- Email: [email protected]
Capabilities, costs, and constraints of space transportation for planetary missions
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Acta Astronautica Vol. 35, Suppl., pp. 587-596, 1995 Elsevier Science Ltd. Printed in Great Britain
Pergamon
0094-5765(94)00226-6
CAPABILITIES, COSTS, AND CONSTRAINTS OF SPACE TRANSPORTATION FOR PLANETARY MISSIONS Karen S. Poniatowski and Michael G. Osmolovsky New Programs and Integration Launch Vehicles Office National Aeronautics and Space Administration Washington, D.C. 20546-0001
SUMMARY Launch vehicles currently fall into roughly four different performance categories: small, medium, intermediate, and large. In the past, most planetary missions relied on launch vehicles in the intermediate to large class, primarily because of heavy spacecraft or high launch energies. Recently, a shift has begun towards lower cost planetary missions that have more narrowly focused science objectives. Accordingly, the launch vehicle focus within NASA is shifting to medium performance class and below for new planetary missions, with an increase in planetary launch opportunities. A variety of U.S. and International launchers are available for this new category of missions, and their performance and capabilities are described in some detail. Included in the discussion are costs (U.S. only) and constraints associated with each launch vehicle. Some are currently in production, and many are just developmental at this point in time. Within NASA, there is a potential procurement for a new class of launch vehicle in between the small and medium classes. This category is termed medium-lite, and could become the primary niche for low-cost planetary missions in the future.
INTRODUCTION Space transportation for low cost planetary missions is an increasingly important topic because of heightened attention to mission life cycle costs and restricted budgets. There is a return to a philosophy more in tune with the earlier days of the U.S. planetary program, in which smaller missions were launched at more frequent intervals. This paper outlines and describes in some detail those launch vehicles which could be used to support planetary missions in the future. The concentration here is on U.S. launch vehicles, although a brief discussion on international launchers available outside of the U.S. is included. Detailed performance curves are provided, as well as a brief discussion of the various cost components that must be considered in any launch service.
PLANETARY MISSION MODEL The planetary mission profile for the United States has been characterized in the pastt by an increasing reliance on large, heavy spacecraft with a wide array of science being performed. This led to a situation where planetary spacecraft became more and more expensive. Since budget growth in the Federal Government did not take place as anticipated, fewer planetary launch opportunities were available. The reliance on large spacecraft also led to a situation where planetary spacecraft mass and launch 5H7
Low-cost planetary missions
energy requirements were such that launching on anything other than a Space Shuttle or large ELV was not possible. Note that for the purposes of this paper, planetary missions are defined as those spacecraft specifically targeted to perform science on or at one of the other planets in our solar system besides the Earth. This does not include the Sun, which more properly falls into the area of Space Physics. So while certain missions may fly an interplanetary trajectory, they may not be specifically counted as a planetary mission (Ulysses, which is a mission to study the Sun, is a primary example) in this paper. Ironically, the early U.S. planetary program was characterized by more frequent, smaller missions with a series of missions (at least two) being targeted for a specific planetary objective. From 1958-1973 there were 38 planetary missions, starting with Pioneer 1 (launched November 11, 1958) through the Ranger series, the Lunar Orbiter series, the Surveyor and Mariner series, and culminating with the launch of Pioneer 10 and 11 (March 2, 1972 and April 5, 1973 respectively). While most of these missions were launched on smaller ELV's (Thor-Able, Juno, Atlas-Able, and Atlas-Agena), some were already requiring the services of an Atlas-Centaur to achieve the proper planetary flyby trajectories. From 1975-1978 there were 6 planetary missions, which were becoming progressively larger and more ambitious. As a result, all of these missions launched on Atlas-Centaurs or on Titan Ill's. This period began with the Viking program (the launch of the first Viking took place on August 20, 1975) and ended with the Pioneer Venus series, the last of which launched on August 8, 1978. Finally, between 1978 and 1994 there were only 4 planetary missions launched. Three of these missions involved highly complex and large spacecraft, and had to be launched on a Space Shuttle/Inertial Upper Stage (IUS) combination or Titan Ill/Transfer Orbit Stage (TOS) combination. The fourth mission, the Clementine mission (launched January 25, 1994 on a smaller Titan II), points the way to a return to a philosophy of launching smaller, more numerous planetary missions in the future. Provided that the budgetary environment remains consistent, the future looks relatively bright for planetary launch opportunities. The projected manifest shows a total of 16 missions planned for the next 10 years 2 . All missions, with the exception of the Cassini mission to Saturn and international cooperative missions, will be launched on medium class or smaller launch vehicles. These missions involve smaller, less expensive spacecraft with more focused mission objectives. The Discovery Program seeks to enable a series of small planetary missions that would perform high quality, focused solar system science and to reduce total mission cost 3. One characteristic of the Discovery missions is that they are constrained to launch on a medium-class or smaller launch vehicle 4 . The first two Discovery missions are the Near Earth Asteroid (NEAR) mission, and the Mars Pathfinder mission (a Mars Lander/Rover combination). NEAR will launch in February 1996, to be followed by the Mars Pathfinder mission in December 1996. Other Discovery launch opportunities will begin in 1999 and result in roughly one launch a year thereafter. The exact makeup of the future Discovery mission set will be determined through an Announcement of Opportunity and selection process. NASA also plans to initiate a new program targeted towards exploration of Mars. This program is called the Mars Surveyor Program. It begins with the launch of a Mars Orbiter in November 1996, followed by two more launch opportunities at the end of
Low-cost planetary missions
51\9
1998. These two launch opportunities would be used to launch a second orbiter, and also a Mars Lander, which would be similar to the Mars Pathfinder Lander that NASA plans to launch in 1996. A second set of 2 landers would be launched at the end of
2001. Joint NASA/International cooperative missions targeted for launch on international launch vehicles include the Pluto Fast Flyby, and Rosetta (comet rendezvous). Figure 1 summarizes future planetary missions in a manifest format>. ELVCLASS
1995
1996
1997
1998
1999
2000
2001
2002
Mare
Olecovery
2003
2004
2005
SMALL
.... ....
MED-L1TE
Lander
Lander
Lander
NEAR
MEDIUM
OIacovery
0rbI18r
Olecovery
Mars
Olecovery
DIscovery
OIecovery
l01I. .
Orbll8r l01I. .
PlIlhnnder
INTERMEDIATE LARGE
easel...
