The Maglifter: an Advanced Concept Using Electromagnetic Propulsion in Reducing the Cost of Space Launch

AlAA 94-2726

The MagLifter: An Advanced Concept Using Electromagnetic Propulsion in Reducing the Cost of Space Launch

John C. Mankins Advanced Concepts Division Office of Advanced Concepts and Technology National Aeronautics and Space Administration

39th Joint Propulsion Conference and Exhibit June 27-29, 1994 / Indianapolis, IN

~ ~~~ For permission to copy or republish, contact the American Institute of Aeronautics and Astronautics, 370 L'Enfant Promenade, S.W., Washington, D.C. 20024 MagLifter - An Advanced Concept AlAA 30th Joint Propulsion Conference 94-2726 June 27-29, 1994

-- . The MagLifter: An Advanced Concept Using Electromagnetic Propulsion in Reducing the Cost of Space

John C. Mankins Advanced Concepts Division Office of Advanced Concepts and Technology National Aeronautics and Space Administration Washington. D.C. 20546

ABSTRACT

Achieving an affordable and reliable launch infrastructure is one of the enduring challenges of the space age. In a marketplace dominated by expendable launch vehicles (ELVs) grounded in the technology base of the 1950s and 1960% diverse innovative approaches have been conceived since 1970 for reducing the cost per pound for transport to low Earth orbit LEO. For example, the Space Shuttle - a largely reusable vehicle - was developed in the 1970s with th goal of revolutionizing Earth-to-orbit (ETO) transportation. Although the Shuttle provide many important new capabilities, it did not significantly lower space launch costs. During the same period, a variety of other launch requirements (e.g., for vehicle research and development (R&D) and microgravity experiments) have been met by relatively expensive, typically rocket-based solutions (e.g., rocket sleds and sounding rockets).

There are several basic strategies for cost reduction, including: (1) reducing the cost of v hardware expended in launcher systems per pound of payload, (2) increasing the reusability per flight of highly reusable vehicles (HRVs), and (3) for both of these, reducing the cost of launch operations. A variety of space launch concepts are still under study in this context, ranging from single-stage-to-orbit (SSTO) vehicles to 'big-dumb-boosters', from air-breathing hypersonic ET0 vehicles like the National Aerospace Plane (NASP) to advanced rocket concepts such as space nuclear thermal propulsion (SNTP). Some exotic concepts involving 'gun-type' systems have also been studied.

However, past analyses of launch systems involving electric propulsion have been largely limited to electromagnetic (EM) versions of 'cannons' such as rail guns and coil guns. Despite significant theoretical advantages, these EM systems have had both technical and programmatic difficulties in maturing beyond R&D and prototype-level demonstrations.

A new approach, involving the use of superconducting magnetically-levitated ("maglev") vehicles has been developed. This ET0 concept, the "MagLiffer", combines the technology base of maglev systems proposed for terrestrial applications with the best planned improvements in ELV and reusable vehicle systems. Together, the result suggests dramatic improvements in ET0 costs may be possible. The MagLifterdraws on a heritage of EM launch concepts in fiction (many) and the technical literature (few), but embodies several new technical characteristics which have not been thoroughly considered to date.

. The MagLifter concept is summarized in the context of a brief review of EM launch approaches and maglev R&D efforts. The results of preliminary analyses are then presented. In addition, the potential benefits of the concept, including strong dual-use technology R&D content are sketched. Finally, some projections concerning potential directions for future study and development of the concept are discussed.

v MagLifter - An Advanced Concept AlAA 30th Joint Propulsion Conference 94-2726 June 27-29, 1994

INTRODUCTION A variety of space launch concepts are still under U - study in this context, ranging from single-stage- Achiehg an affordable and reliable launch to-orbit (SSTO) vehicles to 'big-dumb-boosters', infrastructure is one of the enduring challenges from air-breathing hypersonic ET0 vehicles (like of the space age. In a marketplace dominated by the National Aerospace Plane, NASP) to expendable launch vehicles (ELVs) grounded in advanced rocket concepts (such as space the technology base of the 1950s and 1960s. nuclear thermal propulsion (SNTP). Some diverse innovative approaches have been exotic concepts involving 'gun-type' systems conceived since 1970 for reducing the cost per have also been studied. pound for transport to low Earth orbit LEO. For example, the Space Shuttle - a largely reusable However, past analyses of ET0 systems vehicle - was developed in the 1970s to involving electromagnetic (EM) propulsion have revolutionize Earth-to-orbit (ETO) transportation. been largely limited to EM versions of 'cannons'; During the same period, a variety of other launch e.g., coil guns. Despite significant theoretical requirements (e.g., for vehicle research and advantages, however, these EM systems have development (RBD) and microgravity had technical and programmatic trouble in experiments) have been met by relatively maturing beyond the R&D and prototype-level. expensive, typically rocket-based solutions (such as rocket sleds and sounding rockets). A new approach, involving the use of superconducting magnetic-levitation("maglev") There are at least basic strategies for cost has been developed. This concept, called reduction: (1) reducing the cost of hardware "MagLifter". is a catapult that uses maglev to expended in launchers per pound of payload, achieve dramatically augmented payload (2) increasing the reusability per flight of highly capacity in ET0 transportation systems, while reusable vehicles (HRVs), and (3) for both of reducing mission costs. Figure 1 provides a these, reducing the cost of launch operations. conceptual diagram of the MagLifter system.

Enghne Slail lor Pre-

POWER SvrrEu

EXAMPLE PAYLOAD: HIGHLY REUSABLEVECHILE. (HRv)

MagLev Accelerator- SlNcIural S"pp0iis Carrier Vehicle (Distributionof Loads on Payload \ Vehicle) SYSTEM Maglev Guideway ,! ..... cRoss~sEcr,oN......

