a1=1,sn为an的前n项和。an=sn/n+a(n-1) 若bn=3^n+(-1)^n *an单调递增，求实数a的取值范围（a不等于0）_百度知道
a1=1,sn为an的前n项和。an=sn/n+a(n-1) 若bn=3^n+(-1)^n *an单调递增，求实数a的取值范围（a不等于0）
我有更好的答案
a&lt.5&lt，B2=9+2a，B3=27-2a。Bn=3^n+(-1)^n *an即Bn=3^n+(-1)^n *2a，B4=81+2a。-1;0后面肯定递增,A(n-1)*(n-1)=S(n-1)+a*(n-1)(n-2)②.①-②得;0且B2-B1&gt。求B1=3-2a。解，sn写成Sn要好看一些，只要B3-B2&gt，得An*n=Sn+a*n(n-1) ①。由此可见，B5=243-2a。求导。就用另一种笨方法咯;n+a(n-1) ，不会了，单调递增所以Bn的导数须大于0：因An=Sn&#47；化简得An-A(n-1)=2a:n*An-(n-1)A(n-1)=An+a*n*(n-1)-a(a-1)（a-2）an写成An;4
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出门在外也不愁若公比为c的等比数列{an}的首项a1=1且满足an=[a(n-1)+a(n-2)]/2,（n=3,4.）．（1）求c的值．（2）求数列｛n*an｝的前n项和Sn．_百度作业帮
若公比为c的等比数列{an}的首项a1=1且满足an=[a(n-1)+a(n-2)]/2,（n=3,4.）．（1）求c的值．（2）求数列｛n*an｝的前n项和Sn．
1) an=c^(n-1),则a(n-1)=c^(n-2),a(n-2)=c^(n-3) c^(n-1)=[c^(n-2)+c^(n-3)]/2,因为c^(n-3)不等于0,所以化简为c^2=(c+1)/2,解得c=-1/2或1 (2) 设bn=n*an 当c=1时:bn=n,则Sn=1+2+3+...+n=n(n+1)/2 当c=-1/2时:bn=n*(-1/2)^(n-1) Sn =1+2*(-1/2)+3*(-1/2)^2+4*(-1/2)^3+...+n*(-1/2)^(n-1)----(1) (-1/2)Sn= 1*(-1/2)+2*(-1/2)^2+4*(-1/2)^3+...+(n-1)*(-1/2)^(n-1)+n*(-1/2)^n-----(2) (1)-(2),得 (3/2)Sn=1+(-1/2)+(-1/2)^2+(-1/2)^3+...+(-1/2)^(n-1)-n*(-1/2)^n =[1-(-1/2)^n]/[1-(-1/2)]-n*(-1/2)^n=2/3-[n+(2/3)]/(-2)^n 即Sn=4/9-[2n/3+(4/9)]/(-2)^n bn=n*(-1/2)^(n-1)为等比和等差数列相乘的形式,就用"差项法",(Sn-q*Sn)得到一个等比数列和余项,便可以解出答案
1.a1=1,a2=c,a3=c^2所以c^2=（1+c)/2解得c=1或-1/22.若c=1，n*an=nSn=（n+1)n/2若c=-1/2n*an=n*(-1/2)^(n-1)Sn=Sn-1*(-1/2)+1+(-1/2)+...+(-1/2)^(n-1)Sn=Sn-1+(1-(-1/2)^n)*2/3S1=1所以化简得Sn=2/3n+4/9-(-1/2)^(n-1)/9
1：a2=c,a3=c^2,n=3时，a3=（a2+a1）/2；2c^2=c+1c=1或-1/2；2:an=1或（-1/2）^n-1sn=(n+1)n/2;huo
sn=1+2(-1/2)+3(-1/2)^2+...+
(-1/2)^n-1 -1/2sn=
(-1/2)+2(-1/2)^2+...+(n-1)(-1/2)^n-1+n(-1/2)^n相减3/2sn=1-n(-1/2)^nsn=2/3（1-n(-1/2)^n）
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The N1 (Russian: H1) was a heavy lift rocket intended to deliver payloads beyond , acting as the Soviet counterpart to the NASA
rocket. This heavy lift booster had the capability of lifting very heavy loads into orbit, designed with manned extra-orbital travel in mind. Development work started on the N1 in 1959. Its first stage is the most powerful rocket stage ever built.
