Professional hydro rocket units. We build model rockets, what a beginner should know and where to start. Zenit rocket model

Fuselage

Stabilizers

Rings

Cowl

Parachute

Engine

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On the image:
1 - membrane; 2 - expelling charge; 3 - plug; 4 - thread bandage; 5 - via; 6 - moderator; 7 - reservation; 8 - fuel; 9 - body

Fuel preparation

Pressing in fuel

Stub

Engine assembly

Many fundamental concepts in rocket modeling are explained here. If you are just starting to build your first rockets, check out this material.

Any flying model rocket has the following main parts: body, stabilizers, parachute system, guide rings, nose fairing and engine. Let's find out their purpose.

The body serves to house the engine and parachute system. Stabilizers and guide rings are attached to it. To give the model a good aerodynamic shape, the upper part of the body ends in a head fairing. Stabilizers are needed to stabilize the model in flight, and a parachute system is needed to slow down the free fall. Using guide rings, the model is attached to the rod before takeoff. The engine creates the necessary thrust for flight.

Building the model

The main material for flying model rockets is paper. The body and guide rings are glued together from whatman paper. Stabilizers are made from plywood or thin veneer. Paper parts are glued with carpentry or casein glue, and others with nitro glue.

The production of the model begins with the body. In the simplest rocket models it is cylindrical. The mandrel can be any round rod with a diameter of more than 20 mm, since this is the size of the most common engine. To make it insert easily, the diameter of the housing should be slightly larger.

Important geometric parameters of the model body are: diameter d and elongation λ, that is, the ratio of body length 1 to diameter d (λ = 1/d). The elongation of most rocket models is 15-20. Based on this, you can determine the size of the paper blank for the body. The width of the workpiece is calculated using the formula for circumference L = πd. The result obtained is multiplied by two (if the body is made of two layers) and 10-15 mm is added to the seam allowance. If the mandrel is Ø21 mm, then the width of the workpiece will be about 145 mm.

You can do it simpler: wrap a thread or a strip of paper around the mandrel twice, add 10-15 mm, and it will become clear what the width of the workpiece for the body should be. Keep in mind that the paper fibers must be positioned along the mandrel. In this case, the paper curls without kinks.

The length of the workpiece is calculated using the formula 1 = λ. d. Substituting the known values, we get L = 20*21 = 420 mm. Wrap the workpiece around the mandrel once, coat the rest of the paper with glue, let it dry a little and wrap it a second time. You now have a paper tube, which will be the body of the model. After drying, clean the seam and glue residues with fine sandpaper, and cover the body with nitro glue.

Now take an ordinary round pencil, wind it and glue a tube 50-60 mm long on it in three or four layers. After letting it dry, cut it with a knife into rings 10-12 mm wide. They will be guide rings.

The shape of stabilizers can be different. The best are traditionally considered to be those in which about 40% of the area is located behind the cut of the aft (lower) part of the hull. However, other forms of stabilizers also provide a margin of stability, because the elongation of the model is λ = 15-20.

Having chosen the shape of the stabilizers you like, make a template from cardboard or celluloid. Using the template, cut out stabilizers from 1-1.5 mm thick plywood or veneer (the minimum number of stabilizers is three). Stack them (on top of each other), secure them in a vice and file along the edges. Then round or sharpen all sides of the stabilizers except the one where they will be glued. Sand them with fine sandpaper and glue them to the bottom of the body.

It is advisable to turn the head fairing on a lathe. If this is not possible, plan it with a knife from a piece of wood or cut it out of polystyrene foam and process it with a file and sandpaper.

A parachute, rope or other devices are used as a rescue system. It is not difficult to make a ribbon (see the description of the Zenit rocket model). We will explain in more detail how to make a parachute.

The dome must be cut out of light fabric, tissue or mikalent paper or other lightweight material. Glue the slings to it as shown in the picture. The dome diameter for the first models is better to be 400-500 mm. The installation is shown in the figure.

(This method of stowing a parachute is very suitable for fabric canopies or film. In this case, too thin a film may cake and not open in the flow, so carefully check the operation of the parachute if you are not sure of the chosen material. If you use very thin lines, be careful to ensure that they do not get tangled when laying and opening.).

All parts of the model are ready. Now assembly. Connect the head fairing with a rubber thread (shock absorber) to the upper part of the model rocket body.

