The Integrated Program: Reuse, Commonality, Terrifying Misuse of Blutonium

[architeuthis]

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The time of departure drew near. The hours and minutes ticked away, and with them departed the last fleeting moments of the Kerbal 17 mission, the final ultimate mission of the Kerbal program, and the culmination of a hectic decade of deep sacrifices, and terrific achievements. The Munar Module would dash away from the munar surface and carry the two Kerbal astronauts slowly up out of the Mun’s gravity-well to rendezvous with the command and service module in orbit. All around him the bright regolith of the munar plain stretched away in stark relief to the perfect blackness of the empty gulf of space that is the munar sky. The silence here is more perfect than the stillest winter day; only the sounds of his suit fans and his own breath reach his ears. Jebediah gazes upwards at the distant blue sphere suspended motionless and beautiful in the all-encompassing darkness, an aqua-marine jewel in contrast to the cold, dry, radiation-blasted magnificent desolation of the Munar surface. “What now? Will we return here someday?â€Â

An idle question posed within the unshakable privacy of a small space suit, sheer isolation shared with no more than two fellow kerbals for the next 12,000 km, is an ephemeral thing. No outside observer would ever know of idea contained within that minuscule oasis of survivability in this vast airless desert, and no outside observer here exists. But the question itself is significant, and on a different world the powers that be had convened to ponder this question: the future of the Kerbal Space Program.

. . .

Kerbol's rise above the western mountains filled the offices of the Kerbal Space Center with a bright morning light, reflecting the heady optimism of the new space age. ‘The weather is always so nice here, never a cloud in sight’, thought the administrator absent mindedly. Across the heavy wooden desk from the KSC administrator sat the President, Richard Kerman, whom with regret the administrator presently returned his attention to.

The President was pleading "…but, we're already spending 78% GDP on the space program…"

‘Politicians! Always going on about money’, the administrator’s inner monologue continued, ‘well’ he had no time for them; he had science to do.

Just a few years ago that august body of lawmakers, "the committee for the convening of other committees" was in pandemonium. It had been revealed that Kermunists were building a large launch facility in the mountains, on a scale to rival KSC itself. Such a facility could have but one purpose. Suddenly possessed by the terrible fear the Kermunists might try to use the mun as a base for the working class to share capital and the means of production with each other in egalitarian equality or something similar, the "the committee" was in a nationalistic uproar. 'We have to get a Kerbal up there first! We have to beat the Kermunists to the mun!' To that end the "the committee" voted the KSC administrator incredibly wide powers. For instance, an unlimited budget. In perpetuum. They regretted their votes almost immediately, but alas the measure had already been carved in stone, literally. Legally inviolate.

With a laconic gesture of dismissal the administrator returned from his reverie,

"No. The program must be bigger, more ambitious than before! Huge rockets!!".

The President was weeping, and mumbling incoherently now, but the administrator didn't even notice. ‘Politics eh? What's it good for!’ thought the administrator. ‘Good now that that's all settled’. As a secretary led the inconsolate President out, the administrator turned his attention to the huge chalkboard which dominated the office. It was covered in a chaotic tableau of engineering sketches, equations and unrelated doodles.

"Ahh yes", he said aloud, "The Integrated Plan".

The basic idea of the Integrated Plan was to develop in parallel a modular and reusable space infrastructure using standardized hardware. Reuse and commonality being the guiding principles/marketing buzzwords of this space infrastructure, the hope is that an infrastructure composed of mass-produced reusable modular elements would have greater economies of scale than one composed of specialized throw-away elements and thus make the program ‘relatively inexpensive’. This infrastructure would consist of a fully reusable surface to orbit space shuttle to ferry Kerbalnauts, light cargo and propellant to Low Kerbin Orbit, a large LKO space station with attendant robotic LKO propellant depots, a fleet of robotic space tugs which could do double duty as a Munar Modules, and blutonium powered cis-munar Reusable Nuclear Shuttles for efficiently transferring large cargo payloads to all points in cis-munar space, and eventually to interplanetary space as well. These systems would be designed from the get go with maximum interoperability in mind. Ultimately this space infrastructure would support a Munar Orbit Space Station, a Mun surface base, and manned missions to Duna and perhaps, Jool’s moon Laythe.

The LKO Space Station is the binding element of the plan, and is its single most critical component. Based on a Standard Space Station Module (SSM), the space station will be of modular construction, this way the space station can be continuously expanded as more and more SSMs are coupled together. The bulk of the orbital assembly will be done by fully autonomous and tele-operated Space Tugs, with some Kerbalnaut EVAs necessary for more dexterous construction work. The long term plan calls for the LKO Space Station to gradually evolve into a large ‘Spacebase’ with living quarters for at least a 12-kerbal crew and an array of general purpose laboratory facilities featuring a sea-level ambient pressure 'shirt-sleeve' atmosphere (though one wonders given even this amenity if the Kerbal astronauts will ever feel comfortable outside of their space suits). There would also be multiple standard docking ports for further expansion of the station, including science, habitation and cargo modules as well as surface-to-orbit and orbit-to-orbit transfer vehicles.

The Spacebase's raison d'être may be vaguely defined, but it would likely include the conduct of microgravity physics and life sciences experiments, astronomy, Kerbin science and weather observation. Freefall and high vacuum conditions would also allow all sorts of neat tricks in manufacturing and materials science; for instance the rapid and inexpensive formation of large single-crystal metals, foamed metals, and thin films of extraordinary quality. You even get levitated induction smelting as a free bonus. The LKO Spacebase would also function as a primary node for the planned deep space network of surface stations and communications relay satellites. It would serve as a logistics base and command center for manned and robotic cis-munar and planetary operations. And naturally the Spacebase would be a platform for spying on the pesky Kermunists. The common SSM design would be reused with some modifications for the future Munar Orbit, and Synchronous Orbit Space Stations, as well as mission modules for planetary missions and as building block for the Munar surface base.

A Space Station Module and an experimental Space Tug prototype fly on a standard HLV stack.

The core of the future space base on orbit. KSC censors were unable to hide the damning evidence of a {particularly embarrassing design flaw}REDACTED innovative design feature of the Space Tug prototype, here eminently displayed:

Bob Kerman of Expedition 1 inspecting the Space Station Module on EVA.

The second link in the chain to cis-munar space is the reusable space shuttle. The engineers had originally envisioned a small orbiter that would ride up to altitude on the back of a huge carrier-jet, before decoupling and burning its own little engine the rest of the way to orbit, but it was decided, in a sudden fit of sanity and good sense, that such an ungainly contraption was too monstrously complicated to safely pilot. After many, many design iterations a hybrid air-breathing scramjet/liquid fueled rocket SSTO space plane concept took shape, though the program was not without casualties. Many persistent design issues plagued the large delta-winged space plane, among them an unstable center-of-lift, a too heavy front end, structural issues, insufficient RCS monopropellant, and that perennial concern of the engineers ‘not enough ram intakes’. But as they say ‘there is no expanding of new frontiers without risk’. With unfortunately high frequency the engineers and test pilots chanted this calming ritual benediction; owing to the alarmingly high rate of fatal testing accidents it seemed as if the fate of the entire Integrated Plan was being called into question.

Enter hotshot test pilot Bill "penalty weight" Kerman. Expertly handling the controls of the experimental Valkyrie Mk3, Bill opened the throttle. Unable to keep up, the escort flight of Aeris 3A chase planes was left behind. Variable geometry inlets engaged the scramjets at Mach 4, powering the Valkyrie shuttle upwards towards space through the quickly rarefying atmosphere with horrifying velocity. Though unoriginally named, the Valkyrie shuttle eventually proved itself to be a capable and reliable design. The Mk3 is highly pitch and yaw stable, has a large delta-v budget for quite muscular orbital rendezvous maneuvers and can reach over 1500m/s on its air breathing engines alone.

Valkyrie Mk3 Prototype in flight.

A Mk3 cockpit interior. Note the incomplete Spacebase visible roughly 10 km downrange through the cockpit window.

Success! A Valkyrie shuttle mated to the Spacebase core.

Edited March 8, 2014 by architeuthis

[architeuthis]

Caught up in a sudden desire to 'get their hands dirty' up in space, KSC engineers are hard at work moving the LKO Spacebase off of the drafting boards and into manufacturing. As originally envisioned, the Spacebase would have been powered by two 25 kW Brayton cycle nuclear reactors mounted on telescoping booms but due to the currently primitive state of the science of space nuclear reactors, it was decided that power would instead be provided by a mix of photovoltaics and radioisotope thermal generators. Additionally the initial design had excitingly planned to supply artificial gravity though centrifugal spin but this was sadly determined to be too complicated to implement in practice (flight controllers blanched at the prospect of having to dock large numbers of large and unwieldy space station modules to a rapidly rotating orbital construction site. At the very least the KSC engineers would be finally forced to learn the mysteries of proper RCS placement).

