DPS throttle range

[Obviousman]

Hi!

On this page:

www.clavius.org/techexhaust.html

You report the DPS as being throttlable between 10% and 94%.

Although your page refers to Apollo 12, both the Apollo 11 Press Kit and Apollo Experience Report: Mission Planning for the LM - Descent and Ascent say it was only throttlable up to about 60%.

Can I get a double check on your figures?

[Czero 101]

Dec 20, 2010 17:39:41 GMT -4 Obviousman said:

Hi!

On this page:

www.clavius.org/techexhaust.html

You report the DPS as being throttlable between 10% and 94%.

Although your page refers to Apollo 12, both the Apollo 11 Press Kit and Apollo Experience Report: Mission Planning for the LM - Descent and Ascent say it was only throttlable up to about 60%.

Can I get a double check on your figures?

Lunar Module Handbook, Volume 1 page 2.1-35 (pdf page 76 "Throttle Control") lists the throttle range as 10% - 92.5%, however, a more detailed explanation on page 2.3-2 (pdf page 253 last paragraph) says the following:

Descent engine throttling is controlled by the LGC or the astronauts. The throttling-range limitations are from minimum thrust (approximately 10% of 10,500 pounds) to approximately 65% and full throttle (approximately 92.5%). The range between 65% and 92.5% is a transient region that cannot be used for extended periods because excessive engine erosion occurs in this zone. Under normal conditions, the engine cannot be operated in the transient region because automatic throttle commands above 65% automatically produce a full throttle output. Only in case of malfunction can inadvertent throttling occur in the transient region, in which case manual correction must be made. Automatic throttle increase and decrease signals from the LGC are sent to an integrating counter in the DECA. The analog output of the DECA controls descent engine thrust. In the automatic mode, the thrust / translation controller assemblies (TTCA's) can be used by the astronauts to increase descent engine throttle (overriding the automatic throttle command); the TTCA cannot be used, however, to decrease the throttle command. (Refer to paragraph 2.3.3.3.1) In the manual throttle mode, the astronauts have complete control over descent engine thrust.

Paragraph 2.3.3.3.1 (pdf page 267) discusses the relationship between TTCA inputs and LGC throttle command outputs in the Automatic mode, the transition to Manual mode, and CMD THRUST (desired Commanded Thrust) and ENG THRUST (actual Engine Thrust) readouts.




Cz

[Obviousman]

Thanks for that.

I'm wondering if it might need a little revision then, stating the normal throttle range and the contingency throttle range?

[Czero 101]

Its not incorrect to say that the DPS was throttlable from 10% to 94%, just a little inaccurate, so perhaps a slight revision might be in order. I don't think its of very high priority, though.

Of course, it is still Jay's decision.




Cz