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Naftel, J. C.

Publications and source records attributed to Naftel, J. C..

18 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Ascent abort capability for the HL-20

The HL-20 has been designed with the capability for rescue of the crew during all phases of powered ascent from on the launch pad until orbital injection. A launch-escape system, consisting of solid rocket motors located on the adapter between the HL-20 and the launch vehicle, provides the thrust that propels the HL-20 to a safe distance from a malfunctioning launch vehicle. After these launch-escape motors have burned out, the adapter is jettisoned and the HL-20 executes one of four abort modes. In three abort modes - return-to-launch-site, transatlantic-abort-landing, and abort-to-orbit - not only is the crew rescued, but the HL-20 is recovered intact. In the ocean-landing-by-parachute abort mode, which occurs in between the return-to-launch-site and the transatlantic-abort-landing modes, the crew is rescued, but the HL-20 would likely sustain damage from the ocean landing. This paper describes the launch-escape system and the four abort modes for an ascent on a Titan III launch vehicle.

Naftel, J. C.↗
NASA NTRS1992

The performance of a winged booster powered by combined rocket and airbreathing propulsion

A conceptual level analysis was performed on a horizontal-takeoff, two-stage-to-orbit system consisting of a rocket and turboramjet powered hypersonic booster and a rocket powered orbiter. The analysis includes estimates of vehicle aerodynamics, performance, and weights. Rocket and airbreathing systems on the booster are operated in parallel and at full thrust for ascent to a Mach 6 staging point, while cruise-back is accomplished using airbreathing propulsion alone. Rocket engines on the orbiter are ignited at staging to propel the orbiter. Booster weights were determined for various combinations of rocket and airbreathing propulsion. The combinations that resulted in the lowest vehicle gross and empty weights were determined. Results show that the lowest gross weight occurs when only airbreathing engines are used. The empty weight of the all airbreathing booster, however, is quite high. Significant reductions in booster empty weight is accomplished with the addition of rocket engines. Also, the use of rockets on the booster greatly decreases the time to staging and the cruise-back distance.

Lepsch, Roger A., Jr.↗
NASA NTRS1991

Ascent performance of an air-breathing horizontal-takeoff launch vehicle

Simulations are conducted to investigate a proposed NASA launch vehicle that is fully reusable, takes off horizontally, and uses airbreathing propulsion in a single stage. The propulsion model is based on a cycle analysis method, and the vehicle is assumed to be a rigid structure with distributed fuel, operating under a range of atmospheric conditions. The program to optimize simulated trajectories (POST) is modified to include a predictor-corrector guidance capability and then used to generate the trajectories. Significant errors are encountered during the unpowered coast phase due to uncertainty in the atmospheric density profile. The amount of ascent propellant needed is shown to be directly related to the thrust-vector angle and the location of the center of gravity of the vehicle because of the importance of aim-drag losses to total ideal velocity.

Powell, Richard W.↗
NASA NTRS1991

Ascent performance issues of a vertical-takeoff rocket launch vehicle

Advanced manned launch systems studies under way at the NASA Langley Research Center are part of a broader effort that is examining options for the next manned space transportation system to be developed by the United States. One promising concept that uses near-term technologies is a fully reusable, two-stage vertical-takeoff rocket vehicle. This vehicle features parallel thrusting of the booster and orbiter with the booster cross-feeding the propellant to the orbiter until staging. In addition, after staging, the booster glides back unpowered to the launch site. This study concentrated on two issues that could affect the ascent performance of this vehicle. The first is the large gimbal angle range required for pitch trim until staging because of the propellant cross-feed. Results from this analysis show that if control is provided by gimballing of the rocket engines, they must gimbal greater than 20 deg, which is excessive when compared with current vehicles. However, this analysis also showed that this limit could be reduced to 10 deg if gimballing were augmented by throttling the booster engines. The second issue is the potential influence of off-nominal atmospheric conditions (density and winds) on the ascent performance. This study showed that a robust guidance algorithm could be developed that would insure accurate insertion, without prelaunch atmospheric knowledge.

Powell, Richard W.↗
NASA NTRS1990

Aerodynamic separation and glideback of a Mach 3 staged booster

A study has been conducted of the staging maneuver for a two-stage, vertical-takeoff, launch vehicle and the subsequent glideback of the booster to a launch site runway. The booster and orbiter are both winged, fully reusable, and have liquid rocket main propulsion. for the staging maneuver, which nominally occurs at Mach 3, a flight control system and separation technique were devised which produced successful separations over a wide range of staging angles of attack. A guidance algorithm was developed for the unpowered glide-back of the booster from the completion of the staging maneuver to touchdown on a runway in the vicinity of the launch site. Using this guidance technique, the booster successfully touched down on the runway while being subjected to a wide range of seasonal and perturbed atmospheric conditions with and without wids as well as errors in staging state conditions and errors in predicted aerodynamics.

