Apollo Lunar Module rocket engine
Descent propulsion system (DPS)
Country of origin
| United States
|
---|
Date
| 1964?1972
|
---|
Designer
| Gerard W. Elverum Jr.
|
---|
Manufacturer
| TRW
|
---|
Application
| Lunar descent stage propulsion
|
---|
Predecessor
| None
|
---|
Successor
| TR-201
|
---|
Status
| Retired
|
---|
|
Propellant
| N
2
O
4
/
Aerozine 50
|
---|
Mixture ratio
| 1.6
|
---|
Cycle
| Pressure-fed
|
---|
Pumps
| None
|
---|
|
Chamber
| 1
|
---|
Nozzle ratio
| - 47.5 (Apollo 14 and before)
- 53.6 (Apollo 15 and later)
|
---|
|
Thrust, vacuum
| 10,500 lbf (47 kN) maximum, throttleable between 1,050 and 6,825 lbf (4.67?30.36 kN)
|
---|
Throttle range
| 10%?60%, full thrust
|
---|
Thrust-to-weight ratio
| 25.7
|
---|
Chamber
pressure
|
- 110 psi (760 kPa) (100% thrust)
- 11 psi (76 kPa) (10% thrust)
|
---|
Specific impulse
, vacuum
|
- 311 s (3.05 km/s) (at full thrust)
- 285 s (2.79 km/s) (10% thrust)
|
---|
Burn time
| 1030 seconds
|
---|
Restarts
| Designed for 2 restarts, tested up to four times on
Apollo 9
|
---|
Gimbal range
| 6°
pitch
and
yaw
|
---|
|
Length
|
- 85.0 in (2.16 m) (Apollo 14 and earlier)
- 100.0 in (2.54 m) (Apollo 15 and later)
|
---|
Diameter
|
- 59.0 in (1.50 m) (Apollo 14 and earlier)
- 63.0 in (1.60 m) (Apollo 15 and later)
|
---|
Dry weight
| 394 lb (179 kg)
|
---|
|
Lunar module
as descent engine
|
|
References
| [1]
[2]
|
---|
The
descent propulsion system
(DPS - pronounced 'dips') or
lunar module descent engine
(LMDE), internal designation
VTR-10
, is a variable-
throttle
hypergolic
rocket engine
invented by Gerard W. Elverum Jr.
[3]
[4]
[5]
and developed by
Space Technology Laboratories
(TRW) for use in the
Apollo Lunar Module
descent stage. It used
Aerozine 50
fuel and
dinitrogen tetroxide
(
N
2
O
4
) oxidizer. This engine used a
pintle injector
, which paved the way for other engines to use similar designs.
Requirements
[
edit
]
The propulsion system for the descent stage of the lunar module was designed to transfer the vehicle, containing two crewmen, from a 60-nautical-mile (110 km) circular lunar parking orbit to an elliptical descent orbit with a
pericynthion
of 50,000 feet (15,000 m), then provide a powered descent to the lunar surface, with hover time above the lunar surface to select the exact landing site. To accomplish these maneuvers, a propulsion system was developed that used
hypergolic propellants
and a
gimballed
pressure-fed ablative cooled engine that was capable of being
throttled
. A lightweight cryogenic helium pressurization system was also used. The exhaust
nozzle extension
was designed to crush without damaging the LM if it struck the surface, which happened on Apollo 15.
[6]
Development
[
edit
]
According to NASA history publication
Chariots for Apollo
, "The lunar module descent engine probably was the biggest challenge and the most outstanding technical development of Apollo."
[7]
A requirement for a throttleable engine was new for crewed spacecraft. Very little advanced research had been done in variable-thrust rocket engines up to that point.
Rocketdyne
proposed a pressure-fed engine using the injection of inert helium gas into the propellant flow to achieve thrust reduction at a constant propellant flow rate. While NASA's
Manned Spacecraft Center
(MSC) judged this approach to be plausible, it represented a considerable advance in the state of the art. (In fact, accidental ingestion of helium pressurant proved to be a problem on
AS-201
, the first flight of the Apollo Service Module engine in February 1966.) Therefore, MSC directed Grumman to conduct a parallel development program of competing designs.
[7]
Grumman held a bidders' conference on March 14, 1963, attended by
Aerojet General
, Reaction Motors Division of
Thiokol
, United Technology Center Division of
United Aircraft
, and Space Technology Laboratories, Inc. (STL). In May, STL was selected as the competitor to Rocketdyne's concept. STL proposed an engine that was gimbaled as well as throttleable, using flow control valves and a variable-area
pintle injector
, in much the same manner as does a shower head, to regulate pressure, rate of propellant flow, and the pattern of fuel mixture in the combustion chamber.
[7]
The first full-throttle firing of Space Technology Laboratories' LM descent engine was carried out in early 1964. NASA planners expected one of the two drastically different designs would emerge the clear winner, but this did not happen throughout 1964. Apollo Spacecraft Program Office manager
Joseph Shea
formed a committee of NASA, Grumman and Air Force propulsion experts, chaired by American spacecraft designer
Maxime Faget
, in November 1964 to recommend a choice, but their results were inconclusive. Grumman chose Rocketdyne on January 5, 1965. Still not satisfied, MSC Director
Robert R. Gilruth
convened his own five-member board, also chaired by Faget, which reversed Grumman's decision on January 18 and awarded the contract to STL.
[7]
[8]
To keep the DPS as simple, lightweight, and reliable as possible, the propellants were pressure-fed with
helium
gas instead of using heavy, complicated, and failure-prone
turbopumps
.
Cryogenic
supercritical
helium was loaded and stored at 3,500 psi (24 MPa).
[9]
: 4
The helium was pressure regulated down to 246 psi (1.70 MPa) for the propellant tanks.
[9]
: 4
Pressure from the helium would gradually rise as it warmed and would eventually be vented. The system was also equipped with a rubber diaphragm that would burst when the helium pressure reached a certain level and allow the gas to vent harmlessly into space. Once the helium was gone however, the DPS would no longer be operable. This was not seen as an issue since normally, the helium release would not occur until after the lunar module was on the Moon, by which time the DPS had completed its operational life and would never be fired again.
The design and development of the innovative thrust chamber and pintle design is credited to TRW Aerospace Engineer Gerard W. Elverum Jr.
[10]
[11]
[12]
The engine could throttle between 1,050 pounds-force (4.7 kN) and 10,125 pounds-force (45.04 kN) but operation between 65% and 92.5% thrust was avoided to prevent excessive nozzle erosion. It weighed 394 pounds (179 kg), with a length of 90.5 inches (230 cm) and diameter of 59.0 inches (150 cm).
[6]
Performance in LM "life boat"
[
edit
]
The LMDE achieved a prominent role in the
Apollo 13
mission, serving as the primary propulsion engine after the oxygen tank explosion in the
Apollo Service Module
. After this event, the ground controllers decided that the
Service Propulsion System
could no longer be operated safely, leaving the DPS engine in
Aquarius
as the only means of maneuvering Apollo 13.
Modification for Extended Lunar Module
[
edit
]
In order to extend landing payload weight and lunar surface stay times, the last three
Apollo Lunar Modules
were upgraded by adding a 10-inch (25 cm)
nozzle extension
to the engine to increase thrust. The nozzle exhaust bell, like the original, was designed to crush if it hit the surface. It never had on the first three landings, but did buckle on the first Extended landing,
Apollo 15
.
TR-201 in Delta second stage
[
edit
]
After the Apollo program, the DPS was further developed into the TRW
TR-201
engine. This engine was used in the second stage, referred to as
Delta-P
, of the Delta launch vehicle (
Delta 1000
,
Delta 2000
,
Delta 3000
series) for 77 successful launches between 1972?1988.
[13]
References
[
edit
]
- ^
Bartlett, W.; Kirkland, Z. D.; Polifka, R. W.; Smithson, J. C.; Spencer, G. L. (7 February 1966).
Apollo spacecraft liquid primary propulsion systems
(PDF)
. Houston, TX: NASA, Lyndon B. Johnson Space Center. pp. 8?9.
Archived
(PDF)
from the original on 23 August 2022
. Retrieved
23 August
2022
.
- ^
McCutcheon, Kimble D. (28 December 2021).
"U.S. Manned Rocket Propulsion Evolution - Part 9.42: TRW Lunar Module Descent Engine (LMDE)"
.
enginehistory.org
. Retrieved
23 August
2022
.
- ^
"REMEMBERING THE GIANTS - Apollo Rocket Propulsion Development - NASA"
(PDF)
.
- ^
US Patent 3,205,656
, Elverum Jr., Gerard W., "Variable thrust bipropellant rocket engine", issued 1963-02-25
- ^
US Patent 3,699,772
, Elverum Jr., Gerard W., "Liquid propellant rocket engine coaxial injector", issued 1968-01-08
- ^
a
b
"Mechanical Design of the Lunar Module Descent Engine"
.
- ^
a
b
c
d
"Chapter 6. Lunar Module ? Engines, Large and Small"
.
Chariots for Apollo: A History of Manned Lunar Spacecraft
.
NASA
History Program Office. SP-4205.
Archived
from the original on 11 October 2023.
- ^
"LM Descent Propulsion Development Diary"
.
Encyclopedia Astronautica
. Archived from
the original
on August 21, 2002.
- ^
a
b
Apollo Experience Report ? Descent Propulsion System ? NASA Technical Note: March 1973
- ^
US Patent 3,699,772A
, Elverum Jr., Gerard W., "Liquid propellant rocket engine coaxial injector", issued 1968-01-08
- ^
US Patent 3,205,656
, Elverum Jr., Gerard W., "Variable thrust bipropellant rocket engine", issued 1963-02-25
- ^
Dressler, Gordon A.; Bauer, J. Martin (2000).
TRW Pintle Engine Heritage and Performance Characteristics
(PDF)
. 36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit.
doi
:
10.2514/6.2000-3871
. Archived from
the original
(PDF)
on 9 August 2017.
- ^
Ed Kyle.
"Extended Long Tank Delta"
. Space Launch Report. Archived from
the original
on 7 August 2010
. Retrieved
May 11,
2014
.
External links
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edit
]
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