The N1-L3 version was developed to compete with the United States -Saturn V to land a man on the Moon, using the same
method. The basic N1 launch vehicle had three stages, which was to carry the L3 lunar payload into low Earth orbit with two cosmonauts. The L3 contained an E another stage used for mid-course corrections,
insertion, a single- and a two-pilot
lunar orbital spacecraft for return to Earth. The
was able to carry three astronauts (landing two on the Moon), and did not require the extra two rocket stages.
N1-L3 was underfunded and undertested, and started development in October 1965, almost four years after the Saturn V. The project was badly derailed by the death of its chief designer
in 1966. Each of the four attempts to launch an N1 during the second launch attempt the N1 rocket crashed back onto its launch pad shortly after liftoff and exploded, resulting in one of the
in human history. The N1 program was suspended in 1974, and in 1976 was officially canceled. Along with the rest of the , the N1 was kept secret almost until the collapse of the
in December 1991; information about the N1 was first published in 1989.
Development began under the direction of
Design Bureau. The original design proposed a 50-metric-ton (110,000 lb) payload intended as a launcher for military
and a manned
flyby using a nuclear engine upper stage. The N1 was the largest of th the N2 was somewhat smaller and intended to compete with 's proposed , and the much smaller N3, which would replace Korolev's "workhorse" . At this point the N-series was strictly a "paper project".
In December 1959, a meeting was called with all of the chief designers, who presented their latest designs to the military. Korolev presented the N-series along with a much more modest series of upgrades to the R-7. , Korolev's rival, presented his "Universal Rocket" series, which used a common lower stage in various clustered configurations to meet a wide variety of payload requirements. , perhaps the most successful of the three but with little political power, presented the small
intended to replace the , the much larger
ICBM, as well as the SK-100, a space launcher based on a huge cluster of R-16's. In the end the military planners selected Chelomei's
as the new "light" ICBM, and Yangel's R-36 for the "heavy" role. They saw no need for any of the larger dedicated launchers, but also gave Korolev funding to develop the
(8K78) adaptation of the R-7.
In March 1961, during a meeting at , designers discussed the N1 design, along with a competing
design, the R-20. In June, Korolev was given a small amount of funding for N1 development between 1961 and 1963. In May 1961 a government report, On Reconsideration of the Plans for Space Vehicles in the Direction of Defense Purposes, set the first test launch of the N1 rocket for 1965.
When the US announced in May 1961 the goal of landing a man on the Moon, Korolev proposed a lunar mission based on a new spacecraft, eventually known as , that was designed for . Several launches would be used to build up a complete moon package, one for the Soyuz, another for the lunar lander, and additional launches with cislunar engines and fuel. This approach makes the least demands on the launch vehicle, as the payload mass is reduced for any one launch. This is at the expense of requiring a rapid launch rate to ensure that the modules are built up before running out of consumables while waiting on-orbit. Even using this profile the lunar boosters and fuel were too large for any existing Soviet launcher. Korolev thus proposed development of the N1 with a 50 t (110,000 lb) payload – much smaller than the N1 design that would eventually be delivered.
To power the new design, , who then held a near-monopoly on rocket engine design in the Soviet Union, proposed a new engine, the , running on
(UDMH) and
(N2O4). This formula is
(i.e., its components ignite on contact, reducing the complexity of the combustion system), and was widely used in Glushko's existing engine designs used on various . The propellant pair UDMH/N2O4 has a lower potential
than /, but because the RD-270 used the much more efficient full flow , as opposed to the simple
used on the American , the specific impulse of the RD-270 was higher than the F-1.