L Figure 1 Top-Level Diagram of a MagLifter system (large-scale reference version)

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Unlike other "gun" concepts, MagLifter does However, all of them have several severe arequire extremely high accelerations, does constraints that limit their potential utility. u - ainvolve radical changes in payload (Le., spacecraft) design or components, and does net In addition, all gun concepts are limited in the require very high launch rates to achieve low-end cost performance that can be achieved economical operations. Instead, MagLifter in operations because so much of the hardware marries the promise of low-cost EM launch - - except for the gun itself - is expended with popularized in fiction -with current engineering each launch, including the sabot, the projectile's ideas for improvements in systems and heat shield, and the orbit insertion propulsion operations for space launch (e.g.. ETO). The module. Only for very aggressive traffic models potential appears to exist for a significant (Le., high numbers of launches per year) do the reduction in the cost (per pound of payload) to economies of scale drive the cost per pound (to LEO for a wide range of payload sizes and LEO) into competitive ranges. (For example, as launch vehicle concepts. many as 4 launches per day may be needed to achieve cost goals for some gun concepts.) MagLifter involves the application of superconductive magnetic levitation (maglev) CataDults in %ace Launch. technology - developed for ground transport - to the challenge of reducing the cost of space There have been a number of papers launch. published and concepts developed for the use of EM (and rocket-powered) catapults in space launch systems. For example, in the early This is a summary paper describing the 196Os, a study was conducted at Holloman AFB MagLifter concept and, hopefully, providing a on the effects of changing initial state vectors on point of departure for additional studies of the launch to orbit performance.' Other concepts diverse array of issues and topics - ranging from were also put forward during that same decade. technology development challenges to alternate In the mid-1960s. the "Hyperion" concept was system applications - that need further study. developed, in which an Apollo-derived, large scale SSTO vehicle was to be launched from a 'v rocket-powered sled and track running up the BACKGROUND side of a mountain.

Electromagnetic launchers were considered extensively in the 1970s for applications on the Various gun-based approaches to ET0 lunar surface. These scenarios typically involved transportation - with varying degrees of the launch of extremely large amounts of Lunar feasibility - have been invented, beginning in materials for use in the construction of Solar the last century with the fictional cannon used by Power Satellites (SPS) in high or geostationary Jules Verne in his novel concerning the first Earth orbit. Concepts included 'rail guns' and co- lunarflight. The essence of these concepts is to axial concepts such as 'coil guns'. However, use a single, massive impulse (provided by the preliminary R&D and studies did not result in a gun) to directly (or very nearly directly) propel a major programmatic thrust in this area. payload into space. Some of the most famous of these have involved very large, black powder In the 198Os, consideration of a number of cannons. However, in reality such guns have EM catapulVgun concepts continued. Most of limited muzzle velocities and lack the potential these involved achieving very high velocities at for direct shots to LEO. Recent developments - the release of the vehicle (or payload) being driven by Strategic Defense Initiative Office launched, with the release being made at an (SDIO) - have involved other 'explosive' angle at or near 90 degrees from the horizontal. concepts such as 'light gas guns' (which use a In some cases the length of the catapult was gas such as Helium as a working fluid) and EM driven to absurd extremes in the attempt to gun concepts, (such as coil guns and rail guns) reduce otherwise very high acceleration loads which expel a projectile at much higher speeds. Some of these concepts have been 'This study from 1964 did not address the question of demonstrated at an R&D level with sufficient how the initial state vector was created - Le., what fidelity to suggest that - given time and money - type of catapult might be used. Nevertheless, this they could be brought into operational use. study obtained very promising and early analytlc v results in support of low speed catapult launch iat angles up to 40 degrees from the horizontal)

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- during the launch. An exception to this rule was However, U.S. funding has been intermittent the class of concepts considered for launching and most U.S. programs were canceled in the L/ - largely aerodynamic and potentially air breathing 1970s. Conversely, Japan has been steadily ET0 vehicles such as the NASP. In a concept of developing EDS maglev for 20 years. In fact, 10 this type, a horizontal track and carrier vehicle are years ago, the Japanese National Railway used to accelerate a NASP-like vehicle to sub- demonstrated an unmanned vehicle at more sonic take-off speeds on a horizontal runway. than 300 mph on an open-air, 4-mile track. Such a system - which could be electromagnetic Current Japanese plans call for an EDS system (e.g., LMATO, the Linear-Motor-AssistedTake- to be constructed between Tokyo and Osaka in Off system) - replaced the need for a massive the post-2001 timeframe. Similar maglev landing gear system as well as providing initial developments in Germany have focused on the velocity. * However, neither high-speed I high- EMS levitation approach. The German TR-07 angle, nor low-speed horizontal EM guns or system has been operated by Transrapid catapults were given serious consideration for International, Inc., at speeds near 300 mph. use in developing space launch. At present, US. interest in maglev remains During the three decades of the 1960s. strong, albeit frustrated. The focus of this OS, and %Os, however, there were other interest has been the Department of develoDments beino made in the amlication of Transportation (DOT) Federal Railroad EM systems to ground transportation that may Administration (FRA). which managed the allow a transformat'on in how EM-assist is National Maglev 1n:tiative (NMI). Suspended due appraised for space launch applications. to budget pressures in Winter 1994, the NMI funded several studies and R&D efforts that Maolev for Ground Transoortation were targeted toward a demonstration maglev system in a high-density urban corridor (such as The concept of using magnetic forces for the Northeast). This demonstration would have ground transportation has existed since the 19th been in the 300 mph-class, using century. For example, before 1910 Robert superconducting magnetic systems (SMS) for Goddard made a proposal for a tunnel-based EM both levitation and propulsion. At present, the train system for high-speed transport in New FRA is continuing its studies to determine the u England. In 1966, such ideas became feasible economic viability of introducing maglev into the when two U.S. researchers, James Powell and U.S. transportation infrastructure. Gordon Danby, invented the concept of applying superconducting magnetic systems In addition, the Department of Defense (SMS) for magnetic levitation (maglev) (DOD), US.Air Force (USAF) at Holloman AFB transportation systems. in Southern New Mexico has initiated a program to use SMS for levitation in an upgrade of the During the last 30 years, diverse maglev Base's track for the very-high-speed rock- R&D programs have been implemented. Two propelled sled runs. The target in this principal approaches have been developed for development is speeds in the range of 7-10 levitation: attractive, Electromagnetic times the speed of sound on an open-air Suspension (EMS) and repulsive, operational track. Electrodynamic Suspension (EDS).3 For both levitation systems, a linear synchronous motor On the basis of diverse studies and (LSM), or derivative, would probably be used for development projects, estimates of costs for propulsion. maglev systems have been developed by various organizations. For a guideway in the Baseline technologies for superccnducting 300+ mph class, cost estimates range from $10 and non-superconducting maglev are quite to 20 million per mile. For this guideway, mature. Various concepts were pursued in the estimated costs for maglev vehicles are on the US.in the late 1960s and the early 197Os, order of $3to 5 million per vehicle (for a payload 1 including some sub-scale demonstrations. of approximately 50,000 Ibs.). In addition, annual operations and maintenance (O&M) costs for these systems are projected to be quite 2There have also been a number of developments in modest (e.g., annual maglev O&M has been the use of EM systems to replace traditional steam- estimated to be on the order of 1% of capital drive catapults used on aircraft carriers: these are, costs). L' however, not the subject of this paper. Either of these may be suitable for MagLifter.