An engineering mockup of the final Spacebase design in the VAB.

The Spacebase module HLV launches were deeply unnerving to the KSC engineers. They had this notion that according to something called ‘the Bernoulli equation’ fluid pressure of the atmosphere on the skin of a rocket in flight would be proportional to the square of the rocket's velocity times half of the fluid density. Fluid density drops with increasing altitude naturally, as the air is getting thinner, but on the other hand the rocket continues to accelerate to greater and more horrifying velocities as altitude increases, therefore there is some point of maximum dynamic pressure called max q… or so the engineers thought. Without any kind of protective payload shroud the engineers were quite sure that the fragile SSMs would be turned into 'titanium confetti' by the loading from aerodynamic drag at max q, but it actually turns out there is no such thing.

“You vurry too much†the old timers said, and regaled them with stories of the 50 SRB 'pancake class' HLVs Wernher von Kerman and his company of slightly-crazed but highly efficient ex-fascist rocket scientists had taped together with struts back in the {bad old days before the docking clamp was invented}REDACTED golden age of rocketry. “Hell I remember the 8 gee Immelmanns vee vuhd try to pull during reentry with our Sänger-Schwarzvogel SSTO space planes…just to show em'â€Â. So, against their better judgment the KSC engineers averted their eyes and proceeded anyway, but by golly the somewhat arbitrary gods of physics blessed the venture and the blasted things made it up to orbit all in one piece.

With the rapidly expanding pace of the Spacebase project’s on-orbit construction Kerbal astronauts were acquiring a not insubstantial experience with orbital rendezvous and docking. What had at first been an exercise of unremittant clammy-palmed angst punctuated periodically by screams of sheer terror and curses of the gods, was now via the constant practice of docking of large numbers of unwieldy trusses, pressurized modules, and propellant tanks devolved into an undeniable tedium. Studies were conducted with the aim of mechanically automating the process. ‘Jeb’ Kerman laughed at the thought. Huge analog computers, and spinning wheels of magnetic tape kilometers long necessary to automatically astrogate and pilot the spacecraft could never be squeezed into the tiny confines of a Mk. 1-2 Command Pod. No, there would always be a need for ‘Buck Kerman’, the right stuff that only a true kerbal pilot could provide.

The next Valkyrie mission was a sortie up to a 300 km orbit… for the view.

Two more HLV launches bring an additional hab module, three cargo storage modules, a communications boom, and the two long ‘Power Tower’ solar trusses to the burgeoning space station, and just like that the Spacebase is mission complete… roughly 5 years ahead of schedule. Hey, they were on a roll.

Expedition 5 docks to the Spacebase. The number of Kerbal spacemen, scientists and engineers permanently resident in orbit is now 10.

Concomitant to this flurry of activity in Low Kerbin Orbit, KSC engineers rolled one of their newest top-secret pet projects out of the SPH. Project Plutino was originally envisioned as being an open-cycle nuclear-ramjet powered drone, as this was universally agreed to be an awesome idea, but due to budget cuts the engineers were eventually forced to settle on a final design which was a LV-N powered airframe with radial intakes bolted on for looks. The drone’s mission would be to cruise at supersonic velocities over kermunist territory at basically tree top height and play obnoxiously loud heavy metal music over loud-speakers, all the while spraying screaming hot fissioning blutonium all over the place and just being generally all-around awesome. Spirits were high at KSC as Project Plutino began accelerating down the runway, nosing up and discarding its SRB trolley. Alas due to a slight design flaw regarding the relative positions of center of lift and center of mass, and also the pathetically insufficient amount of thrust and sea-level specific impulse of the LV-N, the prototype drone entered a high-speed uncontrolled spin, whereupon the atomic motor promptly snapped of the end of the aircraft, the rest of which initiated a rapid unplanned disassembly and descent into the ground. Ultimately, the easily distracted KSC engineers chose not pursue the concept further.

Edited October 6, 2013 by architeuthis

[architeuthis]

Presently noting the lamentable lack of rockets and rocketry beyond LKO, KSC Mission planners decide the time is ripe indeed to advance to the next stage of the Integrated Program’s inexorable march of exploration and conquest of trans-Kerbolar space: the long delayed return to the Mun!...Well, sort of. Munar orbit.

The Munar Orbit Space Station (MOSS) is intended primarily to serve as a flexible logistics base for munar surface sorties. It consists of a standard SSM tightly packed with palatial accommodations for up to six Kerbals, cargo storage for surface missions, a propellant tank farm to serve the local fleet of Space Tug/MM-Bs operating on the munar surface, and a small laboratory ‘for analysis of surface samples’. Two standard Space Tugs will remain on station at the MOSS, one for orbital maneuvering and general space tug services, the other to remain available as a rescue vehicle for surface missions should the need (inevitably) arise.

Plans to insert the station into a near polar orbit rather than the venerable and much loved standard equatorial orbit were met with much controversy, name calling, and heated debate. Here is a summary of one of the flurry of internal memos regarding the subject:

Re: The Desirability of a polar orbit for the MOSS

• Like, really nice views… man.

• Since a polar orbit station matches planes with all points on the munar surface twice per munar day (or once every 19 hours), within those launch windows no expensive plane change maneuvers are needed for surface to orbit vehicles to rendezvous with the MOSS. In other words a polar orbit enables inexpensive access to all points on the munar surface.

After being moved to munar polar orbit by a Space Tug, the MOSS soars majestically over the enigmatic and darkly beautiful craters of the Mun’s North Pole, shaded from Kerbol’s piercing rays for a billion years.

Edited June 1, 2013 by architeuthis

[BigBoy734]

I cant see the pictures.

[architeuthis]

To complete the MOSS such that it is 'fully operational' in its primary role as a logistics base for munar surface ops, significant propellant tankage is needed for the station’s resident space tug/MM-B landers. Getting the propellant there simply isn't a mission the venerable standard Space Tug can do economically however. This is where one of the more recent gifts to Kerbalkind by the hugely irresponsible gods of technological progress comes into play. When Kerbal Science unlocked the secret to splitting the heavy blutonium atom, in addition to its other more well known uses, it also hit upon a way to create rockets engines of incredibly improved exhaust velocity heretofore difficult to imagine.

At the LKO Spacebase Jeb and Bill Kerman are admiring by remote camera the KSC’s latest technological wonder: the ‘Hot-rod’ cis-munar Reusable Nuclear Shuttle specially built to keep the MOSS resupplied. Presently, Jeb is excitedly explaining to Bill the shiny new aluminum-lithium hulled atomic rocket’s principle of operation:

“What we have here is the LV-N, a ‘solid-core’ nuclear thermal rocket. Basically you pump liquefied molecular propellium through the reactor core, where the awesome might of the atomic fission in its interior heats propellium to indecently high temperatures and it expands outwards through the rocket nozzle at incredible speed. Unlike a chemical rocket there is no oxium reacting with the propellium, so the unreacted propellium keeps its naturally low molecular weight. Why is that important? Recall that heat is just the average kinetic energy of molecules, and in the case of the propellium molecules they have lots of that thanks to the LV-N reactor core. Also recall that kinetic energy is the same as one half of mass times the square of velocity. Now let’s say a particle is given a certain constant amount of energy, what happens if you then reduce its mass? Damn straight! Its velocity increases! If the velocity increases, the specific impulse increases and so the delta-v increases! These hot-rod Reusable Nuclear Shuttles can ship 40 tonnes out to the mun, burn 90 degrees inclination to match planes with the MOSS polar orbit, drop off their payload, then change inclinations again and fly all the way back to LKO on one tank of gas! These first generation LV-N motors they’re sending up from KSC are a little strange though...â€Â

“How’s that Jeb?â€Â

“Well for one thing they burn oxium… for some reason… an afterburner maybe? Also, I'm not privy to all of the unholy bargain design decisions being made by those jokers planetside but these LV-Ns don’t need reactor warm up or cool down cycles. It is really quite strange. It is almost as if a guy in bed with a coma opened his eyes for the first time in a year, suddenly sat bolt-upright, and then ran a marathon. How the guys at KSC manage this stuff I have no idea.â€Â

