Investing in Satellite Life Extension.
As prices for these items escalate and bandwidth becomes scarce, satellite owner operators can meet the challenge in one of two ways -- they can either invest in new high-throughput satellites or extend lifetimes of existing space assets. With the end goal of minimising the cost per bit paid by their clients, some owner operators are choosing to do both. Life Extension refers to the process of lengthening the period of time that an on-orbit asset can be operated in a manner consistent with its intended purpose while staying within its licenced orbital and operational boundaries. Indeed, the intended purpose of the space asset may change over its lifetime and a life-extended satellite may not provide the same revenue opportunities as originally envisioned, however an attractive return on investment is still possible -- especially at the end of life when the asset has been fully depreciated and the only investment "costs" consist of satellite operations and the expense associated with life extension services.
A previous paper presented at Space 2014 by this same author provided an overview of "in-orbit servicing" and described in some detail the technical progress made by various commercial companies and USG agencies along that path. The intent of this paper is not to provide an update on that initial overview, but rather to focus on the financial benefits provided by one of these services -- specifically "life extension". After several years of hearing satellite manufacturers and some in the USG claim that "there is no business case for" and consequently "no interest in" life extension, perhaps it is time for a commercial company to provide an alternative viewpoint.
Commercial Options Offered to Provide Lifetime Extension Services
Two fundamentally different technologies are being offered to provide life extension services to on-orbit spacecraft. One of the services involves use of an attached tug that replaces the station keeping (orbital control) and momentum dumping function of the host spacecraft. The other service consists of robotic refueling -- transfer of liquid propellants from the servicer to the client allowing the satellite to continue use of its own propulsion and attitude control subsystems. Both of these solutions involve similar orbital rendezvous and docking procedures, however that is where the similarity ends.
A) Tug Services
Tug services are currently being offered by ViviSat (working with ATK) using a platform they have christened the Mission Extension Vehicle (MEV). The MEV remains attached to the client satellite for as long as the service is required and replaces the ACS (Attitude Control System) functions of the client. Orbital drifts, station keeping functions and momentum dumping become the responsibility of the tug.
The business case is challenging as the MEV must remain attached as a "mass tax" for the life of the contract. The mass tax reflects the reality that the propellant must be burned to maintain both the mass of both the entire tug (laden with its lifetime of propellant) as well as the client satellite. Consequently the business case must cover not only the propellant used to station keep the client, but also the propellant to station keep the mass of the MEV. If a tug service is contracted to reduce inclination, the business case must cover the cost of increasing inclination of the MEV to dock with the client, then return of the combined mass to lower inclination. For the first client a portion of this cost could be reduced if the tug were launched directly to the higher inclination of the satellite. An overwhelmingly better financial decision would be to attach the MEV before client inclination was allowed to grow.
At the end of the MEV service contract, the MEV can simply be detached and drifted to its next opportunity. Residual propellant in the client can then be used to supersynch the spacecraft into graveyard orbit. If the client does not have sufficient propellant or its propulsion subsystem is disabled, the MEV can be used to supersynch the spacecraft--but this also involves the propellant cost of the MEV's round trip.
Satellites which become stranded on orbit, either due to malfunction of the spacecraft or poor management of propellant reserves, might have no alternatives to get to graveyard except by use of a tug. It is highly likely that when tug services are readily available at GEO, satellite operators will be legally obliged to remove their derelict spacecraft to prevent possible collision with other objects. Good stewardship of the space environment could easily be enforced by changes in space law which might prohibit space littering on a go-forward basis. While certainly not part of the business plan for commercial servicing, owner/operator's decision to NOT purchase an available tug service for removing their debris could be viewed by a court as negligent, and result in significant financial liability if other space assets are placed in harm's way. Tugs will likely utilise both ion and chemical propulsion systems. Ion systems will be used for delta-V manoeuvres when sufficient time is available to fully leverage its efficiencies. However, if the tug must be drifted in orbit quickly or while in the vicinity of other spacecraft, the higher thrust afforded by chemical thrusters is likely required. This begs the question whether the tugs should be built to be easily refuelled themselves, and might they just buy that propellant from the competing life extension solution -- namely robotic refuellers. Due to lower complexity, a tug service would seem to offer a lower risk approach for life extension. Successful tug operations would likely facilitate the development and acceptance of the more-complex refuelling services. Realizing this socialisation issue, robotic programs at both NASA and DARPA have been on-going to buy down the perception of risk.
ViviSat recently reported that they had bookings for the first three MEVs. Launched in pairs, it is hoped that the fourth booking will provide sufficient confidence in the financial community to get production into high gear.
