This paper reports the findings of a conceptual launch vehicle design study performed by members of the Space Systems Design Laboratory at Georgia Tech. Hyperion is a conceptual design for an advanced reusable launch vehicle in the Vision Vehicle class. It is a horizontal takeoff, horizontal landing single-stageto-orbit (SSTO) vehicle utilizing LOX/LH2 ejector scramjet rocket-based combined cycle (RBCC) propulsion. Hyperion is designed to deliver 20,000 lb. to low earth orbit from Kennedy Space Center. Gross weight is estimated to be 800,700 lb. and dry weight is estimated to be 123,250 lb. for this mission. Preliminary analysis suggests that, with sufficient launch traffic, Hyperion recurring launch costs will be under $200 per lb. of payload delivered to low earth orbit. However, non-recurring costs including development cost and acquisition of three airframes, is expected to be nearly $10.7B. The internal rate of return is only expected to be 8.24%. Details of the concept design including external and internal configuration, mass properties, engine performance, trajectory analysis, aeroheating results, and concept cost assessment are given. Highlights of the distributed, collaborative design approach and a summary of trade study results are also provided. NOMENCLATURE C t thrust coefficient I sp specific impulse (sec.) I* equivalent trajectory averaged I sp (sec.) MR mass ratio (gross weight/burnout weight) q dynamic pressure (psf) T/W e

Effective air launching of a rocket is approached from a broad systems engineering viewpoint. The elementary reasons for why and how a rocket might be launched from a carrier aircraft are examined. From this, a carefully crafted set of guiding principles is presented. Rules are generated from a fundamental foundation, derived from NASA systems study analyses and from an academic vantage point. The Appendix includes the derivation of a revised Mass Multiplier Equation, useful in understanding the rocket equation as it applies to real vehicles, without the need of complicated weight and sizing programs. The rationale for air launching, being an enormously advantageous Earth-ToOrbit (ETO) methodology, is presented along with the realization that the appropriate air launch solution may lie in a very large class of carrier aircraft; the 'pod-hauler'. Finally, a unique area of the system trade space is defined and branded 'Crossbow'. Crossbow is not a specific hardware design for air launch, but represents a comprehensive vision for commercial, military and space transportation. This document serves as a starting point for future technical papers that evaluate the air launch hypotheses and assertions produced during the past several years of study on the subject. gravity constant (9.81 d s 2 ) specific impulse length mass fiaction radius time velocity volume change in velocity propellant mass multiplier (ratio of propellant-sensitive structure mass to expended propellant mass) density dry mass multiplier (ratio of dry mass-sensitive structure mass to dry mass) gross mass multiplier (ratio of gross mass-sensitive structure mass to gross mass) mass I. Introduction modest effort has been dedicated over the past six years by engineers at NASA to air launching a rocket from A a carrier plane. This initially germinated from the first requirement of the Space Launch Initiative (SLI) for improving launch risk to meet a goal of 1-in-10,000 probability of loss of crew.l It was believed by some at the time that efforts to "tweak" hardware or streamline procedures would not come close to achieving that level of safety. Much of what was being done (and often still is) was a call for increased "technological advances" to improve safety, when in fact that can have the opposite effect by introducing unknowns and complexity, while operating at ever slimmer engineering margins. Sticking to "tried and true" old technology neither provides the payloadcost desired or the reliability as illustrated by the recent failed Russian Dnieper rocket.' The physics of vertical launch impose fixed limitations that hamper safety. They are: Each of these is discussed in terms of the economic and safety advantages for air launching the rocket.A classical (university) systems-engineering approach is applied. A trade space is defined, the various options identified (all with the permutations and combinations described), inherent advantages and disadvantages of each are listed, and weighting factors applied for analysis. Much of the technical input has bee...

