Vernier Thrusters Research Articles

Optical effects of running spacecraft engines in the lower thermosphere

This paper provides a brief overview on optical effects during operation of spacecraft (SC) onboard engines in the lower thermosphere according to observational data from the ISTP SB RAS Geophyisical Observatory. We present the results of detected disturbances in the night airglow during operation of SC vernier engines in the F2-region of the ionosphere in the “Radar–Progress” space experiment. With weights of combustion products of ≤10 kg injected by SC vernier engines, the atmospheric emission of [OI] 630.0 nm atomic oxygen is enhanced. We also show optical effects from the launches and passages of heavy launch vehicles “Energiya” from the Skif-DM spacecraft on May 15, 1987 and “Proton-M” from the Yamal-601 spacecraft on May 30, 2019 from Baikonur in the zone far from the launch site. We explore the possibility of enhanced [OI] 557.7 nm atmospheric emission due to chemical modification of the ionosphere in the E-region during the flight of the Energiya space system.

Оптические эффекты работы двигателей космических аппаратов на высотах нижней термосферы

This paper provides a brief overview on optical effects during operation of spacecraft (SC) onboard engines in the lower thermosphere according to observational data from the ISTP SB RAS Geophyisical Observatory. We present the results of detected disturbances in the night airglow during operation of SC vernier engines in the F2-region of the ionosphere in the “Radar–Progress” space experiment. With weights of combustion products of ≤10 kg injected by SC vernier engines, the atmospheric emission of [OI] 630.0 nm atomic oxygen is enhanced. We also show optical effects from the launches and passages of heavy launch vehicles “Energiya” from the Skif-DM spacecraft on May 15, 1987 and “Proton-M” from the Yamal-601 spacecraft on May 30, 2019 from Baikonur in the zone far from the launch site. We explore the possibility of enhanced [OI] 557.7 nm atmospheric emission due to chemical modification of the ionosphere in the E-region during the flight of the Energiya space system.

PRESSURE MEASUREMENT OF INDUCED EXTERNAL ATMOSPHERE ON THE RUSSIAN SEGMENT OF THE INTERNATIONAL SPACE STATION IN EXPERIMENT «CONTROL»

The goals and objectives of space experiment Control to study parameters of the induced external atmosphere of the Russian Segment of the International Space Station are presented. The processing and analysis procedure for telemetry data obtained using scientific equipment Indicator - ISS is described. Numerical calculations were performed by direct statistical modeling of the flow around the pressure sensor by incoming flotation the Earth's outer atmosphere in the background measurement conditions, as well as in disturbed conditions with two vernier engines of the Zvezda module being operated. A correction function of the pressure sensor is obtained depending on the orientation, temperature factor and selected model of interaction of incident flow molecules with the internal and external device surfaces. The results of numerical modeling of the jet discharges of the the Zvezda vernier engine were compared with the data obtained in full-scale pressure measurements in experiment Control. Key words: pressure sensor, orbital station, induced external atmosphere, direct statistical modeling method.

Thermal simulations and experimental validation for the induction of indigenously developed copper alloy in regeneratively cooled Cryogenic vernier engines

Thermal simulations and experimental validation for the induction of indigenously developed copper alloy in regeneratively cooled Cryogenic vernier engines

Investigation of optical laser beam impairment on hypergolic lunarlander exhaust plumes for a lidar feasibility study

