grey Havens Express, the plane-shift maneuver prior to Kerbin encounter (which will happen very close to Kerbin), was already set up and stored (see the plot below). Because it happens way down near Kerbin, the plane shift will require over 500 m/s of delta-V...but the Old Crew was sent home with plenty of extra fuel, just in case, so this won't be a problem.

Nelemy: "Whoa, Dude! What is this strange sensation? My snack bar wants to fall toward the deck. It's been so long since I've felt anything like this."
Kurt: "If you think this acceleration is something, you're going to be in for a big shock when we land on Kerbin. Have you been keeping up on your exercise routine?"
Nelemy: "Dude...there are DAYS left before we reach Kerbin...plenty of time for exercise later."

Kurt: "I've got the Kerbin aerocapture maneuver plotted. The fine-targeting burn will take 192 m/s of delta-V. The aerocapture itself will put us through 2.6 gees...that won't be fun after 270 days in zero-G."
Nelemy: "Ah, it'll be nothing. Aldner and I have been in zero-G even longer than you because we were waiting in Pol orbit while you guys explored the surface."
Kurt: "Well, Pol hasn't got much gravity either."

The fine-targeting burn is seen below. As pointed out before, even with eight nukes pushing, the big beastie that is Grey Havens Express doesn't accelerate very fast.

Hellou: "Look at Kerbin! The city lights on the night side are beautiful. I can't wait to get home."
Aldner: "Yeah. I guess it's been so long since I've been in Kerbin orbit...but I don't really recall all those lights. Maybe everybody is using a lot more electricity nowadays. OK...get strapped into your acceleration couch."

With all those Tugs in the way, there was hardly any noticeable reentry flames on the habitat modules.

Nelemy: "Arrrrgggggghhhh. Dude...Turn off the acceleration!"

The aerocapture pass left the Grey Havens Express in an elliptical orbit with an apoapsis of 337,000 km. A small burn of 6.1 m/s aligned the orbit with the equator, then another burn of 7.6 m/s raised the periapsis (but still left it in the upper atmosphere) for an aerobraking pass to lower the orbit.

After a couple more small burns to slowly raise the periapsis and make some even weaker aerobraking passes, a final 50 m/s prograde burn circularized the Grey Havens Express into an approximately 103 km circular orbit. The ship was home safe.

All of the big central tanks of the Nuclear Tugs were empty, but the picture below shows that there was still a goodly amount of fuel in the side tanks of the nuclear nacelles. There is also propellant in some of the FL-T400 tanks that surround the habitat modules (which acted as cosmic radiation shielding during the return trip).

Ours heros from Jool would be picked up and returned to Kerbin by none other than Jebediah and Bill Kerman, using an 8-kerbal Crew Carrier 6d SSTO rocket. Below, the Crew Carrier takes off on its six RAPIER engines in air-breathing mode.

I always like to fly the Crew Carriers manually into space to see how much delta-V I have leftover for orbital maneuvers. The flight profile starts vertical, then at 5K the ship is tilted 20 degrees downrange to start picking up horizontal velocity. Above 15K, the ship is pitched over more to get the horizontal velocity up over 700 m/s before the RAPIERs need to be switched over to closed-cycle mode. The engines were cut at 44K when the apoapsis hit 115 km. I'm very interested to see if this ship will work well (or at all) under the new aerodynamics coming in version 1.0.

The Crew Carrier made it into orbit with 983 m/s of delta-V remaining for orbital maneuvers. The boost wasn't straight East, so an 11 m/s burn was needed to match orbital planes with the equatorial orbit of the Grey Havens Express.

Jebediah: "And...docked! Are you guys ready to head back to KSC?"
Thompbles: "It's going to take a while to get all these samples and data packs moved over to the Crew Carrier."
Bill: "Remember, we're only bringing half of the samples down on this trip. No use risking everything in one ship that Jeb is driving. We'll send another ship up later to bring back the rest."

Once Thompbles, Kurt, Aldner, Nelemy, Hellou, and Emilynn (and half their samples) got transferred over to the SSTO, the Crew Carrier separated from the Grey Havens Express, and Jeb (or MechJeb, as the case may be) targeted the landing for KSC and set the ship down for a routine landing north of the launch pad.

The crew disembarked and were finally safely back on Kerba firma."

Bill: "Welcome home to Kerbin, folks! It's nice to have you back after seven years."
Kurt: "Seven years and 78 days. But who's counting?"
Thompbles: "That's what happens when you tack on a couple extra years because of Kerbol mega-flares and extended exploration."
Hellou: "Emilynn and I have only been gone for five years...but our mission was supposed to be only half that long."
Bill: "But we really appreciate all the extra work you did, especially in exploring Tylo, Bop, and Pol. It saved us from having to send out extra crews to get that done."