Korolev also felt that the toxic nature of the fuels and their exhaust presented a safety risk for manned space flight. Glushko pointed out that the US
used to launch Gemini spacecraft used identical propellants. The Americans also had a 5-year head start with F-1 engine development, and were still facing combustio Glushko held it was unrealistic and unfair to expect him to stake his reputation on miraculously delivering a similar engine virtually overnight with practically no money, primitive computer technology and an inferior kerosene fuel prone to
(leaving contaminating deposits of unburned ) at high temperatures, as opposed to the rocket-grade kerosene used in the Saturn V.
There were strong personal resentments between the two, Korolev holding Glushko responsible for his near-death at
and the failure of his first marriage as a result, and Glushko considering Korolev to be irresponsibly cavalier and autocratic in his attitudes towards things outside his competence. Glushko refused outright to work on LOX/kerosene engines, and with Korolev in general. He instead teamed up with other rocket designers to build the very successful ,
Later, Glushko did build a LOX/Kerosene engine even more powerful and advanced than the F-1, known as the . Its development took over ten years, despite it being 20 years after the American F-1, due to the relative backwardness of the USSR's industrial base as foreseen by Glushko. This probably vindicated his decision not to support the development of such an engine for the N1 rocket.
The difference of opinions led to a falling out between Korolev and Glushko. In 1962, a committee that was appointed to break the logjam agreed with Korolev. Since Glushko refused to work on such a design, Korolev eventually gave up and decided to enlist the help of , the
Kuznetsov, who had limited experience in rocket design, responded with a fairly small engine known as the NK-15, which would be delivered in several versions tuned to different altitudes. To achieve the required amount of thrust, it was proposed that a large number of NK-15s would be used in a clustered configuration around the outer rim of the lower-stage booster. The "inside" of the ring of engines would be open, with air piped into the hole via inlets near the top of the booster stage. The air would be mixed with the exhaust in order to provide , as well as additional combustion with the deliberately fuel-rich exhaust. The ring-like arrangement of so many rocket engine nozzles on the N1's first stage could have been an attempt at creating a crude version o more conventional aerospike engines were also studied.
Meanwhile, Chelomei's
proposed an alternate mission with much lower risk. Instead of a manned landing, Chelomei proposed a series of circumlunar missions which he felt would be able to beat the US. He also proposed a new booster for the mission, clustering three of his existing UR-200 designs (known as the
in the west) to produce a single larger booster, the UR-500. These plans were dropped when Glushko offered Chelomei the RD-270, which allowed the construction of a much simpler "monoblock" design, also known as the . He also proposed adapting an existing spacecraft design for the circumlunar mission, the single-cosmonaut LK-1. Chelomei felt that improvements in early UR-500/LK-1 missions would allow the spacecraft to be adapted for two cosmonauts.
The Soviet military, specifically the Strategic Missile Forces, was reluctant to support what was essentially a politically motivated project with little military utility, but both Korolev and Chelomei pushed for a lunar mission. For some time, between 1961 and 1964, Chelomei's less aggressive proposal was accepted, and development of his UR-500 and the LK-1 were given a high priority.
Main article:
N1 imaged by US
reconnaissance satellite, 19 September 1968
Since the US
reversed the Soviet lead in human space exploration by 1966, Korolev was able to persuade
to let him pursue his plans to make a lunar landing before the US.[] This required much larger boosters.
Korolev proposed a larger N1, combined with a new lunar package known as the . The L3 combined the lunar engines, an adapted
(the ) and the new
in a single package. Chelomei responded with a clustered UR-500-derived vehicle, topped with the L1 spacecraft already under development, and a lander of their own design. Korolev's proposal was selected as the winner in August 1964, while Chelomei was told to continue with his circumlunar UR-500/L1 work.
