Primer & Results of a 3-track
Mission Control™ Workshop
at the '93 Huntsville ISDC
Peter Kokh* with Mark Kaehny, Bill Higgins, et alii
All illustrations by Peter Kokh
Workshop "Primer"
For a moment after having just been asked to chair a 2 hour "Workshop" session on "Asteroid Base Design" at the upcoming '93 International Space Development Conference in Huntsville, I had the sudden sense of dangling in space weightless without any orientation or reference to up or down, fore or aft, left or right. For as most MMM readers must realize all to well, the word "asteroid" umbrellas a lot of objects dissimilar in physical-chemical-mineral makeup and widely ranging in both size and orbital environment.
On the one hand there is Ceres, a real mini-planet in its own right. Named after the Roman goddess of grain, it lies in the middle of the Main Asteroid Belt, yet in size, if not composition, it is quite atypical. Are we here talking about a Permanent Main Belt Center on Ceres? Or on somewhat smaller but still respectably sized Pallas or Vesta?
At the other end of the scale, we have irregularly shaped mountain-size "astrochunks" that as a rule slip by undetected unless they are in unusual "Earth approaching" orbits and in fact wander within a few million miles of the Earth-Moon system. Are we talking about a Mom & Pop Operation Shepherding a Small Astrochunk into Earth Orbit with the help of a Mass Driver? Often ore-enriched, small enough to be mass-driveable, these rogue mountains offer the earliest opportunity for the return of asteroid resources to the vicinity of the Earth-Moon - L5 System. We should be able to find many of these mineral-rich objects in orbits handy to Earth. They would require comparatively modest fuel expenditures to reach - or to coax into stable parking orbits in Earth-Moon or Earth-Sun Lagrange point areas.
In between are many thousands of bodies ranging from potato-shapes a few miles in cross section to spheres a couple of hundred miles in diameter. Are we talking about a Mining & Shipping Outpost on a Mid-size Asteroid such as Gaspra, recently scanned by the Jupiter-bound Galileo probe? Middle-size asteroids are too big to alter their orbits by mass-drive but with metal- or volatile-enriched compositions that can be mined, the bounty to be shipped Earthwards. Ida and Gaspra examples. This group includes Earth-approachers like Eros and Ganymed as well as Main Belt denizens.
Each of these three scenarios offered very different set of starting points and constraints for "Asteroid Base Design". It instantly seemed clear that all three were worth pursuing. And so we put together a 3 page "primer" for those intending to participate in the Workshop, mentioning whatever we could think of that was intelligent and might be relevant about each of the three scenarios. If we had enough participants, we would break up into three groups, each "brainstorming" a radically different kind of asteroid "base" starting with the givens and constraints listed in the primer, and going - who knows where?
This strategy could not have worked out better. We had 20-some registrants and after a few introductory remarks were able to break into very even groups of 7-8 brainstormers apiece. Adopting three corners of the room, each group began spirited discussion. Eurekas and laughter and excited talk could be heard from all three tables throughout the hour and 20 minutes arbitrarily available before I called a halt and asked the leader of each group to come to the front of the room and report to all what his group had discussed.
Without exception all three group reports were excited and exciting. Each table uncovered unexpected considerations that affected the direction of their design recommendations, each had come up with surprising and ingenious solutions to the problems they had tackled. After all the reports were heard, we gave each other a rousing round of applause. The Workshop was a great success in itself, and more importantly for each of the participants, perhaps the personal highlight of the ISDC.
Group 1: A Permanent Main Belt Service Center on Ceres
Starting Point: Consider:
Ceres, with a diameter of 1000 km or 600 miles has a surface area equal to all of the continental U.S. west of the Mississippi. Pallas and Vesta each have as much surface as the U.S. east of the Mississippi. They are small by Earth-Moon standards, but not insubstantial!
The gravity on Ceres and denser Vesta is about 1/6th Lunar standard or about 3% Earth-normal. Enough to be a mechanical assist and keep things in their place, but possibly below the threshold of impact on the human physiology. I.e., as far as the functioning of our bodies are concerned (mobility aside) the environment there may as well be "zero-G".
Synchronous orbit lies about 782 km or 486 miles above the surface of Ceres.
Ceres' orbit within the Main Asteroid Belt and the swath, in relationship to Ceres' position, in which we'll find asteroids that will orbit in formation with Ceres for many decades.
If the stats for the first 100 asteroids to be discovered are typical, 44% have orbital periods within 10% of Ceres' so that a third of these, almost 15% of all Main Belt Asteroids lie within 60° of Ceres at any given time and remain there for fifteen years or longer before drifting out of range. Some known asteroids (e.g. Pallas, Thisbe, Laetitia) will orbit in formation" with Ceres for centuries, even millennia. Much time and fuel energy may be saved by not having to exit Earth, Moon, or Mars gravity wells to maintain and resupply mining operations in the Main Belt as opposed to using a mini-grav well in the belt itself, say on Ceres. The fuel energy savings can be banked or spent on faster than minimum trajectories (acceleration and deceleration) to shorten trip times.
