Re: The Mega-Module Path To Space Exploration Or: How To Use An HLV
Greetings Mark and Fellow List Members
I can see it now, a Shell and/or BP service station in orbit.
Be Well
Damian
Mark Reiff wrote:
> FYI,
>
> "The Mega-Module Path To Space Exploration Or: How To Use An HLV"
> OpEd by John K. Strickland, Jr.
> Space Daily
> http://www.spacedaily.com/news/oped-05zza.html
>
> : Ever since the abrupt demise of the Saturn V rocket system at the
> : end of the Apollo era, engineers and space advocates have dreamed
> : of what they could do with a booster of similar capacity.
>
> : The recent correct decision by Griffin and his team to go for the
> : largest available booster which can be created at a reasonable
> : cost, will now allow us to make big plans for the first time in
> : 35 years. This article focuses on how to exploit the wide variety
> : of large payloads which an truly large HLV makes possible.
>
> : Replacing the shuttle orbiter and external tank with a second stage
> : based on the ET itself will provide greatly increased flexibility
> : and capability. The only capability lost is that of returning large
> : payloads, and this capability has been used only a few times to
> : advantage.
>
> : The extreme annual cost of maintaining the shuttle system could
> : have paid for duplicating these payloads many times over. The
> : ability to launch payloads of 100 or more tons with a payload
> : shroud diameter of over 27 feet far outweighs that loss. Using
> : a "hammerhead" type shroud could allow payloads of at least 30 feet
> : across.
>
> : There are several obvious reasons for wanting a large booster,
> : (beyond just the ability to launch a bigger payload), such as
> : avoiding multiple launches and the massive complications and delays
> : that would accompany them.
>
> : However, one kind of multiple launch system deserves a second look.
> : Most of the potential problems with supporting a single mission
> : with multiple launches result from launch failures or delays in
> : launching one or more payloads needed for a given mission. But what
> : if one of the two payloads is already in space.
>
> : A large portion of every spacecraft is propellant, and there is no
> : need to launch fully-fueled vehicles if the fuel could be already
> : waiting for them in orbit. Admittedly, this does call for the
> : exploration vehicle to go into orbit instead of on a direct
> : trajectory to the Moon or Mars and it does result in some
> : disadvantages.
>
> : However, in this case, the advantages far outweigh the
> : disadvantages. Launching payloads with empty tanks would in many
> : cases more than double the available launch mass of any integral
> : exploration spacecraft which could be launched on a given HLV,
> : allowing the spacecraft being launched to be larger.
>
> : Every ton of propellant that does not have to be on the spacecraft
> : can be replaced by an equivalent ton of useful spacecraft
> : structure. It would allow post-launch checkout of all spacecraft
> : systems before departure from vicinity of Earth. It would require
> : temporary docking to load fuel, but no assembly of modules in
> : space. The key to this tactic is the orbital fuel (or propellant)
> : depot.
>
> : Having an HLV capable of putting 100 or 120 tons in orbit enables
> : us to launch a complete (but empty) fuel Depot into orbit with a
> : single launch. If the Depot is capable of storing propellant for
> : extended periods, the propellant itself can be delivered long
> : enough in advance of mission dates to prevent any delays.
>
> : In order to do this, the depot needs to be able to continuously
> : re-liquefy propellants as they boil off using solar energy from its
> : own solar panels. The Depot would have several redundant fuel and
> : oxidizer tanks.
>
> : It should be able to handle several types of fuel and oxidizer. It
> : would be human-tended (operated by astronauts to put propellants in
> : from a propellant-carrying launch or to take propellant out for a
> : mission spacecraft.) There would be no permanent human crew needed.
>
> : The Depot would need to be well shielded from space debris and
> : thermal cycling in orbit, as well as extra insulation to reduce
> : boil-off. The external surface of the Depot could also serve as
> : part of the shroud.
