RU2564930C1 - Deployment of space rope system at delivery of lander from orbital station to ground - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to control over displacement of space objects tied by the rope. Proposed process comprises disconnection of said objects to impart to the lander of initial velocity of blowup against orbital velocity vector. Then, the rope is released at invariable tension force at lander ejection to change the bundle into tail pendulum motion mode in shockless manner to fix the rope length. Said rope is cut when lander passes the local vertical of orbital station. Acceleration of said rope tension force at separation of lander from orbital station is $$\overline{J}=\mathrm{0,0534}\cdot \Delta \overline{V},$$

where $$\Delta \overline{V}$$

is the magnitude of transversal impulse of repulsion velocity. These data are related to appropriate parameters of starting circular orbit.

EFFECT: ruled out sections of lander return motion with the rope, simplified control over descent.

4 dwg

Description

The invention relates to space technology, mainly to space cable systems. The invention can be used to deliver a descent vehicle from an orbital station to Earth without using a jet propulsion system and the cost of a working fluid for performing maneuvers.

The space cable system (CTS) refers to a combination of two spacecraft connected by a long thin cable. The presence of this mechanical non-holding connection allows you to purposefully redistribute the total mechanical energy of the entire system between its end elements. In this case, the connecting cable acts as a conductor of mechanical energy. This is the physical basis for using the principle of energy-mass exchange in orbital maneuvers.

Among the target maneuvers of the spacecraft, the descent from the orbit to the Earth of the small descent vehicle (SA) was most fully worked out theoretically and experimentally [2, 4-12].

The transfer of SA from the initial circular orbit to the descent trajectory after its separation from the orbital station (OS) and the exchange of pulses is carried out by redistributing the total mechanical energy of the entire system between its elements. In this case, the total mechanical energy of the SA decreases to the value necessary for entering the Earth’s atmosphere and descent, and the total mechanical energy of the OS increases by the corresponding value. The principle of exchange of mechanical energy in such a system is implemented in accordance with Newton’s third law through a cable tension reaction, which can act as a control action. The magnitude of the cable tension force depends on the ratio of the masses of the elements of the CCC, the parameters of the orbit of the center of mass of the CCC, and the parameters of the relative motion of the CA.

The transition of the CA to the descent trajectory occurs after the separation of the CA from the OS, deployment of the cable to a predetermined length, followed by the transfer of the CCC to the mode of associated pendulum movement and cutting of the cable at the time of passing the CA local vertical OS. This scheme of maneuver is theoretically justified, experimentally tested, and today it is considered the most probable in practical implementation.

Deploying a CCC to a given cable length in the maneuver technological chain is the main task, the technical implementation of which can be achieved in various ways. All known methods for deploying a bunch of two space objects are based on the following general scheme. In the initial state, two objects connected by a cable are docked with each other, and the cable is compactly laid. At a certain point in time, the objects are undocked and one of the objects or both objects is informed of the initial speed of divergence, for example, using spring pushers. After that, the objects carry out a mutual divergence, during which the cable connecting them is released. The release of the cable is carried out using various devices until the specified terminal conditions are reached. If the achievement of the specified terminal conditions is ensured by the initial conditions of the CA movement at the time of separation during the free supply of the cable, then the corresponding deployment scheme is called passive. If a controlled cable feed is made, then the corresponding deployment scheme is called active.

Thus, the passive deployment scheme of the CCC can be exhaustively described by the parameters of the momentum exchange in the separation of related objects. To describe the active deployment scheme of the CCC, it is additionally required to determine a program for the exchange of total mechanical energy between related objects. Note that the intensity of energy exchange in the CCC, which is characterized by the power of the coupling reaction, directly depends on the parameters of the momentum exchange. Consequently, the parameters of the momentum exchange and the parameters of the program for the exchange of total mechanical energy between related objects are the leading design parameters, since they determine the energy efficiency of the maneuver, the circuit diagram of the deployment system of the CCC and the control algorithm of this device.

A fairly detailed analysis of the passive and active deployment schemes of the CCC is presented in [1, 3, 4, 6, 8]. The principal development of CCC deployment schemes from a monolithic state for solving targets is taking place in the framework of these two areas. We highlight the characteristic features of these schemes.

Active deployment. After pulsed separation of objects and their removal to a certain distance with the free supply of the cable, the phase of the controlled supply of the cable from the deposit device begins. Managed deployment is completed programmatically when the required terminal conditions are reached, or completion is determined by the condition for the release of the cable from the full-length deposit device. In some active deployment schemes, impulse exchange and the initial phase of passive deployment may be absent. So it was in the US-Italian space experiments on the Space Shuttle with a tethered satellite weighing 500 kg, relegated to a conductive cable 20 km long. The release of the cable in these experiments was carried out using a winch consisting of a drum with a wound cable, an automated electric drive and a retractable truss. The tethered satellite was equipped with jet engines to disperse the satellite at the beginning of its assignment.