Ceres itself is a carbonaceous chondrite type, and should have a volatile component of about 20%. That means water of hydration and/or permafrost. This will be a blessing, as a resource, but possibly also a bane, as a construction obstacle. The exact proportions and makeup of its hydrated silicates, metal oxides, and permafrost water ice awaits an orbital prospector with a gamma ray spectrometer. Even if the settlement is established and planned as a Main Belt Service Center to facilitate more profitable mining operations on outlying smaller and more ore enriched bodies, it will be logical to do some mining on Ceres itself to provide the building materials out of which the settlement is to be made, and provide the bulk of its ongoing consumption uses.
Ceres lies 2.77 times further from the Sun than Earth-Moon and so if Solar Power is to be considered, keep in mind that collectors sized to provide a given amount of power would have to have an area 7.7 times 'normal' size.
Your Mission: Explore, list, and rate options:
> Should at least part of the outpost settlement have higher Lunar-standard artificial gravity, a level high enough to prevent physiological deterioration beyond a Moon-proved acceptable level? If so, rate these options. Are there others:
A Gravitrack*: part of the habitat area is a Mag-lev "train" on an appropriately banked circular track on the surface, or in a tunnel for shielding.
A Maypole*: part of the habitat is tethered to and spun around a pylon. The Pylon has to be tall enough (or the tether has to be tension-reelable) so that the habitat can come to rest on the surface periodically for boarding and deboarding, and for expansion, maintenance, and re-outfitting.
An Elevator-tethered Synchronous orbit (see specs above) Torus or Cylinder.
Distance to scale of orbital Sync Port above Ceres surface, showing elevator/tether and counterweight. Many of Ceres' port functions will be more efficiently conducted at Sync Port.
All of these would be combined with surface mini-g installations and facilities completing the settlement. If such an artificial Lunar-standard gravity facility is provided, what should settlement functions and areas be on board and what should be on the non-gravity-enhanced surface? Habitat areas with sleeping and off-hours functions? Recreational facilities? Industrial facilities, or at least some of these? Educational, Judicial, and Administrative facilities?
> What are the power options available, and how would you rate their feasibility and expense? Solar? Nuclear fission? Helium-3 fusion? Other options?> What types of building materials could be produced from Ceres' own resources? Besides metals, ceramics, glass and composites, and concrete, are cryoplastics, serviceable in low temperature zones, an option?
> Besides mining, processing, and manufacturing for local needs, the settlement should serve which specifically Main Belt Central functions? A wide range of prospecting and mining activity within the formation-keeping sector asteroids.
• Outfitting, resupply, maintenance and repairs (of ships, drivers, habitats, CELSS systems)
• Warehousing
• Courts, assay offices, mining/extraction/processing R&D
• Hospital, prison, trauma and chemical-abuse rehabilitation facilities
• Boarding/day schools, eventually a university
• Shopping, entertainment, radio, telecommunications social mixers, restaurants, bars, brothels, etc.
• Home port for circuit-making "trader general store ships"
• Agriculture: for own needs and export to outlying outposts that can only provide a demoralizingly low portion of their own food needs.
• Processing, manufacturing, based on both domestic and incoming raw materials, some for local consumption, some to sell back to asteroid boondocks, some to sell to Inner, Outer System markets
Architectural Considerations
> A different suite of building materials (clays, hydrates, water available)than that appropriate for the Moon .
> Permafrost as a potential unknown construction problem
> 3% gravity (19% Lunar standard, 8.3% Martian)
> Regolith shielding overburden has negligible pressurization compensatory value (a bit more than 1/5th that on Moon)
> Transport and personal mobility problems in mini-gravity: pedestrians, vehicles, etc.
> Ceiling heights in mini-gravity, hand holds and railings, moving grab-on cables, etc.
> Fitness considerations:
• Podokinetics (luxury items powered by foot pedals etc.), isometrics, and traditional exercise
• Gravittrak or Maypoles: "sky-side" shielding must be provided (integral, under ramada sheds, or?)
• Elevator-tethered space settlements in synch orbit Gravid space for work, leisure, or sleeping?
Ceres' "day" or "sol" is 9.08 hours long. This could be "rationalized" in two ways. The first option is a two "date" cycle covering 5 periods and would yield "dates" of 22 hrs. 42 min. The second 'improved' option is a three date cycle covering 8 periods giving a "date" 24 hrs. 12.8 min. long. Either is sufficiently close enough to the standard day to work reasonably well. The second option comes much closer, but the varying way the lighting cycle lines up will be harder to get used to. See graphic, top of column 2.
