Space Vehicle Ocean Recovery Considerations - AIAA ARC

AIAA 2006-681

44th AIAA Aerospace Sciences Meeting and Exhibit 9 - 12 January 2006, Reno, Nevada

Space Vehicle Ocean Recovery Environments Vernon W. Keller* and Dale L. Johnson† NASA Marshall Space Flight Center, Huntsville, AL 35812 William W. Vaughan‡ University of Alabama in Huntsville, Huntsville, AL 35899

Knowledge of ocean wave characteristics and statistics is important to aerospace applications such as search and rescue at sea and recovery of Earth returning space vehicles. Space Shuttle design and operations utilized sea state information for the recovery and tow back of the Solid Rocket Boosters (SRB’s). In this instance, sea state information was specifically required only in the Atlantic Ocean recovery area adjacent the Eastern Range. Future space vehicle applications will require sea state information at various locations around the world. The availability in recent years of satellite data coupled with computer model data has made possible the means of providing selected sea state characteristics and probabilities on a more or less global basis in a way that was previously impossible with only Surface-based wind and wave measurements. Capitalizing on these technology advances, a digital global wind/wave atlas has been developed that provides historical sea state characteristics at nearly any designated latitude and longitude ocean location. Sea state characteristics for specific locations, other ocean recovery environment parameters, and associated space vehicle engineering applications are discussed.

Nomenclature Hs KSC LC39 Lat Long MSFC NASA NAVAIR NOAA NWS POR SRB

= = = = = = = = = = = =

significant wave height Kennedy Space Center launch complex 39 latitude longitude Marshall Space Flight Center National Aeronautics and Space Administration Naval Air Systems Command National Oceanic and Atmospheric Administration National Weather Service period of record solid rocket booster

I. Introduction Terrestrial environment phenomena play a significant role in the design and operation of aerospace vehicles and in the integrity of the aerospace systems and elements. Terrestrial environment design criteria guidelines are based on statistics and models of atmospheric and climatic phenomena relative to various aerospace design, development, and operational issues1-3. Aerospace vehicle design guidelines are provided in the NASA Terrestrial Environment Handbook4 for fourteen environmental phenomena including Sea State (Section 14). Publication of an updated version of this Handbook is scheduled for calendar year 2006. In general, the handbook does not specify how the designer should use the terrestrial environment data in regard to a specific aerospace vehicle design. Such specifications may be established only through analysis and study of a particular vehicle design problem. Although of operational significance, descriptions of some terrestrial environment conditions have been omitted since they are not of direct *

Aerospace Engineer, Natural Environments Branch, Code: EV13. Aerospace Engineer, Natural Environments Branch, Code: EV13. ‡ Research Professor, Atmospheric Science Department, 301 Sparkman Dr. †

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American Institute of Aeronautics and Astronautics This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

concern for an aerospace vehicle system’s design, i.e., the primary emphasis of this handbook. Induced environments (vehicle caused) may be more critical than the natural environment for certain vehicle operational situations. In some cases, the combination of natural and induced environments could be more severe than either environment alone. II.

Sea State Example

A.

Introduction The terrestrial example chosen for this paper is an engineering application that is associated with handbook section 14 on sea state. The global sea state wave/wind model chosen as the base model for the Terrestrial Handbooks’ Section 144 is the 2003 update by Young5 from the 1996 Atlas of the Oceans: Wind and Wave Climate, by Young and Holland6. This new information is being incorporated into the current revision of the handbook. The ocean atlas data Period Of Record (POR) was doubled from five years to ten years (1985-1995) for the 2003 update. This new sea state model, along with other models and data bases that extend over various Periods Of Record and incorporate an assortment of English and metric units, was utilized to arrive at results for the following example. B.

Background/Procedure This sea state example is with regard to a hypothetical crewed space vehicle that is launched from Kennedy Space Center (KSC), Florida and then experiences problems during initial ascent which would result in an aborted mission into the Atlantic Ocean along its trajectory. The question being addressed is with respect to what natural environment parameters exist that would affect the vehicle recovery and/or its crew rescue. For mission planning purposes, what would be the best months or the worst months to launch, with respect to the natural environment, should an abort occur? Waves, wind, sea/air temperature, visibility, clouds and fog are all important terrestrial parameters that need to be considered in planning any spacecraft sea-rescue mission scenario contingency. A 51.6 degree inclination orbit, for a vehicle launched from LC39 at KSC was chosen for this example. The ground track is presented graphically in figure 1. In order to establish natural environment design limits for the space vehicle, wave height, along with sea and air surface temperature maximums and minimums are the key natural environment parameters that need to be specified by the vehicle program. Likewise, the key natural environment parameters that affect survivability and rescue at a given splash down location are: Sea state, (i.e., the height and wavelength of the waves) along with the associated descent/surface winds (speed and direction); sea surface temperature of the water; air temperature at the splash down location; precipitation; visibility/cloud cover (including super cooled stratus and low cumulus, fog and thunderstorms), and, of course, the elapsed time between splash down and crew rescue. Calculations along a ground track at approximately every 10 degrees longitude were initiated producing monthly (or seasonal) natural environment results. The three NAVAIR references7-9 indicate that the mean percent frequency values were assembled from what data was available but no diurnal results were calculated. The sea state/wave data along with sea surface temperatures and surface winds were extracted from five sources5-6, 10-12. The eight north latitude/west longitude ground track sites used in this study and shown in figure 1 are: Site # 12345678-