>
> : The depot would have a primary 3-axis attitude control system
> : assisted by its shape, allowing gravity gradient forces to reduce
> : the use of attitude control fuel. The large weight allowances would
> : permit extra shielding, extra insulation and more redundant systems
> : than a minimal version might allow. The total amount of propellant
> : a depot could handle would depend primarily on the propellant's
> : density, since there is no weight penalty in orbit.
>
> : Propellants to fill the depot could be delivered using a second
> : launch of the HLV. Timing for these launches would not be crucial.
> : Propellants could be delivered in a lightweight tank with minimal
> : insulation (similar to the existing ET), and then immediately
> : transferred to the depot. The lightweight tank could then be
> : discarded and set for re-entry.
>
> : Fueling operations in orbit are in some ways safer than on the
> : ground, since any vapors escaping from propellant transfer
> : operations would almost instantly dissipate in the vacuum and would
> : present virtually no explosive hazard. One problem that orbital
> : propellant transfer operations needs to deal with is, of course,
> : the behavior of liquids in micro-gravity. Transfer pumps need to be
> : delivering liquids, not pockets of gas mixed in the liquids. This
> : problem has been solved in the past and there are multiple ways to
> : handle it.
>
> : If an automatic propellant transfer technology could be developed,
> : no on-site crew would even be required. Any such automatic system
> : would depend on a docking system, which (in addition to primary
> : docking), would also have to connect fuel lines, transfer the
> : propellant, and then detach the connections. These operations could
> : be done by using a miniature version of the primary docking system,
> : except that the respective positions of pipe connections would
> : already be known to within about a millimeter.
>
> : Control of such an operation could be handled remotely by a ground
> : crew using video cameras, full data readouts and manual controls
> : for connections, valves and pumps. Alternately, a crew in a CEV
> : could be launched with a lighter version of the tanker.
>
> : Depending on the orbit used by the Depot, the CEV could separate
> : from the tank, and then rendezvous with a space station, or could
> : even be used to deliver a crew to an exploration vehicle. Fuel
> : transfer technology experiments should therefor be given high
> : priority for space on remaining shuttle missions to the space
> : station.
>
> : Such a large propellant depot could be described as one type of a
> : Mega-module. The standard shuttle payload limit for space station
> : modules is about 20 tons, so these payloads would be 5 or 6 times
> : larger than that. Once one type of mega-module, such as a depot,
> : has been defined and designed, it will quickly become apparent that
> : it could be used in multiple locations. It then becomes obvious
> : that you need to build several copies of some kinds of modules,
> : such as the fuel depot.
>
> : A depot could also be used at a transfer location, such as Lunar
> : Orbit, or the Earth-Moon L1 or L2 points. A smaller version would
> : be very useful on the Lunar surface if production of Lunar oxygen
> : begins. A depot would even be needed in Mars orbit once extensive
> : human exploration operations begin. Once you have several copies
> : under construction, there is less of a problem and/or program delay
> : if one copy is lost during a launch failure.
>
> : Once you decide to design and launch one kind, the possibilities of
> : creating other types of mega-modules are immediately obvious. (If
> : we have a big booster, we should use it to full advantage.) Some of
> : these could be components of exploration vehicles, while others
> : could be part of unrelated space development (which includes
> : scientific infrastructure).
>
> : For example, a refuge module, such as would provide a safe retreat
> : from the space station, or at L1, L2, or Lunar orbit, would have
> : much in common with the kind of habitation module used to transit
> : between earth and Mars orbit.
>
> : It would also be much easier to design a solar storm shelter area
> : in a 100 ton module than in a 20 ton module. The large available
> : diameter would provide room to place the "storm cellar" in the
> : middle of a variety of food and water stores. It also might be
> : possible to create refuges at Depot sites, which would already have
> : solar power and attitude control available.
>
> : There are many kinds of integral structures for which it is
> : difficult to design a modular version if they have to be assembled
> : in space. Imagine having to design a large motor home so it can be
> : re-assembled in several pieces with a small crew in a short time.
