PRELIMINARY EVALUATION OF THE OXCART CONTRAIL PROBLEM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81B00879R001000090162-7
• Release Decision: RIPPUB
• Original Classification: T
• Document Page Count: 2
• Document Creation Date: December 15, 2016
• Document Release Date: October 25, 2002
• Sequence Number: 162
• Publication Date: August 10, 1962
• Content Type: MF

Approved For elease 2002/1
OXC-3818-62
10 August 1962
Copy_ Of C
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MEMORANDUM FOR: Chief, Development Division, O.SA/DD/R
SUBJECT Preliminary Evaluation of the OXCART Contrail Problem
REFERENCE OXC-3538-62, dated 23 May 1962, Memo for Chief,
Development Branch, DPD/DD/P
1. The previous paper, referenced above, is a general discussion
of the subject of possible contrail formation at altitudes between
80,000 and 100,000 feet. This paper presents the results of further
investigation, with most of the information summarized in graphic form.
At our request, the Air Weather Service Climatic Center compiled the
necessary temperature data in statistical form. This was no small task,
since representative data could be obtained only by extracting thousands
of interpolated readings from individual analyzed weather charts.
2. Figures 1, 2, and 3 are cumulative frequency graphs of the tem-
perature distribution near the 100,000 foot level, between latitudes of
500 to 800 North. Individual charts are presented for the summer period,
the winter cold period and the winter warm period. Separate charts are
presented for the two types of winter temperature regimes because the
temperature distribution during that season is markedly bimodal. The
colder temperatures are believed to prevail about two-thirds of the time,
while the warmer temperature regimes prevail during the remaining third.
The changes from warm to cold, and vice versa, take place rapidly. Thus,
the arithmetic mean of the observed temperatures occurs only a small per-
cent of the time.
3. Figure 4 is a graph of the probability of contrail formation
versus altitude, temperature and relative humidity. The various contrail
zones determined from this graph are indicated on figures 2 and 3. None
of the temperatures plotted on figure 1, fall within the contrail range.
4. Figure 5 is a graph of the probability of contrail formation
versus altitude and latitude along certain longitudes. The longitudes
were selected on the basis of proximity to possible OXCART mission tracks
and availability of high altitude temperature data. The chart is
applicable to the winter period, October thru March, only. During the
remainder of the year, temperatures at the altitudes and latitudes con-
sidered are not cold enough for contrails to form. Both figures 4 and
5 are based on data and computations pertaining to aircraft with turbojet
engines, using JP-4 fuel.
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5. The most definitive statement that can be made at this time
is that, during the winter months, there is at least a 30% probability
that the A-12 will produce contrails over a significant portion of a
polar mission route. A critical factor in the detection of these
contrails, by an observer on the ground, would be the degree of illu-
mination at the altitude where the contrails were produced.
6. The weakest link in any evaluation of this problem is the lack
of specific flight data from the A-12. Before the critical contrail
formation temperatures applicable to the A-12 can be determined,
numerous positive and negative contrail reports, coupled with specific
altitude and temperature data, must be obtained over the full operating
range of this aircraft. These observations should be made with the
A-12 equipped with the engines and fuel it will use during operational
missions.
Major USAF
Chief, Weather Staff, OSA/DD/R
Distribution:
Copy 1 - AD/OSA/DDR
2 - DD/OSA/DDR
3 - OD/OSA/DDR
4 - Staff Weather Office
5 - Weather Staff, OSA/D
6 - RI/QSA/DDR
This do^cru t acts i Eftr?iation
referring to Project
25X1A
SECRET
Approved For Release 2002/11/14(-: CLA-RDP81B00879R001000090162-7 1`_ cRooi-
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