INTERNATIONAL COOPERATIVES
Pluto Faet Flyby
Rosetta
FIGURE 1: FUTURE U.S. PLANETARY MISSIONS LAUNCH VEHICLE DESCRIPTIONS Figure 2 provides a summary of major U.S. launch vehicles available or soon to be available for planetary missions from small to large class. This section describes a number of those launch vehicles in some detail. A brief summary of international launch vehicles (other than U.S.) capable of launching planetary missions is given at the end of this section. Current U.S. Government policy is fairly restrictive regarding the usage of international launch vehicles for Government payloads, requiring special exemption and approval authority. Scientific missions which are cooperative in nature with another nation have somewhat easier access to that nation's launch services. U.S EXPENDABLE LAUNCH VEHICLES DESCRIPTION There are a variety of U.S. launch vehicles available for planetary missions. Within each launch vehicle family, there can be a number of different configurations. The discussion in this section covering U.S. launch vehicles centers on the Pegasus, Taurus, Lockheed Launch Vehicle (LLV), Conestoga, Delta, Atlas, and Titan II launch vehicles. The Titan IV and Space Shuttle are not discussed any further, as they are
590
Low-cost planetary missions
not compatible with low cost planetary missions. The Medium-lite launch vehicle has yet to be selected, and is discussed further in a later section of this paper. LockMacl
l1lBnlVl
.....ch
VEHICLE
XLwltll PLANETARY CONAGURA1l0N Upper Siege PAYLOAD FAIRING DIAMETER
s.,...
Shutlle I
T......
V_h','_
Coneat0d8
Med-Ute
Delle
AU.a
l1lBnll
Centalr
IUS
SlBndard,
LLV2, LLV3(2) LLV3(4) LLV3 (6)
1662, 3632, 3672, 5672
TBD
7325,7925
II, IIA, liAS
tar 37 or 4. Upper S1age
-
-
92',120', 141'
72' dla 12-24ft Langlh
TBD
9 n, 9.5 n, 10ft
11 n, 14 ft
9.3ft
16.7 ft cia 50-16 ft
NtA
Peaaoua
XL
402ft
5.25n
Langth
a.:P=~~~)
WFF
CCAFS
CCAFS
WFF,CCAA
CCAFS
CCAFS
CCAFS
CCAFS
CCAFS
KSC
STATUS
Av_
Available
In
In
To Be
D,~..~ad
Available
Available
Available
Available
Available
Mld-Latt
1...
Now
Now
Now
Now
Now
530-35M
$45-50M
U5-95M
535-4OU'
NtA'
NtA'
INlllAL AVAILABIUTY
May 1994
Now
Nov 1994 (LLV1l
1994
PROJECTED COMMERCIAL LAUNCH COST
510-12M
519-2OM
52D-26M
511-24M
'NOT COMMERCIALLY AVAILABLE
FIGURE 2: U,S. LAUNCH VEHICLES FOR PLANETARY MISSIONS
PEGASUS Pegasus was privately developed in a joint venture between Orbital Sciences Corporation (OSC) and Hercules Aerospace Company. Pegasus is available in two basic configurations, a standard version and an XL version. The XL configuration utilizes stretched versions of the first and second stage motors. The configuration that would most likely be used for planetary missions is the Pegasus XL, with an added upper stage. That added upper stage could be a solid rocket motor (SRM) such as the Star 27. With a Star 27, the Pegasus XL could achieve roughly 100 kg to a C3 of a km2/sec2, and 85 kg to a C3 of 10 km2/sec2. The Pegasus payload fairing (PLF) is 4.2 feet in diameter, with a dynamic envelope that is 46 inches in diameter. The launch site that would be used to launch planetary missions on the Pegasus would most likely be the Wallops Flight Facility (WFF), located in Virginia. Unlike traditional ground launched vehicles, Pegasus is carried aloft by a carrier aircraft and, in a typical launch sequence, is released from the aircraft at an altitude of approximately 41,000 feet at a speed of Mach 0.8. Stage 1 ignites very shortly after the release, and the vehicle's autonomous flight control system provides the required guidance. Currently a 8-52 serves as the carrier aircraft, but OSC is in the process of replacing this with a commercial L1011. While the standard Pegasus has already flown, the first flight of the XL configuration on the L1011 is expected to occur this summer. Pegasus is available at a projected commercial cost of $10-12M. Four Pegasus flights have occurred. While all launches were successful, the first two missions failed to place their payloads into their desired orbits. TAURUS The core technologies developed by OSC in the Pegasus program have been used under contract to the Defense Advanced Projects Research Agency (DARPA) to develop and launch a ground based vehicle known as the Taurus. The first stage of the Taurus consists of a Thiokol Castor 120 SRM (known as "Stage A" in OSC nomenclature). Stage 1 and 2 consist of the same Hercules Orion 50S and Orion 50 SRM's used by Pegasus. For planetary applications, the current Orion 38 Stage 3
Low-cost planetary missions
591
SRM is replaced by a Star 37. The Taurus can also utilize the same stretched Hercules SRM's developed for the Pegasus XL. Therefore there are both standard and XL versions of the Taurus as well. In addition, another configuration using SRM strap-ons is currently under study, and is designated the Taurus XUS. The standard Taurus PLF has a 54 inch diameter dynamic envelope and is 130 inches in length. Taurus is capable of launching from either WFF or CCAFS for planetary missions. The projected commercial cost for Taurus is $18-20M. One Taurus has been successfully launched from Vandenberg Air Force Base (VAFB), although it had a Peacekeeper Stage 0 rather than a Thiokol Castor 120. All future Taurus launch vehicles will have a Castor 120 Stage O. LOCKHEED LAUNCH VEHICLE (LLV) Lockheed Missiles and Space Company, Inc. has undertaken the development of a modular series of launch vehicles known as the Lockheed Launch Vehicle (LLV) family. The various configurations are known as the LLV1, LLV2, LLV3(2), LLV3(3), LLV3(4), and LLV3(6). The most likely configurations for planetary mission applications would be the LLV2, LLV3(2), LLV3(4), and LLV3(6). The LLV2 and the core of the LLV3 consist of a Thiokol Castor 120 motors for the first and second stages, and an Orbus 21D third stage. The LLV3 uses a variable number of Castor IVA strapon motors to achieve added performance, with either 2, 3, 4, or 6 strap-ons possible. To achieve the necessary performance for planetary missions an additional fourth stage is required. Various options for a fourth stage are under evaluation by Lockheed, and are reflected in the performance curves given later in this paper. There are three PLF's available for use on the LLV. They vary from 92 inches to 141 inches in outer diameter. The dynamic envelope is still under evaluation, but should be about 7 inches less than the outer diameter. For planetary missions, the LLV would launch from Launch Complex 46 at CCAFS. Projected commercial prices for the LLV2 and LLV3 range from $20-26M. Note that these costs do not include the cost of a fourth stage, which could add another $5-1 