“Boy… Wehner von Kerman sure knows his rocketry.â€Â

“That’s the Johnny’s honestâ€Â

“Hey Jeb, why is there only one of those LV-Ns on there, couldn't we get ‘moar power’ if we clustered em’ up?â€Â

“Zam! You know the rocket equation right Bill? Do you see a term for thrust anywhere in there? Propellant load increases exponentially with rocket dry mass. Sure we could make shorter burns, but more LV-Ns would just eat too much into the mission payload. This baby will never grace the surface of a planet, she’s pure orbit-to-orbit, so she doesn’t need a TWR bigger than unity. Besides, she’s got it where it counts: delta-v in fricken spades. Plus if you had more of the LV-Ns you’d have to worry about the radiation.â€Â

Bill does a freefall summersault and drifts away from the glow of the televisor. “Don’t pull one over on me Jeb! Space is already awash in radiation! Who cares if some random space dust picks up a few stray hundred more Sieverts here or there?â€Â

“Well for one thing you would need big heavy neutron shields between each LV-N otherwise you’d have no control over the reactor criticality, and believe me if there is one thing you don’t want to lose control over it is reactor criticality. The blutonium wouldn't outright turn into an atomic fireball… probably. But the high-tech cermet reactor elements would melt and fuse together into one big useless red-hot ball of metal ‘and that’d end your trip real quick wouldn't it’?â€Â

“Wait a second, I thought these things were already shielded? Are you telling me they aren't?â€Â

“You’d better believe it bub. It’s lucky we’re looking at this thing over closed circuit TV cause that little LV-N may look harmless from over here but we’re gazing upon the naked face of the atomic gorgon. There is naught but the scant few centimeters of aluminum of the reactor pressure vessel between us and the heart of the sun. The thing might as well be made of window glass for all the protection from radiation it affords us. Gamma-rays and fast neutrons just go straight through it without even slowing a beat. Even with the motor turned off if you were to get up close to that reactor shell, or the rocket nozzle, without a lead lined space suit and the hard-radiation flux would dancing on your grave in a minute without you even knowing it.â€Â

“Say Jeb, why don’t we just put up a shield around the whole thing?â€Â

“Cause’ we shoot or TWR so badly to niffelheim that we might as well be using ion engines. Even the ultra-minimalistic ‘shadow shield’ that is there, a little disk sitting on top of the reactor, is outrageously heavy. The shield’s planar density is 3,500 kg/m^2 and the reactor’s radius is about .6 m. You do the math.â€Â

Bill does some figuring on his ‘protractor’ hand-held digital computer. “That’s almost 4 tonnes. Ouch! I see what you mean Jeb, but tell me something it says here the LV-N only masses 2.25 tonnes, †he waves some printouts around, “what’s the big idea?â€Â.

"Hmmm." Consciously ignoring the unsettling implications of the statement Jeb responds “ I have no idea. But I’ll tell you what, that’s why the shuttle is shaped the way it is. Do you see how the rocket tapers off at the end?â€Â

“Sure.â€Â

“That’s so the structural members of propellant tanks stay safe in the shadow of the reactor.â€Â

“Radiation damages those too?â€Â

“Yep. It’s because of neutron embrittlement. Basically you've got all those neutrons trying to blast everything into kablak holey cheese, in the process they strain harden the crystal lattice structures of metal the airframe is built out of. If we don’t take some steps to protect the load bearing structural members, when we light the jet and the rocket acceleration strains the airframe, after enough time it will develop lots of brittle cracks. You do not want that.â€Â

“If only the forward section is protected by the shadow shield, how do we dock with the shuttle?â€Â

“Carefully! The shuttle has to maintain a constant forwards aspect relative to us as it approaches otherwise we’re in the line of sight of the reactor. If that single LV-N were to do a burn within 30 meters of us and we happened to be exposed to its unshielded end, we would get a fatal dose more or less instantly. This is why we will never use these nuclear motors for decent stages; the shielding required is utterly prohibitive. Also we don’t want to dock that thing right up to the Spacebase, our cozy little station is way too big to fit inside the shadow for one thing. For another, the parts of the station that are exposed to the hard glare of the nuclear motor will reflect some of the radiation back on us. The reactor stays ‘hot’ for hours after a burn; we don’t want to be in a line within 100 km of its unshielded face, so we’ll leave it station-keeping out by one of the robotic LKO propellant depots in the meantime between mun flights. We’ll scoot over to it with a space tug when it’s our turn to ride the atomic rocket.â€Â

A HLV boosts a zero boil-off cryogenic propellant storage module, and the MOSS’s second Space Tug/MM-B up to LKO.

After rendezvous and mating to the cargo, the hotrod RNS takes two burns to reach Kerbin escape.

To make inexpensive plane changes the RNS burns retrograde to munar capture leaving the orbit highly eccentric, and then completes a single orbit. Once the RNS is back at apoapsis it burns normal to its velocity to match planes and orbital rotation direction with the MOSS. Then it spirals down for rendezvous and docking. The operation is reversed to return to LKO.

Final approach.

The whole jam docked to the MOSS.

Edited March 8, 2014 by architeuthis

[architeuthis]

The Integrated Plan orbital infrastructure construction proceeds apace. The current project: LKO robotic propellant depots!

There are undoubtedly some out there who, even now, are laboriously inputting into their massive KARPANET mainframe terminals electronic ‘posts’ roughly along the lines of: “Commonality my green behind! What’s with all these extra links in the supply chain? Why not just keep it simple and use a RNS up there as a makeshift depot? Or even just transfer fuel from the shuttle or HLV tankers directly? You’d only need to pump gas once per cycle, which is all the less opportunity for propellium to leak out during transfer.â€Â

Jebediah sez, “A depot assuming it is modular and expandable in design can continue to accumulate propellant with launches from Kerbin. In a way it is the crux of the whole reusability shtick the Integrated Plan hinges on. Propellant alone accounts for a small fraction of gross mission costs, but back in the days before docking and proponent transfer had been perfected we had to essentially throw away an entire hideously expensive spacecraft just because it's gas tank was empty. Nowadays we can we can do the whole space exploration thing allot smarter thanks to infrastructure like these orbital propellant depots. We could in principle still do the 'reusability' thing without the depots but then surface to orbit shuttle flights would become a huge bottleneck.Therefore the advantages of propellant depots are thus: The RNS needs only a single rendezvous to refuel, and it’s not constrained by HLV or shuttle launch timetables. This also means the whole operation is less complex and there are fewer issues with nuclear radiation. Additionally, a dedicated propellant depot has the high-mass luxury of fancypants zero-boil off cryogenic refrigerators. Putting those on a RNS would be a little bit like putting a roof mounted bike rack on a Ferrari.â€Â

There is a real trick to long term storage of cryogenic propellium in space. The damn stuff is just so volatile it wants to wiggle its way out through any gasket, tiny crack or seam in the tanks. As we all know, liquid propellant is best stored at 20 K, but due to heat influx the liquid propellium is always slowly boiling away. Boil-off is anywhere between 0.03% loss per Kerbin day (6 hrs), which doesn’t seem like very much now, but in the long run it really adds up, all the way up to 10% per hour! The standardized modular design for the robotic Orbital Propellant Depot is based around a core Rockomax Jumbo 64 Fuel Tank. The propellant depots are miracles of thermodynamic engineering. A combination of high-tech cryocoolers, plus propellant prechilldown, and space-age multi-layer metalized plastic film insulation…and the patented Rockomax Jumbo 64 grape flavored spray-on insulation is used to keep the propellium cryogenically cold and achieve a zero boil-off losses. Prechilldown is a means of taking advantage of the very high specific heat of liquid propellium by cooling it down close to its freezing temperature prior to launch so that it can act as a heat sink. The cryocoolers act to continually recondense the propellium as it evaporates. The depot propellant modules also come ensconced in a double-bumper whipple shield, to defend against micrometeoroids and the ludicrously high velocity bits of space garbage that populate LKO.

Why make the depots robotically operated you ask? Is it because we want to take good blue-collar jobs away from ‘fuel transfer engineers’? No, it is because gas station attendants would get cooked alive by radiation if a RNS used its LV-N to maneuver anywhere within a few hours of rendezvousing with the depot.

The Propellant Depot initiative began with a bit of a rough start. The normally redoubtable Standard HLV logged a series of increasingly embarrassing explosions and disintegrations before a separation fairing was introduced to mitigate rocket ‘flex’ down to acceptable levels.

