System and method for braking flying objects

Abstract

A system for slowing down the speed of flying objects by applying electrodynamic and aerodynamic braking forces. The system is comprised of plurality of stubs, where each stub is made of dielectric material surrounded by metal foil and another metal foil is inserted in the middle of the stub, where the outer metal foil and the inner metal foil are isolated from each other, so that they form a capacitor. Each stub is stored in a barrel before being used. When activated, the stubs are stretched from the barrel as a tail behind the flying object. The area of the stub generates aerodynamic drag. The stub capacitor is charged by a generator so that free electrons are present in the outer metal layer of the stub. The electric field produced by these charges interacts with ions in the atmosphere.

Claims

1. A system for slowing down the speed of a flying object by applying electrodynamic and aerodynamic braking forces, the system comprised of: a. plurality of stubs, where each stub is made of dielectric material surrounded by metal foil and another metal foil is inserted in the middle of the stub, where the outer metal foil and the inner metal foil are isolated from each other, so that they form a capacitor; b. plurality of barrels, each one stores a stub in a folded state before the braking force is activated, the barrels are firmly attached to the flying object; c. a generator located in the flying object for providing high DC voltage to charge the capacitor formed by the stub; and d. control mechanism that activates each of the stubs for slowing down the speed of the flying object.

2. The system of claim 1, where the stub is stored in the barrel as helical shaped ribbon.

3. The system of claim 1, where the stub has rectangular cross section.

4. The system of claim 1, where a generator for each stub is located in the barrel containing the stub.

5. The system of claim 1, where the control mechanism can activate stubs according to pre prepared plan and/or according to real flight conditions.

6. A method for slowing down the speed of a flying object by applying electrodynamic and aerodynamic braking forces, the method is comprised of: a. attaching a plurality of stubs to the flying objects and opening them to slow down the speed of the flying object; b. charging the capacitor built in the stub by a DC generator which causes interaction between ions in the atmosphere and the negative charges on the stub, which absorbs kinetic energy from the flying object; and c. generation of aerodynamic drag by the stub which is a function of the stub area and the object speed.

7. A method of claim 6 where the electrodynamic braking force depends on the size of the stub and the charging current provided by the generator.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1a provides description of the barrel.

(2) FIG. 1b shows the structure of the stub within the barrel.

(3) FIG. 1c shows detailed structure of the open stub.

(4) FIG. 2 presents cross-section of the stub.

(5) FIG. 3 shows schematic view of the stub connected to the generator.

(6) FIG. 4 presents the currents and forces in the system.

DETAILED DESCRIPTION

(7) The invention will be described more fully hereinafter, with reference to the accompanying drawings, in which certain possible embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather these embodiments are provided so that the disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

(8) The disclosed method uses a system that generates electrodynamic deceleration and aerodynamic drag. At high altitudes the electrodynamic deceleration enables to slow down satellite reentrant speed, and the aerodynamic drag supports the final landing phase. The braking system is comprised of plurality of barrels as shown in FIG. 1a 110, where each barrel stores a compressed helical shaped ribbon 120. The structure of the helical shaped ribbon is shown in FIG. 1b. FIG. 1b shows the structure of the stub within the barrel whereby compressed helical shaped ribbon is shown in an open configuration having an outer surface 122 along a longitudinal axis 124. FIG. 1c presents a section of the fully opened ribbon and shows a detailed structure of the open stub having an upper surface 126. The barrels can be securely fixed to the flying object, the speed of which has to be reduced, and when opened, the ribbon travels with the flying object. In another embodiment the barrels can be securely fixed to the object carrying the flying object, such as aircraft or space station, and the stub is fixed to the flying object, and is released from the barrel after it is opened. We shall refer to the opened ribbon from this point on as the stub. Opening the ribbon is referred to as stub activation.

(9) Typical dimensions of the ribbon in a barrel are:

(10) Number of Turns=2000

(11) Length of the ribbon (L)=630 m.

(12) Dielectric constant (ε)=2.

(13) Weight of stub=6 Kg.

(14) Breakout voltage of dielectric material=40 Kg/mm.