Naftel, J. C.↗
NASA NTRS1989

Ascent, abort, and entry capability assessment of a Space Station rescue and personnel/logistics vehicle

The ascent, abort, and entry capability of a vehicle for rescue of the Space Station crew or ferry of personnel and supplies to and from the Space Station are analyzed. The configurations of the Space Station rescue vehicle and the Space Station personnel/logistics vehicle (SSPLV) are discussed and illustrated. The nominal ascent trajectory for the SSPLV delivered to orbit on a Titan II is presented. The ascent abort modes from launch to orbital injection are evaluated. It is shown that five landing sites with runways longer than 10,000 ft could provide a landing opportunity from every orbit of the Space Station in a 220-nmi circular orbit with a 28.5 deg inclination.

Naftel, J. C.↗
NASA NTRS1986

Analysis of separation of a two-stage winged launch vehicle

The feasibility of separating a two-stage winged, parallel configured launch vehicle at Mach 3 has been determined. The two-stage fully-reusable launch vehicle is comprised of an orbiter, which can be used alone as a single-stage-to-orbit vehicle, and a booster which is identical to the baseline orbiter design. A three-degree-of-freedom analysis was conducted on the ascent trajectory of the two-stage concept to determine the optimum staging conditions. The booster provides all propellant for both stages using a crossfeed system until staging occurs. After staging, the empty booster glides back to the launch site for a horizontal landing. To analyze the separation maneuver, the six-degree-of-freedom equations of motion for both stages were numerically integrated using a computer program which incorporates analytically derived interference aerodynamic data. The necessary conditions for a successful separation were determined and required the use of active controls on both the orbiter and booster. Once the booster and orbiter were separated, a three-degree-of-freedom analysis was conducted on the booster's glideback trajectory.

Naftel, J. C.↗
NASA NTRS1986

Performance evaluation of an entry research vehicle

The aerodynamic database upon which the missions and the proposed designs of an atmospheric entry research vehicle (ERV) would be based are discussed, along with a trajectory analysis of two missions proposed for the ERV. The ERV is intended as a means to explore reentry techniques, thermal protection systems and cross-range and orbital change maneuvers beyond the operational envelope of the Orbiter. The 25 ft long ERV would have a 13 ft wingspan, allowing it to be launched from the Orbiter bay. The ERV would have atmospheric maneuvering control surfaces and reaction control systems for orbital maneuvers. The total weight would be 12,000 lb. The aerodynamic design for the ERV was developed from wind tunnel, theoretical and Shuttle data for continuum, transition and free-molecule flight regimes. Typical flight profiles for intended missions are outlined.

Powell, R. W.↗
NASA NTRS1985

Propulsion evaluation for orbit-on-demand vehicles

Future earth-to-orbit vehicles may be required to reach orbit within hours or even minutes of a decision. A study has been conducted to consider vehicles with such a capability. In Phase I of the study, 11 vehicles were designed to deploy 5000 lb to a polar orbit. Changes in the designs were examined parametrically for increased on-orbit maneuvers, increased payload, and other mission variations. Based on the results, two concepts were selected for Phase II design work: a vertical-takeoff, two-stage system and a horizontal-takeoff, two-stage system with an airbreathing subsonic first stage. The results of several propulsion evaluations are presented, including liftoff thrust-to-weight effects, dual-fuel propulsion for a horizontal-takeoff concept, and the effect of using fluorine.

Martin, J. A.↗
NASA NTRS1985

Definition of an entry research vehicle

Within the last year, there has been a growing interest in technology which would support the development of vehicles which can maneuver in the atmosphere while returning from orbit and vehicles which can fly in the atmosphere at hypersonic speeds for sustained periods of time. This rebirth of interest in hypersonics is partly a result of a developing awareness of the potential benefits which can be derived from vehicles with capability to operate between the limits of existing aircraft and spacecraft. Examples of the types of maneuvers which are projected for this new class of vehicles are presented. Challenges provided by the considered maneuvers are summarized, taking into account a synergetic or atmospheric plane change. The plane change maneuver will require a Thermal Protection System (TPS). Attention is given to the definition of a Shuttle launched entry research vehicle experiment. Details regarding the synergetic plane change are considered along with the maneuvering entry, vehicle heating, and experiments and instrumentation.

Freeman, D. C.↗
NASA NTRS1985

Orbit on demand - Structural analysis finds vertical launchers weigh less

Structural considerations arising from favored design concepts for the next generation on-demand launch vehicles are explored. The two emerging concepts are a two stage fully reusable vertical take-off vehicle (V-2) and a horizontal take-off, two stage subsonic boost launch vehicle (H-2-Sub). Both designs have an 1100 n. mi. cross-range capability, with the V-2 orbiter having small wings with winglets for hypersonic trim and the H-2-Sub requiring larger, swept wings. The rockets would be cryogenic, while airbreathing initial boosters would be either turbofans, turbojets and/or ramjets. Dynamic loading is lower in the launch of a V-2. The TPS is a critical factor due to thinner leading edges than on the Shuttle and may require heat-pipe cooling. Airframe structures made of metal matrix composites have passed finite element simulations of projected loads and can now undergo proof-of-concept tests, although whisker-reinforced materials may be superior once long-whisker technology is developed.

