390 Alex Goodman 
Table 1 
Comparison of Experimental Techniques 
(a) Free-Running Model Technique 
1. Direct evaluation of performance of 3. Can be used to study extreme maneu- 
specific designs vers which may be too complicated to 
handle by analytical or computer 
2. Can be economical and expedient methods 
1. Does not provide data which can be 3. Froude or dynamic scaling necessary 
directly related to the design of body for mass, moment of inertia, and meta- 
and individual appendages centric stability 
2. Does not provide data to directly sup- 
port design changes to effect improve- 
ments in performance 
(b) Mathematical Model Techniques 
Advantages 
1. Provides means of evaluating han- 4. Provides measures of capabilities of 
dling qualities or ahaa charac- the design tempered by existence of 
teristics of proposed design well in ad- human operator or automatic control 
vance of construction device in control loop 
2. Provides simple means of studying ef- 5. Can be used in human engineering 
fects of practical variations of basic studies 
design which may be necessary to im- 
prove performance - 6. Can be used to study overall perform- 
3. Can be used to determine effects of ance of various combined systems 
various environmental conditions on 
peeeneanee 7. Can be used to train personnel 
Disadvantages 
1. Requires an accurate set of hydrody- 2. Requires expensive facilities 
namic coefficients of the design for the 
equations of motion 
(c) Captive Model Techniques 
1. Provides basic data on which to sup- 4. Results can be utilized to study ef- 
port design of individual body and fects of proposed design changes 
appendages without additional model tests 
2. Provides basic data which can be used 5. Data are perpetuated so that further 
with the equations of motion in com- studies can be made at a later time 
puter and simulator studies to evaluate without the need for additional model 
inherent and closed-loop performance tests 
3. Provides data which can be directly 6. Provides powerful tool for doing re- 
utilized in design of automatic control search or systematic series work on 
systems stability and control 
7. Dynamic scaling not necessary 
Disadvantages 
1. Data are one step removed from directly 3. Requires expensive facilities 
indicating all the handling qualities 
2. Method ae become uneconomical for eval- 
uating performance of one specific design 