B) Refuelling Services
Considered the "Holy Grail" of in-orbit servicing, refuelling of on-orbit satellites has been the aspiration of USG agencies such as NASA and DARPA for some time. Refuelling provides a viable life extension solution when the client spacecraft's propulsion and attitude control subsystems remain intact. It is likely the most efficient way to extend lifetime, as the only "mass tax" left with the client is that of the propellant itself. However, if propellant is purchased and loaded, the return for that propellant purchased is not realised until that propellant is actually consumed. If that satellite later taken out of service prior to use of that propellant, that investment is lost.
Canada's MacDonald, Dettwiler and Associates' (MDA) Satellite In-orbit Servicer (SIS) robotic refuelling venture was looking very promising when they signed a $280M contract in mid-2011 to provide refuelling services to Intelsat's fleet of over 50 GEO satellites. However, the inability to get commitments from other commercial GEO customers stalled MDA's forward progress. MDA's technical experience with space robotics had already been well established -- building both the Space Shuttle's "Canada Arm" and the Dexter robot currently being used on ISS. Nevertheless, possible competition from NASA to refuel USG satellites using their own robotic refuelling spacecraft being developed under the RESTORE program appears to have been an issue. In subsequent months MDA elected to "cancel their collaborative agreement" with Intelsat and divert investment elsewhere. In late 2012 MDA completed the purchase of Space Systems Loral -- establishing a significant US presence for sales of future services to the USG and mitigating some of the previous ITAR/non-U.S. concerns.
Benefit of Life Extension
A) Several More Years
Frequently heard in discussions about life extension is that it is risky, too difficult, too expensive, and of little interest because the technology on the older satellites is obsolete and the hardware is at the end of its design life. While this is not true, satellite manufacturers should not feel threatened by life extension. The goal of life extension is NOT to add another 10 years of operations to a heritage 15-year spacecraft -- rather to potentially add a few years of life to allow flexibility in fleet planning. Satellite owner operators will make their decisions based upon business plans, and if the business plans indicate that the latest technology will provide the greatest return, that is the path they will take. Owner operators will purchase the new satellites with the latest technology only when the on-orbit asset is no longer producing or it makes "dollar and cents" for them to do so.
B) Proven Reliability
As described in a report done by the Aerospace Corporation, about 1/3 of GEO satellites are operated well past their 15-year design life. If the heritage technology was obsolete and not able to produce valuable services, this certainly would not be the case. As an example, Intelsat's Leasat 5 satellite, launched in 1990, was just retired after 24 years
C) Spin-off Benefits
Tugs and robotic refuellers can perform value-added services for new satellites as well as the propellant-challenged older variety. For example, a new satellite getting a marginal drop-off from its launch service might need to make up the delta-V shortfall by using its own on-board propellant reserves. This could leave the satellite with little remaining station keeping life upon reaching GEO. The ability to replace the propellants could bring SIGNIFICANT value to both the owner/operator as well as the insurance company potentially responsible to pay a claim. The same robotics used to conduct refuelling operations could be used to assist the deployment of a stuck antenna, solar array, or even adjust a loose thermal blanket. Robotic servicers could provide a capability for capture of orbital debris, however, today there is little financial incentive or government regulation motivating investment in a pricy venture to collect yesterday's space trash.
Risks and Security Concerns
The space community is justifiably a very conservative group -- investments in space assets are huge and on-orbit hardware problems are almost impossible to fix. Spacecraft are frequently designed to survive worst-case scenarios and environments. Flight heritage is precious and an entire Technology Readiness Level (TRL) scale has been developed as a measure of flightworthiness to assist in evaluation of survival risk. The future of on-orbit servicing is bright but the industry is full of doubters -- they will buy into servicing only AFTER it has been proven SEVERAL times on SOMEBODY ELSE'S spacecraft. Disruption of services is a near-sacrilegious event with stiff financial consequences.
Orbital debris has been a rising concern over the years and a couple of highly destructive events at LEO have fuelled the fire. While the "vastness" of space once rivalled the perspective of the vastness of the oceans, decades of launches left thousands of objects in orbit -- mostly at lower altitudes. We would like to believe that an understanding of the uniqueness of geosynchronous orbit would be sufficient justification for every space-faring nation to keep the neighbourhood free of litter -- but this has not been the case. In fact, well over half the ~1400 items tracked at GEO altitude are uncontrolled objects. These uncontrolled objects scream North/South through the equatorial plane twice a day, picking up 100 mph closing speed every year. Eventually there will be a collision at GEO that generates many thousands of additional fragments. What is the space community doing about THAT worst-case scenario? Answer is... not enough.
