System is described based on use of arrangement of crushable hollow spheres bonded together in layers of progressively different diameter, with largest diameter spheres positioned to receive impact forces initially. System is particularly useful for delivery of payloads by air-drop techniques

Collins, E. R., Jr.

English

NASA Technical Reports Server

December 1972 B72-10712 
NASA TECH BRIEF 
NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Energy Absorbing System for Mechanical Impacts 
A wide variety of protective impact-absorbing sys-
tems have been studied for interposition between a 
landing spacecraft and the surface of a planet. Un-
fortunately, many shock-absorbing systems are of 
little value for they are based on the use of resilient 
frangible materials, and it is difficult to avoid the 
tendency of an impacting object to rebound with such 
materials. Shock-absorbing systems which employ 
fluids forced through restrictive orifices are also of 
limited use inasmuch as the viscosities of fluids nor-
mally undergo severe changes as a function of tem-
perature. On the other hand, shock-absorbing systems 
which utilize crushable structures for dissipating en-
ergy on a one-shot basis appear to have more readily 
definable and reproducible characteristics; however, 
when metallic structures are used, rebound is not 
entirely eliminated because of the inherent resiliency 
of metals. 
The improved energy-absorbing system shown in 
the diagram is based on the use of an arrangement of 
crushable hollow spheres bonded together in layers 
of progressively different diameter, with the largest 
diameter spheres positioned to receive the impact 
forces initially. The material chosen for fabrication of 
the spheres characteristically must be brittle and 
hence readily fracturable, but it also must be capable 
of suffering minimum deformation prior to sudden 
fracture, so that impact force may first be strongly 
resisted and then absorbed by cave-in of the sphere; 
sudden collapse eliminates possibility of rebound. 
As suggested by the diagram, the payload delivered 
to the planet surface is surrounded by the protective 
device and the larger diameter spheres are first ex-
posed to the force of impact; hence, greater amounts
of impact force will be absorbed initially, with lesser 
and lesser amounts sequentially absorbed by the 
layers of progressively smaller spheres. The overall 
rate of energy absorption may be varied by control of 
(1) the relative size of the spheres in each layer, (2) 
the ratio of wall-thickness to sphere diameter, (3) the 
type of materials used in the spheres in each layer, 
and (4) the characteristics of the adhesive used to 
bond spheres. 
Although the energy-absorbing system is partic-
ularly useful for delivery of payloads by air-drop 
techniques when constructed as a sphere, in the cylin-
drical form, as shown in the following diagram, it 
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000711 2020-03-17T03:43:15+00:00Z
I	 ii 
t	 ii	 I 
II	 ii 
can be used for absorption of impact energy or as a 
protective barrier around impact-prone obstacles such 
as those commonly found along the shoulders of high-
ways or viaducts.
Patent status: 
This invention has been patented by NASA (U S* 
Patent No. 3,637,051). Inquiries concerning nonexclu- 
sive or exclusive license for its commercial develop-
ment should be addressed to: 
NASA Patent Counsel 
NASA Pasadena Office 
Mail Code 1 
4800 Oak Grove Drive 
Pasadena, California 91108 
Source Earl R. Collins, Jr. of
Caltech/JPL
under contract to 
NASA Pasadena Office
(NPO-10671) 
B72-10712
	 Category 06


Energy absorbing system for mechanical impacts

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