Attach the free end of the parachute lines to the head fairing.

To make the model easy to see against the sky, paint it a bright color.

Before launching the model, we will analyze its flight and estimate whether our first launch will be successful.

Model stability

One of complex tasks Both large and small rocket technology is stabilization - ensuring flight stability along a given trajectory. Model stability is the ability to return to an equilibrium position disturbed by any external force, for example, a gust of wind. In engineering terms, the model must be stabilized by the angle of attack. This is the name of the angle that the longitudinal axis of the rocket makes with the direction of flight.

One of the ways to ensure model stability - aerodynamic - is to change the aerodynamic forces acting on it in flight. Aerodynamic stability depends on the location of the center of gravity and the center of pressure. Let us denote them as c. t. and c. d.

With the concept of c. t. are introduced in physics lessons. And it’s not difficult to determine it - by balancing the model on an acute-angled object, for example, on the edge of a thin ruler. The center of pressure is the point of intersection of the resultant of all aerodynamic forces with the longitudinal axis of the rocket.

If c. T. The rocket is located behind the c. etc., then the aerodynamic forces arising as a result of a change in the angle of attack under the influence of disturbing forces (gust of wind) will create a moment that increases this angle. Such a model will be unstable in flight.

If c. t. located in front of c. etc., then when the angle of attack appears, aerodynamic forces will create a moment that will return the rocket to zero angle. This model will be sustainable. And the further c. d. displaced relative to c. i.e., the more stable the rocket is. Ratio of distance from c. d. to c. because the length of the model is called the stability margin. For rockets with stabilizers, the stability margin should be 5 - 15%.

As noted above, c. i.e. the models are not difficult to find. It remains to determine c. d. Since the calculation formulas for finding the center of pressure are very complex, we will use in a simple way his location. From a sheet of homogeneous material (cardboard, plywood), cut out a figure along the contour of the rocket model and find c. t. this flat figure. This point will be c. d. of your model.

There are several ways to ensure rocket stability. One of them is the shift of c. to the tail of the model by increasing the area and location of the stabilizers. However, this cannot be done on a finished model. The second method is to shift the center of gravity forward by making the head fairing heavier.

Having carried out all these simple theoretical calculations, you can be sure of a successful start.

Single-stage rocket model, with parachute

The body is made of two layers of drawing paper, glued with wood glue on a mandrel with a diameter of 22 mm. In its lower part there is a holder for the engine.
The guide rings are made of four layers of drawing paper; the guide for them is a round pencil with a diameter of 7 mm. Three stabilizers made of 1 mm thick plywood are glued end-to-end with nitro glue to the bottom of the body.

The head fairing is turned on a lathe from birch and connected to the body with a rubber thread.

The parachute canopy is round, 500 mm in diameter, made of mica paper. Sixteen lines of No. 10 thread are attached to the head fairing.
After assembly, the entire model is covered with three layers of nitro varnish and painted with nitro paints in stripes of black and yellow. Model weight without engine is 45 g.

Model of the ZENIT rocket

This model is designed for abseil and altitude competitions.

The body is glued together from paper on a 20.5 mm mandrel. Stabilizers are made of plywood. The head fairing is made of linden.

The tape measures 50X500 mm and is made of mica paper. One of the narrow sides is attached to the body using a shock absorber (rubber thread).
The weight of the model without engine is 20 g.

If you do not have the opportunity to get original rocket engines, then you can experiment with homemade ones (without forgetting about safety, of course). Instead of homemade engine You can use fireworks rockets, hunting or rescue flare cartridges.

Source "Modelist-Constructor"

No matter how high the rocket model flies, it will fall and hit the ground. If measures are not taken to reduce the speed of contact with the planet, then losses are inevitable...

Typically, a parachute is used to slow the descent.

Of interest is the design of the parachute release mechanism. Typically a pyrotechnic system is used. Excessive pressure is created in the rocket body, leading to a “break” of the body and the release of the parachute from it. To create increased pressure.

The diagram of the Piro 1 rescue system is shown in the figure...

The parachute (12) together with the fairing (11) is “shot” from the rocket body (8) using a piston (10). All moving parts are held together by an elastic band (7), which is secured in the body (8) with an M5 screw (4). It is also the upper device that holds the rocket on the launch guide.