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-merit of a New ConceDi accelerator-carriervehicles (ACVs) are the first half of the major element of a v - Past space launch studies make it clear that maglev-basedcatapult launch system new systems and new concepts will be needed The ACVs provide the initial acceleration to truly reduce space launch costs. However, for the vehicles to be launched. These using current and near-term traditional carriers, which may need to be 'ganged' technologies, the 'margin' for achieving for launching larger vehicles, would engineering goals in new systems may be very accommodate 'cradles' capable of close. R&D in maglev for ground transportation structural support to vehicles during applications and a reexamination of existing gun acceleration as well as rapid, controlled and EM launch concepts suggest that a hybrid release at the appropriate point in the approach -such as MagLfier - may be a partial catapult launch sequence. They would answer to the space launch cost challenge. also provide any needed support for vehicles during the launch sequence (approximately 1 minute in duration). DESCRIPTION OF THE MAGLIFTER CONCEPT Accelerator-Carrier Staging Facility - a carrier servicing and staging The overall architecture of the MagLifter facility will be needed for maglev carrier system consists of the following major elements: staging, vehicle-carrier integration, the catapult, structural support systems, power launch vehicle staging (specific to systems, and supporting systems. Figure 2 vehicles and payloads), servicing and provides a top-level illustration of this system maintenance facilities, and an operations architecture. The description which follows of control.6 each of these elements corresponds to a large scale version of the MagLifter. Structural SLID DO^^ Svstem. A large maglev catapult would require substantial structural The Cataoult. The MagLifter catapult support for effective operations. A central includes three major component systems: desiy trade (cited below under issues for L4 further study) involves the question of whether - The Maglev Guideway - The maglev or not to place the guideway: (a) on a 'trestle" on guideway is the second half of the major the exterior of a mountain, (b) inside a 'cut' made system element of a maglev-basedcatapult into the side of a mountain, or (c) inside a tunnel' launch system. Central questions inside the mountain. associated with the guideway include the means and cost of construction of the Implicit in the trade just cited, of course, system, tolerances and control, and the is the assumption that the system must use a structure and structural dynamics (see the natural feature - Le., a mountain - as the paragraph that follows). For a full-size foundation for the structural support system. system, the guideway would be This assumption might be premature. For approximately 3-4 miles in length, including a example, a Japanese concept recently

2.5 I mile accelerator svstem and a 0.5-1.O Dresented (see the biblioaraohv). ,, SUOQeStS-1 mile ACV decelerator: In the reference ihat an ext;emely large, engineered concept, the accelerator system will be structure might be used in lieu of a natural enclosed in a tunnel (or pressurized tube). structure, such as mountain as the basis for This tunnel system may (if required for a mechanical support for an electromagnetic particular launch) be filled entirely or partially with Helium gas - with a low density and low drag forces, and a high speed of sound.4

Accelerator-Carrier Vehicles 5 S:nce the total elapsed time from Staging Facil:ty to exit I launch is approximately 1 minute. it is assumed (ACVs) -The fully-reusable that no elaborate omboard vehicle support systems (e.g., for ma'nta'ning cryogenic fluids in vehkle tanks) will be needed. Interestingly, for other reasons, Helium is also used By the nature of the concept. MagLifter operations in liaht aas-" aun conceDts. For MaaLifter. w:ll deDend won raDid turn-around. low.cost consideration may alsb be made or operation in a very (submarine-ityle) lamch opcrat:ons. including - low pressure air environment (near vacuum) for servicing and maintenance of the carriers. compar:son.

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Figure 2 Top-Level Diagram of a large-scale MagLifter system architecture catapult. However, current technology limits the altitude that can be credibly projectedfor - Tunnel Environmental Monitoring such a mechanical system to 5 I mile. If and Control Systems -Within the future developments allowed significantly tunnel, normally an environmentally larger structures to be built, there would be controlled, oxygen-nitrogen major performance advantages. (For atmosphere will be maintained. Near the example, launch at 600 mph from 20,000 to end of the catapult, the option will be 25,000 feet would provide an enormous provided for using a gaseous Helium performance - and thus cost advantage - environment at atmospheric pressure to over a sea level-based SSTO launcher.) provide a low density, low drag medium -typically for launches at speeds greater If a mountain-based tunnel system is that the speed of sound. The tunnel used - as is assumed in the reference will require an internal environmental concept - then the system would include monitoring and climate control system to three major elements: assure that before each launch the tunnel is clear of foreign objects, that the The Tunnel - A highly robust gas is at pressure, etc. structural support system to altitude is needed. In the reference concept, this is assumed to be a tunnel inside a mountain (accelerator phase, approximately 2.5 miles), and an 'The speed of sound in gaseous Helium is in excess External Guideway Support of 2000 mph. thus assuring that even at launched System on the side of the mountain velocities higher than the nominal (600 mph) the (decelerator phase, approximately 0.5- vehicle in the tunnel will stav well below the transonic 1.0 miles). regime.