When Khrushchev was overthrown later in 1964, infighting between the two teams started anew. In October 1965, the Soviet government
the circumlunar mission would be launched on Chelomei's UR-500 using Korolev's Soyuz spacecraft in place of their own
design, aiming for a launch in 1967, the 50th anniversary of the . Korolev, meanwhile, would continue with his original N1-L3 proposal. Korolev had clearly won the argument, but work on the L1 continued anyway, as well as the Zond.
Korolev died in 1966 due to complications after minor surgery, and the work was taken over by his deputy, . Mishin did not have Korolev's political astuteness or power, a problem that led to the eventual downfall of the N1, and of the lunar mission as a whole.
The N1 was a very large rocket, standing 105 meters (344 ft) tall with its L3 payload. The N1-L3 consisted of five stages in total: the first three (N1) for insertion into a low Earth parking orbit, and another two (L3) for
and lunar orbit insertion. Fully loaded and fueled, the N1-L3 weighed 2,750 tonnes (6,060,000 lb). The lower three stages were shaped to produce a single
17 meters (56 feet) wide at the base, while the L3 section was mostly cylindrical, carried inside a shroud 3.5 meters (11 feet) (estimated) wide. The conical shaping of the lower stages was due to the arrangement of the tanks within, a smaller spherical kerosene tank on top of the larger liquid oxygen tank below.
The first stage, Block A, was powered by 30 NK-15 engines arranged in two rings, the main ring of 24 at the outer edge of the booster and the core propulsion system consisting of the inner 6 engines at about half diameter. The engines were the first ever
engines. The control system was primarily based on differential throttling of the engines of the outer ring for pitch and yaw. The core propulsion system was not used for control. The Block A also included four , which were later used on Soviet
designs. In total, the Block A produced 45,310 kilonewtons (10,190,000 lbf) of thrust. This exceeded the 33,700 kilonewtons (7,600,000 lbf) thrust of the Saturn V. The Saturn V used higher-
fuel in the second and third stages, which eliminated one of the stages needed to get to , thus saving weight.
The second stage, Block B, was powered by 8 NK-15V engines arranged in a single ring. The only major difference between the NK-15 and -15V was the engine bell and various tunings for air-start and high-altitude performance. The upper stage, Block V (/V being the third letter in the ), mounted four smaller NK-21 engines in a square.
During the N1's lifetime, a series of improved engines was introduced to replace those used in the original design. The first stage used an adaptation of the NK-15 known as the , the second stage a similar modification known as the , and finally the third stage used the NK-31. The resulting modified N1 was known as the N1F, but did not fly before the project's cancellation.
The KORD (Russian acronym for KOntrol Racketnykh Dvigateley - literally "Control (of) Rocket Engines" - Russian: Контроль ракетных двигателей) was the automatic engine control system devised to throttle, shutdown and monitor the large cluster of 30 engines in Block A (the first stage). The KORD system controlled the differential thrusting of the outer ring of 24 engines for
attitude control by throttling them appropriately and it also shutdown malfunctioning engines situated opposite each other. This was to negate the pitch or yaw
diametrically opposing engines in the outer ring would generate. Block A could perform nominally with two pairs of opposing engines shutdown (26/30 engines), Block B with one pair of opposing engines shutdown (6/8 engines) and Block V with one engine shutdown (3/4 engines). Unfortunately the KORD system was unable to react to rapidly occurring processes such as the exploding turbo-pump during the . Due to the deficiencies of the KORD system a new computer system was developed for the last launch, , called the S-530 . It was the first Soviet digital guidance and control system. The
system relayed data back at a rate of 9.6
per second on 320,000 channels on 14 frequencies. Commands could be sent to an ascending N1 at the same rate.
Main article:
A comparison of the U.S. Saturn V rocket (left) with the Soviet N1/L3.