Building gas stations in space!

The early propellant modules did not have RCS quads, which made them rather onerous for the space tugs to maneuver into place, however the clever engineers at KSC have made ingenious use of a new breakthrough in theoretical physics which allows them to use ‘time acceleration’ to violate the conservation of angular momentum, which they then proceeded to do with much glee and reckless abandon (meanwhile... in another universe things start rotating seemingly without cause). Violations of the laws of physics notwithstanding, the first depot was completed on schedule. The plan (optimistically) calls for an eventual constellation of at least 3 propellant depots in perfectly circular equidistant relative orbits, to aid in ease of rendezvous for spacecraft returning from their missions with only fumes left in their propellant tanks.

Changing gears, Mission planners at KSC decided it was high time to build a space station at Kerbin Synchronous Orbit, you know... for science. KSO is that special place where the orbital period happens to be exactly the length of one Kerbin day. Dandan and Kirdorf Kerman will man the first rotation before a RNS cycles them back planetside at some indeterminate point in the distant future.

Dandan looking severely nonplussed about his current assignment.

Kerbals can be rather 'macho' about not needing to decompress before an EVA. The nitrogen toxicity that ensues does not seem to do any favors for the Kerbalnaut’s already lamentably precarious states of mind. Presently, an epidemic of space fear is brewing. In the contemplation of the abyss, and the impossible Eldrich terrors that must abide there in that frozen infinite darkness, the poor inhabitants of the KSO Station are now but the slightest shred of sanity removed from total abject hysteria. They try futilely to shrug off their increasingly morbid thoughts, but the existential dread of the revenant spirits of the void is palpable and undeniable.

[Guys, seriously... breathe.]

A RNS boosts a Space tug intended for KSO orbital maneuvering out to the station, but offers no further relief. Hopefully Spacemen Dandan and Kirdorf Kerman don't use the tug to do anything ill-considered.

The mass psychosis appears to be contagious, as symptoms are now manifesting on the Spacebase as well. Even Jebediah finds he is restless; his gaze often turning to the airlock. During the long watches he sometimes EVAs, drifting listlessly in the enveloping silence of space, casting his suit lights across the gleaming exterior of the station.

RNS returning to LKO.

When the RNS returns to LKO it is time to refuel. But here we must vanquish the problem of ullage stratification. Down on Kerbin’s surface gravity conveniently makes the propellant puddle at the bottom of the tank where the turbopumps can feed it to the rocket motor, as often seems to be the case, in space it is not so simple. Liquid propellant behaves very differently in free-fall depending on its viscosity and surface tension. In the time that passes between burns the damn stuff might settle over to the to the walls of the tank leaving a large void or gas bubble in the center, or it might ball-up and float away in a random direction. Either way it is very bad if you can’t feed the propellant into your motor, doubly so if you’re working with an atomic rocket, as the propellant also happens to be the reactor coolant. It turns out that this basic problem still applies even if we are only try to pump the propellant instead of burning it. Basically the damn propellant is not at all compelled to move through the fuel lines. Gauge pressure within the tank is rather low, so you cannot 'suction' the fuel out.

It turns out that there are only a few ways to approach the problem. For instance, you can linearly accelerate by turning the rocket motor on to provide some false gravity. It’s definitely the most easy way to settle the propellant down where it belongs, but using this approach for propellant transfer is wasteful, needs a tricky load-bearing hookup for the transfer line, and changes your orbit in unwelcome ways to boot... and in the case of the RNSs you don’t want to light that Jool thrice-cursed nuclear thermal candle any more often than you absolutely have to. For the propellant to properly settle you need around 2E-3 g minimum of linear acceleration, and since the fuel transfer takes quite a while to complete (say 10 hours for this low acceleration... hey we’re working with laughably small fuel lines here... the tyranny of the rocket equation remember?), you’re looking at 700 m/s or so of good propellant being flushed down the toilet. You can land on the Mun with that much delta-v! Since we are in effect moving a whole space station (the ‘hot rod’ RNS plus the propellant depot), 700 m/s is a lot of propellant. Also, we have to do the burn perpendicular to the orbital plane so that we don’t accidentally deorbit or fly off into space. It would be so much easier if the KSC engineers could figure out a way to transfer fuel nigh-instantaneously but what can you do huh?

You can also use a pressure fed system, or one that relies on a mechanically contracted internal bladder, but these systems don’t tend to work very well with ultra-cold cryogenics, or they require infeasibly massive pressure tanks.

Alternatively there is dielectrophoresis. Cryogenically cool propellium is a dielectric material, so it can be polarized and repelled by an imposed electric field into a collector. The advantage here is that there are no moving parts and the required machinery is low-mass. Unfortunately it’s incredibly slow. Propellant transfer using dielectrophoresis makes refuelling via linear acceleration seem as quick by comparison as if it was a hyperactive toddler with a fire hose, ADD and too much coffee pumping the propellium... bring a book.

Lastly there’s angular acceleration, wherein you use the RCS to put a spin on the ol’ can and turn the whole prop tank into a centrifuge essentially, with its inside diameter being made up of a mesh of capillary channels. You get a little dizzy, but it works. In the case of the propellant depots though the axis of symmetry for the depot is not the same as the axes of rotation for the individual prop storage modules, so the propellant is spun on a bearing inside an internal double hull instead. When one of the modules is spun up for transfer or thermodynamic venting the depot would begin to rotate in the opposite direction if not for a huge moment control gyro being used to compensate. No rockets required here but mechanically this is the stuff of engineer’s darkest nightmares. Since the RNS only has passive cryogenic storage it has to use the angular acceleration approach for thermal management on extra long duration voyages (by venting higher-energy propellant vapors).

Mission now complete, the RNS pulls up to the gas station.

Edited June 18, 2013 by architeuthis

[wminsing]

Glad to see this thread back! One of the most inspirational/informative threads we have.

-Will

[architeuthis]

Thanks Will:)

[Itsdavyjones]

Use some image sharing website, can't see the images.

[architeuthis]

Edit: Ignore this post:)

Edited June 27, 2013 by architeuthis

[Tankaa]

It seems to be working fine for me, and you've done a good job with translating those old design studies into flyable craft for the Kerbals to tool around in.

Will we get to see what the Kermunists have been working on at some point? (Maybe if KSC2 is ever implemented as a proper launch site and a few mod pods proved suitable.)

[architeuthis]

It seems to be working fine for me, and you've done a good job with translating those old design studies into flyable craft for the Kerbals to tool around in.

Will we get to see what the Kermunists have been working on at some point? (Maybe if KSC2 is ever implemented as a proper launch site and a few mod pods proved suitable.)

Thanks Tankaa:) I think I will leave the Kermunists as a project for some other enterprising person to tackle. For one thing my specific vision is to recreate, with some artistic license, NASA's 1969 Integrated Program Plan and I want to focus on that. I think it would be really cool if someone else wanted to follow the Soviet side of the alternate history though! Also, I tend to prefer using stock parts (I would love it if squad would add more 'soviet' looking parts to go along with the Stayputnik in future expansions).

That said you started me thinking and there were a lot of remarkable parallels between the Soviet Union's future space vision, if they could be said to have a single one, and NASA's IPP.

• The MKBS (Multi-module Cosmic Base Station) was remarkably similar to the NASA space base. It was in the 250-300 tonnes class, with artificial gravity sections and was powered by 2 100kW nuclear reactors mounted on an extensible boom. The NASA Space base would have been a bit bigger; in it's completed form it could have supported up to 50 astronauts whereas the MKBS, in its most grandiose form, was designed for not more than 30.
  
• Soviet space planning was much less unified and coherent than NASA's (believe it or not). NASA’s structure was relatively top-down and centralized, but in Russia by contrast there were a number of competing design bureaus effectively each persuing their own independent space programs. The MKBS was part of the MOK (Multi-module Orbital Complex) which was an ‘integrated plan’ of sorts for a low-earth orbital infrastructure. It was the brainchild of the OKB-1/Korolev/Energyia bureau.
  
• The MKBS was to be serviced by a fully reusable space plane. As originally envisioned this was to be a SSTO derived from N1 first stage if you can believe that, but the Soviets were also developing multi-stage carrier-space planes similar to those initially planned by NASA, though their program started somewhat later. Of course after the demise of the N1, there was the Buran/Energyia program which got going a few years after the Space Shuttle.
  
• The MOK also called for an autonomous manned station in geosynchronous orbit similar to the IPP.
  