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Launch I Exit Systems - Regardless management and distribution (PMAD) v of whether a tunnel is used, a Launch I system must handle the discharge of the Exit system will be needed that provides a power storage system in approximately managed transition from the environment 30 seconds of operation. inside the tunnel and on the guideway to free flight in the external environment. Thermal Manaaement Svstems. Thermal Active control of both the vehicle and the management will also require a significant accelerator-carrier will be required during engineering development. For example, for a the transition. large-scale system, launching a rocket SSTO will require on the order of 200 GJ, invested over Power Svstems. The three principal issues approximately 60 seconds of the launch m MagLifter power and thermal systems are: (1) sequence. If the maglev system (guideway, the storage or generation of power for launch, ACV, and LSM ) are approximately 80% (2) the management and distribution of power efficient, then the thermal management system during launch, (3)the dissipation of waste heat must be capable of dissipating approximately 40 from the guideway during and immediately after GJ (spread over three miles of catapult). the launch. Technology options for the MagLifter power system include: direct Sumortina Svstems. In addition, the overall generation (e.g., using power directly from a architecture of the launch site including the power grid developed for the purpose) and MagLiier system will require a variety of intermediate storage of power taken from the supporting systems, many of which will depend local commercial power grid. The former on the specific operations (and types of approach might be executed using modular, vehicles) to be supported. In particular, the flexible power generation systems such as gas supporting systems that will be needed include: turbines (a typical gas turbine will produce between 30-50 MW of power.) However, Staging Facility(ies) - A local generating the necessary power for a large scale launched-vehicle and payload staging MagLifter system (e.g., on the order of 10 GW for facility will be required to perform 20 seconds) appears clearly prohibitive. vehicle-carrier jntegration and related 'W launch vehicle staging (specific to The latter represents a potentially superior vehicles and payloads) operations. For approach, with storage being provided by either HRVs, this will include selvicing and a high energy density capacitor system or a maintenance facilities for the vehicle superconducting magnetic energy storage following each flight. (SMES) type system. The reference power system includes two key component systems: - Operations Control Center - An operations control center will be Energy Storage System -A required for both staging facility and substantial local power supply system is launch operations. 10 required. In the reference concept, this is assumed to be a Superconducting . Installation Facilities - Various facilities Magnetic Energy Storage (SMES) will be required for operation of a major system, which charged from the local launch facility of whatever type, including power grid and then discharged during a roads, accommodations for launched vehicle launch sequence. 9 crew (presumably temporaty), etc.

Power Management and Svstems Beina Launched. The vehicle Distribution - The power systems that would be launched by the catapult are the final major elements of a MagLifter-based For a small- to moderate- scale catapult system launch infrastructure. These applicationoptions (e.g.. for payloads on the order of 100,000 Ibs). power include small-, moderate- and large- scale requirements would be approximately 10% of the large systems. system and direct generation might be a more reasonable option. Clearly, other options to the use of a SMES system exist (such as using a battery of gas turbines for lo By the nature of the concept, MagLifter operations v direct power generation during launch). The final will depend upon rapid turn-around, low-cost choice will be based on the results of studies of life (submarine-style) launch operations. cycle costs, R&D investment values, etc.

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- SUMMARY OF POTENTIAL MAGLIFTER Small- to Moderate - Scale Aop lications APPLICATIONS - Several potential applications have been Larae-Scale Aoolications identified for smaller-scale MagLifter systems. These include: sounding rockets, small- to Several varieties of Highly Reusable moderate- ET0 systems, and hypersonic Vehicles (HRVs) are potential candidates for research vehicle launches. launch from a MagLifter catapult pad. Each of these would require a large-scale system (e.g.. Soundina Rockets. In addition to on the order of 3-5 miles of guideway and a significantly increasing the performance to LEO launch altitude of 5-15.000feet), with major of SSTO and ELV systems, MagLifter (perhaps supporting infrastructure. in a smaller focused application) may very well enhance the capabilities of sounding rockets for mcket Sinale-Staae__ to Orb it Vehicles. One lower cost microgravity research or upper straightfoward potential application of a atmospheric science flights. Preliminary superconducting magnetic levitation catapult is analyses indicate, for example, that the duration the launch of a rocket single-stage-to-orbit of microgravity conditions may be increased by (SSTO) vehicle. as much as 30 %for a small sounding rocket with a moderate size MagLifter system (with no Rocket /Air-Breather SSTO Vehicles. Very appreciable increase in costs). similar to the rocket SSTO case described above, the catapult may also be useful in the Small- to Moderate- ETO. MagLifter may be launch of rocket I air-breathing hybrid SSTO useful to enable or enhance performance for vehicles. small- to moderate size ET0 systems of various types. It may also provide lower operating costs Two-Staae-to-OrbitVehicles. In addition to than air launch for very small ELVs or TSTO SSTO cases described, two-stage-to-orbit applications. (TSTO) vehicles may also be launched on MagLifter. However, in studying these cases, Hvoersonic-Research. A variety of research v' the overall economics of developing and programs and experimental flight vehicle manufacturing three major new systems (the two concepts have been defined for hypersonic pieces of the TSTO and MagLifter) seem vehicle R&D. Small flight experiments, intuitively prohibitive. Detailed studies of this however, will require some initial staging (e.g., air option are required. launch or ELV launch) to achieve desired aerodynamic conditions. MagLifter may also be Exoendable Launch Vehicles. Although not useful in the development of concepts for lower as prominent as those for reusable, single-stage costs hypersonics research vehicle flights. systems, the advantages of catapult launch for ELVs)are sufficiently interesting to warrant Other Aoolications. further study. Diverse other potential applications exist - IntercontinentalTransoorl . In addition to near-term and far-term - of maglev catapult space launch application, MagLifter technology technologies. For example, in the near-term could also be used as a basis for lower-cost applications for Department of Defense test and hypersonic intercontinental transportation. evaluation programs (e.g., projectile tracking Such system would entail relatively high launch and acquisition system validation and speeds (Mach 1-3),much higher vehicle demonstration) may be viable. Conversely, in structural and thermal system performance than the very far term, in-space applications of the state-of-the-art(SOA) rocket systems (e.g., same technology base could find applications in SSTO concepts). Also, such applications would Lunar surface launch systems (as have been require deployment of systems in multiple popularized in fiction). countries for return flights (e.g., in Asia, Europe, South America, and Africa).ll

"Although cost and economic analyses are not provided in this paper, it should be noted for l2 In almost all cases, these applications could also W comparison that costs of a MagLifter launch site be performed on a larger MagLifter system, operating appear comparable to the costs of a major airport. with a specialized ACV, etc.