Spacecraft are designed to be somewhat resistant to micrometeoroids, but the debris created by a collision at GEO would dwarf the impact from
those micrometeoroids. The Space Data Association (SDA) works with commercial operators to track debris (and each other's satellites) and provides conjunction warnings to the applicable parties when "resident space objects"
(RSOs) are predicted to get within some predefined distance of an active spacecraft. The controlled spacecraft might be manoeuvred to increase the conjunction distance beyond the range of position uncertainty. However, there is also good chance that both objects might be uncontrolled and the collision unavoidable. Could a robotic servicer prevent such a collision by capturing one of these objects prior to the predicted collision? It would be an expensive undertaking but likely less expensive and more practical than NASA's plan to capture asteroids.
What would be the consequence of a robotic servicer (tug or refueller) colliding rather than docking with an active satellite? Would one or both of the spacecraft become disabled? Would the two become entangled? Would a debris field be created? A previous USG rendezvous mission resulted in a low speed collision and both spacecraft survived. The closing rates between a servicer and a GEO satellite during the docking procedure are extremely slow -- docking simulations and ground testing will assure risk of collisions is minimal. Autonomous procedures kick in automatically to increase the separation in the unlikely event that a command link is lost or the vehicles' closing rate is too rapid.
Maintaining attitude control sufficient to sustain pointing of the client communications antennas is another matter. It is likely that initially there will be a lot to learn regarding optimising the attitude control algorithms of the docked servicer/client composite and that initial missions will not be able to maintain the original "pointing budget" of the client. Is that a risk? -- Only if it was unexpected.
Risk exists that the client's propellant valves might not function (or fully reseal) following 15 years of on-orbit dormancy. Those requirements were never part of the original spec for those valves -- they were not "designed" to be opened/closed after 15 years exposure to corrosive propellants. Will they function properly? There are a lot of on-orbit systems available for a demonstration prior to servicing a high-value spacecraft. It is expected (and likely required) that an on-orbit demonstration on a nearly-identically designed satellite will be required before attempting those same operations on a high-value asset.
Does the presence of on-orbit robotic spacecraft represent an anti-satellite (ASAT) threat? Could the robotic spacecraft be used to intentionally disable somebody else's satellite? The answer is "yes" -- and likely the DoD has put a lot of thought into that possibility. But then, any controlled satellite could be intentionally flown "into" somebody else's spacecraft today -- might miss the first few times but eventually contact could be achieved. At high enough speeds it would likely result in mutual destruction. An intentional collision could be executed -- just as it could be with airplanes, cars, tanks -- even submarines.
Could a tug be used to "capture" and relocate somebody else's spacecraft against their will? Probably so -- but the presence of tow trucks on our roads did not result in a rash of car thefts. Providers of on-orbit services will work closely with both USG and international agencies to minimise the concern over this issue. Future satellites will likely include some sort of localised situational awareness sensors -- this might not prevent tampering problems but certainly could provide attribution. Intentionally approaching another nation's military satellite is already the equivalent of violating territorial waters, and intentionally harming that nation's satellite could be construed as an overtly hostile act. This makes robotic capability in space a very sensitive international issue.
The perspectives provided in this paper for life extension on EOL spacecraft provide sufficient justification for both refuelling and tug services. The business cases definitely provide sufficient ROI (return of investment) to move forward if the satellite can be put back into its operational role. Building a business case for servicing problems that have not yet occurred (BOL anomalies) is a challenge, but waiting until the anomaly has already occurred before launching a solution will not provide sufficient responsiveness to be practical. If interest rates increase (likely with the devaluation of the U.S. dollar on the world market) the business case for life extension of EOL satellites will only improve. From the perspective of the owner/operator, the business case for life extension by either refuelling or tug services does appear compelling. However, the advantages of slightly lower cost of refuelling services is detrimental by the perception of higher risk (due to increased complexity) and the absence of a service provider actively selling these services today.
Satellite owner operators, in general, are a conservative community and hesitant to take any chances with space assets. For revolutionary concepts like in-orbit servicing, they will tend to sit on the sidelines watching to see what happens and will jump in only after it has been proven by somebody else. Intelsat has openly been a notable exception -- advocating on a continuing basis regarding the benefits and needs for in-orbit servicing by our space community and, in fact, being the first major operator to contract for these services. It is expected is that once the technology has been sufficiently socialised and proven on-orbit, the remainder of commercial industry will be swift to fully leverage the possibilities.
Whitepaper by Dr. Bryan L. Benedict, Product Line Manager, Commercial and Civil Hosted Payloads, Intelsat General Corporation.
Dr. Benedict is also a member of the
American Institute of Aeronautics and
Corporate Publishing International. All rights reserved. Provided by SyndiGate Media Inc. ( Syndigate.info ).
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|Publication:||Broadcast Pro Middle East|
|Date:||Oct 23, 2014|
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