• The Russians essentially ceded the Moon and cis-lunar space to NASA by 1972 (ironically right as the Apollo program was ending), and chose to focus on LEO instead. As a consequence they racked up much more substantial achievements in the realm of space stations than NASA did. However they did have some plans for manned Mars missions. The MEK (1969) mission design used nuclear-electric propulsion rather than an NTR as in NASA's plan. Of all the Soviet plans this was the best developed.
  
• There was also the MK-700 Aelita Mars mission design (1972) which used a NERVA style solid-core NTR. While not as far advanced as the Project Rover precursors to NERVA, the Soviets were able to complete some working hardware such as the RD-0410. They ever were in the preliminary stages of desinging a gas core NTR with isp in the 2000 seconds range. Again, as with space planes, Soviet technological development in this lagged behind NASA's. When it was determined that the Americans wouldn't be going to Mars after all Soviet funding for NTR also dried up.
  
• There were several competing architectures for Moon bases. There was Barmin’s DLB or 'Barminograd' which was based around the L3 spacecraft (the Soviet moon lander), but it was nevertheless a flight of fancy, even in comparison to the other bold space plans of the day. Chelomei’s KLE Lunar base would have used the UR-700 super booster instead of Korolev’s N1, but work stopped on this rocket when it became obvious that the moon race was lost.
  
• According to the plan there was even a modified Soyuz 7K with robotic manipulator arms to serve as a Space Tug for the MKBS (though it was not built to double as a Lunar lander like NASA’s space tug).
  
• As a whole the MOK was not as ambitious as NASA’s 1969 IPP. Like the IPP some elements of the plan ultimately did see the light of day (Soyuz, Progress, and Mir were the legacy of this plan, just as the Space Shuttle, and arguably, the ISS were of the IPP).
  
• Most of the Soviet plans rested on the N1 HLV, which being perhaps the ‘most kerbal’ rocket ever built, never actually made it to space in real life (but it did manage to create the largest artificial non-nuclear fireball in human history; 6.5 kt of TNT equivalent). Therefore most of these plans met their end with the last N1 in 1974. In comparison Nixon, and the apathetic American public, had quitely strangled the IPP by 1972.
  

Edited May 8, 2013 by architeuthis

[Specialist290]

I remembered this one from before the crash. It's helped inspire my own modular and semi-reusable space program at present. Glad to see it's back up and running again!

[Wait- Was That Important?]

...however the clever engineers at KSC have made ingenious use of a new breakthrough in theoretical physics which allows them to use ‘time acceleration’ to violate the conservation of angular momentum, which they then proceeded to do with much glee and reckless abandon.

I consider the violation of the laws of physics with experimental possibly universe-destroying mechanics to be a KSP pastime for me.

[Holo]

Where did you find those images? They look very nice.

[nyrath]

Hmm... That's odd, I can see them fine. They're hosted on google drive. Can anyone else see them?

Edit: as a test can anyone see this image? I think people who are logged into their google account may not be able to see the images...

I found that I could not see the images. I followed a link to one of them and wound up at Google Docs. There I was asked to log into my Goggle account. After than, then I could suddenly see the pictures.

[architeuthis]

I found that I could not see the images. I followed a link to one of them and wound up at Google Docs. There I was asked to log into my Goggle account. After than, then I could suddenly see the pictures.

Thanks nyrath. I've migrated all of the pictures to Dropbox now, which I hope means everyone can see them now. Also thank you for Atomic Rockets, your website strongly inspired this mission report besides just being generally awesome. I really hope that you continue to add to the site. I'm also very glad you've joined the KSP community:)

Edited May 8, 2013 by architeuthis

[architeuthis]

Where did you find those images? They look very nice.

Hi Holo,

I found most of them at the Marshall Image eXchange some others were culled from NTRS documents which are sadly no longer online [by the way thanks for that US Congressman Frank Wolf (R-VA), at least we can protect the vital national security interest of stoping Chinese citizens who work at NASA from having porn on their USBs].

[architeuthis]

Space Tugs: they are so useful! Look at this list of things they can do:

• Space station support, assembly, orbit keeping and payload transfer from shuttles.

• Satellite placement and retrieval from high energy orbits.

• Crew shuttle between different orbits.

• Munar orbit-to-surface-back-to-orbit crew and cargo transfer.

• Rescue missions!

• Small payload cis-munar transfer capability.

The current fad at KSC? Using Space Tugs as reusable launchers for robotic planetary precursor missions! Well, it’s actually not really so much a ‘fad’ per se, rather the green eggs and spam in a can to ‘science’ ratio being what it is, disgruntled Kerbal astrophysicists and planetary scientists threatened to visit dire bodily harm upon the mission planners unless they launched more robotic science missions. The planetary scientists, who inwardly worship the pure, impassionate logic of the machines, tend to see manned missions as a ridiculous waste of resources… Perhaps they’re right.

The robotic precursor mission profile offers yet another opportunity for the versatile Standard Space Tugs to amiably comport itself:

1. Probe boosted to orbit piggyback on a Valkyrie Mk3 SSTO shuttle.

2. Shuttle rendezvouses with a Space Tug in a minimum stable altitude orbit.

3. The Valkyrie shuttle deorbits to fly back to KSC.

4. Space Tug mates to the probe.

5. When there is an opportunity the Space Tug burns for a Hohmann transfer orbit.

6. As soon as the burn is complete the probe demates, the Space Tug tumbles 180~ and burns retrograde to lower its apoapsis to within Kerbin’s SOI.

7. At apoapsis, the Space Tug adjusts its orbit to aerobrake in Kerbin’s atmosphere.

8. Space Tug rendezvouses with an orbital propellant depot.

9. Sometime later the Probes make mid-course corrections.

10. Yet later still, the Probe aerobrakes into orbit at its destination planet or else performs a flyby.

When the mission planners first finished cooking up their harebrained robotic precursor mission scheme, some engineer helpfully pointed out that “the next launch window to Duna is…let’s seeâ€Â, fumbling for his slide rule, “uh… tomorrowâ€Â. From the general pandemonium which immediately ensued the double threat Pilgrim 2 orbiter/ Ragamuffin propulsively landed surface rover was the final product. Pilgrim 2 was actually not the first probe to visit Duna, as the lovingly named Vermilion Varmint probe which somebody had assembled out of duct tape and beer cans captured that honor a year earlier.

Pilgrim 2’s mission objective, besides being a golden opportunity to play with what is in essence a billion credit RC miniature-truck, was to search for clues to the presence of life on Duna past or present. This search yielded inconclusive results. But it was not without a herculean effort! Precautions had to be taken to prevent the spacecraft from carrying a cargo of microbial invaders from the planet Kerbin that might unintentionally contaminate the red planet. Prelaunch everything was carefully UV sterilized, and the engineers even took extra special care to not let anything untoward grow in the office fridge, as is usually wont to happen. After encountering Duna, aerocapture and braking took 7 orbits over roughly 5 days. The lander did a deorbit burn, discarded its heat shield and opened its parachute, but over eager mission controllers, in spite of the 12-second light speed delay, had been repeatedly mashing the ‘cut chute button’ at mission control. Suddenly chuteless, and still several hundred meters up, the terminal descent retrorockets fired, but having only 3 seconds of fuel at full thrust, what occurred was an accidentally textbook suicide burn. That Ragamuffin survived its landing, being the cobbled together rush job that it is, is frankly something of a miracle.

Exploring Duna takes teamwork; trying to optimize mass to the surface, engineers decided that instead of making a heavy and power hungry high-gain antenna required for direct communication with KSC integral to the rover, that the rover would instead depend on the orbiter for support. The Pilgrim 2 orbiter acts as a mothership for Ragamuffin and as a comms relay with Kerbin. Ragamuffin has a UHF transmitter and omni-directional antenna for downloading telemetry data to the orbiter, which then beams it back to the Spacebase, its relay satellites in LKO, and the big tracking stations on Kerbin’s surface. The Pilgrim 2 orbiter features an ultra-high bandwidth data rate: 1000 bits per second at opposition! Ragamuffin’s central computer ‘sleeps’ during the nights, because damnit its tired after a long day of space exploration, and also to help conserve power for keeping the critical heating elements alive that warm the rover during the long, frigid Dunan nights. The little rover would likely perish trying to weather a Dunan dust storm, however, should one arise.