Lat.N/Long.W 28.5o/80o 35o/70o 42o/60o 47o/50o 50o/40o 51.5o/30o 52o/16o 51o/4o

C. Sea State (Waves/Wind) Since the Young Atlas of 20035 gives only mean monthly wave conditions, the Caires10 C-ERA-40 30 year POR (1971-2000) significant wave height 90% quantiles for the worst sea state month (January) over the Atlantic Ocean are used for this example. The Caires’ sea state model gives significant wave heights (Hs) between 7 and 8 meters for the months December through March which can extend over nearly the entire north Atlantic between 45o

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to 65o N lat, and 45o to 5o W long, as shown in figure 2. This is equivalent to a Beaufort wind number of 8 and represents a high sea state (with associated winds of 17.5 to 20.6 m/s (34 to 40 knots)). See table 1 State of Sea: International Meteorological Code, World Meteorological Organization (WMO) code 3700. The significant wave height, Hs or H1/3, is defined as the average of the highest 1/3 of the waves. It also corresponds to the value that would be visually estimated by an experienced observer. If the individual waves in the record follow a Rayleigh probability distribution it is possible to relate other representative wave height estimates to Hs. As an example, H1/10, the average of the highest 1/10 of waves is related to Hs by the relationship H1/10=1.27Hs. From the data Atlas of Young5, the 50 year extreme wave height at the location 50oN, 38oW is 21.9 ± 1.6 meters (71.9 ± 5.2 feet). From NAVAIR7 (charts 10; 20; 124), Gale force winds (winds ≥ 17.5 m/s (34 knots)) representing a Beaufort wind number of ≥ 8) along the ground track were determined and showed a percent frequency of 17% to > 20% during December/January/February at sites 5 and 6. The summer months May through August (charts 51; 62; 72; 82) presented Gale problems less than 5% of the time. Likewise, cold sea surface mean temperatures (of < 4.4oC (40oF)) prevailed from December through May (charts 125; 11; 21; 32; 52) at site 4 (-1.1oC (30oF) mean in February). Mean seasonal sea swell height probabilities ≥ 3.7 m (12 feet) were given, which indicated that during Fall (November) and Winter (February) (charts 115; 22) the frequency probability ranges from 25% to > 30% at sites 5, 6, and 7. Spring (May) and Summer (August) (charts 53; 84) months had probabilities ranging from 15% to > 20% at sites 6 and 7. D. Sea Surface Temperature Using the NOAA National Weather Service (NWS) Environmental Modeling Center’s 30 year normal sea surface temperature data of Smith11 for January (December is about as cold), one can see from figure 3 where in the north Atlantic the coldest sea-surface temperatures are likely to be encountered. Figure 4 is a more detailed plot of January sea surface temperature for the North Atlantic using Period Of Record data (1854-1969)12. The black dots numbered 1 through 8 on this plot represent points near the 51.6 degree inclination orbit ground track and are the same locations referenced in figure 1. January sea temperatures in the North Atlantic are normally colder than 5oC (41oF) along the flight track over to ~45oW longitude, and do not get any warmer than 11oC (51oF) along its entire North Atlantic flight path. E. Air-Temperature,Visibility/Clouds, Precipitation Results Figure 5 is a plot of January air temperature for the North Atlantic using Period Of Record data (18541969)12. The black dots numbered 1 through 8 are points near the 51.6 degree inclination orbit ground track and are the same locations referenced in figures 1 and 4. The coldest January mean ambient air temperatures along the ground track occur in the vicinity of Newfoundland with air temperatures below 0oC (32oF). In this area of the North Atlantic a space vehicle splash down just a few hundred miles downrange can make a substantial difference in the normal January sea/air temperatures encountered. The sea surface temperature can increase by 5.5oC (10oF), from 0oC (32oF) to 5.5oC (42oF), if splash down occurs just 800 km (500 statute miles) further downrange of site 4. The sea surface temperature can increase by 7.8oC (14oF), from 0oC (32oF) to 7.8oC (46oF), if splash down occurs just 800 km (500 statute miles) to the South of site 4. Sea surface and air temperature gradients are even more dramatic just south of site 3. The surface air temperature, equal to or below freezing (≤ 0oC), along with the occurrence of supercooled stratus/low cumulus and frozen precipitation peak in the winter months, especially near the site 4 lat/long location. In January and February there is a 40 percent frequency of occurrence of mean air temperatures at or below 0oC at this site (35% in March and 22% in December). The other seven lat/long sites offer less of a probability of occurrence. The percent frequency of supercooled stratus and low cumulus was done by season and indicated a 20% frequency of occurrence in Dec/Jan/Feb at site 4, with a 15% frequency in Mar/Apr/May also at this site. Sites 3 and 5 gave 15% in Dec/Jan/Feb, as did site 5 in Mar/Apr/May. Total cloud (sky ≥ 5/8) frequency also peaks to > 80% at sites 3 to 5 from December through April. However, 70% to > 80% mean total cloud frequency also exists for basically all months of the year, for sites 3 through 7. Frozen precipitation occurs at a 15% to 20% frequency from Dec through Feb at site 4, with lesser values at other sites. Mean precipitation tends to occur more frequently in the winter months (November thru March) with a frequency of 30% to 35% at sites 4 through 7. However, even the warmer months (of April thru October) give a 20% to 30% mean frequency of precipitation occurrence centering near sites 5 thru 7. One Operational Solution: If a winter-time abort situation arises during initial ascent, the crewed vehicle could either steer toward the right (or south) or abort farther down range to avoid the harsher wave, wind, sea/air temperature conditions that exist along the initial ground path track. To minimize a cold air/sea temperature environment and potential icing conditions which could adversely impact helicopter rescue operations, plans could