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PROJECTED PERFORMANCE pressure (a study that has not yet done - - ADVANTAGES in the analysis presented here.) Oriains of Performance Advantaaes Most significant, however, is the timing of these improvements in velocity and reduced Several factors contribute to the losses: at the very beginning of the ascent when Performance advantage provided by the each meter of velocity 'costs' the most in terms of MagLifter concept. These include: propellant 'invested'.

Reduced Rocket Delta-V Reauirement. Perfonance lmorovements Summy System provides about 300 meters per second of the total velocity change of The overall performance improvement for more than 9000 meters per second Easterly launch is dependent on three factors: needed for ET0 transport. altitude, velocity and the angle of the velocity vector. Figure 3 summarizes the results of - Reduced Vehicle Draa and Gravity preliminary analyses illustrating the sensitivity of w.Reduced pressure at altitude injected mass performance as a function of decreases total drag losses. Altitude altitude for two exit velocities (300 mph and 600 and velocity vector reduce time to mph). Clearly. in the absence of other factors, achieve orbit and total gravity losses. higher altitudes and velocity are preferred, while angles above 45 degrees yield minimal - ImDroved Enaine Performance. performance improvements. Reduced pressure also allows better engine performance (the greatest Another factor driving the system to higher improvement is achieved for single exit altitudes is the maximum dynamic pressure stage vehicles). This will allow 'tailoring' experienced by the vehicle (and resulting likely engines to take advantage of the lower impacts on vehicle structure and dry mass).

W -

205 55

200 50 - 195 45 5 190 5 40 0 0 82 165 2 35 oQ u. 2 9 160 9: 30 uI= cm :$ 175 0.g2.. 25 -2s ..0 d 170 ui 20 P e Y I 165 15 BENCHMARK:SSTO (R) LBS 160 10 1.2 MILLION GLOW, 16,000 LBS TO LEO (APPROX.) MPH. 90 DEG. AlTMOE. SEA LEVEL 155 5 0

0 0 0 5,000 10.000 15,000 ALTITUDE (Feel above Sea Level)

Figure 3 Summary of injected mass performance vs. launch altitude and velocity (simplified analysis) u

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55 I I ANALYSISREFERENCE CASE: 50 39,000 LBS TO LEO (APPROX.) 45

190 40 I

i CASE2

ui 170 6 20 P D Y Y 165 15 L

160 10

16,000 LES TO LEO (APPROX.) 155 5 .- 0 MPH, 90 DEG. AVITUDE,,SEI LEVEL oy 0 I I I I I 90.0 75.0 60.0 45.0 30.0 15.0 0.0 ATTITUDE (Degrees from horizontal; launch from 10,000fl)

Figure 4 Summary of injected mass performance vs. velocity attitude and velocity (simplified analysis)

W Figure 4 provides the results of second The SSTO case described above is the series of analvses examining the sensitivitv of amlication that has been most thorouahlv injected mass performance as function of ' analyzed thus far. Similar, but somew6at iesser, velocity vector attitude for two exit velocities advantages have been found for use of the (300 mph and 600 mph). MagLifter in providing a boost-assist for easterly launch of ELVs. For example, a payload On this basis of these studies, and in the improvement of approximately 80% was found in context of a cursory assessment of the launch a very preliminary assessment for a hypothetical sites available (Le., mountain heights and their ELV (specifically increasing the vehicle's payload availability) the reference case was chosen from 2000 Ibs to 3800 Ibs launched to LEO). In involving launch from an altitude of 10,000 feet, a very different case, a preliminary analysis of a at a velocity of 600 mph, and an angle of 45 very small, two-stage-to-orbit (TSTO) (nominally degrees. (This case is discussed in greater with air launch), showed no payload advantage detail in the discussion of a SSTO launch for use of MagLifter at 10,000 ft, 600 mph, and application example provided below.) 45 degrees angle.13

A third series of analyses was also For polar orbit cases, a very cursory analysis conducted to evaluate the effects of velocity, suggests that the benefits of using the maglev altitude and velocity vector angle on the dynamic boost assist may be even greater than for the pressure experienced by the vehicle during 28.5 degree case (Le., perhaps on the order of a ascent following release from the catapult. 3:l improvement in SSTO payload delivery to a These results indicate (1) that nominal loads at polar LEO). 500-600 mph are roughly comparable to current space launch environments (e.g., Shuttle launch): (2) that dynamic pressure increases significantly as Mach 1 is approached, and (3) that dynamic loads can be substantially reduced for launch angles of approximately 55 degrees. l3 Additional studies are needed to determine if higher altitudes, higher angles, andlor higher 'd velocities change this result.

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__ ~ ~ ~~ IOC = 2008 P/L bay = 15 x 30 ft . P/L wgt = 25 klb to 100 n.mi. at 28.5a

Dv wgt = 209 klb Gross wgt = 2.07 Mlb

Figure 5 Illustration of reference rocket SSTO vehicle analyzed

APPLICATION EXAMPLE: A ROCKET SSTO USING MAGLIFTER14 The reference vehicle dry mass was - 209,000 Ibs, with a gross lift off weight (GLOW) Although analytically the addition of a of 2.07 Mlbs.15 Figure 5 provides an illustration MagLifter system to a space launch scenario of this reference vehicle, along with key increases performance for a given vehicle, in parameters. actual practice the catapult system would more likely be used to increase design margins and Vehicle lmoacts reduce costs while holding performance constant. To illustrate this point, a special For the launch of 25,000 pounds to LEO, a application example - a rocket SSTO launched preliminary analysis of the addition of MagLifter from MagLifter - is presented in the paragraphs (for the reference case of 10,000 feet, 600 mph, that follow. including: (1) a brief description of 45 degrees), results in a 25 % reduction in the reference vehicle, (2) potential impacts on vehicle dry mass and a 33 % reduction in engine the reference vehicle as a result of addition mass (assuming use of a Space Shuttle Main MagLifter to the infrastructure, and (3) a Engine, SSME, class propulsion system). description of a top-level hypothetical launch Figure 6 depicts the potential change in size that sequence. might be possible for an conventional SSTO (at sea level ), versus anSSTO (with the same Reference Vehicle technology base) designed for launch from an appropriately sized MagLifter launch pad.16 The reference vehicle for this analysis represented a relatively moderate projection beyond the state-of-the-art. The vehicle was scoped to launch 25,000 Ibs to LEO, using 6 l5This vehicle is somewhat larger than that in other Space Shuttle Main Engine (SSME) class aspects of the analysis presented here (which engines and LOX-Hydrogen propellants. launched16,OOO Ibs to LEO without MagLifter and had a GLOW of approximately 1.2 Mlbs). l6 The importance of this change will become - l4 The case presented here was developed by the apparent when cost and economic analyses are done, Vehicle Analysis Branch at NASA LaRC. since many cost factors vary with vehicle dry mass.