At 105 meters (344 ft), the N1-L3 was slightly shorter and more slender overall, than the American - (111 meters (363 ft)), but wider at the base (17 meters (56 ft) vs. 10 meters (33 ft)). The N1 also produced more thrust in each of its three stages than the Saturn V. It also produced more
in its first four stages than the Saturn V did in its three (see table below).
The N1 was intended to place the ~95-metric-ton (209,000-pound) L3 payload into , whereas the Saturn V placed the roughly 45-metric-ton (100,000-pound) Apollo spacecraft, plus 74.4 metric tons (164,100 pounds) of fuel for , into Earth parking orbit. L3 translunar injection of a 23.5-metric-ton (52,000-pound) payload was to be provided by the fourth stage. The N1-L3 would have been able to convert only 9.3% of its three-stage total impulse into Earth orbit payload
(compared to 12.14% for the Saturn V), and only 3.1% of its four-stage total impulse into translunar payload momentum, compared to 6.2% for the Saturn V.
The N1-L3 used only
in all three of its stages, while the Saturn V used
to fuel its second and third stages, which yielded an overall performance advantage due to the higher . The N1 also wasted available propellant volume by using spherical propellant tanks under its conical-shaped external skin, while the Saturn V used most of its available cyllindrical skin volume to house capsule-shaped hydrogen and oxygen tanks, with common bulkheads between the tanks in the second and third stages.
The Saturn V also had a superior reliability record: it never lost a payload in two development and eleven operational launches, while four N1 development launch attempts all resulted in failure, with two payload losses.
Apollo-Saturn V
Diameter, maximum
33 feet (10 m)
17 meters (56 ft)
Height w/ payload
363 feet (111 m)
105 meters (344 ft)
Gross weight
6,478,000 pounds (2,938,000 kg)
2,750,000 kilograms (6,060,000 lb)
First stage
Thrust, SL
7,500,000 pounds-force (33,000 kN)
45,310 kilonewtons (10,190,000 lbf)
Burn time, s
Second stage
Thrust, vac
1,155,800 pounds-force (5,141 kN)
14,040 kilonewtons (3,160,000 lbf)
Burn time, s
Orbital insertion stage
S-IVB (burn 1)
Thrust, vac
202,600 pounds-force (901 kN)
1,610 kilonewtons (360,000 lbf)
Burn time, s
1,733,600,000 pounds-force (7,711,000 kN)·s
7,944,000 kilonewtons (1.786×109 lbf)·s
Orbital payload
264,900 pounds (120,200 kg)
95,000 kilograms (209,000 lb)
Injection velocity
25,568 feet per second (7,793 m/s)
7,793 meters per second (25,570 ft/s)
Payload momentum
210,500,000 slug-ft/s (936,300,000 kg·m/s)
740,300,000 kg·m/s (166,440,000 slug-ft/s)
Propulsive efficiency
Earth departure stage
S-IVB (burn 2)
Thrust, vac
201,100 pounds-force (895 kN)
446 kilonewtons (100,000 lbf)
Burn time, s
1,803,400,000 pounds-force (8,022,000 kN)·s
8,141,000 kilonewtons (1.830×109 lbf)·s
Translunar payload
100,740 pounds (45,690 kg)
23,500 kilograms (51,800 lb)
Injection velocity
35,545 feet per second (10,834 m/s)
10,834 meters per second (35,540 ft/s)
Payload momentum
111,290,000 slug-ft/s (495,000,000 kg·m/s)
254,600,000 kg·m/s (57,240,000 slug-ft/s)
Propulsive efficiency
Source for Saturn V: Apollo 11 mission, in Orloff, Richard W (2001).
NASA. Also available in . Retrieved on . Published by Government Reprints Press, 2001, .
