Giel, Tom

Philippart, Ken

Strickland, Matt

Vetcha, Naveen

NASA Technical Reports Server

www.jacobs.com | worldwide
Overview of RS-25 Adaptation Hot-Fire Test Series for SLS, 
Status and Lessons Learned
Naveen Vetcha
ERC Inc./Jacobs Space Exploration Group
NASA Marshall Space Flight Center
7/9/2018
Contributions from:
Matt Strickland, Jacobs Space Exploration Group
Ken Philippart, BRC/Jacobs Space Exploration Group
Tom Giel, ERC Inc./Jacobs Space Exploration Group
https://ntrs.nasa.gov/search.jsp?R=20180006349 2019-08-31T18:40:06+00:00Z
1. Introduction
2. System Requirements
3. Controller Development
4. System DDT&E
5. Engine System Testing
6. Conclusion
Outline
Introduction
Product ID: JPID-FY18-01508 
NASA authorization act - 2010
4
Minimum Capability requirements for the launch vehicle are:
• Capability to lift payloads weighing between 70 to 100 metric tons into low-Earth orbit (LEO) in 
preparation for transit for missions beyond LEO,
• Capability to carry an integrated upper Earth departure stage bringing the total lift capability to 
130 metric tons or more,
• Capability to lift the Orion Multi-Purpose Crew Vehicle (MPCV), and
• Capability to serve as a backup system for supplying and supporting International Space Station 
(ISS) cargo requirements or crew delivery requirements not otherwise met by available vehicles. 
Product ID: JPID-FY18-01508 
Space Launch System (SLS)
5 RS-25 engines
Product ID: JPID-FY18-01508 
6
SLS EM-1 Launch Animation
Product ID: JPID-FY18-01508 
Space Shuttle Main Engine (SSME)
7
Image: NASA
Product ID: JPID-FY18-01508 
SSME  RS-25 Adaptation
8
• Four RS-25 engines are used to power the core 
stage of SLS
• Initial flights will use RS-25 engines recovered 
from Space Shuttle program (RS-25 Adaptation 
program)
• Future flights will use the engines manufactured 
using cheaper and more affordable processes 
(RS-25 Restart Production)
• A hot-fire testing program was planned to test 
the engine performance over a range of 
operating conditions to demonstrate the 
capability to meet mission requirements
• Engine static fire testing is conducted on A1 test 
stand at NASA Stennis Space Center
System Requirements
Product ID: JPID-FY18-01508 
RS-25 requirements overview
10
Vacuum Thrust
-Rated = 470,000 lbf
-Precision  = ±6000 lbf
-Closed-loop control
Minimum Vacuum Isp
451.3 s (at 109% rated thrust)
Mixture Ratio
-Nominal = 6.00
-Precision:
±1.7% (65% to 90% rated thrust)
±1% (90% to 109% rated thrust)
-Closed-loop control
Engine Throttling
Steps 1% between 65% to 109% 
of rated thrust
Engine Mass = 8280 lbm
Engine Dimensions = 94" D X 167"  L
Operational Life (Post delivery)
-6 starts, 2500 seconds (1st and 2nd SLS 
flight)
-3 starts, 1100 seconds (3rd and 4th SLS 
flight)
Engine Control system 
-Electronic controller and software
-ReprogrammableEngine Gimbal = 8º circle
Controller Development
Product ID: JPID-FY18-01508 
12
RS-25 ECU
Controller Development
• In the RS-25 Engine Adaptation program, the only engine component that was upgraded 
was the Engine Controller (ECU)
• The Engine Control (EC) system is composed of ECU (hardware/software) and the new 
cabling/harness
ECU Functions
• Receive and respond to commands from the vehicle.
• Provide closed-loop thrust and mixture ratio control of 
the engine during mainstage operation through 
position control of variable position propellant valves 
to the separate preburners.
• Manage engine state (i.e., start enable, start, 
mainstage, shutdown, etc.) transition and timing of 
effectors used during the different states. This 
includes the control of numerous purges and bleed 
flows.
• Continuously monitor engine health.
• Provide data and health status to the vehicle flight 
controllers.
• Provide electrical power to all engine control 
elements, sensors and effectors.
Product ID: JPID-FY18-01508 
13
Controller Development
System DDT&E
Product ID: JPID-FY18-01508 
15
LOX Inlet Pressure (psia)
SSME Start Box RS-25 Start Box
RS-25 Changes: LOX Inlet Pressure
• Increased tank height
• Increased acceleration
• Changes in ullage schedule
• New start box
• New main stage envelope
• Beyond SSME start experience
Product ID: JPID-FY18-01508 
16
RS-25 Changes: Fuel Inlet Pressure
• Increased tank height
• Changes in ullage schedule
• Fuel tank pressurized to maintain gauge pressure
• Modified start box
• Main stage exposed to higher inlet pressure for extended period
• Beyond SSME start experience
LH2 Inlet Pressure (psia)
SSME 
Start 
Box
RS-25 
Start 
Box
Product ID: JPID-FY18-01508 
17
RS-25 Changes: GOX Tank Pressurization
• Increased tank pressurization flow (repress) to maintain ullage 
pressure
• Valve material sensitive to GOX temperature
• Additional requirements as a function of power level and flowrate
• Interface Pressure
• Interface Temperature
• Test Max and Min repress flows at various power levels for a set 