The mortar (6) (I will use Rocki terms) into which the charge (5) is placed is made of a paper tube with a diameter of 20 mm (significantly smaller than the diameter of the rocket body). The bottom of the mortar (6) rests on the screw (4). between the mortar and the rocket body there is a seal made of foamed polyethylene. The power wires (3) are supplied to the charge through the connector (9).

The battery voltage (1) 6F22 (Krona) is supplied to the control unit (2), where a transistor switch switches it to the squib (5).

The flame arrester is made of dishwashing wire.

At the right moment, voltage is applied to the fuse of the powder charge. A “small explosion” occurs inside the mortar. Excessive gas pressure pushes out the piston, which, in turn, pushes the parachute and fairing.

Video recording of the system test is below...

Everything seemed to work as it should! But an inspection of the rocket’s interior showed heavy smoke,
almost complete burnout of the piston seal (10),
heavily burned rubber band (7) of the shock absorber.
Flame extinguisher - failed to cope with the task of “extinguishing the flame”.

Below is a video of a retest of the system. All elements of the system from the first experiment were used here without replacement.

It is clear that the system did not work. The piston seal does not work, so all the gases found their way out of the rocket without shooting off the fairing...

Conclusion: the system is operational, but requires significant restoration of elements after operation.

saperkalori 10-01-2011 04:38

Greetings.
I've encountered a problem - nowhere can I find a simple and effective diagram of a rescue system for a rocket. Preferably mechanics, and not complex electronics (such as an acceleration sensor or a photosensor for changes in sky illumination).
The task is to install it on our PC82. The rocket flies perfectly (launched). But it falls terribly - it rushes towards your head at great speed. In this case, the stabilizers bend and the body is deformed (when hitting rocks, etc.) You need to slow it down with a parachute. But in order for it to open normally at the apogee point, such a system is needed.
This one won’t work due to its complexity - http://serge77.rocketworkshop.net/fotosens2/fotosens2.htm
But you need something like a combination of an inertial fuse for a mortar mine and an electrical contactor. Then the inertia will lower something like a piston down, the ball will fall out to the side, and when the acceleration of the rocket stops (at the apogee) the spring will lift the piston back and close the contacts of the electric igniter. And he will already ignite the ejector and throw the parachute out of the body of the rocket head (the standard cast-iron blank, of course, will be replaced with a lightweight one made of duralumin with a removable aero fairing).
Has anyone done this or knows of links online?

abc55 10-01-2011 06:59

I did something similar as a child.

It is better to view the diagram vertically.
The rocket is launched from a metal launcher.
The fuel is solid (paper impregnated with saltpeter and sugar), in the center of the fuel there is a cavity for rapid ignition - filled with gunpowder (hunting).

The rocket has a drop-down oblique tail.
In flight, the rocket rotates due to its fins to balance the mass of the unevenly burning fuel and the structure.

The flame of burning fuel approaches the wick of the parachute system.
The gunpowder in the parachute system cylinder ignites and pushes the parachute out, the cap is thrown away (secured with a rope to the body).

abc55 10-01-2011 07:12

I also had an idea to install a camera on the rocket.
The rocket was supposed to maximum height turn over, descend with the help of a parachute, and the camera was supposed to photograph the area in the “inverted rocket” position.
The camera consisted of a lens (on the edge there was a blunt Obscura hole) and a camera with 1 frame from the film.
The main problem was the shutter of the camera, driven by a spring, which was triggered by the wick.
There were a lot of problems, and the task was difficult for a boy, in general, I didn’t even try all this
bring.

saperkalori 10-01-2011 08:07

Well, about video shooting it’s just simple. There are good flash cameras the size of a lighter.
But I can’t apply your scheme. I will have standard checkers in my cell. Therefore, the fire will instantly pass to the ignition hole of the parachute release. What is needed here is an indirect launch. And this can only be done either electronically (which is fraught with failures) or inertial mechanics (which is more reliable and simpler). And when launched, the rocket gives 40-50J. After all, its speed is supersonic (about 300 m/s). When launched, the jet tears out a crater in the ground as if from an 8cm mortar mine! No electronics can handle it.
I'll try to do something like this:

A metal tube in which a piston-shaped weight moves, supported by a spring. And on top there is a rubber plug with two contacts. Well, and a ball that fits into the recess on the piston and the half-wall of the tube (until it falls out into the cutout of the tube). I’m just afraid that from a sharp launch of the rocket the piston will go down so quickly that it will bounce off the impact and close the contacts of the plug even before the apogee...