Taylor, A. H.↗
NASA NTRS1984

Performance assessment of aero-assisted orbital transfer vehicles

Aero-assisted orbital transfer vehicles are analyzed. The aerodynamic characteristics over the flight profile and three- and six-degree-of-freedom performance analyses were determined. The important results, to date, are: (1) the aerodynamic preliminary analysis system, an interactive computer program, used to predict the aerodynamics (performance, stability, and control) for these vehicles; (2) the performance capability, e.g., maximum inclination change, maximum heating rate, and maximum sensed acceleration, can be determined using continuum aerodynamics only; (3) guidance schemes can be developed that allow for errors in atmospheric density prediction, mispredicted trim angle of attack, and off-nominal atmospheric interface conditions, even for vehicles with a low lift-to-drag ratio; and (4) multiple pass trajectories can be used to reduce the maximum heating rate.

Powell, R. W.↗
NASA NTRS1984

Performance evaluation of the atmospheric phase of aeromaneuvering orbital transfer vehicles

Studies are underway to design reusable orbital transfer vehicles that would be used to transfer payloads from low-earth orbit to higher orbits and return. One promising concept is to use an atmospheric pass on the return leg to reduce the amount of fuel for the mission. This paper discusses a six-degree-of-freedom simulation analysis for two configurations, a low-lift-to-drag ratio configuration and a medium-lift-to-drag ratio configuration using both a predictive guidance technique and an adaptive guidance technique. Both guidance schemes were evaluated using the 1962 standard atmosphere and three atmospheres that had been derived from three entries of the Space Shuttle. The predictive technique requires less reaction control system activity for both configurations, but because of the limited number of updates and because each update used the 1962 standard atmosphere, the adaptive technique produces more accurate exit conditions.

Powell, R. W.↗
NASA NTRS1984

Impact of atmospheric uncertainties and viscous interaction effects on the performance of aeroassisted orbital transfer vehicles

Simulations of aerobraking trajectories of aeroassisted orbital transfer vehicles (AOTV's) returning from geosynchronous orbit were analyzed to examine the effects of high-altitude viscous interactions and off-nominal atmospheres on AOTV return weight, heating, and loads performance. Viscous interaction effects encountered at high altitudes had little detrimental effect on the return weight capabilities for AOTV's representing a range of lift/drag ratios. Most of the AOTV return weight increase over an all-propulsive OTV occurred for a low lift/drag ratio. Smaller increases in return weight were observed for higher lift/drag ratios, at the expense of significantly higher heating and aerodynamic loads. Off-nominal atmospheres based on Shuttle-derived data and multipliers on a U.S. Standard Atmosphere were considered. AOTV's intended for entry under standard atmospheric conditions either deorbited during the pass through the off-nominal atmospheres or missed the target phasing orbit by wide margins. The AOTV's could successfully negotiate these atmospheres when new bank-angle histories were implemented with little loss and sometimes with a gain in return weight.

Talay, T. A.↗
NASA NTRS1983

Ascent performance and abort analysis for a Future Space Transportation System

The Future Space Transportation System (FSTS) study was conducted by the NASA Langley Research Center to identify the technology requirements for concepts that will replace the Space Shuttle in the post 2000 time frame. The configuration chosen for the study is a two-stage, fully reusable, vertical liftoff, and horizontal landing system with a 150,000 lb. payload capability. The two stages are burned in parallel with the booster providing all the propellant until staging, which results in a large lateral c.g. movement. Nominally, the booster stages at Mach 3 and glides back to the launch site. Because of the large lateral c.g. travel, a scheme to trim the vehicle until staging occurred was developed that used both gimballing and throttling of the engines. Preliminary booster aerodynamics were determined, and the booster glideback trajectory was analyzed with and without winds. Finally, a preliminary abort analysis was conducted for each stage.

Naftel, J. C.↗
NASA NTRS1983

Booster and orbiter configurations

In the recent Future Space Transportation System (FSFS) study, a mission model was selected and a baseline vehicle which best met model requirements was shaped. This baseline was then analyzed for flight performance, structural and subsystem weight, and operation. Figures related to a payload of 150,000 lb in a 20-ft-diam by 90-ft-long envelope became the baseline. The existence of both space-based orbital transfer vehicles (OTVs) and a space station was assumed, taking into account a transfer of the payload from the launch vehicle to OTVs at the space station for final delivery to geosynchronous orbit (GEO). A computer-aided engineering system called Aerospace Vehicle Interactive Design (AVID) was employed in connection with baseline vehicle development. It was found that approximately three-fifth of the payload weight would be cryogenic propellants for OTVs. Attention is given to problems regarding the packaging of cryogenic tankage, a payload shroud, and studies of staging for two different booster propulsion units.

Wilhite, A. W.↗