SEARCH · Search NASA

Results for “decelerators”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13

All sources NASA NTRS DOE OSTI

NASA NTRS1961

Aerodynamic Characteristics of Towed Cones Used as Decelerators at Mach Numbers from 1.57 to 4.65

Towed and sting-supported cones were tested in the wake of various payloads at supersonic speeds to determine their drag and stability characteristics. The investigation extended over a Mach number range from 1.57 to 4.65 and included such variables as Reynolds number, cone angle, ratio of cone base diameter to payload base diameter, and trailing distance. The results of this investigation showed that the cones towed in the wake of a symmetrical payload at supersonic speeds, in general, have good drag and stability characteristics if towed in the supersonic flow region. A cone with an included angle between 80 deg and 90 deg will give maximum drag while still maintaining stability in the Mach number region of this investigation. In order to minimize wake effects, the ratio of cone base diameter to payload base diameter should be at least one and preferably around three. A trailing distance of three times the payload base diameter, in most cases, is of sufficient length to avoid low drag and instability of the decelerator.

Charczenko, Nickolai↗

NASA NTRS2000

Gamma-Ray Burst Spectral Indices: Evidence for Deceleration of Synchrotron Shocks

The current scenario for gamma-ray bursts (GRBs) involves internal shocks for the prompt GRB emission phase and external shocks for the afterglow phase. Assuming synchrotron emission from energetic shocked electrons. GRB spectra observed with a low-energy power-law spectral index greater than -2/3 (for positive photon number indices E(sup alpha) indicate a problem with this model. The remaining spectra can test the synchrotron shock model prediction that the emission from a single distribution of electrons, cooling rapidly, is responsible for both the low-energy and high-energy power-low portions of the spectra. We find that the inferred relationship between the two spectral indices of observed GRB spectra is inconsistent with the constraints from the model, posing another problem for the synchrotron shock emission model. To overcome this problem, we describe a model where the average of -1, rather than the value of -3/2 predicted for cooling electrons. Situations where this might arise have been discussed in other contexts, and involve deceleration of the internal shocks during the GRB phase.

Preece, R. D.↗

NASA NTRS2002

Decelerated Magnetoshealth Plasma Flow at High Latitudes Behind the Cusp Region: Interball Tail Observations

On May 25, 1996 the Interball Tail spacecraft was moving through the northern hemisphere of the high-latitude magnetosphere on its outbound trajectory. It successively crossed lobe field lines followed by the high latitude magnetopause, then entering the magnetoshealth proper near the cusp region covering magnetic local time from 8h20m to 9h30m at magnetic latitudes of about 770. IMF observed by WIND was northward during the time interval of interest and favorable for reconnection at high latitude magnetopause. The well-defined De Hoffmann Teller frame and stress balance indicate that the magnetopause was a rotational discontinuity with ongoing reconnection. After the magnetopause crossing, the spacecraft observed decelerated magnetoshealth flow in the sub-Alvinic regime. A gradually increasing of the flow velocity is observed and the plasma flow regime changed from sub-Alfvnic through Alfinic to super-Alfvnic one. We explain these results by direct passing of the Interball Tail through the secondary stagnation point, which has been predicted by theoretical and semiempirical models of the high latitude magnetopause.

Avanov, L. A.↗

NASA NTRS1961

Experimental Evaluation of the Deceleration of Aluminum Cylinders Rotating in a Magnetic Field and Comments on Magnetic Damping of a Flywheel Control

An experimental investigation has been made to determine the magnetic deceleration of a closed-end cylinder rotating in a magnetic field by use of opposed ball and socket air bearing support. The theories of smythe and Hooper were compared with the experimental data for aluminum cylinders with fineness ratios of 9:1, 4:1, and 2:l and a wall thickness of 0.254 centimeter and one cylinder with a fineness ratio of 6:1 and a wall thickness of 0.508 centimeter. A method is outlined by which the magnetic damping coefficient for the spinning motion of a body of revolution may be determined experimentally. The theory of Smythe for a thin-walled cylinder predicts values greater than experimental results for fineness ratios of less than 6:l. Hooper's theory is in agreement with the experimental results through-out the range of fineness ratios tested. A utilization of the magnetic damping to prevent overspeeding of a flywheel used in a satellite orientation system is discussed.