Duna has so many anomalous features. A chain of what appear to be small impact craters lie centered on a great north-south axis canyon and its web of vein like channels and arroyos. Are they relics of an ancient orbital carpet bombing by fragments of a comet? What formed the datum maria, are they ancient seabeds dry for a billion years? By the fact that the datum maria have so few impact craters they must be extraordinary young by geological standards. Perhaps only 100 million year ago or so Duna had cold, sparkling oceans of its own. What caused them to dry up? Due to its small mass, Duna has a low escape velocity which makes it difficult for the red world to retain much thickness to its atmosphere. Given the low atmospheric pressures scientists had imagined that the Dunan sky would appear black or perhaps deep blue, but surprisingly the sky has a pink hue. It is thought that this is caused by extremely fine dusts suspended in the upper atmosphere. The orbiter’s first impression of Duna was of a heavily cratered world, implying the world has been geologically dead for eons and that the rusty surface rocks are incredibly ancient, perhaps going back nearly to the original formation of the red world. Duna’s moon Ike by contrast is odd in that it has so very few impact craters. More tests are needed.

Ragamuffin is currently investigating a medium sized crater near Duna’s North Pole, while Pilgrim 2 is currently walkabout visiting Ike.

The Vagabond 1 spacecraft was a Jool Flyby and Laythe Orbiter. This was the first mission launched of the robotic precursor program and among the last to arrive at its destination. The Space Tug booster did not have enough delta-v to return to Kerbins SOI and so it was expended for this mission. With its propellant tanks empty the poor workhorse was left to silently sail away from Kerbin into a lonely Kerbolorcentric orbit, there to remain... forever. This mission suffered from a regrettable series of poor design decisions. Because of the position of the docking ring fairing that Vagabond 1 required to mate with its Valkyrie shuttle and Space Tug carrier craft the maneuvering engine could not be placed along the main axis of the spacecraft. Instead the motor was mounted radially, and the heavy boom mounted RTG powerplant positioned to balance the center of mass. Nevertheless the thrust vector still ended up located along a line of action not passing though the center of mass, and this made the vehicle want to tumble wildly under thrust. Additionally the maneuvering engine’s asymmetry with respect to the probe core made for very problematic navball references. Several harrowing mid-course corrections were required since the Vagabond 1 had to ‘eyeball’ a star as a fixed point of reference for the probe core and then rotate with respect to it until the engine was pointed in the correct position. With the aforementioned torque acting on spacecraft, the difficulty of maintaining attitude during a burn without even the help of useful navball was basically a nightmare. Though solar power would have been technically more efficient for this mission, the RTG was brought along just to be safe (engineers can’t shake their primitive superstitions that solar insolation should drop exponentially with distance from Kerbol rather than linearly as has been repeatedly determined by experiment).

Jool is an incredibly alien object compared to more familiar rocky planets like Kerbin or Duna. The world is humongous: it holds 100 times the enclosed volume of Kerbin, and it exceeds the combined mass of every other body in the system by a factor of 16. It reigns over a solar system in miniature; several of its myriad of satellites rival Kerbal itself in size. Its dark and hugely turbulent atmosphere flows in an unending gale of slipstream velocities, plunging to murky depths truly unfathomable to the merely Kerbal mind. It is difficult not to wonder whether there is even any solid surface at all under those cold green clouds. Scientific instruments were unable to directly measure the temperature of the giant planet, but a value of between 30-80K has been estimated for the upper clouds based on the supposition that Jool’s escape velocity must greatly exceed the rms speed of gaseous propellium (which is believed to make up the bulk of the titanic green world’s mass) for the planet to not gradually boil off its atmosphere. It is thought that far below the outer layers of green chlorine… ...uh…chlorineium clouds, there exists a shell of metallic propellium congealed around a small core of incredibly dense exotic matter.

The light-speed lag problem compelled the engineers to push a number of technological envelopes for this mission. Unlike rudimentary self-test and repair electronic circuits used on previous missions, Vagabond 1 features a digital microcomputer, with a full 10kB of memory! These truly automatic probes will be able to ‘think for themselves’. Naturally, appropriate precautions are being taken to prevent a revolt of the robots against the {harsh taskmasters} REDACTED enlightened benefactors of KSC mission control. Considering the lengthy Jool transit time (229 days) the microcomputer will come with solitaire preinstalled to help it cope with the boredom. Telemetry is transmitted and command uplink is received via a 1-meter X-band high-gain paraboloid; it’s almost big enough to get signal on your TV antenna back home on Kerbin! Actually no, don’t get excited, the last sentence was a lie. Vagabond 1’s onboard thermoelectric nuclear power provides about as much power to the communications system as is needed to light a small lightbulb: 20W. At Kerbin’s distance from Jool, the power flux density from Vagabond 1’s transmissions is only 1.13E-18 W/m^2. If you had a parabolic dish the size of Kerbin itself it would take 82 years to accumulate the energy of released by a single burning match (it’s amusing to imagine a world sized antenna dish all wired up to a solitary AA battery). Therefore a phased array receiver equivalent to a 28 meter diameter parabolic antenna is required for good telemetry. The KSC engineers were heartbroken to discover that they couldn't use the dish to steal the Kermunists’s wifi.

Kerbal scientists were quite curious to study Jool’s hypothesized magnetic field and trapped radiation belts. It is thought that Foucault currents within the metallic propellium core of the world power a terrifically strong magnetic field which traps charged particles from Kerbol. Trapped, these cosmic rays clang around, tirelessly ricocheting of the interior of the great magnetic field and presenting a major radiation hazard to any would be gallant space explorers flying close by to Jool to aerobrake. Hence mission planners decided to ‘send the droid’, in advance of any future manned missions. We must feel some regret at the peril facing Vagabond 1: 54 million kilometers from home, alone but for a great and horribly ancient entity, a god who though totally ambivalent to the probe’s tiny existence, the merest lingering proximity to whom is death. And all the while forced listen to the eerie, soul scarring song of the alien world: radio noise resulting from colossal discharges of electricity in Jool’s upper atmosphere. Well… have fun!

Mission controllers, having been heckled endlessly by queries of “are we there yet†by the planetary scientists over the long transit were understandably restless at the prospect of a gentle capture and arobraking at Jool over 3-4 orbits, and subsequent aerocapture at Laythe. They opted instead for a direct aerocapture by Laythe with 8km/s relative velocity. What could go wrong? Much hull carburization later the Vagabond 1 orbiter found itself soaring high above the cloudless oceanic moon.

It was only when at long last the probe arrived that Kerbal engineers realized what it was they were forgetting: scientific instruments of any kind! Well, that’s not completely true, they did bring along a thermometer (thank god), a barometer and a ‘GRAVMAX Negative Gravioli Detector’; the planetary scientists were most displeased.

Vagabond 2 was an Eeloo flyby mission. Transit time for the Hohmann transfer was 323 days. Questions regarding the distant, Kerbol forlorn snowball abounded. Is Eeloo an escaped moon of Jool? Given its eccentric orbit does Eeloo’s albedo change as it swings by its closest approach to Kerbol produce a fleeting tenuous atmosphere? Also, how to explain Eeloo’s relatively large size; is it representative of the dark shroud of icy worlds though to exist far beyond Jool’s orbit?

What made this mission unique was its pioneering use of a 2-stage ‘mostly reusable’ mission design. Two Space Tugs are used in this mission profile. The 1st Space Tug in the stack burns till it has just enough delta-v left to return to LKO, whereupon explosive bolts on the launch separation fairing are fired and the tug burns retrograde back to Kerbin while the 2nd-stage tug continues the burn prograde. When the desired transfer orbit is achieved, the 2nd tug demates from the probe, which is left to continue on its merry way, while it follows its sibling down a long elliptic back to the homeworld. Compared to the Vagabond 1 Jool flyby, this mission profile expends roughly twice as much propellant but this is compensated by the fact that all of the Space Tugs were recovered to be reused another day, and we all know how important this reusability shtick is to the Integrated Plan. Frankly KSC engineers are baffled that this maneuver works without the tugs possessing a dedicated heat shield, but it is speculated that should a Kerbin aerocapture ever prove infeasible for some reason, a ‘hot-rod’ RNS could rescue a Space Tug stranded in a highly eccentric Kerbin orbit, though it is currently unknown how economical that this procedure would be. Mission planners are hoping to use this style of mission architecture as inspiration for a much larger scale manned planetary mission to Duna featuring outboard flyback RNS kick stages. After the Eeloo encounter flight controllers initiated a bi-elliptic sundive transfer which utterly fried all of the delicate deep-cold adapted instruments. “Uhhh…why were we thinking that would be awesome again?†On the bright side… literally… the spacecraft reached a velocity of 28 km/s at periapse as it swung by Kerbol.