- 11 Maglifter - An Advanced Concept AlAA 30th Joint Propulsion Conference 94-2726 June 27-29, 1994

Launch: Altitude, ft 0 10,000 Velocity, fifsec 0 880 Attitude, deg 90 45 Gross weight, Ib 2,070,000 1.,350,000 Dry weight, Ib 209,000 156,000 Number of engines 6 4

Figure 6 Illustration of potential size changes in a rocket SSTO using MagLifter v Nominal Launch Seauence horizontal), and at increased acceleration, reaching an altitude of A nominal launch sequence for the rocket approximately 7000 feet and a velocity SSTO-class MagLifter system described here of 450 mph after 10 seconds (and shown inf Figure !) might consist of the following events: (4) At T + 50 seconds, final check out and test of the vehicle in motion begins. The (1) At TP hrs, the ACV with vehicle to be engines of the vehicle are started to idle launched and payload leaves the and checked out; if they perform to staging facility on the initial section of the specification, a 'go' decision is made, guideway and is transported to the and acceleration continues. propellant loading site for fueling. (5) At T + 58 seconds, a velocity of (2) At T = 0 seconds, following fueling and approximately 650 mph is reached. The final check-out, the ACV and vehicle to cradle on the ACV releases the vehicle be launched are disconnected from being launched, which separates ground support equipment and travel on (engines remaining at idle). The ACV the guideway to into the MagLifter begins to decelerate. tunnel (reference case). (6) At T + 60 seconds, the vehicle leaves (3) At T + IO'seconds, the vehicle and ACV the end of the guideway at 600 mph and slowly begin accelerating . This at an angle of 45-55 degrees, and an acceleration lasts for approximately 30 altitude of 10,000 feet (nominal). The seconds, at the end of which time the vehicle's engines power up and it ascent phase of the sequence begins. begins its ascent to orbit. The ACV continues to decelerate, leaving the (4) At T + 40 seconds, the vehicle and tunnel (in the reference case) and carrier begin ascending (at a nominal exiting on the external section of W' final angle of 45 - 55 degrees from the guideway.

- 12- MagLifter - An Advanced Concept AlAA 30th Joint Propulsion Conference 94-2726 June 27-29, 1994

\ - * Parameter Gas Gun Rail Gun Coil Gun MagLifter

Exit Velocity 19000 12000 13000 5 600 (mph) (varying)

Acceleration 2000 5000 2500 $3 (gravities) (varying)

Payload >20 c3 c3 1000 (kilo-pounds) (varying)

Table 1 Comparison of MagLifter to 'Other' Gun Concepts

COMPARISON OF PERFORMANCE TO 'OTHER' GUN CONCEPTS Core areas, such as:

Although MagLifter is not properly a 'gun', a the large mass EM levitation system comparison is useful by indicating how the high energyhigh acceleration EM dramatically thi catapult concept differs from propulsion system 'other' types of gun launch concepts . MagLifter developing a low-cost. highly reliabilyty ACV can launch much larger payloads, with lower system, including the payload cradle system W accelerations during launch and closer ties to extremely high-power power systems existing space launch and ground transportation (storage and PMAD) technologies. For example, a typical advanced - high-load thermal management systems gun concept, the light gas gun, would in an high reliability and low-cost range and site operational system be capable of 'firing' only 100 safety systems kg-class payloads to LEO, and only by low-cost operations subjecting them to 1000 G-class accelerations at launch. Table 1 summarizes some of the And &h-Leveraae tec hnology relevant characteristics for several gun concepts Q!2J70fiU nities, such as: (in projected operational systems) and compares them to MagLifler. high temperature superconducting materials and EM systems MagLifter - plus an HRV - could provide a far * low-cost tunnel systems broader range of payload performance, with low.cost maglev guideway systems much more benign environmental conditions. (structure, EM systems. construction, repair and maintenance)

MAGLIFTER TECHNOLOGY In summary. although the parameters associated with MagLifter are aggressive (600+ Technoloav Challenaes mph speeds, 3-Gaccelerations, large payloads, etc.), at the present level of definition, no major The major research and engineering issues have been identified that might be development challenges associated with technological 'show-stoppers' for the concept. investigating the potential of maglev technologies for space launch applications Dual-Use Technolpgy ADDlicationS include both core areas (where technology research is completed andlor capabilities exist There are diverse opporfunities for dm-use that could be applied 'as is'), and opportuntities applications of the technologies req Jired for W (where further advances could make a significant MagLifter R&D and eventual development. cost or performance difference). 13- MagLiier - An Advanced Concept AlAA 30th Joint Propulsion Conference 94-2726 June 27-29. 1994

in payload, however, appears to be acceptable at - Advanced Electromaanetic SvstemS. At a launch latitudes in the U.S. subsystem level, MagLifter development could .. Li - drive R&D.and industrialization of various Areas for Add itional StLlziy advanced EM systems, including high-power level energy storage (e.g., SMES) and PMAD Tunnel Svstem. As discussed previously, systems, superconductors and high the use of a tunnel or other approach to basing temperature superconductors. and protecting the maglev guideway system is a major design trade issue to be considered. Top- Ground Maalev Transoortation Svstems. At level arguments in favor of a tunnel approach a system level, many or most of the technologies include protection from weather (a significant needed for the implementation of a MagLifter issue at high altitudes) and for security. launch pad are also needed for the development Conversely, wall effects during acceleration and and deployment of a 'leap-frog' maglev ground launch failure and risk scenarios must be transportation system infrastructure. assessed as potentia! arguments against this approach.