Plumes of two hypergolic bipropellant thrusters of a LunarLander application, developed by ArianeGroup® Lampoldshausen, were optically examined regarding their potential to interfere with laser beams of a nearby LIDAR system. On one hand, hot exhaust gas of a 22 N Vernier thruster was used to investigate the scattering of a λ = 632.8 nm HeNe laser beam. A series of several engine pulse modes were conducted. An obvious correlation between engine pulse duration and backscattered light intensity is revealed. The shortest pulses result in the most intense backscattering, indicating an incomplete combustion process between the hypergolic constituents MMH = monomethylhydrazine and NTO = (di)nitrogen tetroxide for very short pulse lengths. On the other hand, a prolonged pulse mode of 120 ms firing time causes only marginal deflection of the laser beam. Furthermore, steady operation leads to a negligible signal of backscattered photons, accompanied by increasing emission bands of combustion products such as CN, O2, and CO2. However, the disappearance of the OH* emission band, typical for this hypergolic combustion, shows a nearly complete reaction of the hydroxyl radical within the combustor for all pulse modes. Mie scattering calculations show a correlation between the incident laser beam wavelength and the backscattered light intensity. On the other hand, near infrared spectroscopy on the exhaust plume of a 500 N apogee thruster revealed that interfering flame emission and absorption in the optical range around λ = 1064 nm can be neglected. The relatively intense flame emission measured for λ ≥ 1300 nm, on the other hand, is a potential risk for the application of a laser beam of a similar wavelength.

Development of intelligent peripheral devices of control and emergency protection systems for ground testing of liquid-propellant rocket engines

One of the promising trends in the improvement of stand test data management and control systems and emergency protection systems involves the development of intellectual peripheral devices that provide communication with test articles. Due to the incorporation of their own processors in such devices they can solve problems of receiving data from sensors and initiating lower level control actions (independently from the master controller) on the actuators of controlled objects, which enhances the reliability and quality of control. The paper presents the latest developments directly related to the control of liquid-propellant rocket engine (LRE) parameters during stand tests, i.e. control of electro-hydraulic tilt actuators of LRE combustion chambers; control of stepping motors for the regulation of mixture ratio and control of vernier engines; receiving, processing and recording of signals from turbine flow meters and turbopump RPM sensors.

Negative shuttle charging during TSS 1R

We studied 21 intervals during the TSS 1R deployment with a 15 Ω or 25 kΩ resistor connecting the tether to shuttle ground. Ion spectral peaks detected by the Shuttle Potential and Return Electron Experiment indicate that the shuttle consistently charged negatively with respect to the local plasma. With the 15 Ω shunt in the circuit, shuttle potential, Φs, decreased from −17 to −245 V as tether length, L, increased to 2.6 km. Current in the circuit depended strongly on ionospheric density. With the 25 kΩ resistor in place, Φs ≈ −300 V in the low density, nightside ionosphere with L = 5.1 km. Near local noon Φs ≈ −80 V with L = 17.2 km. The shuttle charged to ∼−600 V during two dawn terminator crossings, one with and one without thruster firings. As on TSS 1, firings of two aft vernier thrusters significantly increased |Φs|. In the case without thruster firings, simultaneous variations of Φs, tether current, and the inferred satellite potential are consistent with strong azimuthal and vertical ionospheric density gradients. These are the first known direct measurements of strong negative shuttle charging.

Negative pickup ions detected during the TSS 1 mission

We report the occasional detection of negative pickup ions by the Shuttle Potential and Return Electron Experiment (SPREE) in the shuttle payload bay during the first Tethered Satellite System (TSS 1) mission. These ions appear as arch‐like structures of enhanced fluxes in energy versus time spectrograms for the SPREE electron zone looking in the plane perpendicular to the Earth's magnetic field. Maximum energies of ∼56 eV were measured when the sensor looked closest to the shuttle ram direction. Empirically, the energy of associated spectral peaks decreases as cos2 ξ, where ξ is the angle between the sensor look direction and the projection of the shuttle's velocity onto the plane perpendicular to the magnetic field. These signatures may be found under day or night conditions and always in conjunction with positively charged pickup ions generated as a result of firings by the L5D and/or R5D vernier thrusters. We show that positive ion contamination and accelerated electrons cannot be the responsible agents. Observed spectral characteristics are most easily explained as either NO2− or MMH− ions created near the shuttle and accelerated by the motional electric field to energies detectable by SPREE.