* NAME POOL: Ceres was discovered in Palermo, Sicily by Giovanni Piazzi, on the first day of Century Nineteen. The mortal through which the Roman goddess Ceres passed her agricultural secrets to humanity was Triptolemus.
WORKSHOP RESULTS: Group 1
GROUP: Peter Kokh, Tomas L. Gonzalez, Joseph S. Kirlik, Julius M. Martin, Peter Palumbo, and Bryce Walden.
We spent some time better defining which functions the Ceres Settlement* would fill, and of these, which were appropriate for Ceres' low mini-gravity, which would be better placed in a surface artificial gravity environment, and which would best be filled in an elevator and pipeline cluster tethered synchronously orbiting space facility, the Sync Port", 486 miles above the main Surface Settlement.
ORBITAL SYNC PORT
SURFACE, FIXED (some within the main settlement area, some without it)
SURFACE, GRAVID (Artificial gravity via Maypole and/or Maglev facility)
Simply by better defining what activity or function most appropriately goes where, a much clearer picture of the Ceres Settlement Complex arises. And only with that in hand are we ready to begin looking at architectural considerations.
Next, as the design possibilities for artificial gravity habitat facilities in orbit are already fairly well explored, we spent the balance of our time discussing the engineering and design options for providing artificial gravity on the surface.
Schematic Design: Main Ceres Surface Settlement Complex
KEY: 1 auxiliary crater rim
surface facilities, elevator and corridor to
2 main crater bottom natural-G installations.
3 Maglev Habitat areas with 'standard' 1/6th G lunar gravity
shown 'riding' two crater slope rails, with third support rail for
deceleration to stop for maintenance and adding new modules
4 "Maypole" pylon and bedrock anchor;
5 counterbalanced pair of shuttle modules (original 'starter'
habitat modules prior to building the settlement expansion Maglev
habitat facility), shown both at rest docked with main crater bottom
facility and at Maglev matching velocity for docking and transfer of
personnel especially at shift change; 6 shuttle tethers which
lengthen by reeling out as centrifugal force increases; 7
cantilevered shielding retainer lip; 8 undisturbed soil and rock; 9
shielding soil.
Designing a finished, mature stage complex for Ceres without attention to how it might develop to that final level of complexity as the population grows from say a hundred or so to several thousand, would be an exercise in building sand castles. Thus there is no decision to be made between a Maypole-tethered artificially increased gravity habitat and a Maglev-based facility. Both are needed, and appropriate, at different phases of the settlement's growth and development.
First a suitably-sized crater must be chosen, straddling Ceres' equator, or as close to it as possible. Inside, a Maypole-based facility would be easily the simplest to install and to engineer and yet be quite adequate for initial foot-in-the-door population levels, especially if it is used just for dormitory purposes, to give everyone some fraction of the day at higher than Cerian mini-G levels. Once the initial "starter" settlement complex is in place and population growth is called for to realize the full potential of this Main Belt center of operations, a Maglev "Gravittrak™" Facility can be built.
When the first Gravittrak car modules are in place and ready to use, the original Maypole-tethered dormitories can be transformed into shuttle transfer cars to ferry personnel to and from crater bottom areas of the settlement, and by transfer there to other outlying surface installations. These shuttles are best operated in counterbalanced pairs, even if at first there is only one Gravittrak module operating. Shuttle service is needed before and after shift changes especially, and perhaps at some scheduled intervals in between.
The Maglev Gravittrak-based complex can be grown sausage-link style from one module to several, up to a filled ring, as the total population on Ceres grows perhaps to several thousand. To make sure there is enough capacity for growth, the car modules can be double or even multi-decked. But the circumference of the Gravittrak being perhaps one to several kilometers in length (depending on the speed of the modules on the track, or rpm), there should be ample room to grow before it is necessary to expand further by building an additional similarly architectured settlement at another site. As the Gravittrak modules and population grows, it will be necessary to add additional and larger capacity Maypole shuttle cars.
The individual car modules might be slung each in a pair of Mag-lev track riding suspension rings, within which they could freely rotate from a highly inclined orientation to one perpendicular to Ceres' surface as they are decelerated to a stop for maintenance work or for coupling additional modules. Normally operational pressurized vestibulation of the modules to one another for passage between them might be inactivated during acceleration and deceleration at such times.
Gravittrak car modules could be clustered into three "villages" according to shift. Each shift could then use artificial lighting so that its members work 'by day' and sleep 'by night'. This arrangement could also simplify shuttle docking schedules. These three villages could either be physically linked or spaced out at 120° intervals along the Gravittrak.