OM to the cost. Lockheed plans to conduct the first launch of the LLV (LLV1 configuration) in November, 1994. CONESTOGA EER Systems is developing a series of launch vehicles known as the Conestoga. They have taken a modular approach, and as a result many different possible configurations of the Conestoga are available. The primary configurations that would be used for planetary mission applications are the 3632 and the 5672. In the Conestoga nomenclature, the first digit refers to the core (center) motor. For instance, a 3 designates the use of a Castor IVB XL, and a 5 the use of a Graphite Epoxy Motor (GEM) VN. The second digit designates the number of strap-on motors, which for the 3632 and 5672 is six. The strap-on motors are 2 Castor IV AXL and 4 Castor IV BXL for the 3632, and 2 GEM and 4 GEM VN for the 5672. The third and fourth digits identify the motors used for the mid and upper stages. For the 3632, an Orion 50XL serves as the mid stage, and a Star 48V as the upper stage. For the 5672, a Star 63F serves as the mid stage, and a Star 48V as the upper stage. Various PLF's are available, all of which are 72 inches in outer diameter (64 inch dynamic envelope) and range from 12 to 24 feet in length. EER has established the capability to launch from WFF for the upcoming COMET mission. Launch from CCAFS is also possible, and the performance numbers given later assume a CCAFS launch. Projected commercial
592
Low-cost planetary missions
cost for the Conestoga varies from $22-25M for the 3632 and 5672 configurations. Conestoga has not launched yet in an orbital configuration, but is due to launch the COMET mission sometime in mid to late 1994 (1620 configuration). DELTA II McDonnell Douglas Corporation is currently producing and launching the Delta II for Department of Defense (DOD), NASA, and commercial missions. The Delta II consists of various configurations. The primary configurations for planetary missions are the 7925 and the 7235. The main difference in the configurations is that the 7925 uses 9 GEM solid strap-on motors, whereas the 7325 uses only 3. The Delta performance curves given later in this paper assume the use of the 9.5 foot outer diameter PLF. The use of an 8 foot outer diameter PLF would increase performance by about 20-30 kg for the range of C3's considered. The use of a 10 foot PLF would reduce performance by about 40-60 kg (7925) and 30-40 kg (7325) for the range of C3's considered. A 10 foot composite fairing will replace the present aluminum fairing beginning in late 1996. Note that spacecraft weights of less than 680 kg above the third stage separation interface require a nutation control system modification. Planetary missions launching on the Delta II would lift-off from Launch Complex 17A or 17B located at CCAFS. The two launch pads could potentially support launches within a few days of each other if necessary to support more than one planetary mission within a specified planetary launch window. Commercial launch costs for the Delta II vary from $45-$50M. There have been a total of 226 Delta launch attempts, of which 23 have been the 7925 configuration. The overall Delta success rate is 214 out of 226 and all 7925's flown have been successful. The 7325 configuration has not flown yet. ATLAS General Dynamics is currently producing and launching the Atlas for DOD, NASA, and commercial missions. The Atlas is available in several configurations: the Atlas I, Atlas II, Atlas IIA, and Atlas liAS. This paper focuses on the various Atlas II configurations, as the Atlas I will complete its final mission in the 1995/96 timeframe. All Atlas configurations utilize the Centaur as an upper stage, with the same version of the Centaur on each version of the Atlas II. The difference between the Atlas II and the Atlas IIA involves an RL-10 engine upgrade. The Atlas liAS adds 4 Castor IVA strapon motors to boost performance over the Atlas IIA. The performance curves shown later in this paper for the Atlas assume the use of the large 14 foot outer diameter PLF. A smaller 11 foot diameter PLF is also available. The use of the 11 foot PLF adds about 80 kg performance to the Atlas IIA and anywhere from 0-40 kg for the Atlas liAS within the range of C3's considered. Atlas launches from Complex 36A and 36B at CCAFS. Commercial launch costs for the Atlas II family vary from $75-95M. All three versions of the Atlas II family are operational and flight validated. There have been a total of 82 Atlas-Centaur missions, of which 68 have been successful. Seven Atlas I's have flown, with three failures. Five Atlas II's have flown, with no failures. One Atlas lIa and one Atlas liAS have flown, with no failures. TITAN II Martin Marietta is currently launching Titan II's for DOD missions. The space launched version of the Titan II involves a conversion of the Titan II Intercontinental Ballistic
Low-cost planetary missions
593
Missile (ICBM). The Titan II utilizes N204 and Aerozine 50 as propellant in a two stage configuration. The first conversions of the Titan II to space launch configuration were used to launch the Gemini missions from 1964·1966, demonstrating a 100% reliability with 12 successful flights. The Titan II ICBM's were deactivated from 19821987 and placed into storage at Norton Air Force Base. A U.S. Air Force/Martin Marietta contract provided for refurbishment and launch of 14 Titan II's. The first flight under this program occurred in 1988, and there have been five Titan II flights from 1988 to the present, all successful. In order to achieve the necessary planetary performance capability, the performance curves shown later assume the use of a Star 48 upper stage for a Titan II launch out of CCAFS. While all Titan II launches since 1988 have occurred from VAFB, the Titan II also has the capability to launch from CCAFS with a new launch pad. The Titan II PLF has a 111.7 inch diameter dynamic envelope, and is available in several lengths ranging from 16 to 26 feet. The Titan II is not currently available as a commercial launcher, but projected commercial launch costs range from $35·40M, not including the cost of the upper stage. OTHER Two other potential small launch vehicle candidates for planetary missions are the PacAstro, in development by PacAstro Corporation, and Orbex, in development by International Microspace, Inc. (IMI). Planetary performance capabilities for these launch vehicles has not been determined yet. McDonnell Douglas Corporation is also considering new Delta launch vehicles targeted towards the Med-Lite category. They are known as Delta-Lite, and will provide roughly half the capability for planetary missions of the Delta 7925.
u.s.
