Ram Burn Observations (RAMBO) - 05.13.15
Ram Burn Observations (RAMBO) is an experiment in which the Department of Defense uses a satellite to observe space shuttle orbital maneuvering system engine burns. Its purpose is to improve plume models, which predict the direction the plume, or rising column of exhaust, will move as the shuttle maneuvers on orbit. Understanding the direction in which the spacecraft engine plume, or exhaust flows could be significant to the safe arrival and departure of spacecraft on current and future exploration missions. Science Results for Everyone
Satellite to Shuttle: Your exhaust is showing. The Department of Defense uses optical sensors on a satellite to observe Shuttle engine firings and maneuvering burns as part of work to improve models that predict the direction its exhaust plumes will move as the Shuttle maneuvers on orbit. Understanding this exhaust flow could help ensure safe arrival and departure of spacecraft on future exploration missions. This experiment is ongoing and results are pending, but will be important in developing better models for high-temperature, high-velocity atomic and molecular collisions caused by spacecraft operations. Experiment Details
William L. Dimpfl, Ph.D., Aerospace Corporation, Los Angeles, CA, United States
United States Department of Defense Space Test Program, Johnson Space Center, Houston, TX, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Department of Defense (DoD) - Retired
ISS Expedition Duration
April 2006 - April 2008
Previous ISS Missions
RAMBO has been performed on the following Shuttle missions: STS-110, STS-111, STS-112, STS-121 and STS-107 (Columbia), which was lost in 2003.
- Department of Defense (DoD) optical sensors, located on a DoD satellite, make observations of timing and spectral pattern of radiance produced by the plumes from normal Space Shuttle engine firings as well as from dedicated burns of the Space Shuttle Orbital Maneuvering System (OMS) engines.
The Ram Burn Observations (RAMBO) experiment uses a satellite to observe the spectral characteristics and direction of movement of plumes created from Shuttle Orbital Maneuvering System (OMS) burns in low Earth orbit. The engine burns create high temperature, high velocity molecular collisions between the chemical species in the engine exhaust (e.g., H2O and CO) and atomic Oxygen. Three specific objectives are listed below:
- Determination of the distribution of internal states of carbon monoxide excited through collisions with atomic oxygen at hyperthermal collision velocities. Past experiments have shown that CO is efficiently excited to high internal (vibrational and rotational) energy states in collisions with Atomic Oxygen at high temperature (hyperthermal) energies. The theory is that such atom-molecule collisions are generally inefficient at transferring collision energy to internal states (the state at which an object is in regards to its internal properties). The Atomic Oxygen (O) + Carbon Monoxide (CO) system represents an interesting scientific anomaly. The anomaly is attributed to a chemical interaction in the O + CO system, which allows the exchange of O atoms to take place. A rigorous theoretical treatment of this system has been developed and predictions of the energy transfer have been calculated. RAMBO measurements are a method by which the theoretical development of understanding can be validated over the range of collision velocities from 4 to 11 km/s by observing CO radiant emission excited by collisions between CO in the plume and O atoms in the atmosphere.
- Determine the total scattering cross section for atomic and molecular species at hyperthermal energies. Analysis of the Space Shuttle orbiter engine plumes while in orbit have indicated that models for molecular scattering that are based on laboratory interactions of flame temperatures up to 2000 through 4000 K are not accurate in the hyperthermal regime experienced by orbiting spacecraft. Analysis of infrared plume radiance resulting from single collision atmosphere-plume excitation of molecules in the range of 4 to 11 km/s from the RAMBO experiment will help quantify total collision cross sections in the hyperthermal regime.
- Determining the rate constants for hydroxide producing reaction at hyperthermal energies. Emission in high altitude rocket plumes in the region from 3 to 4 microns has generally been attributed to emission from water. Better understanding has indicated that there is also significant emission in that region from internally excited hydroxide (OH) radicals that are formed through the reaction of atmospheric atomic oxygen and plume water and molecular hydrogen. Rate constants that have been determined in the laboratory for these reactions are generally limited through practicality to the thermal regime of energies below 1 electron volt (eV). (An eV refers to the energy gained by an electron as it moves through a potential difference of one volt.)