Uncle PU 10-01-2011 09:42

aerodynamic feather, there are diagrams on the net.

saperkalori 10-01-2011 10:00

Good idea. The first thing I found...

Now we just need a pyrotechnic version of this device. So that the pen, when triggered, closes the expelling charge circuit. Which is not difficult.

abc55 10-01-2011 10:19

If the flame instantly reaches the wick, no problem.
As I understand it, your rocket engine runs for 2-3 seconds.
Make a wick with a burning time of 4-5 seconds.
While the rocket will fly 20-30 meters by inertia, it will begin to turn over. . .

Even in front of the wick, you can place a certain circle plate.
This circle will press against the wick and prevent the flame from immediately setting it on fire.
The circle should burn slowly.

According to the inertial-gravity system.
Why use a spring?
Let the locking cylinder fall down from the mounting when accelerating.
The fastener should move to the side and freeze (not return).
When the rocket turns over, the cylinder, under the influence of gravity, will close the contact.

Why electric ignition?
This is a battery and other belongings - extra weight and complication.
Why not the chemical-mechanical method?
Like a cheerleader and a match?
A very reliable system, tested it many times in childhood.

Yes, today there are no problems with aerial photography, but in the 80s there was only analogue, only analogue.

Recently (after 30 years) I visited aircraft model makers. As a child I dreamed so, I dreamed so,
Yes, I went to the artists on the floor below.
What kind of planes are they sculpting there?
I told them - what about how to control an airplane from a camera and a laptop?
Electrical is a problem, but wood is no problem, we can build any plane.
In principle, if you splurge on electrics, you can create such an aircraft - a reconnaissance aircraft.

I also dreamed of putting a machine gun on such a car and fighting in the sky at an adult - without panties.
This is what I understand, gentlemen - place your bets!
ta-ta-ta-ta-ta-ta-taaa!!! die!!!

saperkalori 10-01-2011 10:44

On a PC, the engine runs for one second. Or even less. But during this time the rocket is thrown up almost a kilometer (and at 45 degrees - 3-4 km!) This is a very strong thing.
Therefore, it is better not to play with delays and wicks. You can also make an aerofoil with aerodynamics. And it already ignites the required charge of the knockout. That is pure mechanics. Which will increase simplicity and reliability.

wyatcheslav 10-01-2011 13:00

What if you install a mercury switch? When the rocket turns over, the contacts close and there is no electronics. And to protect against accidental operation on the ground, additionally install a regular mechanical toggle switch in conjunction with it.

abc55 10-01-2011 13:16

Between mercury and meth. No prince with a top hat. difference.
Mercury is more difficult (well, harmful).

yura7 10-01-2011 14:05

What if it’s barometric? The stupidly soft container straightened out a kilometer away and brought the chenit into action. And with a spring, it seems to me that it will work too early.

wyatcheslav 10-01-2011 14:56

quote: Mercury is more difficult (well, harmful).

wyatcheslav 10-01-2011 14:56

PS: And so that it doesn’t break, wrap it in foam rubber!

wyatcheslav 10-01-2011 15:01

quote: What if it’s barometric? The dull-soft capacity at a kilometer straightened out and brought into action

abc55 10-01-2011 15:31

Atmospheric pressure is constantly changing.
Varies depending on the weather and terrain.

The air in the rocket body will be rarefied during flight.
Remember the experiment with the pipe and glass.
You start blowing past the tube and the water in it rises.
The air flow creates a vacuum at the top of the tube and atm. pressing pressure on water
in the glass drives it up the tube.

saperkalori 10-01-2011 16:49

In general, I settled on the aero feather. By the way, the principle of piercing the chewed shell will be the same as in the famous German unloading fuse (the ball falls out into the hollow firing pin). Plus there is also a safety system in the form of a thin pin wire (it is pulled out during takeoff).
As soon as there is a photo of the finished RSS on the pen, I will post it.

abc55 10-01-2011 18:33

Is the system ok?