Momentum-exchange / electrodynamic reboost (MXER) tether systems show great promise for use in propellantless orbital transfer. In 1998, MSFC and Boeing conducted a simple, preliminary examination of the system requirements of a tether facility to boost payloads from LEO to GTO. Work conducted at MSFC and TUI over the last two years has updated and refined these results, and led to alternate configurations and concepts that show greater promise for successful utilization. Two appendices are included that detail analysis techniques and mathematical derivations that can be used in tether facility design. IntroductionThe development of tether technology has opened up an exciting new possibility for spacecraft-propellantless propulsion. Rockets push against their own exhaust, but an electrodynamic tether pushes against the Earth's magnetic field, and in essence, the Earth itself, to enable payloads to acquire higher-energy orbits.A pure momentum-exchange (MX) tether does not create orbital energy; it only exchanges it. If it catches and throws a payload, its orbital energy will be reduced, and it will assume a lower orbit. Without reboost, it will soon lose too much orbital energy and enter the atmosphere and burn up.Any type of propulsion system, in theory, could be used to reboost an MX tether. Chemical, nuclear, and electric are all options, but if any rocket reboost technologies are chosen, the MX tether will have a payload fraction that is governed by the specific impulse of the propulsion system, according to the rocket equation.On the other hand, a pure electrodynamic (ED) tether is limited to the regions above the Earth where the ionosphere and magnetic field are relatively strong (<1000 km). It collects electrons from the ionosphere to flow current through its conductive tether 1 . That tether acts like a wire moving through the field lines of the Earth's magnetic field; consequently a J x B force is exerted on the system. The ED tether can passively generate power (at the expense of orbital energy) or use a power supply to drive current through the tether and generate motive force (increasing orbital energy).In theory, an ED tether could dock with a payload and slowly spiral up to a higher orbit, then release it and spiral back down. However, again the ED tether is limited to altitudes less than 1000 km, and achieves performance similar to other low-thrust, high-power propulsion systems that have very low thrust-to-weight ratios.The MX and ED tethers, by themselves, do not achieve exceptional improvements in performance over existing technologies, but a hybrid of the two, the momentumexchange/electrodynamic reboost (MXER) tether, may have capabilities far beyond either technology separately.In principle, a rotating MXER tether in an elliptical orbit could catch a payload in a low Earth orbit, carry it for a single orbit, and than throw it into a higher energy orbit, all in a short period of time. It can then employ electrodynamic reboost over a period of weeks to restore the orbital energy it gave to the p...

The MXER Tether technology development is a high-payoff/high-risk investment area within the NASA In-Space Propulsion Technology (ISPT) Program. The ISPT program is managed by the NASA Headquarters Science Mission Directorate and implemented by the Marshall Space Flight Center in Huntsville, Alabama. The MXER concept was identified and competitively ranked within NASA's comprehensive Integrated In-Space Transportation Plan (IISTP)'; an agency-wide technology assessment activity. The objective of the MXER tether project within ISPT is to advance the technological maturation level for the MXER system, and its subsystems, as well as other space and terrestrial tether applications. Recent hardware efforts have focused on the manufacturability of spacesurvivable high-strength tether material and coatings, high-current electrodynamic tether, lightweight catch mechanism, high-accuracy propagator/predictor code, and efficient electron collection/current generation. Significant technical progress has been achieved with modest ISPT funding to the extent that MXER has evolved to a well-characterized system with greater capability as the design has been matured. Synergistic efforts in high-current electrodynamic tethers and efficient electron collectionhrrent generation have been made possible through SBIR and STTR support. The entire development endeavor was orchestrated as a collaborative team effort across multiple individual contracts and has established a solid technology resource base, which permits a wide variety of future space cablekether applications to be realized.

The International Space Station (1%) currently experiences significant orbital drag that requires constant make up propulsion or the Station will quickly reenter the Earth's Atmosphere. The reboost propulsion is presently achieved through the firing of hydrazine rockets at the cost of considerable propellant mass. The problem will inevitably grow much worse as station components continue to be assembled, particularly when the full solar panel arrays are deployed. This paper discusses many long established themes on electrodynamic propulsion in the context of Exploration relevance, shows how to couple unique ISS electrical power system characteristics and suggests a way to tremendously impact ISSs sustainability. Besides allowing launch mass and volume presently reserved for reboost propellant to be reallocated for science experiments and other critically needed supplies, there are a series of technology hardware demonstrations steps that can be accomplished on ISS, which are helpful to NASA's Exploration mission. The suggested ElectroDynamic (ED) tether and flywheei approach is distinctive in its use of 'free' energy currently unusable, yet presently available from the existing solar array panels on ISS. The ideas presented are intended to maximize the utility of Station and radically increase orbital safety.