vashu11 (vashu11) wrote,
vashu11
vashu11

О лжи проекта OTRAG

Прочел замечательную статью о концепции Big Dumb Booster(http://lozga.livejournal.com/92027.html). Проект OTRAG меня лично восхитил - в модульных ракетах точно что-то есть.

К сожалению, покопавшись в материалах, пришел к выводу что конструктор был полумошенником.


- В расчетах упомянуты скорости истечения 2646, 2910. Перерыл уйму доков, насколько я понимаю лучший результат, достигнутый на испытаниях был 2433(воздух), 2709(вакуум, оценка). См., например тут http://www.rexresearch.com/kayser/OTRAGRocket.pdf, Достаточно характерная цитата "Two former employees OTRAG me consistently confirmed that the calculated value of me was incorrect and the flights at a specific impulse of 1800 m / s was measured on the ground. When I pointed this discrepancy Lutz Kayser, there were suddenly new values."

- Вес ракеты упоминается как
Mass total: 1,500 kg
Mass empty: 150 kg

Про баки:
Each tube is 10.63 in [27 cm] th
ick and 9.84 ft [3 m] long. It consists of
0.020” – 0.040” [0.5-1 mm] thick, low-carbon steel.

13.5 м2 стали миллиметровой толщины сами по себе весят больше ста кило. Уместить перегородки, двигатель, электронику, покрытие бака с азоткой, крепления килограммов в 40 малореально. Обычно структурные компоненты забирают половину сухого веса ракеты, половина уходит на все остальное.

- Давление
Injection pressure: 40 - 15 bar
Harry O. Ruppe writes of 0.015” [0.38 m], but at 435 PSI [30 bar] pressure.

10 атмосфер в трубе толщиной 1 мм это еще более менее реально. 30-40 атм и/или 0.5 мм нет - разорвет.