Lebanon 11-01-2011 12:37

maybe simpler.... the fairing stands like a cone in the body. it is pressed by the oncoming flow. at its apogee it falls off, pulling out the parachute.

abc55 11-01-2011 05:34

Too simple, somehow not cosmic.
Possibly the most reliable system.
The cap must be made of plastic.

saperkalori 11-01-2011 06:15

You probably didn’t understand - the rocket’s speed is about 300 m/s. Faster than a bullet from a Makarov! What flying caps! Nothing will hold. Only strong threaded connections and a powder expelling charge. And the aerodynamic head fairing will have to be made with a very tight fit of 0.05-0.1mm. Something like that:

abc55 11-01-2011 09:06

Will it hold or not?
But it depends on how you plant it.
In your diagram, the cap is not screwed on either.

True, there is a doubtful point.
If you shoot at an angle of 90 degrees, the cap may fall off when turned over,
and if at an angle of 45 degrees, then the oncoming flow will not allow the cap to fall.

saperkalori 12-01-2011 01:17

Eh, today an acquaintance of mine, having learned about my reconstruction of the RSK, promised to fit a blank from the 132nd RS. This is the devil's trumpet!!! There is no warhead, the empennage flew off (from the impact, a conscientious objector). But everything else is unwinding. So after testing with the 82nd RS, it will be possible to switch to this space version. After all, the coming year is the Year of Cosmonautics! :-)

yura7 12-01-2011 01:45

Sapper. Just don’t launch the animal into them, otherwise in childhood the older guys launched the hamster on a much weaker rocket model... In short, the hamster did not survive. And he didn’t look like a hamster.

saperkalori 12-01-2011 02:30

We should have started with cockroaches. I think they will withstand the starting overloads. After all, they don’t care about nuclear weapons either :-)

abc55 12-01-2011 03:50

I was launching a fly. The fly was sitting in a capsule covered with cotton wool.
The rocket burst at the start and the body could not stand it.
The fly survived, but did not fly immediately; it was knocked down and somewhat wobbled after the explosion.

saperkalori 12-01-2011 04:24

quote: Originally posted by abc55:
she felt a lump and was somewhat wobbling after the explosion.

Mild contusion:-)))))))))))))))

abc55 12-01-2011 06:22

By the way, shell shock is also inherent in insects.
As children, we used a stick to drill a hole into an anthill, 30 cm deep, and put it there
AKM sleeve with sulfur, potassium permanganate and magnesium. The whole thing was burned long
with a cord made of newspaper soaked in saltpeter.
After the explosion, a crater 30 cm deep was formed.
The poor ants then crawled and shook.

How to ensure reliable and trouble-free landing of model rockets? Many modellers are struggling to solve this technical problem. According to statistics, more than half of the models break down after launch. But time passes, experience is gained, and methods for saving models become more and more diverse.

And although we still hope for a parachute, work continues on the creation of other rescue systems. This is largely dictated by the fact that multi-stage models have appeared, models that are copies of launch vehicles spaceships: modellers spend a lot of time and energy on their production.

One of the mandatory requirements of the “Rules for Model Rocket Competitions” is the descent of stages on a fall-slowing device. Ribbon parachutes and pennants began to be used. There are even international competitions held abroad for the duration of descent of model rockets on a tape measuring 50X500 mm. In model competitions for the duration of parachute descent, Soviet modelers achieved high results - more than 20 minutes.

In the Moscow region they decided to complicate the competition for the duration of the descent - for the first time they began to hold starts in several rounds with a limited number of models. This order made it necessary to “plant” the models after a certain time and deliver them to the judges for control.

The way out of this predicament may be, as leading modellers believe, the use of a timer. It should be noted that for the first time a primitive timer (smoldering wick) was used by Gomel rocket modelers in 1970 at the All-Union competitions in Zhitomir.

1 - engine compartment, 2 - engine compartment bushing, 3 - nichrome thread, 4 - cover, 5 - imitation frame, 6 - parachute compartment bushing, 7 - parachute compartment, 8 - shock absorber, 9 - parachute.

A crash-free landing is the number one problem for rocket scientists building replica models. They demonstrate flight characteristics very similar to the flight of prototypes: full-scale division of stages, separation of side blocks. And to restart it is necessary to ensure a reliable landing of the model.

Interesting work in this direction is being carried out in the rocket modeling circle of the branch of the Central Scientific and Technical School of the Latvian SSR. The proposed developments, in our opinion, are of interest to readers.

Analysis of the causes of failure of rescue systems prompted us to develop and test several new options. The most interesting one - saving the side blocks of launch vehicles - is shown in Figure 1.

The side block in the area where the frame is placed is cut into two parts: the lower one is the engine compartment, the upper one is the parachute one. They are separated by a cover, which is inserted into the sleeve after the parachute is stowed. The sleeve is glued into the upper part of the side block. The upper and lower parts are joined (connected) by a sleeve glued into the lower part. The junction of the two parts is covered with an imitation frame made in the form of a strip of paper, half of which is glued to the parachute compartment, and the second hangs over the parting line, covering it.

The system works like this: after the engines of the side blocks have finished operating, the latter are separated from the central block of the second stage, and after one second (and this is exactly what the retarder should be) the expelling charge is triggered. The upper part flies out of the sleeve along with the cover, but the ni-chrome threads sharply slow down its movement, tearing out the cover and parachute.

Now let's look at the design of the first stage rescue system using the example of the Cosmos rocket. As can be seen from Figure 2, an oval hole is cut out on the side surface of the cylindrical body into which the container is glued. The outside of the container is closed with a lid, which fits tightly around its perimeter and is thus held in the container. The cover is glued to the body with a thread so that it does not get lost when the parachute is shot. The shooting mechanism itself resembles a slingshot, with the only difference being that it shoots with a parachute.

1 - body, 2 - container, 3 - cover, 4 - parachute, 5 - first stage truss, 6 - second stage, 7 - bead, 8 - spacer tube, 9 - thread, 10 - bracket, 11 - elastic bands of the slingshot.

The design of this mechanism is as follows: two elastic bands are attached diametrically opposite inside the parachute compartment container at a distance of up to 1 mm from the inserted lid. The parachute lines are tied to the place where the elastic bands cross on the outside, and on the inside - a thread (0.5 mm fishing line), which passes through the holes in the bracket attached to the rocket body and is brought out.

The bracket must be installed so that the rubber bands pass to the side of the remote tube. You can tie a bead to the end of the thread so that after docking with the second stage of the rocket, it, together with the thread, seems to be wedged between the body of the second stage and the truss. In this case, the length of the thread should be such that the elastic bands are stretched. Now you need to fold the parachute and place it in the container, close the lid - and the model is ready to launch. After undocking the steps, the thread releases the elastic bands that it held, and the parachute is fired. This rescue option is convenient for copy models in that a well-fitted container lid does not damage general view model and does not affect its copyability. Make sure that the lid does not fit too tightly into the container. The system can be easily checked without running engines.

And another option for saving the first stage of a copy model, where there is no space to install a container, that is, the case when the diameter of the rocket body is only a few millimeters larger than the diameter of the engine compartment. Docking diagram and comparative sizes stages using the example of a missile defense system (Fig. 3).

A - starting position, B - moment of parachute deployment. 1 - body, 2 - engine, 3 - tube, 4 - parachute, 5 - thrust ring, 6-7 - guide bushings, 8 - restrictor ring.

In this case, there is space for installing a parachute only in the annular gap, between the rocket body and the engine bushing.

The design of the rescue system is as follows. The housing contains a motor inserted into a tube, to the ends of which guide bushings are glued. The thrust ring is attached to inner surface body at the very base. It is best to make the ring from D16T duralumin. It needs to be glued in only after the tube with bushings has been inserted into the body. The parachute is tied to the tube and fits into the annular gap between the body and the tube. A stop ring can serve as a stop to prevent movement of a running engine. To make the bushing move easily in the body, rub it with paraffin. The stage is prepared for launch as follows: you need to pull the tube out as far as it will go, place the parachute around it, then carefully, so as not to tear the parachute, place it in the body, install the engine. After installing other stages, the model can be launched. As soon as the second stage engine starts, a high blood pressure, which will push out the tube with the parachute laid around it. In this case, the bushing will rest against the thrust ring. The parachute, leaving the hull area, will open. At the same time, the stages are uncoupled. The tube moves instantly, and therefore the impact of the sleeve on the ring can cause the parachute compartment to bounce back into the body. Therefore, the mating surfaces of the sleeve and ring are made conical so that, firstly, the parachute does not catch on the edges of the ring, secondly, to reduce the vertical component upon impact, and thirdly, to fix the extreme position of the parachute compartment due to “jamming” of the sleeve in the ring. This system works reliably, but the parachute must be stowed carefully. Do not wrap the engine compartment with slings. Several test runs - and trouble-free operation of the proposed system is guaranteed.

I. ROMANOV, engineer