Eide, Donald G.↗

NASA NTRS2001

Estimation of left ventricular operating stiffness from Doppler early filling deceleration time in humans

Shortened early transmitral deceleration times (E(DT)) have been qualitatively associated with increased filling pressure and reduced survival in patients with cardiac disease and increased left ventricular operating stiffness (K(LV)). An equation relating K(LV) quantitatively to E(DT) has previously been described in a canine model but not in humans. During several varying hemodynamic conditions, we studied 18 patients undergoing open-heart surgery. Transesophageal echocardiographic two-dimensional volumes and Doppler flows were combined with high-fidelity left atrial (LA) and left ventricular (LV) pressures to determine K(LV). From digitized Doppler recordings, E(DT) was measured and compared against changes in LV and LA diastolic volumes and pressures. E(DT) (180 +/- 39 ms) was inversely associated with LV end-diastolic pressures (r = -0.56, P = 0.004) and net atrioventricular stiffness (r = -0.55, P = 0.006) but had its strongest association with K(LV) (r = -0.81, P < 0.001). K(LV) was predicted assuming a nonrestrictive orifice (K(nonrest)) from E(DT) as K(nonrest) = (0.07/E(DT))(2) with K(LV) = 1.01 K(nonrest) - 0.02; r = 0.86, P < 0.001, DeltaK (K(nonrest) - K(LV)) = 0.02 +/- 0.06 mm Hg/ml. In adults with cardiac disease, E(DT) provides an accurate estimate of LV operating stiffness and supports its application as a practical noninvasive index in the evaluation of diastolic function.

Non-NASA Center↗

NASA NTRS2005

5.0 Aerodynamic and Propulsive Decelerator Systems

Contents include the following: Introduction. Capability Breakdown Structure. Decelerator Functions. Candidate Solutions. Performance and Technology. Capability State-of-the-Art. Performance Needs. Candidate Configurations. Possible Technology Roadmaps. Capability Roadmaps.

Cruz, Juan R.↗

NASA NTRS2005

Rotary-Wing Decelerators for Probe Descent Through the Atmosphere of Venus

An innovative concept is proposed for atmospheric entry probe deceleration, wherein one or more deployed rotors (in autorotation or wind-turbine flow states) on the aft end of the probe effect controlled descent. This concept is particularly oriented toward probes intended to land safely on the surface of Venus. Initial work on design trade studies is discussed.

Young, Larry A.↗

NASA NTRS1959

Flow Studies of Decelerators at Supersonic Speeds

Wind tunnel tests recorded the effect of decelerators on flow at various supersonic speeds. Rigid parachute models were tested for the effects of porosity, shroud length, and number of shrouds. Flexible model parachutes were tested for effects of porosity and conical-shaped canopy. Ribbon dive brakes on a missile-shaped body were tested for effect of tension cable type and ribbon flare type. The final test involved a plastic sphere on riser lines.

Source record↗

NASA NTRS1968

Summary of Attached Inflatable Decelerator (AID) Development

Attached inflatable decelerators (AID) were tested in an environmental chamber, a spin tunnel, and a wind tunnel. Deployment tests were conducted in environmental chamber to examine guided and unguided water alcohol vapor inflation. Subsonic performance tests were conducted in the spin tunnel. The full-scale wind tunnel was used for AID gust and supersonic performance tests. The supersonic tests were conducted at Mach number 3.0 with 12 ounces of fluid and Mach number 2.2 with six ounces of fluid.