Due to confusing mission naming conventions, Pilgrim 1 actually launched later than Pilgrim 2. This mission comprised a ‘mini-tour’ of the inner planets, being the very first gravity assisted multi-planet flyby of Eve and Moho. Eve is a world wreathed in enigma. Since the dawn of time Kerbals have gazed upon that bright morning star and wondered. Was Eve a sweltering, humid hothouse of continent swathing tropical rainforest and swamp? Was it a boiling hellhole crushed under the tremendous pressure of a world’s worth of evaporated oceans? Well, neither it turns out.

Eve is a deep indigo marble covered with what look like seas of liquid metal. This makes the planets lack of clouds easier to explain considering the lack of water oceans; given Eve’s relatively rapid rotation it was posited the world would poses a magnetic field that would keep atmospheric water from being ionized and blown away by Kerbol’s wind. But the shining metal oceans are tantalizing to say the least. Some have suggested that oceans are composed of molten blutonium. If this is true it means not only that you probably wouldn’t want to let the kiddies swim in it, but that the whole damn planet of Eve would be in essence one huge nuclear reactor!

Eve’s atmosphere, while dense, appears to be composed of inert gases, which sadly means no flying around with air breathing engines for future Kerbalnauts, unless the greatly missed Project Plutino nuclear-ramjet blueprints are retrieved from whichever Tartaruian hellwell an intern errantly tossed them in. The inert atmosphere also renders difficult an explanation of Eve’s perplexing purple color; afterall it might have been expediently explained as a result of some strange oxidization chemistry. Given the multitudes of organic chemical reactions that can produce a purple color, planetary scientists are very anxious for a follow up mission to include a surface probe.

At any rate Pilgrim 1 continued on to flyby sunblasted Moho. With the unprecedentedly low mission perkerbolion, of 0.38 KU, the spacecraft design had to somehow deal with the solar heating problem. Because the intense radiant energy flux from Kerbol at Moho’s orbit, the number of solar arrays needed (in theory) was one half to one eighth of those required at Kerbin’s orbit, but due to the questionable literacy of some of the engineers at KSC engineers the design requirements documentation was read upside down and double the number of arrays was installed instead… whoops.

To keep the heat from building up to intolerably high levels, the spacecraft was spin-stabilized such that its spin axis remains normal to the plane of the solar elliptic and therefore the solar panels present the smallest angle to Kerbol. Thanks to the magic of angular momentum, the spin stabilization would also help keep small torques from throwing off the probes attitude. That was the idea anyway, but unfortunately it was realized rather late that the solar panels rotate on bearings, utterly defeating this plan. Ah well. Anyway, for good measure any reasonably useful scientific instruments such as spectrometers, or magnometers were left at home as well, as is now the custom. Not even a proper telescope, alas. It does turn out that Moho is not tidally locked to Kerbol after all, so there is one mystery solved, though it does have very long days: only 1.3 of them in its whole year.

What does the future hold for robotic precursor missions? There is much enthusiasm for a ‘Grand Tour’ to the outer plants (here defined specifically to mean a mission that uses gravitational assist trajectories to make flybys of several plants during an alignment), perhaps to visit one of the heretofore undiscovered outer planets beyond Eeloo. While Hohmann transfer windows to the outer planets are frequent, (on account of their low orbital velocity Kerbin constantly overtakes and passes them), Grand Tour opportunities are far less so. There is also talk of a mission to visit the supposed ‘asteroid garter’ at 3 KU, but astronomers seem, leaving aside Dres, to be unable to locate any other objects out there bigger than dust specks. Of course Dres is the last planet that remains unvisited. A liquid metal sample return mission from the seas of Eve holds tremendous interest to the planetary scientists but the mass ratios required drive one to nihilism. Also, there is a general consensus that there needs to be far more ‘atmospheric probe’ (i.e. impactor) missions … planned ones that is … because they are awesome.

Edited September 3, 2013 by architeuthis

[Specialist290]

Nice to see this is up and running again

Hope to see some more manned missions soon!

[nyrath]

I have some specifications on the NASA space tug here

http://www.projectrho.com/public_html/rocket/realdesigns.php#id--NASA_Space_Tug

And don't forget NASA's concept of a reusable nuclear shuttle

http://www.projectrho.com/public_html/rocket/realdesigns.php#id--Reusable_Nuclear_Shuttle

[wminsing]

Great update, still my favorite AAR on this forum. I like the the idea of using the space tug as a reusable booster stage for interplanetary missions.

-Will

[architeuthis]

Thanks again Will:) I cannot take any credit for the idea, but I agree it's cool one.

Speaking of the Space Tug, nyrath your website gives a mass ratio of 2.3 (for a lunar surface mission), based on what I've read this is inaccurate. The Space Tug was one of the last of NASA's Integrated Plan (IPP) schemes to die, the last design document I can find for it is dated 1975, but I don't think they fully gave up on the idea until the Challenger explosion in 1986 (of course the design by then had transformed into the somewhat smaller OMV). Anyway the specs were pretty consistent from 1969 to 1975 and between the different bids put in by the big aerospace corporations; 29500 kg gross weight (the design constraint here was the assumed maximum payload of the Space Shuttle at the time), 3000 kg burn out weight and 1400 kg payload (delivered to and returned from synchronous orbit to 185 km 28.5 degree inclination standard low Earth orbit) gives a propellant mass fraction of .9 (sans payload) and R=6.7 with payload included. Even in 1969 design specs called for the airframe to be constructed of space-age graphite-epoxy composite. One RL-10 derived motor with a specific impulse of 470 s gave the tug a maximum of 8773 m/s of delta-v, a requirement which was defined by the synchronous orbit mission. The Space Tug, in essentially the same configuration, would have been used for Lunar surface sorties, though the documentation for that is somewhat confusing... because NASA realistically expected the Tug would mostly be used for moving satellites to synchronous orbit, the level of serious inquiry into the Lunar mission role was at a substantially lesser lever than that of the synchronous mission mode. The first designs were an in-house NASA space tug and one designed by North American Rockwell. After the demise of the IPP General Dynamics, Boeing, McDonnell Douglass and Martin Marietta submitted bids, and though the lunar lander mission was kaput the overall design specifications remained very similar to the IPP era ones, particularly in terms of mass fraction, wet mass and specific impulse. Some of the IPP documents assumed a mass fraction of .8 whereas other assumed .85 or .9. The is a lot of variability in the payload to lunar surface numbers, because of sensitivity to the assumed mass fraction. Also the Space Shuttle ended up actually being a bit more powerful than originally assumed in 1969; the big bird was theoretically capable of hauling 65,000 lb payload gross weight, so the later tug designs are a bit heavier than the IPP era ones which had assumed a somewhat smaller orbiter. The lunar mission profile would have the tug Hohmann transfer from a 111.2 km circular orbit (60 n.m., the orbit of the Orbiting Lunar Station) down to about 15 km above the Lunar surface before burning off its tangential velocity. This mission profile was very similar to the one used by the LM for the Apollo missions, which is why the Space Tug was fittingly also referred to as the LM-B. One RL-10 only gives enough thrust for a 'lithobraked' terminal descent mode, so with additional motors added (4 in total), plus the requisite landing gear it is likely that a Lunar Space Tug would have a lower mass fraction than the .9 NASA doggedly insisted upon. This mission requires about 2200 m/s delta-v and so the we get a mass ratio of R=1.6. If we reserve enough propellant for the Space Tug to return and rendezvous with the OLS, unless I've fubar'd the algebra (certainly a possibility), then this would've enabled the Space Tug/LM-B to bring 38,500 kg of cargo down to the lunar surface, which is in the specification range examined by Bellcom in 1971. The NA Rockwell designs would have had disposable propellant drop-tanks to enable an even heavier payload capacity. If we assume the more conservative numbers (λ=0.8, Isp=460) we end up getting a surface payload of 17,200 kg for the unmanned tug (with 2900 kg propellant reserved for the return trip), or 12,000 kg for a tug with a 3200 kg crew module (and 4900 kg reserved propellant). Naturally if all of the propellant is expended on the descent a substantially larger payload is allowed: 24,000 kg total.

Since the tugs would be delivered and returned from LEO by the Space Shuttle, the tug would have to land with empty propellant tanks (after all can you really blame them for not wanting to reenter and land with 26,000 kg of rapidly warming and highly explosive LH2 riding shotgun?) This made for some spectacularly hair-raising Space Shuttle boost phase abort modes, venting the hydrogen in-flight during ascent...

