2949775333

Comparison ofLiąuid Pr opel lani Rocket Engine Feed Systems - 1 - 18

Table 6: Proposed batteries technologies data.
Batteiy type	Power Density [W/kBl	Energy Density rwh/kal	Celi Nominał Voltage [VI	References
Li-Ion	3000	100- 180	3.6	[81[10][11|
Li-Po	6000	130	3.7	[6]
Li-S	670	350	2.15	_[TL
Li-S (under development)	2000	220	2.15	_[2L

The values presented for the first three cases are estimations madę over currently marketed products. Worth to mention that the battery developments are continously evolving and the tabulated values can be enhanced in short term. The fourth case presented is a good example of this, which is an improvement on the Lithim-Sulfur technology. It is actually in development but it could be available as a commercial product in short term.

Finally, is necessary to foresee a batteiy sizing margin. In this case, it is assumed that a margin in the batteiy' mass of 20% will be adeąuate. Hence:

\k_b =1.2

IV. RESULTS

Next, the results of the calculations are presented. Such calculations were done with the data estimated in the previous section. The curves parameters are shown with legends in each graphic. An important remark valid for all the following sections is that (unless otherwise specified) the electric systems are powered by Li-Po batteries.

4.1. Comparison with the work done in [3]

In this firt estimation the same original work data are used. For morę detail, below are listed all those parameters which were changed respect to the ones firom the previous section:

| pc = 30 Bar \		1OIF	=1.641
\Yc -1-2251	K =22% |		Apin =0.8 * pc
|a,i =l-8*Pc|	\p,p2 — 0.3 * /7C|		* co o II
|*« = 2.4|	l*„2=^125l		=1.2S|

Also, it is mentioned that, for the electric feed system, Li-Po batteries are adopted. It is interesting, also, to tracę a curve that was not included in the original work, to analyze what happens if the propellants mass is taken as calculation parameter. The results obtained are shown below: