Modul lunar Apollo

Grumman Apollo LM
Modulul lunar Apollo pe suprafaţa Lunii
Descriere
Rol:	Aselenizare
Echipaj:	2; Comandant, Pilot
Dimensiuni
Înălţime:	6.37 m	20.9 ft
Diametru:	4.27 m	14 ft
Anvergura "trenului" de aselenizare:	9.07 m	29.75 ft
Volum:	6.65 m³	235 ft3
Mase
Modulul de ascensiune:	4,547 kg	10,024 lb
Modulul de coborâre:	10,149 kg	22,375 lb
Total:	14,696 kg	32,399 lb
Motoare
SRC (Sistemul de control cu reacţie) (N2O4/UDMH) x 16:	45 kgf (441 N)	100 lbf
Motorul de ascensiune (N2O4/Aerozine 50) x 1:	1591 kgf (15.6 kN)	3,500 lbf
Motorul de coborâre (N2O4/Aerozine 50) x 1:	4530 kgf (44.40 kN)	9,982 lbf
Performanţe
Anduranţă:	3 zile	72 ore
Aposelene:	160 km	100 mile
Periselene:	suprafaţă	suprafaţă
Variaţia de viteză:	4,690 m/s	15,390 ft/s
Diagrama ML Apollo
Diagrama ML Apollo (NASA)
Grumman Apollo LM

The LEM flight instrumentation panel and front windows. Credit: Alexandre Sabbatini

Modulul lunar Apollo (ML) a fost una din componentele Astronavei Apollo al cărei principală funcţie era transportul astronauţilor de pe orbita Lunii pe Lună şi înapoi. Astronava Apollo a fost construită în cadrul Programului Apollo de aselenizare, al guvernului SUA.

Modulul avea 4,4 m înălţime, 4,3 m diametru şi avea un echipaj format din 2 persoane. "Trenul" de aterizare avea 4 picioare. Masa totală a modulului era de 15.264 kg din care 10.334 kg cântărea modulul de coborâre şi restul modulul de ascensiune.

Istoric

Modulul lunar Apollo a fost creat deoarece NASA a optat pentru o schemă de aselenizare simplificată de tipul întâlnire pe orbita Lunii (în engleză, lunar orbit renedevous - LOR), în defavoarea metodelor ascensiune directă şi întâlnire pe orbita Pământului (în engleză Earth orbit rendevous - EOR). Metodele EOR şi ascensiune directă presupuneau mai multe lansări de pe Pământ şi aselenizarea întregii astronave Apollo. Metoda aleasă, LOR, presupunea ca doar o componentă a astronavei să aselenizeze şi apoi să revină pe orbita Lunii pentru întâlnirea cu modulul de comandă.

Contractul pentru Modulul lunar a fost atribuit firmei Grumman Aircraft Engineering şi câtorva subcontractori. Grumman a efectuat studii asupra metodei LOR încă de la sfârşitul anilor 1950 şi din nou în anul 1962. În iulie 1962 11 firme au fost invitate să înainteze propuneri pentru Modulul lunar, şi în luna septembrie a aceluiaşi an 9 dintre acestea au dat curs invitaţiei. Firma Grumman a fost decalartă câştigătoare pe 7 noiembrie 1962. Contractul avea o valoare de aproximativ 350 de milioane dolari SUA. Iniţial au existat patru subcontractori majori: Bell Aerosystems (motorul de ascensiune), Hamilton Standard (sistemele de control al habitatului), Marquardt (sistemul de control cu reacţie) and Rocketdyne (motorul de coborâre).

Sistemul principal de navigaţie, ghidaj şi control al Modulului lunar a fost dezvoltat, la MIT, în Laboratorul Charles Stark Draper; computerul de ghidaj a fost construit de către Raytheon. Un sistem de neavigaţie de rezervă, numit Abort Guidance System (AGS) a fost furnizat de către TRW.

Astronauţii au efectuat simulări şi antrenamente, pentru a învăţa manevrele necesare aselnizării, într-un vehicul numit LLRV (din engleză - Lunar Landing Research Vehicle). Acesta era supendat de o macara montată pe o structură metalică care avea 61m înălţime şi 122m lungime. Mişcarea modulului era simultă prin mişcarea macaralei conform comenzilor date de piloţi. Întregul ansamblu a fost construit de NASA la Langley Research Center.

Early configurations of the LEM included a forward docking port; initially, it was believed the LEM crew would be active in the docking with the CSM. Early designs included large curved windows and seats for the astronauts. A configuration freeze did not start until April 1963, when the ascent and descent engine designs were decided. In addition to Rocketdyne, a parallel program for the descent engine was ordered from Space Technology Laboratories in July 1963, and by January 1965 the Rocketdyne contract was cancelled. As the program continued, there were numerous redesigns to save weight (including "Operation Scrape"), improve safety, and fix problems. The final design eliminated seats (the astronauts stood while flying the LM), and allowed the design of smaller windows and a lighter structure, resulting in significant weight savings. The LM was initially supposed to be powered by fuel cells built by Pratt and Whitney, but in March 1965 they were discarded in favor of an all battery design.

The initial design iteration had the LEM with three landing legs. As any particular leg would have to carry the weight of the vehicle if it lands at any significant angle, three legs was the lightest configuration. However, it would be the least stable if one of the legs were damaged during landing. The next landing gear design iteration had five legs and was the most stable configuration for landing on an unknown terrain. That configuration, however, was too heavy and the designers compromised on four landing legs.