Of course, there can be no protruding surface installations anywhere within the crater that would interfere with the operation of the Maypole shuttles. Such things as radiators and antennae are best located on the crater rim anyway where lines of sight are less restricted. Initial antennae will be relegated to auxiliary standby usage once the Sync Port is built overhead in orbit and the elevator-pipeline-cable-tether complex is in place. For then communications will be routed by cable to orbit-based relay antennae.
On the crater rim, there needs to be a Depot with multiple docking ports for surface transportation to outlying facilities such as mining and processing plants, He-3 fusion plant, and of course to the settlement's auxiliary spaceport used for spacecraft large and small having a reason or desire to land directly on Ceres' surface rather than dock at the Sync Port.
Attention was also given to modes of personal mobility in Ceres' low mini-gravity environment. This can be taken up separately. In sum the workshop's Ceres' team was quite excited about its satisfying brainstorming results. Others are free to use any of the above as a basis for further work. PK
Group 2: A Mining & Shipping Outpost on Mid Size Gaspra
Workshop "Primer"
Starting Point: Consider:
There is some level of false expectation about how rich the ores might be on various asteroid bodies. This hope comes from the now discredited notion that the asteroids are the debris of some former hapless planet that blew up between the orbits of Mars and Jupiter and that had previously differentiated into an iron rich core and mantle and crust areas. At the same time, it is clear that some of the original "planetesimals" did undergo some sort of differentiation, if not from the heat of radioactive uranium and thorium etc. as on Earth, which have relatively long half-lives and take a long time to heat up the masses in which they are embodies, then possibly something with a shorter lifetime such as radioactive Aluminum 40. This seems to have occurred on Vesta at least. We also have evidence from meteorites that some parent asteroid bodies are ore-enriched. Some of these will be too big to herd back Earthwards by mass driver.
These midsize bodies will have negligible or 'micro'-gravity environments. Gravity there is enough to keep undisturbed items in place, but insufficient to facilitate human locomotion, or to be much of a mechanical assist for mining and processing. If people are to be stationed there for any length of time, some sort of appropriately sized rotating facility in which they can spend a routine portion of their time may have to be provided if their physiologies are not to adapt beyond recovery to the effective absence of gravity.
Small outposts will likely consist of prefabricated modules, and the use of local resources for add-on construction needs requiring low performance will be minimal.
Your Mission: Explore, rate (discuss, vote, review), list options:
> Shielding requirements using local regolith soils.> Surface gravitrack or centrifuge or tethered rotating structure to provide at least part time artificial gravity?
> Should a Mass Driver be employed anyway to make use of processing tailings to slowly "improve" either the orbit of the asteroid or to make its rotational period more convenient?
> Landing facilities for visiting resupply and trader ships or or orbital rendezvous?
> What is an ideal population size and gender and age mix and talent pool considering the tasks of such a mining/shipping outpost? Given that, what sort of facilities and functions ought to be provided for education, recreation, etc.
> Given all the above, what further design constraints do you see? What are the design options and your recommendations?
Workshop Results: Group 2
GROUP: Bill Higgins, (moderator) Lucien Faust (Author of the report that follows), Clarice Lolich , David Kalman, Welburne D. Johnson II, M.D., and Jay Robinson.
Assumptions:
1. Gaspra (or similar target asteroid) has been probed and determined to have exploitable volatiles, worth mining.
2. Gaspra resembles a potato, about 19x18x12 km, i.e. about 1800 km3 volume; virtually negligible gravity.
3. Gaspra has a "slow" rotation around one major axis, and little if any wobble about any other axis.(Bill Higgins brought a handbook, but time did not permit a thorough review of its entry on Gaspra. [Ed. actually, little was known prior to the Galileo flyby, i.e. when the book was written.])
4. Travel time to Gaspra, about 18-22 months (8 months via nuclear vehicle proposed by Robert Zubrin'). No calculations were done at the workshop.
5. Supplies are available from cislunar vicinity, and will not all have to be lifted out of Earth's gravity well.
Mission Needs:
Crew - about 18 people, to include many skills, manpower, 3-shift rotation as needed (6 on duty, 6 off duty but on stand by, 6 asleep - this allows some off-time for 'just living" and allows for coverage needed because of accident or illness.) It was assumed that major medical care would not be needed, but that emergency medicines and a substantial medical kit would serve the expedition adequately.
Radiation shelter
Onsite power
Life support - recycling system with biological assist.
Consumables - Air, water, food; food may be part packaged, part fresh-grown veggies (tending the salad garden would provide a therapeutic change of pace while on-station).
Tools - basic and also high-tech: The crew needs the ability to repair anything. Yet the tool manifest should be compact and lightweight. And provision should be made to allow repairs in shirtsleeve environments where possible. Question: what sort or operations are possible without EVA?