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be developed to avoid splashing down near Newfoundland or in the North Atlantic between longitudes 63oW and 40oW. However, since search and rescue capabilities will vary along the trajectory ground path, trade-offs may be required to land the crew in regions with less desirable weather conditions but that are more accessible for rescue. This would shorten the elapsed time between splash down and crew rescue, thus enhancing survivability.

F. Fog and Thunderstorm Results When considering possible launch abort scenarios, avoiding operations during the winter months (December through March) and only launching between late spring and early fall might at first blush be considered most appropriate from a sea state natural environments assessment. However, various other natural environment parameters need to be considered as well. The percent frequency of fog in any form and of thunderstorms is higher in the north Atlantic Summer months than in the Winter months. Regarding fog, the site 4 location has the highest frequency percentage of 60% which peaks in July. The months May though August also offer > 40% frequency of occurrence of fog at site 4. Site 3 peaks at 40% in July, while site 5 peaks at 30% in July. The occurrence of fog during the winter months, though less, is between 10% and 20% at site 4. See table 2 which presents the average percentage frequency of fog as a function of the time during that month. Thunderstorm days were recorded by month, and also peak during the summer months along this ground track. Site 1 near KSC gives the highest average number of days for thunderstorms with 20 (or a 65% monthly frequency) during June and July, and with 10 to 15 days from May through September. Site 2 is next highest with 7 days in July and August (6 in September and 4 in May and June). Site 3 peaks at 5 in August and 4 in July. The remainder of the northern Atlantic sites offer only 1 or 2 thunderstorm days during any month of the year, except as one nears the British Isles the number increases slightly to 3 in July at site 7 (and 4 at site 8). Table 2 also presents the thunderstorm percentage frequency results along the ground track. This table clearly shows the Summer time maxima for both north Atlantic fog and thunderstorms.

III. Conclusion This example on ocean recovery environments has shown a range of natural environment parameters that can affect vehicle design and mission planning scenarios. The Terrestrial Handbook 10014 provides the engineer and manager with various natural environment statistics, figures, tables, and models that can be utilized to develop requirements for use in engineering vehicle design and development programs based on the vehicle’s operational requirements to meet mission objectives.

Note This paper is based partially on the paper by the authors entitled "The Definition and Interpretation of Terrestrial Environment Design Inputs for Vehicle Design Considerations", presented at the 12th AMS Conference on Aviation, Range, and Aerospace Meteorology, 29 January – 2 February 2006.

Acknowledgments The authors acknowledge and thank Dr. Ian Young of Swinburne University of Technology, Hawthorn, Victoria, Australia for his assistance in developing for NASA an update to his Atlas of the Oceans book of 1996, and in helping update Section 14 of NASA Handbook 1001. The authors acknowledge and thank Dr. Jere Justus of Morgan Research, Huntsville, Alabama for his assistance with figures 4 and 5.