Нарезка из первоисточников:
A CRPU was essentially a steel tube, 27 cm in diameter and 16 meters long, joined from a few shorter tubes. The CRPU was divided into three sections by aluminium bulkheads, with additional stiffening rings between bulkheads. Forward, the majority of the tube contained a mixture of nitric acid and nitrogen tetroxide oxidisers. Next was a section of kerosene fuel. This was commercial-grade kerosene, not the more expensive RP-1. Last was the engine section. A fuel line carried nitric acid around the kerosene, into the engine.
The design of the CRPU was extremely simple. The tubing was strong enough that the propellants were fed to the engine by pressure alone.[citation needed] This eliminated the need for turbopumps. The engine was ablatively cooled, eliminating the need for fine fuel passages and heat-resistant kerosene. The engine did not gimbal; instead, the vehicle was steered by throttling one side's CRPUs versus the opposite side. Thus, the engine was simply built into the tube walls, with the only mechanisms being the throttling valves. No separate pressurising system was included; the tanks were simply left with an ullage space, which was then filled with gas to a few hundred psi. Because of the narrow tubing, the bulkheads between sections could be simple plates, instead of domes like virtually all other rocket stages. There was no ignition system; instead, a slug of furfuryl alcohol was injected before the kerosene. The furfuryl alcohol ignited spontaneously upon contact with the nitric acid.
The use of ablative cooling, high-pressure steel construction, and large "empty" spaces meant that a CRPU was heavy, with relatively low performance. The diameter of the tubing also put a hard limit on the engine diameter, preventing use of an efficient, high-expansion nozzle for the upper stages. However, ganging CRPUs into three stages was sufficient to reach orbit.
...
Thrust: 25,000 N (5,000 lbf)
Oxidiser: High Density Acid (HDA) (50% N2O4- 50% HNO3) Den: 1.66 gr/cm^3
Fuel: Diesel fuel or Kerosene
Specific Impulse: First stage - 270 seconds, Stages 2 and 3 - 297 seconds vacuum
Injection pressure: 40 - 15 bar
Thrust control: 100% - 40 %
Pressurization: Compressed air, 66% tank filling in blow-down mode
Injector: Radial like on like
Chamber cooling: Ablative phenolic
Mass total: 1,500 kg
Mass empty: 150 kg
Material of injector, valves, bulkheads: AlMg5
Material of cylindrical tank sections: cold-rolled low-carbon stainless steel
Dimensions: Diameter 0.27 m, Length: 16 m
...
Vehicle LEO-payload
tonnes Launch mass
tonnes Cost: $ million
(2005)
KAYSER 1 1 100 2.5
KAYSER 2 2 200 5
KAYSER 4 4 400 10
KAYSER 8 8 800 20
KAYSER 16 16 1.600 40
KAYSER 32 32 3.200 80
KAYSER 64 64 6.400 160
KAYSER 128 128 12.800 320
...
In principle, the first and second stage clusters could easily be recovered on land or sea. However, the very low mass production cost of $25,000 per CRPU and the estimated recovery and refurbishing cost of $20,000 per CRPU could be used to justify either expendable or reusable units.
...
The tanks consisted of modified pipeline pi
pes from the petroleum industry. They were
manufactured in a special cold-rolling pr
ocess for the relatively high empty weight
required. The steel had ² a st
ress limit of 232,000 PSI [1600 N
/ mm^2]. The weld seam
needed to be made with a spiral welding pr
ocess. One important however to normal deep-
drawn tubes. Each tube is 10.63 in [27 cm] th
ick and 9.84 ft [3 m] long. It consists of
0.020” – 0.040” [0.5-1 mm] thick, low-carbon steel. A machine could produce 10 tanks a
day largely automatically. Thickness for the
tank was in a 1979 report called a value of
0.040” [1.0 mm] and Lutz Kays
er stateed in 2005 that it
was 0.020” [0.5 mm]. Harry O.
Ruppe writes of 0.015” [0.38 m], but at 435 PSI
[30 bar] pressure.
...
The
only moving parts are the valves which regulat
e the fuel flow. The ball valves are from
Argus in the chemical industry and are driv
en by DC electric motors in the automotive
industry. (First it was 50 watts
Bosch motors for windshield
wipers, but they were not
powerful enough, so the third launch failed in
a push system, so you went to 100-120
watt motors).
...
The
engine lost during the operat
ion 15 kg mass, because the ab
lation evaporated. By burning
this mass is the specific impulse
by 1-2% have been increased.
...
The roll control is considered first, the
engines of the outermost ring at
10 degrees to the thrust axis
to install.
...
There is no Vorbeschleunigungstriebwerke, whic
h earn a start in zero gravity, the fuel on
the ground. Since the first furfuryl alcohol
in the combustion chamber must flow, the
stage will be ignited hot, ie The upper stage will
be ignited, while the lower one is still in
operation. The staging was therefore not when
the fuel is exhausted, but the rocket had
reached a predetermined speed.
...
OTRAG was a payload of the De
lta Class (2.5 tonne weight) for 7 million, an Atlas of
the class (5t weight) for 12 million and a start of the Titan Class (10 tons) for $ 15
million.
Type Dimensions Level 1 Level 2 Module
Module Module Level 3 Level 4 Level 5
modules modules payload launch mass
Pak-64 2.4 x 2.4 mx 25 m 48 12 4 - - 1 t 97 t
Pak-128 2.4 x 4.8 mx 25 m 96 24 8 - - 2 194 t t
Pak-256 4.8 x 4.8 mx 25 m 192 48 16
(12) (4) - 4 388 t t
Pak-512 8.4 x 9.6 mx 25 m 384 96 32
(24) (8) [6] [2] 8 t 784 t
Pak-1024 9.6 x 9.6 mx 25 m 768 192 64 (
48) (16) [12] [4] 16 t 1578 t
Pak-676 8.0 x 8.0 x 25 m 508 131 36 (27) (9) [6] [3] 10 t 1031 t
Pak-289 5.0 x 5.0 mx 25 m 225 48 16
(12) (4) - 5 388 t t
Pak-169 4.0 x 4.0 x 25 m 121 36 12 (10) (2) - 2.5 t 255 t
Pak-100 3.0 x 3.0 x 25 m 75 21 4 - - 1.5 t 151 t
Pak-36 1.8 x 1.8 x 25 m 27 8 1 - - t 0.5 54.3 t
Pak-25 1.5 x 1.5 x 13 m 16 4 2 - - 0.2 t 2.20 t
...
Level 1 Level 2 Level 3
Engines 6 * 36 = 216 36 36