The “classical” scheme for active deployment of the CCC in the task of launching a light capsule from orbit to the Earth’s surface was implemented in the YES2 space experiment on the Foton-M spacecraft in September 2007: pulsed separation of the SA down the local vertical followed by the deployment of the cable in a two-stage program with various laws of controlling the force of tension [5]. The first stage is the removal of the SA to the local OS vertical at a distance of 3-5 km. The control of the tension force of the cable at the first stage is carried out according to a complex law and almost immediately after the separation of the SA. The control of the tension force in the second stage is of a relay nature. The control aims to deploy the CCC to a predetermined length of the cable, providing at the end of the section of breeding conditions for the system to transition to a stable mode of associated pendulum motion with the maximum possible amplitude.

.Passive deployment. The initial phase of deployment is the exchange of momenta, usually along the line of the orbital velocity vector. Next, the uncontrolled release of the cable is performed in the process of diverging objects (Fig. 1). In accordance with the laws of orbital relative motion, the duration of the passive deployment process is a multiple of the period of rotation of the center of mass of the CTS [8, 9]. The cable is usually produced using a non-rotating ("inertialess") coil, which should provide an ordered output of the cable with a small resistance. Such free cable feeders developed by Carroll J.A. and tested in the SEDS orbital experiment [13], showed the level of relative resistance acceleration $$\overline{J}\approx {10}^{-5}$$

.

The passive deployment scheme of the CCC has worked well in space experiments: in 1966, with the Gemini ships and the Agen rocket stage connected by a 30 m long synthetic tape; in 1981-1985 in four US-Japanese experiments on sounding missiles with payloads weighing 75 kg, allotted on conductive cables 400 m long; in two Canadian experiments on sounding missiles with payloads of 100 kg weighing on conductive cables 958 m long OEDIPUS-A in 1989 and OEDIPUS-C in 1995; in 1993, in the American SEDS-1 experiment on a Delta-2 rocket with a payload of 25 kg weighed on a polyethylene cable 20 km long; in 1993, in the American PMG experiment on a Delta-2 rocket with a payload carried on a 500 m cable.

The scheme for maneuvering a spacecraft from orbit to the Earth’s surface based on passive deployment of the spacecraft [7–9] compares favorably with controlled deployment by the possibility of using simpler technical devices, simple control algorithms for these devices, and also provides the maximum energy potential difference between related objects [10].

The closest analogue of the invention is a method of delivery from orbit to the surface of the Earth of a small spacecraft, the description of which is described in [7]. The method provides the following sequence of technological operations. Separation of the SA from the OS located in near-Earth circular orbit is ensured by the message of the SA of the initial velocity of divergence against the orbital velocity vector using a transverse braking pulse. Then the passive deployment of the CCC is carried out by the free release of the cable with the mutual removal of objects. At the end of the stage of passive deployment of the CCC on the trajectory of the relative motion of the CA, a short-term section of the reverse movement begins, where, in order to avoid sagging of the cable, it is necessary to select excess cable length with the speed of approach of the CA and the OS. At the end of the reverse section, at a relative relative speed of zero, the cable is fixed, which creates the conditions for a smooth transition to the mode of associated vibrational motion of the CCC. The passive pendulum movement of the CCC until the CA passes the local vertical of the OS is completed by separation (by cutting the cable) and the transition of the CA to the descent trajectory.

The disadvantage of this method, adopted as a prototype, is the presence of loops on the trajectory of passive deployment - these are the so-called reverse sections of the SA movement (Fig. 2). In these sections, in order to avoid sagging and tangling of the cable, it is necessary to select a free cable in order to ensure at the end of the reverse section the conditions of shock-free transfer of the CCC to the mode of associated pendulum movement. Performing this very short time operation significantly complicates the design and deployment of the CCC.

To eliminate this significant drawback, a method is proposed for deploying a space cable system for delivering a descent vehicle from an orbital station to Earth, in which there are no reverse motion sections, and the advantages characteristic of passive deployment schemes are preserved.

The idea of the proposed method is based on the fact that under the influence of small perturbations (or control actions) from the cable tension force at the stage of passive deployment of the CCC, the loops on the trajectory “contract” (Fig. 3, 4), and the time and length of the sections of the return movement are reduced [8 ]. An ideal condition for pairing the deployment trajectory and the pendulum motion trajectory is to turn the loop into a break point under the influence of targeted control. At the kink point of the velocity projection in the orbital coordinate system, zero values are assumed, while the projection of the velocity on the ordinate axis changes sign.

The implementation of the proposed method is as follows. Separation of the SA from the OS located in near-Earth circular orbit is ensured by the message of the SA of the initial velocity of divergence against the orbital velocity vector using a transverse braking pulse. After the separation of the CA from the OS, the deployment of the CCC is performed with the effect on the produced cable of a constant and determined by the magnitude of the tension force. This allows you to eliminate the loop on the trajectory of the CA and completely exclude the reverse movement on the trajectory of the relative motion of the CA. When the break point is reached at a relative relative speed of zero, the cable length is fixed and a smooth transition to the mode of associated vibrational motion of the CCC is made. At the moment of passing the CA line of the local vertical line of the OS, it is separated (by cutting the cable) and the transition of the CA to the descent trajectory.