High altitude plumes involve energies that extend into the hyperthermal regime up to about 10 eV. Extrapolation of laboratory-measured rate constants into the hyperthermal regime is typically done to satisfy modeling needs, but is notoriously suspect for producing values that have a significant error. RAMBO experiments sample OH emission that is produced directly from the relevant reactions at hyperthermal energies, and are being use to establish valid hyperthermal rate constants.
Applications in space include an understanding of plume flow fields that could be relevant to the safe approach and departure of shuttles or supply ships to the ISS or other spacecraft. They also include an understanding of background radiance produced by plumes, impacting sensors designed for other observations. More generally the applications include a contribution to understanding any phenomenon related to spacecraft that are impacted by the poorly understood interactions of atoms and molecules at hyperthermal energies that govern the environment about spacecraft in low earth orbit.
While interactions at hyperthermal energies are relatively rare on the surface of the earth there are potential applications relevant to the cutting edge of technology, including the understanding of high temperature plasmas and the production and derivation of energy from controlled fusion power sources.
The DoD Space Test Program support includes providing predicted space shuttle orbiter state vectors to the experiment PI in a timely fashion for setting up and running the experiment. To facilitate the analysis for this experiment the following must be provided: truth data, including engine chamber pressures, orbiter attitude and state vector information.
The Space Shuttle will activate the OMS engine(s) during normal procedures en route to the ISS and deorbit burns. Each burn will last for at least 10 seconds. During the burn observations, pre-determined vectors plus real time data will be used for the analysis.
This experiment continues on the ISS. Results are pending, but are important for better constraining models for the high-temperature, high-velocity atomic and molecular collisions induced by spacecraft operations.^ back to top
Ground Based Results Publications
Dimpfl WL, Light GC, Bernstein LS. Molecular Dynamics From Remote Observation of CO(a) from Space Shuttle Plumes. Journal of Spacecraft and Rockets. 2005; 42(2): 352-362. [Also: AIAA Space 2003, Sept 23-25, 2003, Long Beach CA, 2003-6204.]
Viereck RA, Murad E, Knecht DJ, Pike CP. The Interaction of the Atmosphere with the Space Shuttle Thruster Plume: the NH(A-X) 336 nm Emission. Journal of Geophysical Research. 1996; 101(A3): 5371-5380. DOI: 10.1029/95JA03635.
Broadfoot AL, Anderson EE, Sherard P, Knecht DJ, Vierek RA, Pike CP, Murad E, Elgin JE, Bernstein LS, Kofsky IL, Rall DL, Blaha J, Culbertson FL. Spectrographic Observation at Wavelengths Near 630 nm of the Interaction Between the Atmosphere and the Space Shuttle Exhaust. Journal of Geophysical Research. 1992; 97(A12): 19501-19508.
Duff JW, Braunstein M. Electronic Structure and Dynamics of O(3P) + CO(1S+) Collisions. Journal of Chemical Physics. 2000; 112(6): 2736-2745.
Bernstein LS, Chiu Y, Gardner JA, Broadfoot AL, Lester MI, Tsiouris M, Dressler RA, Murad E. Molecular Beams in Space: Sources of OH (A yields X) emission in the Space Shuttle environment. Journal of Physical Chemistry A. 2003; 107(49): 10695-10705. DOI: 10.1021/jp035143x.
Dimpfl WL, Braunstein M. Recommended Upgrades to the Variable Hard Sphere Model in Direct Simulation Monte Carlo Molecular Scattering Codes. JANNAF Exhaust Plume Technology Subcommittee and 10th SPIRITS User Group Joint Meeting, San Diego, CA; 2004
NASA Image: STS007-18-0778 - This image shows the Glow experiment documentation of OMS/RCS pods and vertical stabilizer from STS-007.
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Comparison of plume radiance and model prediction from related PLUMES experiment. The agreement represents understanding gleaned through analysis. Image courtesy of NASA, Johnson Space Center.
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