Thruster firing effects in the shuttle environment: 1. Neutral gas composition

The changes in the composition of the neutral gas in the space shuttle payload bay caused by the shuttle's vernier reaction control system rocket engines were measured with a quadrupole mass spectrometer aboard STS‐4. The average hydrogen level during thruster firings was approximately 25 times greater than nitric oxide, NO, which was previously found to be one of the largest components of the gas in the payload bay during firings. The attitude of the orbiter also influenced the effects of the vernier engines as measured in the payload bay. When the mass spectrometer was pointed into the velocity vector, thrusters whose exhaust plumes were directed approximately upstream into the flow of ambient neutral species caused decreases in atomic oxygen signals. NO was enhanced in the payload bay during thruster firings primarily when the shuttle was in a bay‐to‐ram attitude. The return flux from the left‐side, downward pointing vernier thruster was detected by the mass spectrometer only when the shuttle was in a belly‐to‐ram attitude. All of these results are consistent with earlier observations that the kinematics of gas phase and surface scattering are important in determining the effects of the thruster firings on the payload bay environment.

Dynamics and control of the Shuttle based large antenna system during slewing maneuvers

A relatively general formulation for studying dynamics of a large class of interconnected flexible and/or rigid bodies forming a chain type topology is developed. The problem is approached using the Lagrangian procedure with the generalized forces accounting for the environmental effects, damping and control. The flexible members are taken to be the Euler-Bernoulli beams with their bending and torsional deformations discretized using a series of admissible functions. As a particular case, the general formulation is applied to study complex dynamics of the SCOLE (Spacecraft COntrol Laboratory Experiment) system as proposed in the NASA's design challenge. The classical infinite time linear state feedback regulator utilizing the Shuttle's primary and vernier thrusters is designed to suppress the vibrations as well as control the Shuttle attitude motion. The results suggest that flexibility of the mast during the prescribed slewing maneuver substantially induces the line-of-sight error if the Shuttle is uncontrolled. However, the proposed control strategy can damp both the vibrational motion of the mast and librational motion of the Shuttle to the specified acceptable limit within 5 s of the completion of the maneuver.

Docking of spacecraft in an elliptical orbit

It is an accepted fact [3] that the docking stage commences at the instant of first contact between the docking devices and is completed as soon as the vehicles are rigidly locked into a unit system. If an impact docking mechanism is used, the actual docking process is divided into two phases. The first phase includes first contact, meshing of the docking devices, and mutual stabilization of the vehicles. The second stage comprises the subsequent locking-in of the bodies. In the first phase the kinetic energy of relative motion is converted into potential energy of elastic deformations, thermal energy, vibrational energy, etc. In the second or locking phase the potential energy of the elastic deformations created in locking together two massive vehicles along a line that does not pass through the centers of mass is partially converted into kinetic energy. Our main objective here is to construct a fairly simple mathematical model of the docking of two spacecraft in an elliptical orbit. Such a model is needed primarily to ensure on-line analysis and drafting of recommendations for the suppression of vibrations of the investigated vehicle coupling in the first docking phase and to control the motions of the vehicles in the second phase with allowance for the possibility of employing vernier engines of one or both vehicles in manual control.

Application of actuators to control beam flexure in a large space structure

This paper describes a flexible-body control methodology for performing a nonlinear slew of a large space structure and simultaneously regulating the associated flexural vibrations by linear methods. Degree of controllability methods are used as guidelines for the positioning of proof-mass actuators on the structure. The goal is to determine the importance of location of the actuators on regulator performance, and the utility of the degree of controllability methods. A numerical simulation is made of a 20 deg slew maneuver of the spacecraft laboratory experiment (SCOLE). The SCOLE model treated here is the spacecraft version. It includes three bodies: the Space Shuttle, a reflector antenna, and a flexible beam of length 39.62 m connecting them. In the simulation, the beam vibration is fully coupled to the dynamics of the slewing motion. Regulation of the beam vibration is addressed by means of proof-mass actuators on the beam, and by vernier thrusters on the Shuttle and antenna bodies. Repeated simulations are made with different actuator placements. The results show that with the actuators placed within a region of strong control effectiveness, damping and flexural amplitude are changed only slightly by changes in actuator location. However, the damping is significantly reduced for actuator location in regions of low-control effectiveness, although the amplitude of the vibrations changes only slightly.