(15) Cross-section A-A in FIG. 1b of the stub is shown in FIG. 2. The stub 200, is made out of a dielectric tape 230 of width We and height H. The outer perimeter of the stub is a metal foil 210 and in the middle of the stub there is a metal foil 220 of width Wi. Typical dimensions of the stub are: We=0.1 m, Wi=0.09 m, H=0.00005 m.

(16) The stub is built as a capacitor. The capacitance of the stub capacitor having the dimensions presented above is:
C=2 ε.sub.0εL Wi/0.5H≈0.0016C
where ε.sub.0 is vacuum permittivity and is relative permittivity.

(17) First we refer to the aerodynamic drag. This drag force F.sub.d, can be computed by the following formula:
F.sub.d=ρAC.sub.dV.sup.2/2  (1)
Where: ρ is air density [kg/m.sup.3]; A is stub area in open state [m.sup.2]; C.sub.d is drag coefficient which depends on the shape of the body; V is the velocity of the body [m/s].

(18) As an example, let us consider a case where the weight of a satellite is 5 Kg. to slow down to a constant speed, a drag force of 50 N is required (compensation for gravity acceleration). From equation (1) we can find the required area of the stub:
A=2F/(ρC.sub.dV.sup.2)  (2)

(19) We can assume that C.sub.d=1, taking into consideration that in open state there is interaction between spirals of the open ribbon. We also assume that during landing the speed of the satellite is 5 m/s. Air density ρ=1.2 Kg/m.sup.3. Using these value we get that the required area is 3.33 m.sup.2. Using the dimensions of the stun given above, and assuming stub material density of 1440 Kg/m.sup.3, the mass of the stub is 0.24 Kg.

(20) Let us refer now to the electrodynamic drag generated by the same stub. A cross section of the stub along line B-B in FIG. 2 is presented in FIG. 3. The stub 300 is in open state and is connected to the satellite 310. In the satellite there is a generator that is charging the stub capacitor. As described earlier, the stub capacitor is comprised of the metal layers 210 at the outer side of the stub and an inner metal layer 220 within the dielectric material 230 of the stub. The outer metal plates are connected to the negative terminal of the generator 320 and the inner metal layer is connected to the positive terminal of the generator 320. On the surface of the stub there are free electrons 330 and in the atmosphere there are positive ions 340.

(21) We can view the charged stub moving in the speed of the satellite V, as a wire having negative charge density Q Cb/m moving at speed of V m/s as carrying a constant current J given by:
J=V.Math.Q  (3)

(22) This is demonstrated in FIG. 4. The stub 410 moves at a speed V with the free electrons, thus a positive current J is generated. A circular magnetic field 430 is generated around the stub 410, the intensity B of which depends on the radius r. The magnetic field B(r) is given by:
B(r)=μ.sub.0J/(2πr)  (4)

(23) Where μ.sub.0 is the magnetic permeability of air (which we assume is equal to the magnetic permeability of vacuum).

(24) At the same distance r there is a positive ion 420 with charge p that is attracted to the negative charge in the stub with electric force E(r) given by:
E(r)=Q.Math.p/(2ε.sub.0r.sup.2)  (5)
where p is the charge of the ion. The electric force E(r) 440 acting on the ion 420 causes it to move with speed of w(r) towards the stub. That generates a Lorentz force F 450 on the ion 420 directed in the direction of the stub velocity V, where the magnitude of the force is given by:
F(r)=p.Math.w(r).Math.B(r)  (6)

(25) The work done on the moving ion 420 is taken from the kinetic energy of the satellite, thus the kinetic energy is reduced, so the satellite slows down.