duration during the mainstage and also during the start and shut 
down.
109%
Max flow
109%
Min flow
109%
Max flow
109%
Min flow
65% 65%
Product ID: JPID-FY18-01508 
18
RS-25 Changes: Fuel Tank Pressurization
• Increased tank pressurization flow (repress) to maintain ullage 
pressure
• Core stage auxiliary power unit (CAPU) now driven by GH2 tap
• Will power all hydraulics including thrust vector & valves
• Additional requirements as a function of power level and flowrate
• Interface Pressure
• Interface Temperature
• Test Max and Min repress flows at various power levels for a set 
duration during the mainstage and also during the start and shut 
down.
109% to 65%
Max flow
109% to 65%
Min flow
109%
Max flow
109%
Min flow
65%
Product ID: JPID-FY18-01508 
19
RS-25 Changes: Nozzle Heating
• Engine is now close to in-plane with Solid 
Rocket Boosters (SRBs) resulting in 
increased convective and radiant heating
• Additional heating due to plume 
recirculation and radiant heat
• GH2 dumped overboard is ignited to 
prevent free hydrogen buildup which will 
cause some more heating
• Test strip of nozzle ablative (Adhesion 
test)
Product ID: JPID-FY18-01508 
20
RS-25 Adaptation Testing - Summary
• Vehicle Changes & Engine Effects
• Thermal conditioning
• Higher power level
• Higher inlet pressures
• Higher tank pressurization flows
• Helium ingestion
• Nozzle Heating
• Controller Changes & Engine System 
• Mixture ratio control
• Throttle control
• Adaptation Plan
• Green Run
• Life Extension
• DVR Verification Requirements
• Development Objectives
Engine System Testing
Product ID: JPID-FY18-01508 
RS-25 Adaptation Test: A-1 Test Stand
22
• The A-1 test stand located in NASA’s Stennis 
Space Center was chosen to conduct all the tests
• Capabilities
• Maximum test article size 33 ft in diameter
• 1.1 M-lb (vertical)
• 0.7 M-lb (horizontal)
• Supplied with cryogenic fluids
• LOX and LH2 are supplied from cryogenic barges
• Propellant feed lines and other run lines were 
changed as per RS-25 requirements
• Thrust Measurement System (TMS) was updated
• LOX runline piping spools were electropolished ro
remove any metal particles
Engine test on A1 test stand
RS-25 Engine 
mounted on 
the stand
Product ID: JPID-FY18-01508 
23
0
500
1000
1500
2000
2500
3000
3500
4000
Se
co
nd
s
RS-25 seconds at RPL
RS-25 Adaptation Test
• A total of 18 hot-fire tests were performed as part of the Adaptation test series between 
Jan 2015 – Jan 2018.
• Two of the tests were engine acceptance tests where flight engines were tested and 
tagged.
• Sixteen tests were performed on two development engines
Product ID: JPID-FY18-01508 
24
RS-25 Adaptation Test
168
170
172
174
176
178
180
182
102 104 106 108 110 112 114 116 118 120 122
LO
X 
In
le
t T
em
p 
(R
)
LOX Inlet Pressure (Psia)
LOX Start Box
36
37
38
39
40
41
47 48 49 50 51 52 53 54 55
LH
2 
In
le
t T
em
p 
(R
)
LH2 Inlet Pressure (Psia)
Fuel Start Box
SSME RS-25
176
178
180
182
184
186
188
102 104 106 108 110 112 114 116 118 120 122
PB
P 
Di
sc
h 
Te
m
p 
(R
)
LOX Inlet Pressure (Psia)
LOX Start Box (PBP Ds)
SSME RS-25
SSME RS-25
▲ RS-25 
adaptation 
tests
• The first test in the series was a baseline of the 
engine performance at SSME start propellant 
inlet conditions
• Some tests were conducted at the corners of 
the start boxes to test the system to component 
hardware operating limits
Product ID: JPID-FY18-01508 
25
RS-25 Adaptation Test
5.8
5.9
6
6.1
6.2
0.6 0.7 0.8 0.9 1 1.1 1.2
En
gi
ne
 M
R
Commanded Power Level
Mixture Ratio (MR) Precision
-10000
-8000
-6000
-4000
-2000
0
2000
4000
6000
8000
10000
0.7 0.8 0.9 1 1.1 1.2
De
lta
 T
hr
us
t (
lb
f)
Commanded Power Level
Thrust Precision
99.75
99.8
99.85
99.9
99.95
100
020406080100
LO
X 
Pu
rit
y 
(%
)
Tank Volume (%)
In-Run LOX Samples x RS-25 adaptation tests
Product ID: JPID-FY18-01508 
26
RS-25 Adaptation Test
-3
-2
-1
0
1
2
3
4
5
si
gm
a 
fro
m
 m
ea
n OPB Ignition Spike B1-AB1-B
STS-A
STS-B
A1-A
A1-B
RS-25-A
RS-25-B
A2-A
A2-B
-3
-2
-1
0
1
2
3
4
5
6
si
gm
a 
fro
m
 m
ea
n
FPB Ignition Spike B1-A
B1-B
STS-A
STS-B
A1-A
A1-B
RS-25-A
RS-25-B
A2-A
A2-B
Product ID: JPID-FY18-01508 
Summary
27
- RS-25 adaptation test series successfully demonstrated that the flight 
controllers meet the mission requirements
- All the other RS-25 requirements have been successfully tested
- Lessons learned during the test program will help the future tests in the RS-25 
restart production program
Product ID: JPID-FY18-01508 
Acknowledgements
28
The authors wish to thank the following those who made valuable suggestions 
and helped in completion of this package and the manuscript: Richard Ballard 
(XP20), Michael Nelson (ER22), John Butas (ER21), and Tim Duquette (ER21).


Overview of RS-25 Adaptation Hot-Fire Test Series for SLS, Status and Lessons Learned

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server