Observations of glow from shuttle surfaces during mission STS 41-G

Two sets of observations, made during the STS 41-G mission in October, 1984, obtained measurements of the quiescent orbiter glow at high spectral resolution over limited spectral regions, and of the vernier thruster induced glow. The spectral results indicate that the brightness of the quiescent glow was considerably less than values reported on previous flights at a similar altitude, and exhibited a diffuse spectrum at 0.4 nm resolution. The thruster induced glow observations indicate both a surface component and an apparent gas phase glow standing away from the surface. The lifetimes of these two components and the temporal histories of each thruster firing are shown to be different. These results are discussed in terms of presently suggested mechanisms for the glow.

Lunar surface mechanical properties

The surface material at the Surveyor 5 site is granular and slightly cohesive. Spacecraft footpads plowed trenches in this material as the spacecraft slid during landing. For a compressible soil model, a static bearing capacity of 2.7 newtons/cm^2 gave best agreement with the observations. Static firing of the vernier engines against the surface moved surface particles; a crater 20 cm in diameter and about 1 cm deep was produced, apparently at engine shutdown. The permeability of the soil to gases, to a depth of about 25 cm, is 1 × 10^(−8) cm^2, corresponding to soil particles mostly 2 to 60 μ in diameter.

Transient rocket-engine gas flow in soil.

As a result of an examination of the behavior of soils subjected to rocket and jet exhaust gases. it was concluded that the gas pressure in the pores of the soil played an important part in the process of soil removal which occurred. Consequently, a numerical study of axially symmetric isothermal nonlinear gas flow ill a porous medium was undertaken. The paper presents the results and interpretations of the calculations for the particular boundary pressure conditions developed by a Surveyor spacecraft vernier engine mounted 12 in, above a granular material.

Surveyor Vernier engine fuel blend - A constrained optimization.

Propellant composition variation for improving cooling characteristics of Surveyor vernier propulsion system

Vernier exhaust perturbations on radar and altimeter systems during a lunar landing

A PROCEDURE that has been proposed to accomplish a soft lunar landing to use a high thrust main engine stage to remove most of the approach velocity in an open loop fashion, and a low thrust vernier engine stage to control the spacecraft to a soft landing. The vernier stage employs terminal sensors to measure altitude [altimeter] and velocity [Doppler], throttling to control descent rate, and may employ body maneuvering to control horizontal velocity. It is the purpose of this paper to make an estimate of the interference that the vernier rocket exhaust may exert on the performance of the Doppler and altimeter systems of the lunar landing vehicle. The subject of rocket exhaust interference on missile guidance and communication has been under considerable study in the past. The most detailed on this topic are in the form of unpublished company reports and studies. We shall make use of the results and conclusions of some of these studies to provide upper bound estimates of flame effects on the guidance of the lunar vehicle. The main results of these are as follows: 1) Molecular absorption and polarizability are insignificant in determining the electrical properties of the rocket exhaust; the free electrons play the dominant role. 2) The electron collision frequency is determined (and therefore predictable), in the main, by the presence of those molecules with permanent electric dipole moments. 3) The observed degree of ionization of liquid rocket exhausts at exit plane conditions is enormously larger than predicted by equilibrium theory. The ionization can be explained as due to the thermal ionization of low-ionization fuel impurities (e.g., sodium) in the combustion chamber followed by slow electron-ion recombination as the combustion products accelerate, expand, and cool through the thrust chamber. The possibility of chemi-ionization as the cause of the observed ionization is not ruled out, however. 4) Computer programs were developed to predict the spatial distribution of the exhaust gases (flow pattern) for vacuum operation of the rocket motors. 5) The exhaust gas flow patterns combined with knowledge of electron collision frequency and fractional ionization (considered frozen beyond the exit plane) allow prediction of the complex electrical conductivity throughout the exhaust flare. The propagation of electromagnetic waves (of not too large