EXPENDABLE LAUNCH VEHICLE PLANETARY PERFORMANCE
Planetary performance (in terms of injected payload mass) for the U.S. launch vehicles described above is shown in Figures 3 and 4 as a function of launch energy (C3). For OSC, only the performance for the Taurus is shown (Pegasus performance is described in the text above). The Taurus performance assumes a standard Taurus configuration with a Star 37 SRM replacing the Taurus third stage. For EER Systems, performance is shown for the two most likely planetary mission configurations, the 3632 and the 5672. For Lockheed, performance is shown for the LLV2 and the LLV3(6) in order to bound the various LLV configurations. The LLV performance curves assume the use of various fourth stages as described in the text above. The LLV performance also assumes the use of the 120 inch payload fairing, with the 141 inch fairing reducing performance by up to 50 kg (although a fiberglass version of the PLF is under development, in which case there would not be a performance hit). Figure 4 shows the performance for Titan II, Delta II, and Atlas launch vehicles. The Titan II performance assumes the use of a Star 48 upper stage. The Delta II performance assumes the use of the larger 10ft payload fairing, and the Atlas performance assumes the use of the large 14 ft payload fairing. While the Delta 7920 configuration could be used to support planetary missions with low C3 requirements, it is not reflected in the performance curves. All launches are assumed to occur out of Cape Canaveral Air Force Station (CCAFS).
594
Low-cost planetary missions
200+------+------+------+-------+-------; o 10
-5
20
15
C3 (km21sec2)
FIGURE 3: LAUNCH VEHICLE PLANETARY PERFORMANCE 1
2500
..-
--~.••.
:E
110
1500
..
>. a.
1_ DELTA 7325·10 500
nTAN IUSTAR 41
0 -5
0
5
10
15
20
C3 (km2lsec2)
RGURE 4: LAUNCH VEHICLE PLANETARY PERFORMANCE 2 MEDIUM-LITE LAUNCH SERVICES
NASA is currently planning a procurement for a new class of launch services to be known as Medium-Lite. The purpose is to fill a niche between the small and medium class launch categories, and to provide a less expensive route to space for low cost planetary missions in the future. Many of the U.S. launch vehicles discussed above
Low-cost planetary missions
595
are potential candidates for the Medium-Lite procurement. With almost half of the future U.S. planetary missions targeted for a medium-lite launch, this category of launch services could become the primary niche for low cost planetary missions. NASA currently plans to initiate the procurement with a Request for Proposal release sometime in late 1994, with a first launch opportunity sometime in 1998.
INTERNATIONAL EXPENDABLE LAUNCH VEHICLES There are a number of other international launch vehicles that could be used for planetary missions. All NASA missions that have launched or are planned to be launched on an international launch vehicle have done so as part of a cooperative venture in which the U.S. and various international partners have participated in various aspects of the missions, sharing roles and responsibilities . Launch on an international launch vehicle in any other arrangement by a U.S. planetary mission would be difficult at best given current U.S. Government law and policy regarding use of foreign launch vehicles. This section briefly describes some of the available international launch vehicles. Note that most of these launch vehicles are in the intermediate or above class, and do not lend well to low cost planetary missions by themselves. Their attractiveness comes into play primarily when their use is as a part of a cooperative venture, or for small planetary missions requiring high launch energies (such as the Pluto Fast Flyby mission). For Russia, the primary launch vehicle that would be considered for use in a cooperative planetary mission is the Proton. The Proton has considerable performance capability, ranging from roughly 7000 down to 4000 kg for C3's of 0-20 km2lsec2. The largest PLF available is about 13.5 feet in outer diameter. The Proton launches from Baikonur in Russia. The Proton has had a total of 212 launches, with 187 successes. The Proton is commercially available, with some restrictions. The Ariane 5 is in development by Arianespace, and is slated for a first launch sometime in 1995. The Ariane 5 would have planetary performance capability at least on par with the Proton. The Ariane 5 PLF is 17.7 feet in outer diameter. Arianespace maintains a launch complex at Kourou, located in French Guiana. The Ariane 5 will be commercially available. The H2 was developed by the National Space Development Agency (NASDA) of Japan. It currently has had one successful launch. Performance capability varies from roughly 2500 kg (C3 of 0 km2/sec2) to 1500 kg (C3 of 20 km2/sec2). The PLF is about 13.4 feet in outer diameter. The H2 launches from Tanegashima in Japan. and is not currently commercially available. The H2 is constrained to 2 relatively brief launch periods each year.
LAUNCH SERVICE COSTS There are various components of cost common to any launch service. The basic launch services cost includes the vehicle cost itself, which is in turn dependent upon the configuration chosen as well as PLF size. Range services, payload processing, and propellants are other necessary components of the total launch service cost. Then there are additional costs associated with particular missions, and these are known as mission unique costs. These include mission unique changes or additions
596
Low-cost planetary mi ssions
to the basic launch vehicle, mission peculiar payload processing, support for nuclear material (such as radio-isotope thermal generators) environmental and launch approval processes, etc. If an additional upper stage is required, this can also be a separate, additive cost component. And finally, insurance is yet another component of cost. Insurance costs may come in several different flavors, including damage to government property, liability, and reflight insurance. All of these costs have to be considered in any launch service, and projected commercial launch cost quotes may or may not include all of these elements (e.g. the cost of an added upper stage). In addition, commercial quotes from different manufacturers may not all contain the same elements, so it is not strictly possible to compare quotes on an exact apples-to-apples basis.
CONCLUSIONS It is clear that the wave of the future for planetary missions is smaller and less expensive. As a result, there will be an increase in planetary flight opportunities compared to what has happened since the late 1970's. With an increased attention to reducing overall life cycle costs on planetary missions, developing less expensive launch alternatives is imperative. The launch vehicle industry appears ready to meet the challenge with various alternative concepts.
ACKNOWLEDGEMENTS The authors would like to thank the companies of the respective launch vehicles discussed in this paper for providing detailed descriptions and performance data.
REFERENCES 1 NASA Pocket Statistics, January 1993. 2 NASA Headquarters Launch Vehicles Office Manifests, "ELV and Upper Stages Program Planning- and "NASA ELV Long Range Planning - Potential Missions", published monthly. 3 "Discovery's Lure Prompts a Dozen Proposals at JPL", Space News, February 7-13, 1994, pg 8. 4 NASA Announcement of Opportr.nlty, Discovery Missions, draft version, March 1994. 5 "U.S. Civilian Government Expendable Launch Vehicle Payload Compendium", Seventh Edition, April 1994.