и относительная длина троса $${\overline{l}}_1$$

в точке излома траектории 1 линейно зависят от относительной величины импульса отделения СА $$\Delta \overline{V}$$

: $${\overline{l}}_1/\Delta \overline{V}=\mathrm{18,93}$$

; $$k^{\ast }=\overline{J}/\Delta \overline{V}=\mathrm{0,0534}$$

; при $$\Delta \overline{V}\le \mathrm{0,005}$$

[8].Studies of the trajectories of the relative motion of the tethered SA with a small value of the constantly acting acceleration of tension (dashed curve in Fig. 4), directed along the line of sight of the end objects, showed that the relative magnitude of the control acceleration of the cable tension $$\overline{J}$$

and relative cable length $${\overline{l}}_{\mathrm{one}}$$

at the break point of trajectory 1 linearly depend on the relative magnitude of the separation pulse SA $$\Delta \overline{V}$$

: $${\overline{l}}_{\mathrm{one}}/\Delta \overline{V}=18.93$$

; $$k^{\ast }=\overline{J}/\Delta \overline{V}=\mathrm{0,0534}$$

; at $$\Delta \overline{V}\le 0.005$$

[8].

The considered dimensionless quantities were obtained by normalization to the corresponding parameters of the motion of the center of mass of the CCC. The parameters of the relative motion of the SA at the break point are ideally suited as initial conditions for the transfer of the CCC from the deployment mode to the pendulum motion mode. Firstly, the derivatives of the position parameters are equal to zero, which corresponds to a “soft” stop of the cable feed - unstressed pairing of trajectories. Secondly, the second derivatives of the position parameters are positive, which corresponds to the conditions of a stable transition to the pendulum motion mode from the maximum angular phase. These conditions exclude the effect of “freezing” of the orbital pendulum at the return point.

, что эквивалентно величине силы реакции троса F_n=0,25 Н, приложенной к МКА массой 100 кг.We note that the relative magnitude of the controlled acceleration of tension, at which the loop on the trajectory of relative motion turns into a break point, is very small. Its maximum value $$\overline{J}=k^{\ast }\cdot \Delta {\overline{V}}_{\max }=2.67\cdot {10}^{-\mathrm{four}}$$

, which is equivalent to the value of the reaction force of the cable F _n = 0.25 N applied to the MCA weighing 100 kg.

достигается на этой траектории в точке 1 (фиг. 4). Например, при условии k=2·k* получаем, что $${\overline{l}}_1/\Delta \overline{V}=\mathrm{18,84}$$

и $${\overline{i}}_1/\Delta \overline{V}=\mathrm{0,92}$$

, то есть относительная скорость удаления СА в конце развертывания КТС соизмерима с величиной импульса скорости расталкивания объектов. Скорость удаления СА равна половине величины импульса расталкивания при значении параметра управления k=1,55·k*. Это позволяет сделать вывод об устойчивости траекторий развертывания КТС с малыми значениями постоянно действующего ускорения натяжения и их малой чувствительности к погрешностям управляющих воздействий.The study of the trajectories of the relative motion of the SA with "large" perturbations k> k * shows that the trajectories become smooth (dashed curve in Fig. 4). On such trajectories, the conditions of an unstressed transfer of the CCC from the deployment mode to the pendulum motion mode are not satisfied. The minimum value of the relative speed $${\overline{i}}_{\mathrm{one}\min }>0$$

achieved on this trajectory at point 1 (Fig. 4). For example, under the condition k = 2 · k *, we obtain $${\overline{l}}_{\mathrm{one}}/\Delta \overline{V}=18.84$$

and $${\overline{i}}_{\mathrm{one}}/\Delta \overline{V}=0.92$$

, that is, the relative rate of SA removal at the end of the CCC deployment is commensurate with the magnitude of the momentum repulsion rate of objects. The SA removal rate is equal to half the magnitude of the repulsion pulse with the control parameter k = 1.55 · k *. This allows us to conclude that the stability of the trajectories of the deployment of the CCC with small values of the constantly acting acceleration of tension and their low sensitivity to errors of control actions.

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Claims (1)

A method for deploying a space cable system for delivering a descent vehicle from an orbital station to Earth, including undocking two objects connected by a cable, informing the descent vehicle of the initial speed of divergence against the orbital velocity vector, releasing the cable when the descent device is removed, fixing the cable length, associated pendulum movement and cutting the cable at the moment the descent vehicle passes the line of the local vertical of the orbital station, characterized in that the cable feed during descent is descent of the device from the space station produces with constant tension $$\overline{j}=\mathrm{0,0534}\cdot \Delta \overline{V}$$

where $$\overline{j}$$

and $$\Delta \overline{V}$$

- the relative values of the acceleration of the tension force of the cable and the pulse of the repulsion speed, normalized by the parameters of the starting circular orbit.

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