R&R [Rest and Recreation] for "off-duty" time. The quality of life must be bearable.
Laboratory; Millwright shop; Refinery equipment
Packing/Shipping facility - Afterthought (Faust): Mission will need shipping containers (tanks) if product is volatiles. [Ed. or the capacity to manufacturer them on site from local materials. This capacity is essential if the operation is to be open-ended!]
Lots and lots of delta-V capability for:
Afterthought:
(Faust): Should the expedition depend on resupply, or include sufficient energy and reaction mass so the entire crew could move about the Asteroid Belt, visit larger bases, if not all the way home to Earth-Moon space? The mission will need sufficient reaction mass/energy to ship its product, unless it depends on an "ore-boat" which visits only after sufficient "mined" product has been accumulated.
[Editor: it seems highly unlikely that asteroid belt missions, whether specifically targeted or seeking successive targets of opportunity, will ever be launched unless equipped to produce fuel on site from any of the major types of local resources. Such a facility would be marginal at Belt distances if dependent on solar power, but quite feasible with a small "nuke". Taking all the fuel along from Earth or Moon would be prohibitive, if not impossible.]
Elaborating on the Above
Crew skills: First Phase tasks will include initial on site analysis of Gaspra's mineral resources and assembly of habitat and mill/ refinery. This phase might occupy 6 months. Skills needed next could come with a relief crew tasked with more detailed physical and chemical analysis, mining, producing, and/or refining "product", packing and storing it, and launching it towards near-Earth recovery areas. Both teams need pilot/ navigator skills and personnel with medical/emergency skills.
Duration of "tour": Each mining crew's tour might last 5-6 years, with one-third arriving about every 20-24 months, with needed renewable supplies. Crew members might renew their tour for up to 10 years. The minimum period of base operation is assumed to be about 10 years.
(Kalman): The team discussed desirability of some effective combination of suspended animation and yoga, to reduce metabolic consumption during trips out and back. The need, desirability, and reliability of such technology needs a great deal of exploration and discussion. [Editor. Current thinking is that simply to minimize total radiation exposure, trips of more than a few month's duration are unacceptable - and that therefore missions to Mars and the asteroids will use nuclear power or not be undertaken at all. Shorter trip times will greatly reduce this en route consumption problem.]
(Faust): Tour length could also depend on the success of recruitment efforts and on the training of replacements; the "reenlistment bonus"; crew members' ability to adjust to fellow crew members, tolerate limited environments, and postpone gratifications; and the rate of compounding of deferred compensation "at home".
(Faust): Depending on demand and value of product, the base might be in operation for just a few tours, or even for generations. Extent of economically recoverable materials (demand market), durability of airlock and other seals, equipment, life support system and power supplies in the deep space environment, security of resupply, lifespan of support organization, care for leadership and selection of compatible crews - all would affect how long such a base might last.
Arrival and method of braking:
a. Normal retro-braking: could begin slowly at the midpoint of travel, or could be at higher Gs towards the end of the trip.
b. Tethered penetrator: As vehicle flies by, it could "harpoon" Gaspra with an anchoring device on a high-tensile-strength line and convert its velocity to a tethered orbital form. Some members were concerned that 1) the moment of impact would strain the "saddle horn", i.e. bring on too-sudden a g-force jerk and/or 2) the tether would wrap around Gaspra and bring the vehicle to final contact at the surface with excessive velocity. The benefit of this method is reduced travel time, with braking concentrated at the end of the trip. Concept needs considerable development as to anchor mechanism and reliability, and the specifications for the tether and its tie to the vehicle.
[Ed.: But why not this instead?
[Editor. Of itself, it would seem a tether would only revector the momentum of the incoming ship, not reduce it. Why not consider how a navy carrier jet is stopped by a flight-deck tension-reeled cable? You'd have to fly past the target asteroid, harpoon its back side, and then pay out the cable, gradually applying the brakes. Questions: Can a secure enough harpoon be devised that the great momentum of the ship wouldn't simply pry loose? How much heat would be produced in the shipboard tension reel and how would it be dissipated? How many kilometers of cable would be needed and would the mass of cable involved be less than the braking fuel avoided?]
Sources of operating energy:
a. Nuclear reactor: standard fission type or He-3 fueled fusion.
b. Solar-voltaic: solar panels in this vicinity would gather only about a sixth of the solar energy available in Earth-Moon space so they'd need to be proportionately large. (1) panels could be deployed near Gaspra, keep station, and beam power to the base, with the disadvantage of reaction mass/fuel for station-keeping and orientation [Ed. why not a Gaspra-synchronous site which would need no such fuel?] or (2) in the negligible gravity, a large tower could be installed with extended panels, with the problem of maintaining orientation depending on Gaspra's rotation system. Afterthought (Faust): cable-linked leaf-like solar panels might be deployed all around Gaspra's equator [circumference c. 60 km) so that no matter what Gaspra's attitude, there would be enough exposure to solar insolation for operational power needs.
c. Mass-converter. Direct mass to energy conversion is too hypothetical a prospect to merit attention at this time.