SELECTED ISSUES AND AREAS FOR Cost Estimation. A detailed cost analysis is ADDITIONAL STUDY not being presented in this paper. However, preliminary analyses have been developed for Several options in the system design purposes of comparative assessment of options. require further study to resolve issues that have These studies indicate that, depending on the arisen in preliminary analyses. Also, several size of the system constructed, the MagLifter important areas need first-order examinations. would range in cost from approximately $0.26 for a small- to moderate- scale system (e.g., for a Performance 1ssues17 100 klbs vehicle), to $28 for a large-scale system (e.g., for a 1-2 Mibs vehicle). In addition, costs of Effect of Off-Inclination Launches. Initial supporting infrastructure must be evaluated studies of propulsive vehicle maneuvers to (e.g., launch vehicle and payload processing, adjust from a due Easterly launch direction on operations control center, etc.). the catapult to other orbital inclinations indicate W minimal losses in injected mass system In addition, MagLifter catapult operations performance. For example, for a due East costs must be analyzed, including: (1) labor, (2) launch from a 28.5 degree latitude site to a 51.6 consumables (including power and potentially degree inclination orbit at 220 nm altitude, the gaseous Helium), (3) expendable systems (such injected mass fell by less than 3%. The as the 'burstable' membrane at the tunnel exit, if corresponding drop in payload mass was one is used), and (4) refurbishment and approximately 15%. The effects of these maintenance of tunnel, guideway and ACV maneuvers are modest because of the relatively systems as required between launches. low starting velocity of the vehicle being launched. Economics. A preliminary analysis of potential MagLifter resource-streams is needed. Effect of Launch Site Latitude. A preliminary This analysis should be grounded in initial analysis of the effect of changing launch site estimates for MagLifter development costs, and latitude has been conducted. The effect of should be directed at enabling a notional sense translating the MagLifter launch site from of how this system might integrate into plans for approximately 30 degree latitude to tha Equator space launch and ET0 transportation. A variety is an increase in injected mass of approximately of inputs will be needed in the development of 5%, The corresponding improvement in paylaad such an analysis, including: is approximately 20% (for due East launch). Clearly, in terms of payload launched to LEO, an (1) For ET0 studies, annual launch optimal MagLifter launch site would be a 10- requirements must begin with the NASA 15,000 ft peak near the equator. The reduction Civil Needs Data Base (CNDB). As excursions from the baseline, additional launches, such as new LEO " In the cases listed below, the vehicle in question telecommunications satellite was a reference LOX-Hydrogen rocket SSTO vehicle with a 1.2 Mlbs GLOW unless othewise stated; W conclusions pertain to projected changes in injected mass.

14 - MagLifter - An Advanced Concept AlAA 30th Joint Propulsion Conference 94-2726 June 27-29. 1994

constellations should be assessed for MagLifter and that needed for many types of inclusion. I* guns (e.g., power supplies, physical infrastructure such as the tunnel used in the -- - (2) HRV tnd other vehicle costs used in the reference concept). analysis should be developed from a credible, independent source. SUMMARY (3) MagLifter system development and operations costs must be estimated with This paper has provided a preliminary significant uncertainly to allow for the low discussion of the MagLifter concept. Many level of maturity in the concept. topics have been raised, but not resolved - ranging from diverse vehicle mission analyses, to (4) Many staging facility costs will depend system basing and range safety considerations; on the number and types of vehicles from system functional studies to identifying and payloads to be processed and technology development challenges. details of operational scenarios. A consistent approach to this area is It is clear that a revolutionary 'launch pad needed. such as the MagLifter catapult makes no sense without new, tailored space launch vehicles to (5) The overall economics analysis should use it. Conversely, if developments in low-cost consider financing alternatives for the vehicles are fully successful, no new launch pad MagLifter infrastructure and launch technology may be needed. However, based vehicles. on preliminary analyses, the application of maglev to space launch appears to have Finally, a number of cases must be analyzed, considerable promise across a w:de variety of representing various alternative infrastructure applications, ranging from ET0 transportation developments and vehicles over an extended (HRV and ELV), hypersonics research, period (e.g., 1995-2024). sounding rocket launches, and more futuristic concepts (such as intercontinental hypersonic Market Analvsis. Market factors must be transports). By providing an initial, 'free' delta- L./ examined carefully. The recent CSTS analysis velocity, MagLifter may represent 'insurance' for suggests that if overall ET0 launch costs were other developing space launch systems reduced to $600 per pound that the mass-to- concepts. At the same time, maglev and orbit market could almost triple compared to advanced, high power electromagnetic systems current annual levels. However, their analysis have diverse potent;al terrestrial dual-use also indicates that an additional reduction of 33% commercial appl'cations. (to $400 per pound) could stimulate massive market growth. ACKNOWLEDGMENTS

Comoarisons to Comoetina Similar The MagLifter concept has been defined at Conceots. An immense number of space a preliminary level with analysis, inputs, and launch concepts have been studied during the comments on earl'er versions by a variety of past half century. Although a smaller number, individuals at NASA, at various National there also are a variety of alternate approaches Laboratories, and several companies; these that involve the same basic principles as the have included: L. Whitt Brantley (MSFC), Tony MagLifter; i.e., adding initial altitude or velocity to Clark (MSFC), Joe Howell (MSFC). H. Huie a projectile or vehicle. For example, the (MSFC), John Niehoff (SAIC). Gordon operational Pegasus system developed by the Woodcock (Boeing), and James R. Powell (BNL) Orbital Sciences Corporation involves air launch and John D.G.Rather (NASA OACT). and a as an assist to ET0 transport. number of others; many (hopefully all) of these contributions are recognized bnder the selected ComDarison to Gun Conceots. Additional bioliography that follows as 'personal comparisons to proper gun concepts are also communications.' needed. It may well be that synergism will be found between the infrastructure needed for Special thanks are due lo Mr. V'nce Dauro of MSFC for his efforts in conducting innumerable mission performance analyses and to Mr. Charles Eldred and the stalf of the Vehicle Analysis I8Tne recent Commercial Space Transportation L Branch at LaRC for their analysis of the SSTO Study (CSTS)Executive SJlnmary provides a option. po!ent:al roadmap lor th:s analys's.

