494 PHYSICS: R. H. GODDARD Proc. N. A. S. 
feet, the rocket should, in principle, be capable of reaching much greater 
altitudes. 
A theory, together with estimates as to what should be attainable under 
realizable conditions, is given in Smithsonian Miscellaneous Collections, 
Vol. 71, No. 2. It is intuitively evident, however, that a great elevation 
must be obtainable provided a large part of the heat energy of the pro- 
pellant is converted into kinetic energy of the ejected gases, and also pro- 
vided the proportion of mass of propellant to total mass is high. 
It should be understood that although theory indicates the possibility 
of reaching great altitudes, the application discussed in the present paper 
is solely the raising of recording instruments to a moderate height. 
As regards the conditions to be satisfied by the most desirable method 
above outlined, other than the mere attainment of the altitude, the rocket 
method is ideally suited to the raising of apparatus rapidly and without 
jar, inasmuch as the propulsive force is sensibly constant, and, therefore, 
the apparatus, starting from rest, will rapidly attain a high velocity. 
After the propellant has been completely expelled, the apparatus will 
gradually be brought to rest by gravity. A parachute device, carried by 
the rocket, could permit of any desired speed of descent; the details of 
construction and operation being, of course, well understood. 
Concerning the maintenance of high level for an appreciable interval 
of time, the rocket apparatus can contain, besides instruments and para- 
chute, a rubber balloon of the usual size, compactly folded, together with 
a steel sphere containing compressed hydrogen, to be released into the 
balloon when the upper limit of flight has been reached, as suggested in 
principle by Dr. Abbot. The parachute would be brought into action, 
and the balloon released, a predetermined interval of time after the balloon 
had been inflated. 
Extent to Which the Conditions Necessary for a Satisfactory Rocket 
Method have been Realized. — The first condition for increasing the range 
of the rocket apparatus is the ejection of the powder gases with as high 
a velocity as possible. This feature has already been developed to a satis- 
factory degree. The velocity of the ejected gases has been increased from 
1000 ft./sec. to over 7,500 ft./sec; or, expressed differently, the fraction 
of the heat energy of the powder that is transformed into energy of motion 
of the ejected gases has been increased from one-fiftieth to over a half; 
the propellant being a dense smokeless powder. It is important that the 
velocity of ejection be large, as it enters exponentially in the expression 
for the initial mass necessary to propel a rocket to any given height. 
Regarding the second condition for a great range, namely, the em- 
ployment of a large proportion of weight of propellant to total weight, 
it should be understood that this proportion need not be large for a range 
as low as 10 km. It is necessary to employ the principle of multiple 
charges, as explained in the above Smithsonian publication, if the pro- 