This section does not
any . Please help improve this section by . Unsourced material may be challenged and . (January 2015)
Complex plumbing was needed to feed fuel and oxidizer into the clustered arrangement of rocket engines. This proved to be extremely fragile, and was a major factor in the design's launch failures. Furthermore, the N1's Baikonur launch complex could not be reached by heavy barge. To allow transport by rail, all the stages had to be broken down and re-assembled. The engines for Block A were only test fired individually and the entire cluster of 30 engines was never static test fired as a unit.
stated that only two out of every batch of six engines were tested. As a result, the complex and destructive vibrational modes (which ripped apart propellant lines and turbines) as well as exhaust plume and fluid dynamic problems (causing vehicle roll, vacuum cavitation, and other problems) in Block A were not discovered and worked out before flight. Blocks B and V were static test fired as complete units.
Because of its technical difficulties and lack of funding for full-up testing, the N1 never successfully completed a test flight. All four unmanned launches out of 12 planned tests ended in failure, each before first-stage separation. The longest flight lasted 107 seconds, just before first-stage separation. Two test launches occurred in 1969, one in 1971, and the final one in 1972.
Mishin continued with the N1F project after the cancellation of plans for a manned Moon landing, in the hope that the booster would be used to build a . The program was terminated in 1974 when Mishin was replaced by Glushko. Two N1Fs were being readied for launch at the time, but these plans were canceled.
The program was followed by the "Vulkan" concept for a huge launch vehicle (with /, later replaced by / as fuel on the 2nd and 3rd stages), and then in 1976, by the commencement of the / program.
N1 1L - full scale dynamic test model, each stage was individuall the full N1 stack was only tested at 1/4 scale.
N1 2L - (1M1) - Facilities Systems Logistic Test and Training Vehicle (FSLT & TV); two first stages painted gray, third stage gray-white and L3 white.
N1 3L - first launch attempt, engine fire, exploded at 12 km.
N1 4L - Block A LOX t never launched, parts from Block A used rest of airframe structure scrapped.
N1 5L - pa first a launch failure destroyed pad .
N1 6L - launched from the second pad 110 West, deficient roll control, destroyed after 51s.
N1 7L - all white, engine cutoff at 40 kilometres (22 nmi) caused propellant line , rupturing the fuel system.
N1 8L and 9L - flight ready N1Fs with improved NK-33 engines in Block A, scrapped when the program was canceled.
N1 10L - uncompleted, scrapped along with 8L and 9L.
The two flight-ready N1Fs were scrapped and their remains could still be found around Baikonur years later used as shelters and storage sheds. The boosters were deliberately broken up in an effort to cover up the USSR's failed moon attempts, which was publicly stated to be a paper project in order to fool the US into thinking there was a race going on. This cover story lasted until , when the remaining hardware was seen publicly on display.
The advanced engines for the N1F escaped destruction. Although the rocket as a whole was unreliable, the
engines are considered rugged and reliable when used as a standalone unit. About 150 engines survived, and in the mid-1990s, Russia sold 36 engines to
for 1.1 million each. This company also acquired a license for the production of new engines.
Supplied through Aerojet, three of the engines were incorporated into Japanese rockets
and . The US company
worked on incorporating these engines into a new rocket design, with which Kistler sought to eventually offer commercial launch services, before declaring bankruptcy. Aerojet also modified the NK-33 to incorporate thrust vector control capability for 's
launch vehicle. Antares used two of the modified NK-33's, which Aerojet renamed the AJ-26, for first stage propulsion. The first four launches of the Antares were successful, but on the fifth launch the rocket exploded shortly after launch. Preliminary failure analysis by Orbital pointed to a possible turbopump failure in one NK-33/AJ-26. Given Aerojet's previous problems with the NK-33/AJ-26 engine during the modification and test program (two engine failures in static test firings, one of which caused major damage to the test stand) and the later in-flight failure, Orbital decided that the NK-33/AJ-26 was simply not reliable enough for future use and switched to a different engine.
In Russia, N1 engines were not used again until 2004, when the remaining 70 or so engines were incorporated into a new rocket design, the Soyuz 3. As of 2005, the project has been frozen due to the lack of funding. Instead, the NK-33 was incorporated into the first-stage of a , which was first launched on 28 December 2013.