Bibliography 1

Vaughan, W.W.; and Brown, S.C., “Natural Environment Considerations for Space Shuttle System Development Support,” Journal of Spacecraft and Rockets, Vol. 22, No. 3, 1985, pp. 355–360.

2

Pearson, S.D.; Vaughan, W.W.; Batts, G.W.; and Jasper, G.L., “Importance of the Natural Terrestrial Environment With Regard to Advanced Launch Vehicle Design and Development,” NASA TM 108511, 1996. 3

Vaughan, W.W., Johnson, D.L.; Pearson, S.D.; and Batts G.W., “The Role of Aerospace Meteorology in the Design, Development and Operation of New Advance Launch Vehicles,” Proceedings of the Seventh Conference on Aviation, Range and Aerospace Meteorology, American Meteorological Society, Boston, MA, 1997.

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4

Johnson, D. L., “Terrestrial Environment (Climatic) Criteria Handbook for Use in Aerospace Vehicle Development,” NASAHDBK-1001, 2000. (http://standards.nasa.gov)

5

Young,

Ian,

2003:

private

communications

and

software,

MSFC

Atlas

of

the

Oceans

(1985-1995).

6

Young, I.R. and G.J. Holland, Atlas of the Oceans: Wind and Wave Climate, Elsevier Science (Pergamon), 1996, 241 pp.

7

NAVAIR 50-1C-54, “U.S. Navy Marine Climatic Atlas of the World, Vol. VIII-The World”, for Naval Weather Service Command, 1969.

8

NAVAIR 50-1C-60, NOAA-NCC developed U.S. Naval Weather Service Command, “Study of Worldwide Occurrence of Fog, Thunderstorms, Supercooled Low Clouds and Freezing Temperatures”, by N. Guttman, 1971. 9 NAVAIR 50-1C-60 CH-1, update of “Study of Worldwide Occurrence of Fog, Thunderstorms, Supercooled Low Clouds and Freezing Temperatures” atlas, 1978. 10 Caires, Sofia, et.al.; 2004: The Web-Based KNMI/ERA-40 Global Wave Climatological Atlas, Bulletin of the World Meteorological Organization, 53(2), 142-146. 11

Smith, T.M. and R.W. Reynolds, 1998: A High Resolution Global Sea Surface Temperature Climatology for the 1961-90 Base Period, J. Climate, 11, 3320-3323. 12

Naval Oceanography Command Detachment Asheville, North Carolina, March 1992: U.S. Navy Marine Climatic Atlas of the World for 1854-1969 Period Of Record, Version 1.0.

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Figure 1. Typical 51.6 degree orbit inclination launch (ground track) from KSC, FL.

Figure 2. North Atlantic January Significant Wave Height in meters, 90% Quantiles. Caires (2004)

6 American Institute of Aeronautics and Astronautics

Figure 3. NOAA 1961-1990 January Normal Sea Surface Temperature (oC). Smith (1998).

Figure 4 North Atlantic January Sea Surface Temperature (oF) Period Of Record (1854-1969).


Figure 5 North Atlantic January Ambient Air Temperature (oF) Period Of Record (1854-1969). Table 1 State of Sea: International Meteorological Code, WMO code 3700

Sea State Code 0

*Beaufort Wind No.

1 2 3 4 5 6 7 8 9

2 3 4 5 6 7 8 9 10-12

0-1

Sea State *Associated Beaufort Descriptive Terms Wind Speed (m/s) (knots) 64 Phenomenal

H 1/3 of Waves (m)

(ft)

0

0

0-0.1 0.1-0.5 0.5-1.25 1.25-2.5 2.5-4 4-6 6-9 9-14 Over 14

0-0.3 0.3-1.7 1.7-4 4-8 8-13 13-20 20-30 30-45 Over 45

Note: Exact bounding height is assigned to lower code; e.g. a height of 4 m is sea-state coded 5. * The Beaufort wind numbers and their associated wind speeds are included here.


Table 2. North Atlantic Fog and Thunderstorm Percentage Frequencies by Month. (Note the higher frequency of fog during Summer time). * All table values are in percent. Site No. = Lat/Lon =

1 28.5/80

2 35/70

3 42/60

4 47/50

5 50/40

6 51.5/30

7 52/16

8 51/4

Month January

Fog - TS 3 6.5

Fog - TS 3 6.5

Fog - TS 4 6.5

Fog - TS >10 3.2

Fog - TS 8 3.2

Fog - TS 9 6.5

Fog - TS 10 6.5

Fog - TS 10 3.2

February

3

7.1

4

7.1

6

7.1

>10 3.6

5

3.6

4

7.1

6

7.1

10 10 3.2

April

4

10

4

10

10

6.7

30

3.3

10

3.3

10