Location of base:
a. On Gaspra, anchored to surface, but with radiation and flare shelter bored into Gaspra to a sufficient depth; this may be the second most economical location as to energy requirements.
b. Tethered at a distance [past Gaspra-synchronous orbit] such that Gaspra-locked rotation will provide for a fractional gravity, for long-term health of miners; winch a vehicle along the tether to go to work or to reach radiation shelter. Low-energy method of obtaining at least a fractional g may be essential to preserve bone mass, fluid distribution, and similar human physiological essentials. A fractional g for extended periods, by rotation, elastic resistance, or other means, is probably a necessary aspect of life support. This solution might develop from the "tethered penetrator" braking approach, and may be the lowest-energy solution. {Editor, assuming Gaspra's mass but not knowing Gaspra's rotation period, a calculation of its synchronous orbit height and thence of the length of the tether needed can't be made. I'd assume we are talking 30-50 km.]
[Ed. cont.: This is an ingenious and elegant solution. In the classic space settlement design, a sphere, torus, or cylinder of substantial radius (1,000 m or more) rotates at 1-3 rpm. There is a noticeable gravity gradient as one climbs inwards towards the axis, or descends toward the periphery. The large radius is needed to produce the desired gravity (1 G or 1/6 G) at tolerable rpm rate. Faster rates result in disorientation, dizziness.]
[Ed. cont.: With a whip tether, however, the habitat or vehicle can be small or large and the floors can run any way so long as they are perpendicular to the tether. There is no noticeable gravity gradient. And the slow asteroid-linked rotation takes hours not minutes or seconds. A glimpse of the future?]
c. Entire base bored into body of Gaspra (no estimate of energy needed to do this). Has advantage of radiation shielding close at hand, enlarging living and working areas with a shirtsleeve environment, for greater productivity than space-suited work.
Consumables and life support:
Fuel, reaction mass, air/oxygen, water, food, repair materials, and machines, spare parts and "stock", back-up materials and manuals and recreational materials including musical instruments, all need to be taken in sufficient quantities. Recycling of air and water, food and human wastes appears to be essential to keeping take-along mass in bounds.
Amplification (Kalman): A first, automated mission might deliver supplies and consumables with less on route consumption than a the manned mission. [Editor: as in Dr. Zubrin's Mars Direct scenario, a first uncrewed mission could deliver a reactor and chemical plant to process local volatiles into the consumables that the crew would need in greater abundance upon arrival.] (Team): as many automated missions or craft as necessary might be used for risk reduction, redundancy of supplies. Not everything anticipated may be needed. The other error, leaving out something essential, may be the worst.
Afterthoughts (Faust): A pure "plumbing" system [chemical-mechanical recycling?] probably needs to be supplemented by biotic systems, i.e. plants and bacteria and grow lights to recycle oxygen, purge carbon dioxide, scavenge and reuse human wastes, and grow "fresh" food. The mass, volume, maintenance/training needs and robustness of the two types of systems over the required periods of time need careful review and comparison.
A communication capability and a voluminous technical and cultural library of an evolved CD-ROM type should be taken along. Role-playing and other interactive games may need supervision of psychologically trained crew member(s) to moderate interpersonal relationship strains.
Workshop Postscript: (Faust)
Clearly our team was a self-selected "grab-sample" of attendees at the Huntsville ISDC, rooted in the "here and now", not yet thinking of our task from a projected perspective of members of a successful spacefaring society; and with only a smattering of the basic information needed for our task. We had a doctor, a physicist, a city planner, a teacher, and two kinds of engineers; we lacked such useful perspectives as those of a contractor, a foreman, a submariner, a construction worker, a miners, a test pilot etc.
Last May when the workshop took place, Biosphere II had not yet cracked open. No one knows yet the workable proportions of air to soil to large animal [humans] to bacterial mass, for a long-term mission in such an environment. Of-hand, probably we need more air mass than we think. And we probably need ways to keep down rusts and algal blooms and mildew and such.
As yet we have no economics. We can only speculate who might pay for exploration, for the journey out, for shipping product back, for the trip home, and retirement benefits and in what coinage; but we think it will be expensive.