February 21, 1969 – Vehicle serial number 3L – Zond L1S-1 (Soyuz 7K-L1S (Zond-M) modification of
spacecraft) for Moon flyby –
A few seconds into launch, a transient voltage caused the KORD to shut down Engine #12. After this happened, the KORD shut off Engine #24 to maintain symmetrical thrust. At T+6 seconds,
vibrations ruptured the oxidizer line feeding the #2 engine gas generator and at T+25 seconds, further vibrations ruptured a fuel line and caused
to spill into the aft section of the booster. When it came into contact with the leaking gas, a fire started. The fire then burned through wiring in the power supply, causing electrical arcing which was picked up by sensors and interpreted by the KORD as a pressurization problem in the turbopumps. The KORD responded by issuing a general command to shut down the entire first stage at T+68 seconds into launch. This signal was also transmitted up to the second and third stages, "locking" them and preventing a manual ground command from being sent to start their engines. Telemetry also showed that the power generators in the N-1 continued functioning until impact with the ground at T+183 seconds. Investigators discovered the remains of the giant rocket 32 miles (52 kilometers) from the launch pad. The investigative team did not speculate as to whether the burning first stage could have continued flying if the KORD system had not shut it down.
was activated and did its job properly, saving the mockup of the spacecraft. All subsequent flights had freon fire extinguishers installed next to every engine. According to , the logic of the command to shutdown the entire cluster of 30 engines in Block A was incorrect in that instance, as the subsequent investigation revealed.
July 3, 1969 – Vehicle serial number 5L – Zond L1S-2 for Moon orbit and flyby and intended photography of possible manned landing sites –
The second N-1 vehicle carried a modified L1 Zond spacecraft and live escape tower. Boris Chertok claimed that a mass model lunar module was also carried, however most sources indicate that only the L1S-2 and boost stages were onboard N-1 5L. Launch took place at 11:18 PM Moscow time. For a few moments, the giant rocket lifted into the night sky. As soon as it cleared the tower, there was a flash of light and debris could be seen falling from the bottom of the first stage. All the engines instantly shutdown except one. This caused the N-1 to lean over at a 45-degree angle and drop back onto launch pad . The nearly 2300 tons of propellant onboard triggered a massive blast and shock wave that shattered windows across the launch complex and sent debris flying as far as 6 miles (10 kilometers) from the epicenter of the explosion. Launch crews were permitted outside half an hour after the accident and encountered droplets of unburned RP-1 still raining down from the sky. As it turned out, for all the fury of the explosion, it was far less damaging than it could have been. The majority of the N-1's propellant load had not been consumed in the accident and most of what had burned was in the first stage of the rocket. Moreover, the worst-case scenario, mixing of the RP-1 and LOX to form an explosive gel, had not occurred. Total estimated force of the explosion was about 4-5 tons of TNT despite the propellant load theoretically being enough for a 400 ton blast. The launch escape system had activated at the moment of engine shutdown and pulled the L1S-2 capsule to safety 1.2 miles (2 kilometers) away. Launch Complex 110 East was thoroughly leveled by the blast, with the concrete pad caved in and one of the lighting towers knocked over and twisted around itself. Despite the devastation, most of the telemetry tapes were found intact in the debris field and examined.
Just before liftoff, the LOX turbopump in the #8 engine exploded (the pump was recovered from the debris and found to have signs of fire and melting), the shock wave severing surrounding propellant lines and starting a fire from leaking fuel. The explosion damaged cables linked to adjacent engines and this led to the instant shutdown of 29 of the 30 engines. Engine #18 remained active and continued operating until impact with the ground and its thrust had caused the 45-degree tilt of the booster as it fell back onto the pad. It could not be determined exactly why the #8 turbopump had exploded. Working theories were that either a piece of a pressure sensor had broken off and lodged in the pump, or that its impeller blades had rubbed against the metal casing, creating a friction spark that ignited the LOX.