Acta Astronautica Vol. 35, Suppl., pp. 587-596, 1995 Elsevier Science Ltd. Printed in Great Britain
Pergamon
0094-5765(94)00226-6
CAPABILITIES, COSTS, AND CONSTRAINTS OF SPACE TRANSPORTATION FOR PLANETARY MISSIONS Karen S. Poniatowski and Michael G. Osmolovsky New Programs and Integration Launch Vehicles Office National Aeronautics and Space Administration Washington, D.C. 20546-0001
SUMMARY Launch vehicles currently fall into roughly four different performance categories: small, medium, intermediate, and large. In the past, most planetary missions relied on launch vehicles in the intermediate to large class, primarily because of heavy spacecraft or high launch energies. Recently, a shift has begun towards lower cost planetary missions that have more narrowly focused science objectives. Accordingly, the launch vehicle focus within NASA is shifting to medium performance class and below for new planetary missions, with an increase in planetary launch opportunities. A variety of U.S. and International launchers are available for this new category of missions, and their performance and capabilities are described in some detail. Included in the discussion are costs (U.S. only) and constraints associated with each launch vehicle. Some are currently in production, and many are just developmental at this point in time. Within NASA, there is a potential procurement for a new class of launch vehicle in between the small and medium classes. This category is termed medium-lite, and could become the primary niche for low-cost planetary missions in the future.
INTRODUCTION Space transportation for low cost planetary missions is an increasingly important topic because of heightened attention to mission life cycle costs and restricted budgets. There is a return to a philosophy more in tune with the earlier days of the U.S. planetary program, in which smaller missions were launched at more frequent intervals. This paper outlines and describes in some detail those launch vehicles which could be used to support planetary missions in the future. The concentration here is on U.S. launch vehicles, although a brief discussion on international launchers available outside of the U.S. is included. Detailed performance curves are provided, as well as a brief discussion of the various cost components that must be considered in any launch service.
PLANETARY MISSION MODEL The planetary mission profile for the United States has been characterized in the pastt by an increasing reliance on large, heavy spacecraft with a wide array of science being performed. This led to a situation where planetary spacecraft became more and more expensive. Since budget growth in the Federal Government did not take place as anticipated, fewer planetary launch opportunities were available. The reliance on large spacecraft also led to a situation where planetary spacecraft mass and launch 5H7
Low-cost planetary missions
energy requirements were such that launching on anything other than a Space Shuttle or large ELV was not possible. Note that for the purposes of this paper, planetary missions are defined as those spacecraft specifically targeted to perform science on or at one of the other planets in our solar system besides the Earth. This does not include the Sun, which more properly falls into the area of Space Physics. So while certain missions may fly an interplanetary trajectory, they may not be specifically counted as a planetary mission (Ulysses, which is a mission to study the Sun, is a primary example) in this paper. Ironically, the early U.S. planetary program was characterized by more frequent, smaller missions with a series of missions (at least two) being targeted for a specific planetary objective. From 1958-1973 there were 38 planetary missions, starting with Pioneer 1 (launched November 11, 1958) through the Ranger series, the Lunar Orbiter series, the Surveyor and Mariner series, and culminating with the launch of Pioneer 10 and 11 (March 2, 1972 and April 5, 1973 respectively). While most of these missions were launched on smaller ELV's (Thor-Able, Juno, Atlas-Able, and Atlas-Agena), some were already requiring the services of an Atlas-Centaur to achieve the proper planetary flyby trajectories. From 1975-1978 there were 6 planetary missions, which were becoming progressively larger and more ambitious. As a result, all of these missions launched on Atlas-Centaurs or on Titan Ill's. This period began with the Viking program (the launch of the first Viking took place on August 20, 1975) and ended with the Pioneer Venus series, the last of which launched on August 8, 1978. Finally, between 1978 and 1994 there were only 4 planetary missions launched. Three of these missions involved highly complex and large spacecraft, and had to be launched on a Space Shuttle/Inertial Upper Stage (IUS) combination or Titan Ill/Transfer Orbit Stage (TOS) combination. The fourth mission, the Clementine mission (launched January 25, 1994 on a smaller Titan II), points the way to a return to a philosophy of launching smaller, more numerous planetary missions in the future. Provided that the budgetary environment remains consistent, the future looks relatively bright for planetary launch opportunities. The projected manifest shows a total of 16 missions planned for the next 10 years 2 . All missions, with the exception of the Cassini mission to Saturn and international cooperative missions, will be launched on medium class or smaller launch vehicles. These missions involve smaller, less expensive spacecraft with more focused mission objectives. The Discovery Program seeks to enable a series of small planetary missions that would perform high quality, focused solar system science and to reduce total mission cost 3. One characteristic of the Discovery missions is that they are constrained to launch on a medium-class or smaller launch vehicle 4 . The first two Discovery missions are the Near Earth Asteroid (NEAR) mission, and the Mars Pathfinder mission (a Mars Lander/Rover combination). NEAR will launch in February 1996, to be followed by the Mars Pathfinder mission in December 1996. Other Discovery launch opportunities will begin in 1999 and result in roughly one launch a year thereafter. The exact makeup of the future Discovery mission set will be determined through an Announcement of Opportunity and selection process. NASA also plans to initiate a new program targeted towards exploration of Mars. This program is called the Mars Surveyor Program. It begins with the launch of a Mars Orbiter in November 1996, followed by two more launch opportunities at the end of
Low-cost planetary missions
51\9
1998. These two launch opportunities would be used to launch a second orbiter, and also a Mars Lander, which would be similar to the Mars Pathfinder Lander that NASA plans to launch in 1996. A second set of 2 landers would be launched at the end of
2001. Joint NASA/International cooperative missions targeted for launch on international launch vehicles include the Pluto Fast Flyby, and Rosetta (comet rendezvous). Figure 1 summarizes future planetary missions in a manifest format>. ELVCLASS
1995
1996
1997
1998
1999
2000
2001
2002
Mare
Olecovery
2003
2004
2005
SMALL
.... ....