-15- MagLiier - An Advanced Concept AIAA 30th Joint Propulsion Conference 94-2726 June 27-29, 1994

SELECTED BIBLIOGRAPHY C. Eldred, et al. "Assessment of MagLifter" - NASA internal memorandum. February 1994. H. Alscher, et al; "Propelling Passengers u - Faster than a Speeding Bullet," IEEE Fairchild Space; personal Spectrum.' August 1984. correspondence in response to first edition MagLifter white paper 'dear BDM Federal, Inc.; personal colleague' request. January 1994. correspondence in response to first edition MagLifter white paper 'dear R.H. Frisbee, et al, "Evaluation of Gun colleague' request. January 1994. Launch Conceots" (Jet Propulsion Laboratory). November 1993. I. Bekey; personal communication in response to first edition MagLifter white J.S. Greenberg (PSI); personal paper 'dear colleague' request. January correspondence in response to first 1994. edition MagLifter white paper 'dear colleague' request. January 1994. 1. Blankston; personal communications, 1993-1994. M.D. Griffin and W.R. Claybaugh, The Cost of Access to Space" (Presented at the 60th R.E. Bolz and G.L. Tuve, editors, "CRC Annual Meeting of the British Interplanetary Handbook of tables for Aoolied Society). October 1993. Ensineerina Science" (CRC Press, Inc.). 1976. Grumman Corporation: personal communication in response to first P. Bono and K. Gatland, "The Pocket edition MagLifter white paper 'dear Encvclooaedia of SDacefliaht in Colour: colleague' request. January 1994. Frontiers of Soace" (Blandford Press, London, England). 1969. Institute for Defense Analysis (IDA): personal correspondence in response to first edition MagLifter white paper 'dear R. H. Borcherts, et al, "Baseline W Specifications for a Magnetically colleague' request. January 1994. Suspended High-speed Vehicle," Proceedings of the IEEE, Vol. 61, No. 5, May Intermagnetics General Corporation (IGC); 1973. personal correspondence in response to first edition MagLifter white paper 'dear C.R. Carlson and J.S. Simpson, "Low-Cost colleague' request. January 1994. ELV Technology Applicability to Spacelifters" (AIAA 93-4124). September L. Kingsland, jr., "The Effect of Launch 1993. Conditions on the Performance of Track Launched Orbtial Vehicles" (Technical T. Clark, "An Electromagnetic Documentary Report No. MDC-TDR-64-2. Compatibility Assessment of the Holloman Air Force Base, New Mexico). June Conceptual Magnetic Levitation Launch 1964. System: MagLifter," technical correspondence to J. Mankins. November 4, W.J. Larson and J.R. Wertz, editors, "m 1993. Mission Analvsis and Desian" (published jointly by Microcosm, Inc., and Kluwer Academic CSTS Alliance, Commercial Space Publishers). 1992. Transportation Study (CSTS) Executive Summary (Phase 1 Report). April 1994. Lawrence Berkeley Laboratory, University of California; personal correspondence in V. Dauro. et al, numerous NASA internal response to first edition MagLifter white memoranda providing results of specific mission paper 'dear colleague' request. January analysis runs; September 1993 - April 1994. 1994.

C. Eldred. et ai, "Single Stage Rocket Maglev Technology Advisory Committee, Options for Future Launch Vehicles" "Benefits of Maaneticallv-Levitated (AIAA 93-4162). September 1993. Hiah-SDeed Transportation for tht: v United States" (Grumman Corporation, publisher). March 1992.

16- MagLmer - An Advanced Concept AlAA 30th Joint Propulsion Conference 94-2726 June 27-29, 1994

M. Nagatomo and Y. Kyotani. "Feasibility GLOSSARY OF ACRONYMS Study on Linear-Motor-Assisted Take- i_- - Off (LMATO) of Winged Launch A CV Accelerator-Carrier Vehicle Vehicle" [Acta Astronautica, Vol. 15, No. 11). AFB Air Force Base 1987. ALS Advanced Launch System B M DO Ballistic Missile Defense Organization Office of Technology Assessment, Congress of C NDB Civil Needs Data Base the United States, New Wavs - Tiltrotor C STS Commercial Space Transportation gnd Maaneticallv Levitated Vehicles. Study 1991. DOD Department of Defense DOT Department of Transportation J.R. Powell, 'Larae Scale Maqlev EDS Electrodynamic Suspension ImDlementation in the United States" EM Electromagnetic (presented at the AAAS Annual Meeting). EMS EM Suspension February 1992. ET0 Earth-to-Orbit fps feet per second J.R. Powell, personal communications: FRA Federal Railroad Administration August-September 1993. G Gravities (of acceleratlon) GJ Gigajoules S. Pace (RAND/Critical Technologies GLOW Gross Lift-off Weight Institute, CTi); personal GW Gigawatts correspondence in response to first HRV Highly Reusable Vehicle edition MagLifter white paper 'dear klbs Thousands of Pounds colleague' request. December 1993. LaRC Langley Research Center Ibs Pounds J. Rather, personal communications: LE0 Low Earth Orbit August-October 1993. LMATO Linear Motor Assisted Take-Off LSM Linear Synchronous Motor Rockwell International Corporation: M Millions Maglev Magnetic Levitation W personal correspondence in response to first edition MagLifter white paper 'dear MJ Megajoules colleague' request. January 1994. Mlbs Millions of Pounds mPh miles per hour R.D. Thornton. "Design Principles for MSFC (NASA) Marshall Space Flight Center Magnetic Levitation," Proceedings of MW Megawatts the IEEE, Vol. 61, No. 5, May 1973. NASA National Aeronautics and Space Administration 0. Scott, "Workin' on the Railgun" (Ad NASP National Aerospace Plane Astra). June 1990. N LS National Launch System - NMI National Maglev Initiative O&M Operations and Maintenance G. Woodcock to J.C. Mankins: personal PMAD communication. November 1993. Power Management and Distribution R&D Research and Development SDlO Strategic Defense Initiative Office SMES Superconducting Magnetic Energy Storage SMS Superconducting Magnetic Systems SNTP Space Nuclear Thermal Propulsion SSME Space Shuttle Main Engine SSTO Single-Stage-to-Orbit TSTO Two-Stage-to-Orbit USAF U.S. Air Force

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