No one has reviewed the oceanic exploration analogs; might our leader be a Captain Ahab, a Captain Bligh, or a Captain Cook? Once people are out there, the High Frontier will be a bigger romance than sail, the railroads, and aviation all combined. But the world needs cheaper launch capability for that to open up. Perhaps the old game of China-goads-Japan-goads-America-goads-France-goads-Russia is a viable game, and nationalism on Earth has a high purpose. LF (Lucien Faust)
Group 3: "A Small-Operation Mass Driver Rig on an Astrochunk to be nudged in to High Earth Orbit"
Workshop "Primer"
Starting Point: Consider:
1. Potential loot is an appreciable fraction of the astrochunk's mass. The most profitable approach will be to in effect mine the chunk en route, using the unwanted tailings as mass driver fodder, at least until they run out. Upon arrival at L5 or other destination, we will be left with a processed or beneficiated mass of pure or almost pure ore.2. Meanwhile, the "Mom & Pop" team must have comfy quarters for the long journey, a suitable lab, and a "yolk sack" of provisions to see them through with plenty of margin.
3. Shepherding such an astrochunk may be a trickier-than-you-would-think operation requiring a) first stopping the chuck's interfering rotation and b) placing the facility so that the center of mass stays directly ahead of the mass driver's axis.
YOUR MISSION: Explore, rate, list options:
WORKSHOP RESULTS: Group 3
Report by Mark Kaehny, Group
Leader
Also participating: Richard McNeil and John Turner
Moving Flying Mountains (hills really)
Consider a small (+/- 100 meter diameter) asteroid or comet chunk in an orbit in the inner solar system. The goal is to change its orbit and move it to where it is needed - the Earth-Moon system, the Mars system, etc. Ad described in the workshop primer, this is to be a "Mom and Pop" operation of a small number of people who may stay with the asteroid. Is this feasible, and what considerations would there be?
Setting the Stage
First some simplifying assumptions. This takes place in a future with a spacefaring civilization. There would be settlements on the Moon, Mars, and perhaps space colonies in some form. This is the only scenario which might make this economically justifiable. It is assumed that this asteroid or comet chunk (we'll call it the "Rock" from now on) consists in large part of "volatiles", Carbon, Hydrogen, Nitrogen, etc. This probably takes the form of water, hydrocarbons, and perhaps ammonia.
Given this composition a logical destination would be the Earth-Moon system for use on the Moon, or in space colonies. This scenario assumes that the asteroid is small enough that it is better to actually move it, rather than process and ship it. (See the other scenarios for that discussion.) For comparison, this Rock, if melted, would fit into one or two large tankers on Earth. It would fit inside the Superdome. This is the size of object we are dealing with.
There is no appreciable surface gravity. A human can't walk on this object -- he or she would take one step and be in orbit, or actually out of orbit depending on the strength of the step. This means that our rock could very easily fall apart if jarred. That puts a limit on the amount of acceleration that may be applied to it.
Other assumptions that we will make is that we have well designed space nuclear power systems, and an efficient and reliable means to use regular mass (stuff we are getting from the Rock) as reaction mass. The power density requirements for this operation make it look like solar power might not be workable. although some kind of beamed power system instead of nuclear might work. The reaction drivers could be some kind of mass driver, or some kind of "dust blaster" (electrostatic and thermal system) or depending on how materials are processed some kind of nuclear thermal or electric thermal rocket. This would need high reliability (say fire constantly for a month at a time) and high thrust (pump out many kilograms of material constantly).
Technical Questions
Is actually moving an object like this technically feasible, and if so, what are the constraints? The mass of the Rock itself would be used for reaction mass. Back of the envelope calculations show that this a time vs. mass tradeoff. The mass we are discussing is on the order of a couple of million tons of material. To move an object this size from an orbit outside that of Mars in to Earth orbit will either take up a significant amount of mass of the Rock (well over a third) to change the orbit in three or four years, or by using less mass, one can move the it in about a decade.
For the fast route --
Only nuclear power or some kind of beamed power will have enough energy density for this method. This would not be a small plant!
The amount of mass to be shifted per day, broken down and used for reaction mass would rival the most efficient mining operation on Earth today in terms of tons of material processed per person per day. (Sudbury type figures are comparable.)
Machinery would need to run continuously for long periods with little repair or breakdowns.
The stability of the Rock would become an issue. The center of gravity would be changing, and the stresses might pull the thing apart.
"Mom and Pop?"
All of these problems suggest that a longer transit time would be chosen. In that case the problem of closed cycle life support would become more challenging. The movement and use of local reaction mass will still be a big deal. Moving tons of material, and using it in one of several ways as propellant is not a trivial operation! The group decided that this could not be a "Mom and Pop" operation unless Mom and Pop had a lot of resources available to them. It would most likely be a corporation, or perhaps some kind of wildcatting group. This would mean that they would have some kind of home base somewhere else available to them.