MED-L1TE
Lander
Lander
Lander
NEAR
MEDIUM
OIacovery
0rbI18r
Olecovery
Mars
Olecovery
DIscovery
OIecovery
l01I. .
Orbll8r l01I. .
PlIlhnnder
INTERMEDIATE LARGE
easel...
INTERNATIONAL COOPERATIVES
Pluto Faet Flyby
Rosetta
FIGURE 1: FUTURE U.S. PLANETARY MISSIONS LAUNCH VEHICLE DESCRIPTIONS Figure 2 provides a summary of major U.S. launch vehicles available or soon to be available for planetary missions from small to large class. This section describes a number of those launch vehicles in some detail. A brief summary of international launch vehicles (other than U.S.) capable of launching planetary missions is given at the end of this section. Current U.S. Government policy is fairly restrictive regarding the usage of international launch vehicles for Government payloads, requiring special exemption and approval authority. Scientific missions which are cooperative in nature with another nation have somewhat easier access to that nation's launch services. U.S EXPENDABLE LAUNCH VEHICLES DESCRIPTION There are a variety of U.S. launch vehicles available for planetary missions. Within each launch vehicle family, there can be a number of different configurations. The discussion in this section covering U.S. launch vehicles centers on the Pegasus, Taurus, Lockheed Launch Vehicle (LLV), Conestoga, Delta, Atlas, and Titan II launch vehicles. The Titan IV and Space Shuttle are not discussed any further, as they are
590
Low-cost planetary missions
not compatible with low cost planetary missions. The Medium-lite launch vehicle has yet to be selected, and is discussed further in a later section of this paper. LockMacl
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VEHICLE
XLwltll PLANETARY CONAGURA1l0N Upper Siege PAYLOAD FAIRING DIAMETER
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LLV2, LLV3(2) LLV3(4) LLV3 (6)
1662, 3632, 3672, 5672
TBD
7325,7925
II, IIA, liAS
tar 37 or 4. Upper S1age
-
-
92',120', 141'
72' dla 12-24ft Langlh
TBD
9 n, 9.5 n, 10ft
11 n, 14 ft
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CCAFS
CCAFS
WFF,CCAA
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CCAFS
CCAFS
KSC
STATUS
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Available
In
In
To Be
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Available
Available
Available
Available
Available
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Now
Now
Now
Now
530-35M
$45-50M
U5-95M
535-4OU'
NtA'
NtA'
INlllAL AVAILABIUTY
May 1994
Now
Nov 1994 (LLV1l
1994
PROJECTED COMMERCIAL LAUNCH COST
510-12M
519-2OM
52D-26M
511-24M
'NOT COMMERCIALLY AVAILABLE
FIGURE 2: U,S. LAUNCH VEHICLES FOR PLANETARY MISSIONS
PEGASUS Pegasus was privately developed in a joint venture between Orbital Sciences Corporation (OSC) and Hercules Aerospace Company. Pegasus is available in two basic configurations, a standard version and an XL version. The XL configuration utilizes stretched versions of the first and second stage motors. The configuration that would most likely be used for planetary missions is the Pegasus XL, with an added upper stage. That added upper stage could be a solid rocket motor (SRM) such as the Star 27. With a Star 27, the Pegasus XL could achieve roughly 100 kg to a C3 of a km2/sec2, and 85 kg to a C3 of 10 km2/sec2. The Pegasus payload fairing (PLF) is 4.2 feet in diameter, with a dynamic envelope that is 46 inches in diameter. The launch site that would be used to launch planetary missions on the Pegasus would most likely be the Wallops Flight Facility (WFF), located in Virginia. Unlike traditional ground launched vehicles, Pegasus is carried aloft by a carrier aircraft and, in a typical launch sequence, is released from the aircraft at an altitude of approximately 41,000 feet at a speed of Mach 0.8. Stage 1 ignites very shortly after the release, and the vehicle's autonomous flight control system provides the required guidance. Currently a 8-52 serves as the carrier aircraft, but OSC is in the process of replacing this with a commercial L1011. While the standard Pegasus has already flown, the first flight of the XL configuration on the L1011 is expected to occur this summer. Pegasus is available at a projected commercial cost of $10-12M. Four Pegasus flights have occurred. While all launches were successful, the first two missions failed to place their payloads into their desired orbits. TAURUS The core technologies developed by OSC in the Pegasus program have been used under contract to the Defense Advanced Projects Research Agency (DARPA) to develop and launch a ground based vehicle known as the Taurus. The first stage of the Taurus consists of a Thiokol Castor 120 SRM (known as "Stage A" in OSC nomenclature). Stage 1 and 2 consist of the same Hercules Orion 50S and Orion 50 SRM's used by Pegasus. For planetary applications, the current Orion 38 Stage 3
Low-cost planetary missions
591
SRM is replaced by a Star 37. The Taurus can also utilize the same stretched Hercules SRM's developed for the Pegasus XL. Therefore there are both standard and XL versions of the Taurus as well. In addition, another configuration using SRM strap-ons is currently under study, and is designated the Taurus XUS. The standard Taurus PLF has a 54 inch diameter dynamic envelope and is 130 inches in length. Taurus is capable of launching from either WFF or CCAFS for planetary missions. The projected commercial cost for Taurus is $18-20M. One Taurus has been successfully launched from Vandenberg Air Force Base (VAFB), although it had a Peacekeeper Stage 0 rather than a Thiokol Castor 120. All future Taurus launch vehicles will have a Castor 120 Stage O. LOCKHEED LAUNCH VEHICLE (LLV) Lockheed Missiles and Space Company, Inc. has undertaken the development of a modular series of launch vehicles known as the Lockheed Launch Vehicle (LLV) family. The various configurations are known as the LLV1, LLV2, LLV3(2), LLV3(3), LLV3(4), and LLV3(6). The most likely configurations for planetary mission applications would be the LLV2, LLV3(2), LLV3(4), and LLV3(6). The LLV2 and the core of the LLV3 consist of a Thiokol Castor 120 motors for the first and second stages, and an Orbus 21D third stage. The LLV3 uses a variable number of Castor IVA strapon motors to achieve added performance, with either 2, 3, 4, or 6 strap-ons possible. To achieve the necessary performance for planetary missions an additional fourth stage is required. Various options for a fourth stage are under evaluation by Lockheed, and are reflected in the performance curves given later in this paper. There are three PLF's available for use on the LLV. They vary from 92 inches to 141 inches in outer diameter. The dynamic envelope is still under evaluation, but should be about 7 inches less than the outer diameter. For planetary missions, the LLV would launch from Launch Complex 46 at CCAFS. Projected