(26) We continue with the computation of the power spent by the stub for the attraction of the ion. The ion is initially at a distance L from the stub. It moves, due the forces acting on it, towards the stub until it picks up an electron, and is neutralized. The ion picks up the electron at a distance δ from the stub. This distance is of the order of magnitude of the ion (10.sup.−9). The work A done by the force F(r) over the entire region L is given by:
A=∫.sub.δ.sup.LF(r).Math.dr=∫.sub.δ.sup.Lp.Math.w(r).Math.B(r).Math.dr  (7)

(27) And after substituting the value of B(r) from equation (4) above we get:

(28) $\begin{array}{cc}A=\frac{\mathrm{\mu 0}.Math.J.Math.p}{2\pi }{\int }_{\delta }^{L}w\left(r\right).Math.\frac{1}{r}.Math.\mathrm{dr}& \left(8\right)\end{array}$

(29) The average power P spent by the stub for the attraction of the ion is:

(30) $\begin{array}{cc}P=\frac{A}{T}& \left(9\right)\end{array}$
where T is the time the ion moves till it is neutralized be an electron in the stub. By carrying out the above calculations it can be seen that the average power P increases sharply when δ decreases. Since the exact value of δ is unknown, we will assume that P=10.sup.−10 W. (This value is determined on the basis of mathematical modelling).

(31) We shall define the relative average power with respect to stub speed as:

(32) $\begin{array}{cc}{P}_v=\frac{P}{V}=1.2.Math.{10}^{-14}\text{W/m/s}\mathrm{for}V=8000\text{m/s}& \left(10\right)\end{array}$

(33) The power for the entire stub is:
M=P.sub.v.Math.v.Math.N  (11)
where N is the number of ions captured by the stub in one second. Obviously N is equal to the number of electrons in the stub which were lost for neutralizing the ions. Thus the charge loss per second by the stub which equals the stub discharge current is given by:
J=e.Math.N;e=1.610.sup.−19Cb(the electron charge)  (12)

(34) The discharge current is compensated for by charging current provided by the generator installed in the satellite 320 in FIG. 3. From equations (11) and (12) we can write the expression for the braking power developed by the stub as:
M=P.sub.v.Math.v.Math.J/e≈10.sup.5.Math.J.Math.V  (13)

(35) And the braking force:
F.sub.T=M/V≈5.Math.10.sup.12J  (14)

(36) The design should be such that the generator constantly replaces the lost charge in the stub capacitor so there are enough electrons to neutralize the ions. The power M is received from the atmosphere. To obtain it, the device must consume its own power for the current generation Γ. Initially the generator must charge the stub capacitor to a certain charge density, and then add charge as the density decreases by the current of the ions. The current of the generator is:

(37) $\begin{array}{cc}J=L\frac{dQ}{dt};& \left(15\right)\end{array}$
L is the length of the stub.

(38) Note that the device will be effective if Γ<<M.

(39) Also, in order for the device to operate there must be sufficient number of ions in the atmosphere. We assume that the number of ions is sufficient if
K.sub.e=ζ.Math.10.sup.6.Math.K.sub.i;  (16)
where Ke represents the number of electrons in the stub,
Ki is the number of ions in a volume equal to the volume of the stub,

(40) The coefficient ζ>>1.

(41) Note that due to the structure of the stub, when the external metal plates are negatively charged and the inner metal plate is positively charges, positive ions from the surrounding space come closer to the stub while negative ones move away. This is despite the presence of positive and negative ions in the atmosphere.

(42) Using the equations presented above, the parameters of a stub and the generator for providing require braking force and power can be evaluated. A braking force of 250 N for a satellite traveling at a speed of 8000 m/a can be achieved by a 500 m long stub which weights 6.3 Kg, where the generator provides 1 Watt at 800V supplying current of 0.5 mA. A similar braking force can be achieved by 100 m long stub weighting 1.26 Kg, where the generator provides 2 Watt at 800V supplying current of 2.5 mA.

(43) Plurality of barrels can be attached to a flying object, each storing a stub. The barrel contains stub opening mechanism that is activated by a control unit. The control unit activates the stubs according to pre planed program and/or as response to real time flight information.

(44) Note that the disclosed system enables to adjust the electrodynamic drag force by controlling the charging current of the stub capacitor

(45) What has been described above are just a few possible embodiments of the disclosed invention. It is of course, not possible to describe every conceivable combination of components and/or methodologies, but one of ordinary skill in the art may recognize that many further combinations and permutations are possible. Accordingly, the invention is intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the invention.