16 245 kN thrust 2008 kN 1035 kN
Length 22 m 13.9 m 8.1 M
Diameter 2.54 m 2.54 m 2.54 m
Take Off Weight (estimated) 831500 kg 94900 kg 51 100
Empty weight (estimated) 76800 kg 11900 kg 9700 kg
Burn time 113 seconds 112 seconds 112 seconds
specific impulse (estimated) 2433 m / s 2709 m / s 2800 m / s
...
Many innovative concepts were pursued initially Kayser phased out. So should the tanks are manufactured in the spiral welding process. It then went on to "normal" deep drawn steel tubes.
...
kayser runway while always stressed that
the OTRAG would be
inappropriate as a
ballistic missile, because they have insufficien
t accuracy, would have believed him, this
has none
...
Also required a OTRAG missile laun
ch preparations extending over several
hours.
...
The construction is ve
ry susceptible to POGO oscillations. POGO
oscillations in rocket technology feared becau
se they can not be simulated on the ground.
Several rockets were suffering from the fi
rst flights under POGO oscillations, the Titan,
Saturn V and the Ariane. Is caused by engine
vibrations which are tr
ansferred to the tanks
and bring the liquid to spill. This then amplifies the vibrations again so that it may in
extreme cases to a fraction of the structure,
as it happened in the second flight of the
Ariane first
This affects almost only first steps because
they have very long tanks. In addition, the
phenomenon usually occurs only after some
time when the tanks are no longer full.
Looking at the OTRAG rocket, so the tanks ha
ve a length of up to 24 m and a width of
only 0.27 m. Representing a ratio of 80:1 mean
s of length to width. In contrast, rocket
stages, it is from 4:1 to 8:1. Furthermore, th
e tanks are already at
the start only partially
filled with fuel. Speaks against a vulnerabl
e print promotion. There is no turbo pumps
and portable engines, which come as
sources of vibration in question.
All tests which has made the OTRAG were re
latively short modules
(6 or 12 m length)
instead. The shorter due to their length do not re
act quite as sensitive. It should also take
into account that the tanks are very thin and,
therefore, a break is easier.
...
Each engine also indirectly affects the
other. It transmits vibrati
ons it gives off heat, it loads the structure. The best known
example of the consequences is the Russian
moon rocket N-1. Their engines have been
tested extensively on the ground and were cons
idered flight qualified. The block A, the
first stage with 30 engines, but has no one test
ed as a whole, because it was the cost of a
test stand of the enormous thrust force
of 46000 kN has wanted to save. This took
revenge. All four launches of the N-1 faile
d because of problems with the block A.
...
Another point concer
ns the effects of engine failure. In the
experiments until 1974, there were 3 failures in
200 trials. Later, it was only known that
there should have been more than 2,000 tests,
but no success rate. 3 failures in 200 trials
is a standard in rocketry size that I want
to talk to include in the considerations.
...
Fuel residues that can not be used ther
e in an order of magnitude of 1% on each rocket
...
Two former employees OTRAG me consistently
confirmed that the calculated value of
me was incorrect and the flights at a speci
fic impulse of 1800 m / s was measured on the
ground.
When I pointed this discrepancy Lutz Kayser
, there were suddenly new values. Now the
thrust should be on average 25 kN and the bur
ning time of 150 seconds. Thus the specific
impulse of 2740 m / s would be even higher
than previously indicated. Only you need
according to my calculations, a combustion pres
sure to mouth pressure ratio of 100:1 to
these specific impulse to achieve. As the e
ngine but operate at 1
bar ambient pressure
must be no higher than 30:1 ratio possible
...
There were
speaking technically not mind switching to
hydrazine and nitrogen tetroxide. The
employee who had chosen the combination was due
to the high price of these fuels. In the
past 20 years, prices remained fairly consta
nt while rockets were expensive. The price
advantage would therefore no longer exists on this scale.
...
In test flights, according to Kayser's successor, Frank
Wukasch of a specific impulse
of 1800 m / s was measured. Ta
king this for the first and
2100-2200 for the upper levels, then the payload
is reduced considerable. The three-stage
design is not possible and a four-stage vers
ion is necessary.
Module for the 256
version I calculate a
maximum payload of 800 kg instead of 4000th
...
The high
pressure of the fuel, the engines react slow,
for a large rocket which requires much more
sensitive towards disturbing forces is likel
y to slow. Ruppe said only after 1 second
would occur if a large rocket a tax effect.
...
http://www.b14643.de/Spacerockets_1/West_Europe/OTRAG/Description/Frame.htm
Isp vac
HNO3 oxidizer 2064 (1800)
HDA oxidizer 2476 (Isp s.l. 2251)
...
Prediced data (realistic Isp; thickness of the tanks 1.0 mm; structural mass 17.2 % = one modul 278 kg) 7,755 [m/sec]
Optimistic OTRAG data (high Isp; thickness of the tanks 0.5 mm; structural mass 12.2 % = one modul 186 kg) dV Total* 10,084 [m/sec]
...
Date Site Vehicle Mission Results
17 May 1977 (Shaba) OTRAG 01 Technology S (20 km)
20 May 1978 (Shaba) OTRAG 02 Technology S (30 km)
05 Jun 1978 (Shaba) OTRAG 03 Technology F
01 Mar 1981 (Lybia) OTRAG ? Technology ?
19 Sep 1983 KIR OTRAG 1-3-B Technology F
...
The second pair of engines suffered a 0.1 second difference in shutdown time causing a 4000 Nm torque, but the resulting pitch and yaw rates were quickly dampened by the fins. The “cold-gas” thrust of the flow of nitric acid continued long after burnout and could be seen as a contrail in the sky. The gas flow also reduced the “base drag” of the vehicle.
Tags: игра ума, космос
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