RU-1841398-C - A method for determining the density of a planet's atmosphere

Abstract

FIELD: atmosphere. SUBSTANCE: use: to determine the density of a planet's atmosphere. The essence of the invention is that when a hypersonic ballistic probe passes through the atmosphere, the probe's trajectory parameters are measured using a remote radar, and the density of the atmosphere is calculated based on the measurement results. Simultaneously with the measurement of the trajectory parameters, the radio signal characteristics of the plasma formations created by the probe are measured. EFFECT: technical result is to enable the determination of the density of a planet's atmosphere along the flight path of a hypersonic ballistic probe. 1 cl, 1 tbl

Inventors

• Kachalov Boris Alekseevich
• Legkij Igor Alekseevich
• Pukhov Mikhail Georgievich

Assignees

• Акционерное общество "Центральный научно-исследовательский радиотехнический институт имени академика А.И. Берга"

Dates

Publication Date

20260506

Application Date

19770908

Claims (1)

1. A method for determining the density of a planet's atmosphere, which consists of passing a hypersonic ballistic probe through the atmosphere, measuring the trajectory parameters of the probe with a remote radar, and calculating the density of the atmosphere based on the results of the measurements, characterized in that, in order to expand the range of measurements, simultaneously with measuring the trajectory parameters, the radio signal characteristics of plasma formations created by the probe are measured.

Description

The invention relates to the field of space research and can be used to determine the characteristics of the atmospheres of planets in the solar system. Current and planned space exploration utilizes ballistic probes that enter a planet's atmosphere at hypersonic speeds. One of the purposes of these probes is to measure atmospheric characteristics (including density) along the probe's trajectory. Direct methods of density measurement (for example, using interferometers [1] and hot-wire anemometers [2]) have a number of disadvantages. In addition to design difficulties, the use of such methods is hampered by the fact that the parameters of the atmosphere near a hypersonic body are distorted. In addition, the use of such methods requires the installation of additional measuring and radio transmitting equipment on board the ballistic probe. In this case, radio communication with the ballistic probe passing through the atmosphere can be unstable [3]. Finally, the method based on the creation of a luminous sodium cloud in the atmosphere and visual determination of its size [4] allows one to obtain density data only at several fixed altitudes, i.e., it does not provide the possibility of obtaining a continuous dependence of density on the probe's flight altitude. A known method for determining atmospheric density is based on the deceleration of a ballistic body entering the atmosphere (the prototype of the present invention [5]). In this method, atmospheric density is calculated based on trajectory parameters: the body's velocity and deceleration, measured by a remote radar. The density is correlated with altitude by simultaneously measuring the probe's flight altitude using radar. The main drawback of the known method is the fundamental impossibility of determining density in a rarefied atmosphere. Indeed, from the equation of motion of a body entering the atmosphere, one can derive an expression for determining the atmospheric density. along the probe's flight path: Where - aerodynamic braking of the probe; - probe flight speed; - ballistic coefficient of the probe. Considering that the relative error in determining the speed is small enough (at hypersonic atmospheric entry speeds this is always true), from formula (I) follows an expression for determining the absolute error in determining the density : Where - absolute error in determining braking. From formula (2) it follows that the known method is not suitable for flight altitudes where The aim of the present invention is to extend the range of density measurements to a rarefied region of the atmosphere. The stated goal is achieved by the fact that in the known method of determining the density of the planet's atmosphere along the flight trajectory of a hypersonic ballistic probe, which includes observing the probe with a remote radar, measuring the trajectory of the probe's parameters, and calculating the density of the atmosphere based on the results of the measurements, measurements are made of the radio signal characteristics of the plasma formations created by the probe. The proposed invention is based on the research conducted in [6]. This work shows that many radio signal characteristics of plasma formations created by a ballistic body are directly related to the density of the surrounding atmosphere. When special plasma sources are installed on the body, the effective scattering surface bodies with plasma jets (excluding the trace) turns out to be related to the density ratio: Where - mass flow rate of ionized gas from the source. The width of the scattering spectrum from plasma jets D is equal to (in Doppler velocities): Where - relative amplitude of density fluctuations; - scale of density fluctuation; - radar wavelength. Formula (4) allows us to use radio signal characteristics to determine not only the average, but also the fluctuation component of the atmospheric density. Furthermore, the distance to the point of formation of the radio reflective trail (provided that plasma is introduced into the flow) obeys the relation: (The quantities included in formulas (3) ÷ (5) are specified in the SI system.) Some other radio signal characteristics also depend on density, such as the total effective scattering surface of a body with plasma jets and the wake behind it. A characteristic feature of formulas (3) and (5) is the inversely proportional relationship between density and measured quantities. , which leads to an increase in the accuracy of density determination under conditions of high vacuum. For example, from formula (I), neglecting, as above, the quantity , you can get: Where - error in measuring the EPR value. From the obtained formula it is clear that with an increase in vacuum (a decrease in density) not only the absolute but also the relative error in determining the density decreases, which is the fundamental advantage of the proposed method over the known one. Example The table shows the EPR values of an experimental ballistic body equipp