commercial prices for the LLV2 and LLV3 range from $20-26M. Note that these costs do not include the cost of a fourth stage, which could add another $5-1 OM to the cost. Lockheed plans to conduct the first launch of the LLV (LLV1 configuration) in November, 1994. CONESTOGA EER Systems is developing a series of launch vehicles known as the Conestoga. They have taken a modular approach, and as a result many different possible configurations of the Conestoga are available. The primary configurations that would be used for planetary mission applications are the 3632 and the 5672. In the Conestoga nomenclature, the first digit refers to the core (center) motor. For instance, a 3 designates the use of a Castor IVB XL, and a 5 the use of a Graphite Epoxy Motor (GEM) VN. The second digit designates the number of strap-on motors, which for the 3632 and 5672 is six. The strap-on motors are 2 Castor IV AXL and 4 Castor IV BXL for the 3632, and 2 GEM and 4 GEM VN for the 5672. The third and fourth digits identify the motors used for the mid and upper stages. For the 3632, an Orion 50XL serves as the mid stage, and a Star 48V as the upper stage. For the 5672, a Star 63F serves as the mid stage, and a Star 48V as the upper stage. Various PLF's are available, all of which are 72 inches in outer diameter (64 inch dynamic envelope) and range from 12 to 24 feet in length. EER has established the capability to launch from WFF for the upcoming COMET mission. Launch from CCAFS is also possible, and the performance numbers given later assume a CCAFS launch. Projected commercial
592
Low-cost planetary missions
cost for the Conestoga varies from $22-25M for the 3632 and 5672 configurations. Conestoga has not launched yet in an orbital configuration, but is due to launch the COMET mission sometime in mid to late 1994 (1620 configuration). DELTA II McDonnell Douglas Corporation is currently producing and launching the Delta II for Department of Defense (DOD), NASA, and commercial missions. The Delta II consists of various configurations. The primary configurations for planetary missions are the 7925 and the 7235. The main difference in the configurations is that the 7925 uses 9 GEM solid strap-on motors, whereas the 7325 uses only 3. The Delta performance curves given later in this paper assume the use of the 9.5 foot outer diameter PLF. The use of an 8 foot outer diameter PLF would increase performance by about 20-30 kg for the range of C3's considered. The use of a 10 foot PLF would reduce performance by about 40-60 kg (7925) and 30-40 kg (7325) for the range of C3's considered. A 10 foot composite fairing will replace the present aluminum fairing beginning in late 1996. Note that spacecraft weights of less than 680 kg above the third stage separation interface require a nutation control system modification. Planetary missions launching on the Delta II would lift-off from Launch Complex 17A or 17B located at CCAFS. The two launch pads could potentially support launches within a few days of each other if necessary to support more than one planetary mission within a specified planetary launch window. Commercial launch costs for the Delta II vary from $45-$50M. There have been a total of 226 Delta launch attempts, of which 23 have been the 7925 configuration. The overall Delta success rate is 214 out of 226 and all 7925's flown have been successful. The 7325 configuration has not flown yet. ATLAS General Dynamics is currently producing and launching the Atlas for DOD, NASA, and commercial missions. The Atlas is available in several configurations: the Atlas I, Atlas II, Atlas IIA, and Atlas liAS. This paper focuses on the various Atlas II configurations, as the Atlas I will complete its final mission in the 1995/96 timeframe. All Atlas configurations utilize the Centaur as an upper stage, with the same version of the Centaur on each version of the Atlas II. The difference between the Atlas II and the Atlas IIA involves an RL-10 engine upgrade. The Atlas liAS adds 4 Castor IVA strapon motors to boost performance over the Atlas IIA. The performance curves shown later in this paper for the Atlas assume the use of the large 14 foot outer diameter PLF. A smaller 11 foot diameter PLF is also available. The use of the 11 foot PLF adds about 80 kg performance to the Atlas IIA and anywhere from 0-40 kg for the Atlas liAS within the range of C3's considered. Atlas launches from Complex 36A and 36B at CCAFS. Commercial launch costs for the Atlas II family vary from $75-95M. All three versions of the Atlas II family are operational and flight validated. There have been a total of 82 Atlas-Centaur missions, of which 68 have been successful. Seven Atlas I's have flown, with three failures. Five Atlas II's have flown, with no failures. One Atlas lIa and one Atlas liAS have flown, with no failures. TITAN II Martin Marietta is currently launching Titan II's for DOD missions. The space launched version of the Titan II involves a conversion of the Titan II Intercontinental Ballistic
Low-cost planetary missions
593
Missile (ICBM). The Titan II utilizes N204 and Aerozine 50 as propellant in a two stage configuration. The first conversions of the Titan II to space launch configuration were used to launch the Gemini missions from 1964·1966, demonstrating a 100% reliability with 12 successful flights. The Titan II ICBM's were deactivated from 19821987 and placed into storage at Norton Air Force Base. A U.S. Air Force/Martin Marietta contract provided for refurbishment and launch of 14 Titan II's. The first flight under this program occurred in 1988, and there have been five Titan II flights from 1988 to the present, all successful. In order to achieve the necessary planetary performance capability, the performance curves shown later assume the use of a Star 48 upper stage for a Titan II launch out of CCAFS. While all Titan II launches since 1988 have occurred from VAFB, the Titan II also has the capability to launch from CCAFS with a new launch pad. The Titan II PLF has a 111.7 inch diameter dynamic envelope, and is available in several lengths ranging from 16 to 26 feet. The Titan II is not currently available as a commercial launcher, but projected commercial launch costs range from $35·40M, not including the cost of the upper stage. OTHER Two other potential small launch vehicle candidates for planetary missions are the PacAstro, in development by PacAstro Corporation, and Orbex, in development by International Microspace, Inc. (IMI). Planetary performance capabilities for these launch vehicles has not been determined yet. McDonnell Douglas Corporation is also considering new Delta launch vehicles targeted towards the Med-Lite category. They are known as Delta-Lite, and will provide roughly half the capability for planetary missions of the Delta 7925.
u.s.