Edited June 9, 2013 by architeuthis

[architeuthis]

The administrator entered the office break room with great stealth. Menacingly brandishing a meter stick, the administrator gestured violently towards the chalkboard with a master schedule for the Integrated Plan. No one speaks. An atmosphere of baffled horror pervades the room; one engineer's donut in hand poised in still-life tableu at the moment before biting, mouth gaping wide. The administrator casts a fierce gaze about the room before leaving as suddenly and silently as he had entered. One engineer peering at the scrawled chalk though his thick plastic framed glasses, is the first to break the silence. Reading the notes for mission year three he utters

"...does that say '100 men in LEO’? Assuming that's not just the name of an obscure adult film, we are way behind scheduleâ€Â.

So with the advanced mission planners already bored with the old Spacebase design engineers began work on a new, bigger and better Spacebase. The new design will make use of the newly introduced Clamp-O-Tron Sr. as well as the PPD-12 Cupola Module with the core being made up of standardized SSM modules. The Clamp-O-Tron Sr. allows for a substantially more rigid docking of the large 2.5m SSMs enabling a truly modular approach to space station design. As equipment becomes obsolete entire modules can be straightforwardly replaced by shiny new ones shipped up from Kerbin. Thus the Spacebase can constantly renew itself rather than being deorbited wholesale when is approaches the limit of its service life. Also should lawmakers ever find a way to throw off the budgetary shackles of the space program, a modular system is an inherently more fiscally flexible one. This new Spacebase will feature downright swanky accommodations for up to 38 Kerbal astronauts. There will also be two sets of docking trusses for free-flying experiment modules.

The Cupola modules will take advantage of the Spacebase’s scenic new 190 km orbit. In theory this will also mitigate the heretofore unobserved effects of atomic oxium corrosion, and atmospheric drag on the space station. These KSC engineers are a superstitious lot.

With the announcement of the new project the ever persistent din of demands for artificial gravity is again heard. Though scientists would prefer pure free fall for their experiments, to placate the artificial gravity zealots the new Spacebase will be built around a central hub with RCS thruster ports positioned such that they can spin the station about its long axis. Concerns regarding the vexing lack of bearings which would allow the habitation modules to be spun independently of the hub were brushed aside. Ideally the hub would be non-rotating for ease of docking, and the furthering of zero-g science. With the station rotating at 4.5 rpm, the centrifugal acceleration at the ends of the roughly 13m long attached Cupola and Hab modules is enough to simulate gravitational acceleration of 2.94 m/s^2 : Duna’s surface gravity. Just don’t try to use the urinals on walls perpendicular to the spin direction, as you will find your accuracy somewhat diminished courtesy of Coriolis acceleration. The KSC experimental physics lab’s ongoing experiments with time acceleration leave the potential station inhabitants with a feeling of unease however. Perhaps unease is too modest a word. Basically, the instantaneous angular deceleration which must occur when the Spacebase ceases spinning stokes primal fears in the Kerbal astronauts of horribly grisly blood splattered death on the interior walls of the SSMs. Again, primitive superstitions die hard. Regardless, scientists have not detected any adverse biological effects on the body of the Kerbal astronaut due to prolonged stays in a zero G environment, so perhaps this particular experiment can wait… for now.

Engineers were initially divided between two alternative space station designs. One was for a high-power station with four nuclear power systems mounted on two booms and a single large hab module whereas the other would have a much longer zero-g core section for experiments and manufacturing activities as well as at least four hab modules with artificial gravity. Eventually the quandary was resolved in favor of the second camp.

How to provide adequate power this expanded Spacebase? Well, nukes naturally. Was that really a question? And we are not talking about scrawny little RTGs here either, but honest to Heinlein Space Nuclear Reactors. Nuclear has big advantages over solar for space applications: it’s potentially scalable to very high power outputs drastically above what’s practically achievable with solar, it’s not dependent on Kerbol-angle or occultation period, and it’s not degraded by trapped Van Allen or solar radiation. The real question here is what type of electrical conversion process to use. Heat pipe thermoelectrics, the Brayton cycle and thermionics all appear to be contenders.

Using the thermoelectric approach heat pipes are used to extract thermal energy from the core and transport it to electrical conversion equipment. The heat pipe is a tube containing a working fluid that is vaporized in the heated end and liquid at the electrical converter end. A wick in the flow path along the tube wall returns the liquid by capillary action to the reactor. Thermoelectrics at the end of the heat pipes generate electricity on the same principle as the venerable RTG. Additional heat pipes form radiator panels which remove waste heat from the electrical converters. This reactor architecture requires no moving parts, but thermoelectric generators have laughably low efficiency and generally do not scale well. You wouldn’t want to use these for your multi-megawatt ion drive Duna missions, and for similar reasons the KSC brass refuses to consider the technology for the Integrated Program on grounds of that most hallowed of guiding principles: ‘moar power’.

Next up are thermionics. In a thermionic reactor electrical power is produced by direct conversion of heat to electricity, essentially by boiling electrons from a hot cathode surface to a cooler anode collector surface. Since this is technically a heat engine it is limited to something below Carnot efficiency but it is still substantially better off than a thermoelectric generator. Other advantages to this approach are that they work at much higher temperatures than thermoelectrics, they are compact and they don’t have pesky to maintain moving parts. High temperature radiators with eutectic NaK liquid metal working fluid are required to remove the large amounts of waste heat generated by the reactor. But there are a couple of problems with thermionics. One is that if your thermionic cells are interior to the reactor the then they tend to become embrittled by neutron flux. Also the heat may cause warping in the gap between electrodes; you can avoid this by cladding the surfaces with refractory materials but then you pay a penalty in voltage. Another issue is that it is difficult on general principle to wrangle both high current and high voltage out of thermionics.

Lastly there is the Brayton cycle. Similar to the more well known Rankine cycle, in the Brayton cycle a working fluid is driven through an adiabatic compressor to the reactor which heats it. The single-phase working fluid is free to flow so the heating in the reactor is a constant pressure process. The heated high pressure working fluid drives a turbine before being run through a heat exchanger to discharge waste heat. The Brayton cycle has higher efficiencies by far than either thermionics or thermoelectric generators but vibrations from the compressor and turbine may ruin your fragile zero-g science experiments. Alas.

Because it is difficult for a space station to maintain a constant aspect with respect to many orbiting bodies at once (Docking ships, distant satellites, free floating experiment modules, EVA’d Kerbals, etc.) the reactor will need a big side shield in addition to the requisite shadow shield. Lithium hydride is used for neutron attenuation and tungsten for gamma attenuation. But who’s afraid of a little radiation?

The engineer’s endearing enthusiasm for nuclear power aside, research is still ongoing into space nuclear power, and alas the technology remains immature. Therefore the Spacebase will be powered by an array of 8 RTGs producing less than 2kW electric in total, with the SSM core’s Gigantor solar array on hand for auxiliary power. Better get used to taking cold showers boys! Oh and don’t forget to turn off the lights when you leave a room!

Lament and let us sing a requiem for the Dream of Space Nuclear Power!

The new generation SSM on its way to orbit.

The Space Tug seconday payload partially disintegrated during boost.

Cupola modules being boosted on a standard HLV stack. Built to lift Rockomax Jumbo 64 propellant tanks up to high orbit, the HLV is ludicrous overkill for such a light payload. At some point a standard design for a medium lift launch vehicle needs to be developed...

Spaceman Lendo Kermin preparing to complete the final rendezvous and docking with the growing Spacebase.

Artificial-g Hab modules waiting on the launch timer.

Bill Kerman inspecting the space station hull.

Vertigo...

A HLV streaks upwards into the starry path of the galactic elliptic, carring power modules and auxiliary propellant tanks.

With the power modules docked the station is now 'fully operational'.

Perhaps it’s a good thing that the Nuclear Reactors didn’t work out after all, intrepid Spaceman Danberry Kermin would be getting quite a sunburn right about now…

A Valkyrie Mk3 SSTO Shuttle ferrying crew to the station.

[Designer225]

Hmm... That's odd, I can see them fine. They're hosted on google drive. Can anyone else see them?

Edit: as a test can anyone see this image? I think people who are logged into their google account may not be able to see the images...

Putting pictures on Google Drive does not do you any good. That is a link.

http://drive.google.com/uc?export=download&id=0B5irBl_D7OtgSlV6RnhPQUZNcXM