Nelemy: "Whoa, Dudes! Look at the KSC! New buildings everywhere."
Kurt: "Yeah...I like what you've done with the place."
Jebediah: "Yup, we've come a long way since the old Barn."
Nelemy: "Barn?"
Bill: "Back before your time."
Nelemy: (opens the faceplate of his helmet) "What's that weird smell?"
Hellou: "That's fresh air, Nelemy."
Aldner: "Air that doesn't smell like you, Little Buddy."
Nelemy: "Dude."

Just for reference, below is a picture of what the KSC looked like when Thompbles, Kurt, Aldner, and Nelemy left for their Laythe mission. You can see why they are impressed.

Jebediah: "Uh oh...here come the reporters."
Bill: "Get lined up for some photos. And then we'll have the medical checks, debriefings, press conferences, meetings with the President, ticker tape parades, and all that."
Hellou: "Not before I get a chance for a bath, I hope. I haven't had a proper bath in years."
Nelemy: "My feet hurt. When do we get to sit down?"


One Month Later...

After all the weeks of parades and parties and press conferences, the lives of our heros quickly reverted back to the normalcy of a kerbalnaut's time on Kerbin. Below, we see Kurt happening to run into Adlner on his way from the Astronaut Complex over to the VAB.

Aldner: "Yo, Kurt. I see they have you suited up...you don't have a mission, do you?"
Kurt: "Nah. They are doing vacuum pressure checks on the re-modeled Mk1 Inline Cockpit, and I'm the guinea pig."
Aldner: "I'm glad they're reworking the Inline Cockpit. The visibility from the old version was lousy -- it seemed like I could hardly see anything out of it."
Kurt: "True. What are you suited up for?"
Aldner: "They had me doing 'reach around' tests in the new Mk3 Cockpit mockup, just to be sure all the controls are where a suited pilot can reach them well. I've been doing a lot of boring stuff like that since we got back. The life of an astronaut on the ground is not nearly as exciting as being on a mission."

Kurt: "Well, you were never stranded for over three years around Moho like I was...not all missions are exciting. Besides...haven't you been entertaining yourself with that bevy of beauties that you named planetary features after during our mission?"
Aldner: "Sadly, no. They've all moved on."
Kurt: "What? Joysina from the Satellite Pub?"
Aldner: "She finished her Ph.D. in Astrophysics, and now she's teaching at West Kafrica University. And they closed the Satellite Pub, anyway."
Kurt: "Jenfir from the Launch Pad Tavern?"
Aldner: "She now works as a distributor for Blastoff Beer Company up north in Koor City."
Kurt: "Klaudiya from the Booster Bay Bar?"
Aldner: "She's now managing the joint...which is now the Booster Bay Family Restaurant...and she says she's not interested in fly-boys anymore."
Kurt: "Ah. How about Itsii from the Refueling Station Bar & Grill?"
Aldner: "She married mission controller Gene Kerman, and now they have three kids."
Kurt: "Wow. I guess a lot can happen in seven years."

Aldner: "You know, what really hacks me off are all these changes around the KSC. All these eggheads and their big R&D center...which were hardly any help at all during our mission. And the young guys they have nowadays as astronaut recruits, shooting pool all day in the Astronaut Center. A couple of those punks were actually making fun of my Ban-Lon shirts! Ban-Lon is what an astronaut is supposed to wear."
Kurt: "Yeah. They are all into that polyester crap."
Aldner: "I tell ya...I need another mission so I can get out of this place."

Thompbles: "Well, well! If it isn't the two guys I've been looking for!"
Kurt: "Oh...Hi, Thompbles."
Aldner: "Hey there, Thompbles. Nice polyester shirt."
Thompbles: "Thanks. I don't suppose you guys would be interested in a new mission, would you?"

Kurt: "New mission? Where are we going?"
Aldner: "Yes, I'm interested. And you better not be joking, or I'll make you eat that shirt."
Thompbles: "No joke. I was talking to Deke Kerman in the Astronaut Office, and they need astronauts for a long-term Duna mission. He asked me to put together a crew."
Kurt: "I haven't heard anything about this."
Aldner: "When do we go?"
Thompbles: "It's a big project that Elon Kerman of Kerbodyne has been working on in secret. They've been designing and building the hardware, and they sold the idea to the Big Brass. We have one year to do the necessary training and get the ships boosted before the next Duna transfer window."
Kurt: "Another big Kerbodyne project? I'll bet the Rockomax Mafia aren't too happy about this."
Thompbles: "Rockomax will be doing some subcontracting. And they appeased them some by letting them choose one of the crew."
Kurt: "Ah...so Nelemy is coming?"
Thompbles: "Yes."

Aldner: "Is there any airplane flying to be done on this mission? I hear that the air is pretty thin on Duna."
Thompbles: "Yes...Elon says they have designed a plane they think will be useful to us on Duna. But mostly we'll be hopping and roving around."
Aldner: "OK. I'm in."
Kurt: "Me, too. No use sticking around here when some far lands are calling."
Thompbles: "Great. We're having a briefing tomorrow at eight hundred in the Administration building. Be there."


...Which is why it took me a while to get around to posting this... I've been designing and testing ships for Developing Duna. See you there!