After the accident, , who was in overall charge of the launch facilities at Baikonour, demanded that a feature be installed in the KORD computer to prevent the engines from being cut off until at least 50 seconds into launch to prevent the vehicle from coming down on or around the pad again.
The destroyed complex was photographed by American satellites, disclosing that the Soviet Union was building a Moon rocket. The rescue system saved the spacecraft again. After this flight, fuel filters were installed in later models. It also took 18 months to rebuild the launch pad and delayed launches. This was one of the
in human history and was visible that evening 22 miles (35 kilometres) away at
June 26, 1971 – Vehicle serial number 6L – dummy
(Soyuz 7K-L1E No.1) and dummy
module-spacecraft  –
Soon after lift-off, due to unexpected
and counter-currents at the base of Block A (the first stage), the N-1 experienced an uncontrolled roll beyond the capability of the control system to compensate. The KORD computer sensed an abnormal situation and sent a shutdown command to the first stage, but as noted above, the guidance program had since been modified to prevent this from happening until 50 seconds into launch. At T+39 seconds, the
of the booster went into
and at T+48 seconds, the vehicle disintegrated from structural loads. The interstage truss between the second and third stages twisted apart and the latter separated from the stack. Meanwhile, at T+50 seconds, the cutoff command to the first stage was unblocked and the engines immediately shut down. The upper stages impacted about 4 miles (7 kilometers) from the launch complex. Despite the engine shutoff, the first and second stages still had enough momentum to travel for some distance before falling to earth about 9 miles (15 kilometers) from the launch complex and blasting a 50 foot (15 meter) deep crater in the steppe. It was a small consolation to the launch team that the first stage engines had not malfunctioned at all and performance was normal until cutoff. This N1 had dummy upper stages without the rescue system. The next, last vehicle would have a much more powerful stabilization system with dedicated engines (in the previous versions stabilization was done by directing exhaust from the main engines). The engine control system would also be reworked, increasing the number of sensors from 700 to 13,000.
November 23, 1972 – Vehicle serial number 7L – regular
(Soyuz 7K-LOK No.1) and dummy
module-spacecraft for Moon flyby  –
The start and lift-off went well. At T+90 seconds, a programmed shutdown of the core propulsion system (the six center engines) was performed to . Because of large non-stationary loads caused by a
when the six engines were shut down abruptly, lines for feeding fuel and oxidizer to the core propulsion system burst and a fire started in the boattail of the booster. At T+107 seconds, the first stage exploded. The launch escape system activated and pulled the Soyuz 7L-LOK to safety. The upper stages were ejected from the stack and crashed into the steppe. An investigation revealed that the abrupt shutdown of the engines led to fluctuations in the fluid columns of the feeder pipes which ruptured and spilled fuel and oxidizer onto the shutdown, but still hot, engines. It was believed that the launch could have been salvaged had ground controllers sent a manual command to jettison the first stage and begin second stage burn early.
A planned fifth launch with vehicle serial number 8L was prepared for August 1974. It included a regular 7K-LOK
and a regular LK module-spacecraft of the L3 lunar expedition complex. It was intended for a Moon flyby and unmanned landing in preparation for a future manned mission. As the
program was canceled in May 1974, this launch never took place.
There is a great deal of confusion among Russian online sources as to whether N1-L3 (Russian: Н1-Л3) or N1-LZ (Russian: Н1-ЛЗ) was intended, because of the similarity of the
for "Z" and the number "3". Sometimes both forms are used within the same Russian website (or even the same article). English sources refer only to N1-L3. It is clear from the writing of a leading project designer that the correct designation is L3, representing the third stage of Soviet lunar exploration. Stage 1 would be an unmanne stage two would be a manned circumlunar flight, and stage 3 would be the manned landing.
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