Source record↗

NASA NTRS1970

Deployment and Performance Characteristics of 5-Foot Diameter (1.5m) Attached Inflatable Decelerators from Mach Numbers 2.2-4.4

Deployment characteristics and steady-state performance data were obtained over the Mach number range from 2.2 to 4.4 and at angles of attack from 0 degrees to l0 degrees. All attached inflatable decelerator (AID) models deployed successfully and exhibited flutter-free performance after deployment. Shock loads commonly associated with inflation of parachutes during deployment were not experienced. Force and moment data and ram-air pressure data were obtained throughout the Mach number range and at angles of attack from 0 degrees to l0 degrees. The high drag coefficient of 1.14 was in good agreement with the value predicted by the theory used in the design and indicated other AID shapes may be designed on a rational basis with a high degree of confidence.

TESTS↗

NASA NTRS1969

Flight Tests Results from Supersonic Deployment of an 18-Foot Diameter (5.49 meter) Towed Ballute Decelerator

A ram-air-inflated, towed ballute decelerator having a maximum frontal diameter of 18 feet (5.49 meters) was deployed during free flight at a Mach number of 3.15 and a dynamic pressure of 38.5 lb/ft(exp 2) (1843.4 newtons/m(exp 2)). Deployment and extraction of the test ballute were normal but inflation stopped about 1 second after mortar firing and produced an average plateau drag force of 1500 pounds (6.7 kN) for about 1 second. Approximately 30 percent of expected total frontal area was obtained.

TESTS↗

NASA NTRS2009

Aerodynamic and Aeroelastic Characteristics of a Tension Cone Inflatable Aerodynamic Decelerator

The supersonic aerodynamic and aeroelastic characteristics of a tension cone inflatable aerodynamic decelerator were investigated by wind tunnel testing. Two sets of tests were conducted: one using rigid models and another using textile models. Tests using rigid models were conducted over a Mach number range from 1.65 to 4.5 at angles of attack from -12 to 20 degrees. The axial, normal, and pitching moment coefficients were found to be insensitive to Mach number over the tested range. The axial force coefficient was nearly constant (C(sub A) = 1.45 +/- 0.05) with respect to angle of attack. Both the normal and pitching moment coefficients were nearly linear with respect to angle of attack. The pitching moment coefficient showed the model to be statically stable about the reference point. Schlieren images and video showed a detached bow shock with no evidence of large regions of separated flow and/or embedded shocks at all Mach numbers investigated. Qualitatively similar static aerodynamic coefficient and flow visualization results were obtained using textile models at a Mach number of 2.5. Using inflatable textile models the torus pressure required to maintain the model in the fully-inflated configuration was determined. This pressure was found to be sensitive to details in the structural configuration of the inflatable models. Additional tests included surface pressure measurements on rigid models and deployment and inflation tests with inflatable models.

Clark, Ian G.↗

NASA NTRS2009

Test Plan for the Technology Maturation of Supersonic Inflatable Aerodynamic Decelerators

Supersonic inflatable aerodynamic decelerators (IADs) are drag devices intended to be deployed at high Mach numbers. In the application considered here they assist in the descent and landing of spacecraft on Mars. Although promising, present IAD technology is not yet sufficiently mature for use in the near future. This paper describes a technology maturation plan for tension cone IADs using subscale test articles to reduce development costs. As envisioned, the proposed test plan includes three phases: wind tunnel tests (subsonic), unpowered high-altitude flight tests (transonic), and powered high-altitude tests (supersonic). This test plan is based on a building block approach in which successful completion of each phase adds to the understanding of the behavior of IADs and reduces the risk of the subsequent, more expensive phases. By properly scaling the IADs, test articles of the same size and nearly the same construction can be used for all three phases. The final phase is a dynamically scaled flight test with IAD deployment at the same Mach number as the full-scale vehicle on Mars. Two full-scale example cases are presented: one for a single-stage system (15 m dia. IAD to subsonic retropropulsion), and another for a two-stage system (10.5 m dia. IAD to subsonic parachute). Using scale factors of 0.333 and 0.476 yield subscale test IADs of 5 m dia. The dynamically scaled powered flight test starts at Mach 4 and an altitude of 33.5 km. Existing balloons and rocket motors are shown to be adequate to meet the required test conditions.