Living on the "Rock"? or Human-tending it?
The previous point led the group to discuss whether the Rock would have continuous habitation. It might be better, especially if the longer itinerary is used, to just have the Rock be human-tended, that is, someone comes to visit now and again. The arguments for this is that consumables do not need to be taken. Even if we assume a quite good closed life support system, the closed system itself is likely to be a quite massive environment. By only having people on the Rock for a short time, this mass is avoided. This assumes fast, relatively cheap and fast passages to and from the Rock of less total duration than the periods when the Rock is unoccupied. Otherwise, of course, the crew might as well stay put.
[Editor's Comment: But in most cases, especially with Earth-approaching bodies, there is a Catch-22 which works against this idea. The closer two bodies are in their orbital period, the less frequent are the launch windows to and from!]
On the other hand, one reason to keep people on the Rock is to start "beneficiating" the materials. That is, separating and processing the valuable stuff. In our example this means the volatiles. This also becomes almost a necessity, since a long transit time in the inner solar system would mean that much material could be lost to the Solar Wind. Also, since one would want to be very careful how this was moved into the Earth-Moon system, it may be that the Rock is sent closer to the Sun into an orbit whose aphelion is at Earths orbit, so that the Rock catches up to the Moon with a smaller difference in velocities. So, as material is used for reaction mass, it could be processed to remove the most valuable components.
However, the massive quantities used might make it more practical just to waste some mass solely as propellant, without using any machinery (which would need servicing). It can't be forgotten that this Rock masses millions of metric tons, this is not small scale for humans even though it is nothing in Solar System terms. Separating materials must be done sometime so to do it in transit time does make sense.
Mine in a Bag
One idea for processing is to "bag" the Rock, that is enclose it in a close-to-airtight container. This wouldn't be that difficult - all one would need is the equivalent of five or six tarpaulins that cover baseball fields in the rain. Obviously they would be made of a much lighter material and thus would make a small cargo. Assume 100 thousand square meters of material (probably far more than needed since a cube 100 meters per side has a surface area of 60 thousand square meters) and 10 kilograms per 100 square meters, which is quite feasible, and we get a total mass of 10 thousand kilograms, about 12 American tons. Not an outrageous mass, and most likely an upper limit.
Given this bag, we can heat up the Rock and separate the gases that are given of with a pump. We can also use this gas (say oxygen fraction, since that won't have a lot of value) as propellant, a perfect source of course correction power.
Another suggestion is to work the Rock from inside out. That is, tunnel inside the Rock, make an airtight (or as close to it as practical) chamber, then start processing the materials in a close-to-shirtsleeves environment. This would allow for much more efficient use of human labor.
These two ideas work well together, in that the inside area could be over-pressured relative to the outside bagged area, so that if there are any leaks, the inside air is not lost. This provides an extra layer of security for those working inside.
Also even if the inside air was not breathable, if the pressure can be brought up to a reasonable level,workers could just use some type of air-mask, yet still get the benefit of working unencumbered. Just listen again to some tapes of the astronauts working on Hubble, and what they were actually doing, to see how strenuous it is to work in current space suits.
Living Quarters
Given that people will be living on the Rock for extended periods, artificial gravity might be desirable. In this case (and in any other as well) the living quarters should not be on the Rock, but right next to it, connected directly by flexible connections. This allows for people moving around, shifting things on the Rock without throwing the living quarters around as well.
Consumables vs. Yield: Tradeoffs for Profitability
No matter what style mission, a few years or a decade, we must hold the assumption that closed cycle life support systems will be much advanced from what we have now. Otherwise no matter whether the workers stay uninterruptedly or not, the amount of consumables would amount to something tremendous -- several tons per year per person. Since these would be high cost much processed items, they would probably make the whole capture idea uneconomic. This tradeoff will most likely be the determining factor in what type and speed of orbit is taken, what type of "Rock" that is aimed at, etc. Given a very closed system then some of the objections of permanent habitation go away, and this also changes things in terms of propulsion.
A different , better reason for moving the Rock
If we can process the thing where it is, perhaps small motors that just put the Rock in an intersecting orbit could be used, then as the Rock is processed the different products are shipped as the Rock moves. In this case the Rock may never get to the destination, and the reason for "moving" it is to provide more efficient orbits for "freighters". MK (Mark Kaehny)
[ED.: One thing this workshop team (nor, to our knowledge, any previous advocates of asteroid moving) did not consider was the extra challenge posed to any Rock-moving plans by the body's rotation and axial orientation. Unless (illustration below) there are a pair of non-co-rotating mass drivers, dust rockets, etc. at each pole of the body, it may be very difficult to achieve the desired result. It may make more sense to use waste tailings and waste gasses first to zero-out rotation. PK]