>
> : Segmentation of structures and space vehicles causes a lowering of
> : structural integrity, and requires additional horrendously
> : expensive crew time to re-assemble them in space. It is also better
> : for vehicles that will be subjected to thrust to be orbited as one
> : piece. This also reduces the amount of potential air leakage at
> : permanent seal joints of a composite structure.
>
> : Any kind of integral re-usable vehicle tends to be larger than the
> : equivalent set of expendable components. Re-entry vehicles are a
> : good example of something with a minimum functional size. For
> : example, a re-usable Mars orbit to surface ferry needs to enter the
> : Martian atmosphere, and be large enough to reach Mars orbit after
> : re-fueling on the surface.
>
> : Such a ferry would need to have a very large integral aero-shell
> : which itself could not be launched on a small vehicle due to its
> : bulk. The same is true of a re-usable lunar ferry, even though it
> : does not need an aero-shell. The expendable ferry can discard the
> : descent stage when returning to lunar orbit or a nearby L-point.
>
> : The re-usable ferry must carry enough fuel to lift the equivalent
> : of the descent stage back into orbit. On the other hand, less
> : structure is needed, since only a single module (for ascent and
> : descent) is needed. Such a ferry could carry either a CEV with
> : passengers or bulk cargo. For all these reasons, having a very
> : large booster makes the design of fully re-usable deep-space
> : vehicles much easier.
>
> : In a similar fashion, a host of other types of mega-modules would
> : practically demand to be built. For exploration purposes, lunar
> : transfer vehicles are needed for people and cargo, possibly using a
> : CEV as the primary crew cabin and emergency capsule. The 60 day
> : report indicates that an expendable trans-lunar stage would be used
> : for lunar expeditions. There is no reason why this stage could not
> : be re-designed into a re-usable Cis-lunar "tug", which could return
> : to LEO using aero-braking.
>
> : A large space tug with crew cabin which could also retrieve space
> : station modules or even do repair missions to Geosynchronous orbit
> : would be very useful. This tug should be able to re-fuel from the
> : depot. For Mars expeditions, a standard Earth orbit to Mars Orbit
> : propulsion module would be needed. Such a module could also use
> : fuel brought in tanks from the surface of Mars to send crews back
> : towards Earth orbit.
>
> : The use of multiple types of Mega-modules would make it easier for
> : international space expeditions to cooperate, since each country
> : could build one or more types of modules. Since each module type
> : would be integral, and have standardized interfaces, the complexity
> : of having several countries work on the same module would be
> : minimized.
>
> : Astronomers would love to be able to design a space telescope with
> : a 25 foot or larger diameter mirror. Some of the incipient flagship
> : space telescope missions currently delayed by cost over-runs might
> : be able to save money and greatly increase their light-gathering
> : capacity by being re-designed as a 100 ton instrument.
>
> : With 100 tons, you could also place a large outer-solar-system
> : probe on a very fast trajectory by using additional boost stages.
> : You could also build an oversize space station module complete with
> : human-sized centrifuge.
>
> : Last but not least, the HLV makes it possible to build and test a
> : full-scale collector module for a Solar Power Satellite. It would
> : be uneconomical to launch enough modules for a functional Powersat
> : on the proposed NASA HLV, but such a test could prove out the
> : ability of the module to fully deploy its huge array of solar film.
> : Such a single module, if fitted with a microwave transmitter, could
> : provide power for a solar-powered tug or other heavy power demand.
>
> : Based on advanced designs done in the late 1990's, a 100 ton
> : collector module could theoretically deploy solar (photo-voltaic)
> : film with a total area up to 1 square kilometer, intercepting
> : 1.3 Gigawatts of sunlight, and providing about 100-150 Megawatts of
> : power if the film is about 12% efficient. If this test was
> : successful, it could stimulate enough business interest to create a
> : really cheap, fully re-usable and privately owned large HLV.
>
> : With that, we could build a full system of PowerSats to supply the
> : Earth with pollution-free power and permanently end both the energy
> : and global warming problems within a single generation.
>
> --
> Mark Reiff <markreiff@xxxxxxxxxxxxx>
>
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