Kelly, Jenny R.↗

NASA NTRS2009

Flight Dynamics of an Aeroshell Using an Attached Inflatable Aerodynamic Decelerator

An aeroelastic analysis of the behavior of an entry vehicle utilizing an attached inflatable aerodynamic decelerator during supersonic flight is presented. The analysis consists of a planar, four degree of freedom simulation. The aeroshell and the IAD are assumed to be separate, rigid bodies connected with a spring-damper at an interface point constraining the relative motion of the two bodies. Aerodynamic forces and moments are modeled using modified Newtonian aerodynamics. The analysis includes the contribution of static aerodynamic forces and moments as well as pitch damping. Two cases are considered in the analysis: constant velocity flight and planar free flight. For the constant velocity and free flight cases with neutral pitch damping, configurations with highly-stiff interfaces exhibit statically stable but dynamically unstable aeroshell angle of attack. Moderately stiff interfaces exhibit static and dynamic stability of aeroshell angle of attack due to damping induced by the pitch angle rate lag between the aeroshell and IAD. For the free-flight case, low values of both the interface stiffness and damping cause divergence of the aeroshell angle of attack due to the offset of the IAD drag force with respect to the aeroshell center of mass. The presence of dynamic aerodynamic moments was found to influence the stability characteristics of the vehicle. The effect of gravity on the aeroshell angle of attack stability characteristics was determined to be negligible for the cases investigated.

Cruz, Juan R.↗

NASA NTRS2009

Reefing of Quarter Spherical Ribbon Parachutes Used in the Ares I First Stage Deceleration System

This paper introduces the parachutes that have been drop tested in support of the Ares I first stage deceleration system development. The results of the tests show that the reefing ratios for these quarter spherical ribbon parachutes provide the same reefed drag area as historical conical ribbon parachutes. Two sources are investigated for properly normalizing the parachutes relative to their suspension line length, and one is found to be superior.

Schmidt, Jason R.↗

NASA NTRS2010

Aero-Structural Assessment of an Inflatable Aerodynamic Decelerator

NASA is conducting an Entry, Descent and Landing Systems Analysis (EDL-SA) Study to determine the key technology development projects that should be undertaken for enabling the landing of large payloads on Mars for both human and robotic missions. Inflatable Aerodynamic Decelerators (IADs) are one of the candidate technologies. A variety of EDL architectures are under consideration. The current effort is conducted for development and simulations of computational framework for inflatable structures.

Sheta, Essam F.↗

NASA NTRS2002

Technology Development for Deployable Aerodynamic Decelerators at Mars

Parachutes used for Mars landing missions are only certified for deployment at Mars behind blunt bodies flying at low angles of attack, Mach numbers up to 2.2, and dynamic pressures of up to 800 Pa. NASA is currently studying entry vehicle concepts for future robotic missions to Mars that would require parachutes to be deployed at higher Mach numbers and dynamic pressures. This paper demonstrates the need for expanding the parachute deployment envelope, and describes a three-phase technology development activity that has been initiated to address the need. The end result of the technology development program will be a aerodynamic decelerator system that can be deployed at Mach numbers of up to 3.1 and dynamic pressures of up to 1400 Pa.

Masciarelli, James P.↗

NASA NTRS2011

Methods to Determine the Deformation of the IRVE Hypersonic Inflatable Aerodynamic Decelerator

Small resonant targets used in conjunction with a microwave reflectometer to determine the deformation of the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) during reentry are investigated. The reflectometer measures the distance to the targets and from this the HIAD deformation is determined. The HIAD is used by the Inflatable Reentry Vehicle Experiment (IRVE) which investigates the use of inflatable heat shields for atmospheric reentry. After several different microwave reflectometer systems were analyzed and compared it was determined that the most desirable for this application is the Frequency Doubling Target method.

Young, William R.↗