The first LM flight was on January 22, 1968 when the unmanned LM-1 was launched atop a Saturn IB for testing of propulsion systems in orbit. The next LM flight was aboard Apollo 9 using LM-3 on March 3, 1969 as the first manned test flight (crew McDivitt, Scott and Schweickart) to test a number of systems in Earth orbit including LM and CSM crew transit, LM propulsion, separation and docking. Apollo 10, launched on May 18, 1969, was another series of tests, this time in lunar orbit with the LM separating and descending to within 10 km of the surface. From the successful tests the LM successfully descended to and ascended from the lunar surface with Apollo 11. The Apollo 12 and Apollo 14 LMs achieved precision landings with upgraded computers and navigational techniques.

In April 1970, the lunar module Aquarius played an unexpected role in saving the lives of the three astronauts of the Apollo 13 mission after an oxygen tank in the service module exploded. Aquarius served as a refuge for the astronauts during their return to Earth, while its batteries were used to recharge the vital re-entry batteries of the command module that brought the astronauts through the Earth's atmosphere and to a safe splashdown on April 17, 1970. The LM's descent engine, designed to slow the vehicle during its descent to the moon, was used to accelerate the Apollo 13 spacecraft around the moon and back to Earth. The LM's systems, designed to support two astronauts for 45 hours, actually supported three astronauts for 90 hours.

The Lunar Modules for the final three Apollo missions (15, 16, and 17) were significantly upgraded to allow for greater landing payload weights and longer lunar surface stay times. The descent engine power was improved by the addition of a ten-inch (254 mm) extension to the engine nozzle, and the descent fuel tanks were increased in size. Hover times and landing weights were also maximized by having the CSM perform the intitial deorbit burn of the attached CSM-LM (a practice begun on Apollo 14), with the LM then separating for the final powered descent to the surface. The most important cargo on these missions was the Lunar Roving Vehicle, which was stowed on Quadrant 1 of the LM Descent Stage and deployed by astronauts after landing. The upgraded capability of these "J-Mission" LMs allowed three day stays on the moon.

Lunar Module specifications

The Lunar Module was the portion of the Apollo spacecraft that landed on the moon and returned to lunar orbit. It is divided into two major parts, the Descent Module and the Ascent Module.

The Descent Module contains the landing gear, landing radar antenna, descent rocket engine, and fuel to land on the moon. It also had several cargo compartments used to carry among other things, the Apollo Lunar Surface Experiment Packages ALSEP, Mobile Equipment Cart (a hand-pulled equipment cart used on Apollo 14), the Lunar Rover (moon car) used on Apollo 15, 16 and 17), surface television camera, surface tools and lunar sample collection boxes. It also carried the majority of the LM's battery power and oxygen, along with the single water tank needed to both cool the electronics and provide the astronauts with enough drinking water for a two- to three-day stay. Also, on the ladder of the descent stage is attached a plaque.

The Ascent Module contains the crew cabin, instrument panels, overhead hatch/docking port, forward hatch, reaction control system, radar and communications antennas, ascent rocket engine and enough fuel, battery power, and breathing oxygen to return to lunar orbit and rendezvous with the Apollo Command and Service Modules.

• Specifications: (Baseline LM)
  • Ascent Stage:
    • Crew: 2
    • Crew cabin volume: 6.65 m³ (235 ft³)
    • Height: 3.76 m (12.34 ft)
    • Diameter: 4.2 m (13.78 ft)
    • Mass including fuel: 4,670 kg (10,300 lb)
    • Atmosphere: 100% oxygen at 33 kPa (4.8 lb/in²)
    • Water: two 19.3 kg (42.5 lb) storage tanks
    • Coolant: 11.3 kg (25 lb) of ethylene glycol/water solution
    • RCS (Reaction Control System) Propellant mass: 287 kg (633 lb)
    • RCS thrusters: 16 x 445 N; four quads
    • RCS propellants: N2O4/UDMH
    • RCS specific impulse: 2.84 kN·s/kg
    • APS Propellant mass: 2,353 kg (5,187 lb)
    • APS thrust: 15.6 kN (3,500 lbf)
    • APS propellants: N₂O₄/Aerozine 50 (UDMH/N2H4)
    • APS pressurant: 2 x 2.9 kg helium tanks at 21 MPa
    • Engine specific impulse: 3.05 kN·s/kg
    • Thrust-to-weight ratio: 0.34 (in Earth gravity - The thrust was less than the weight on Earth, but enough on the Moon)
    • Ascent stage delta V: 2,220 m/s (7,280 ft/s)
    • Batteries: 2 x 296 Ah silver-zinc batteries
    • Power: 28 V DC, 115 V 400 Hz AC
  • Descent Stage:
    • Height: 3.2 m (10.5 ft)
    • Diameter: 4.2 m (13.8 ft)
    • Landing gear diameter: 9.4 m (30.8 ft)
    • Mass including fuel: 10,334 kg (22,783 lb)
    • Water: 1 x 151 kg storage tank
    • Power: 2 x 296 Ah silver-zinc batteries (secondary system)
    • Propellants mass: 8,165 kg (18,000 lb)
    • DPS thrust: 45.04 kN (10,125 lbf), throttleable to 4.56 kN (1025 lbf)
    • DPS propellants: N₂O₄/Aerozine 50 (UDMH/N₂H₄)
    • DPS pressurant: 1 x 22 kg supercritical helium tank at 10.72 kPa.
    • Engine specific impulse: 3050 N·s/kg
    • Descent stage delta V: 2,470 m/s (8,100 ft/s)
    • Batteries: 4 x 400 A·h silver-zinc batteries

Apollo Spacecraft: Apollo Lunar Module Diagram.

Apollo Lunar Module

A Lunar Module in the National Air and Space Museum.