EXPENDABLE LAUNCH VEHICLE PLANETARY PERFORMANCE
Planetary performance (in terms of injected payload mass) for the U.S. launch vehicles described above is shown in Figures 3 and 4 as a function of launch energy (C3). For OSC, only the performance for the Taurus is shown (Pegasus performance is described in the text above). The Taurus performance assumes a standard Taurus configuration with a Star 37 SRM replacing the Taurus third stage. For EER Systems, performance is shown for the two most likely planetary mission configurations, the 3632 and the 5672. For Lockheed, performance is shown for the LLV2 and the LLV3(6) in order to bound the various LLV configurations. The LLV performance curves assume the use of various fourth stages as described in the text above. The LLV performance also assumes the use of the 120 inch payload fairing, with the 141 inch fairing reducing performance by up to 50 kg (although a fiberglass version of the PLF is under development, in which case there would not be a performance hit). Figure 4 shows the performance for Titan II, Delta II, and Atlas launch vehicles. The Titan II performance assumes the use of a Star 48 upper stage. The Delta II performance assumes the use of the larger 10ft payload fairing, and the Atlas performance assumes the use of the large 14 ft payload fairing. While the Delta 7920 configuration could be used to support planetary missions with low C3 requirements, it is not reflected in the performance curves. All launches are assumed to occur out of Cape Canaveral Air Force Station (CCAFS).
594
Low-cost planetary missions
200+------+------+------+-------+-------; o 10
-5
20
15
C3 (km21sec2)
FIGURE 3: LAUNCH VEHICLE PLANETARY PERFORMANCE 1
2500
..-
--~.••.
:E
110
1500
..
>. a.
1_ DELTA 7325·10 500
nTAN IUSTAR 41
0 -5
0
5
10
15
20
C3 (km2lsec2)
RGURE 4: LAUNCH VEHICLE PLANETARY PERFORMANCE 2 MEDIUM-LITE LAUNCH SERVICES
NASA is currently planning a procurement for a new class of launch services to be known as Medium-Lite. The purpose is to fill a niche between the small and medium class launch categories, and to provide a less expensive route to space for low cost planetary missions in the future. Many of the U.S. launch vehicles discussed above
Low-cost planetary missions
595
are potential candidates for the Medium-Lite procurement. With almost half of the future U.S. planetary missions targeted for a medium-lite launch, this category of launch services could become the primary niche for low cost planetary missions. NASA currently plans to initiate the procurement with a Request for Proposal release sometime in late 1994, with a first launch opportunity sometime in 1998.
INTERNATIONAL EXPENDABLE LAUNCH VEHICLES There are a number of other international launch vehicles that could be used for planetary missions. All NASA missions that have launched or are planned to be launched on an international launch vehicle have done so as part of a cooperative venture in which the U.S. and various international partners have participated in various aspects of the missions, sharing roles and responsibilities . Launch on an international launch vehicle in any other arrangement by a U.S. planetary mission would be difficult at best given current U.S. Government law and policy regarding use of foreign launch vehicles. This section briefly describes some of the available international launch vehicles. Note that most of these launch vehicles are in the intermediate or above class, and do not lend well to low cost planetary missions by themselves. Their attractiveness comes into play primarily when their use is as a part of a cooperative venture, or for small planetary missions requiring high launch energies (such as the Pluto Fast Flyby mission). For Russia, the primary launch vehicle that would be considered for use in a cooperative planetary mission is the Proton. The Proton has considerable performance capability, ranging from roughly 7000 down to 4000 kg for C3's of 0-20 km2lsec2. The largest PLF available is about 13.5 feet in outer diameter. The Proton launches from Baikonur in Russia. The Proton has had a total of 212 launches, with 187 successes. The Proton is commercially available, with some restrictions. The Ariane 5 is in development by Arianespace, and is slated for a first launch sometime in 1995. The Ariane 5 would have planetary performance capability at least on par with the Proton. The Ariane 5 PLF is 17.7 feet in outer diameter. Arianespace maintains a launch complex at Kourou, located in French Guiana. The Ariane 5 will be commercially available. The H2 was developed by the National Space Development Agency (NASDA) of Japan. It currently has had one successful launch. Performance capability varies from roughly 2500 kg (C3 of 0 km2/sec2) to 1500 kg (C3 of 20 km2/sec2). The PLF is about 13.4 feet in outer diameter. The H2 launches from Tanegashima in Japan. and is not currently commercially available. The H2 is constrained to 2 relatively brief launch periods each year.
LAUNCH SERVICE COSTS There are various components of cost common to any launch service. The basic launch services cost includes the vehicle cost itself, which is in turn dependent upon the configuration chosen as well as PLF size. Range services, payload processing, and propellants are other necessary components of the total launch service cost. Then there are additional costs associated with particular missions, and these are known as mission unique costs. These include mission unique changes or additions
596
Low-cost planetary mi ssions
to the basic launch vehicle, mission peculiar payload processing, support for nuclear material (such as radio-isotope thermal generators) environmental and launch approval processes, etc. If an additional upper stage is required, this can also be a separate, additive cost component. And finally, insurance is yet another component of cost. Insurance costs may come in several different flavors, including damage to government property, liability, and reflight insurance. All of these costs have to be considered in any launch service, and projected commercial launch cost quotes may or may not include all of these elements (e.g. the cost of an added upper stage). In addition, commercial quotes from different manufacturers may not all contain the same elements, so it is not strictly possible to compare quotes on an exact apples-to-apples basis.
CONCLUSIONS It is clear that the wave of the future for planetary missions is smaller and less expensive. As a result, there will be an increase in planetary flight opportunities compared to what has happened since the late 1970's. With an increased attention to reducing overall life cycle costs on planetary missions, developing less expensive launch alternatives is imperative. The launch vehicle industry appears ready to meet the challenge with various alternative concepts.
ACKNOWLEDGEMENTS The authors would like to thank the companies of the respective launch vehicles discussed in this paper for providing detailed descriptions and performance data.
REFERENCES 1 NASA Pocket Statistics, January 1993. 2 NASA Headquarters Launch Vehicles Office Manifests, "ELV and Upper Stages Program Planning- and "NASA ELV Long Range Planning - Potential Missions", published monthly. 3 "Discovery's Lure Prompts a Dozen Proposals at JPL", Space News, February 7-13, 1994, pg 8. 4 NASA Announcement of Opportr.nlty, Discovery Missions, draft version, March 1994. 5 "U.S. Civilian Government Expendable Launch Vehicle Payload Compendium", Seventh Edition, April 1994.