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Re: Space rockets that are used to launch satellites into orbit protect [#permalink]
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Since this question was bumped up and caught my eye, I thought I would take the time to share my thoughts, in hopes that someone else may find them useful.

Raxit85 wrote:
Space rockets that are used to launch satellites into orbit protect their engine components from violent turbulence and G forces by encasing them in hard metals. The most common metal used for this purpose is Titanium; yet, even with its tensile strength of nearly 100,000 psi, engine components can still be damaged during missions. Tungsten Carbide, a synthetic metal, is four times harder than Titanium and considerably more resistant to G forces and heat. Therefore, to better protect rocket engines, engineers should use Tungsten Carbide for engine encasing instead of Titanium.

Which of the following, if true, best supports the conclusion of the above argument?


To support the conclusion, it is necessary to understand that conclusion and follow the linear logic of the passage. The conclusion is easy to spot here, since we have a conclusion-trigger in the transition therefore. What is that conclusion? Engineers should use Tungsten Carbide for engine encasing instead of Titanium so that rocket engines are better protected. There are a few premises brought up in the passage by way of comparisons between Titanium and Tungsten Carbide:

(1) Tungsten Carbide is four times harder than Titanium
(2) Tungsten Carbide is considerably more resistant to G forces and heat than Titanium

Such comparisons would be irrelevant if not applicable to the background information provided earlier in the passage. But those bases are covered in the first sentence. Space rockets protect engine components from violent turbulence and G forces, so (2) above is pertinent, and this protection comes about by encasing [the engine components] in hard metals, so (1) above is also pertinent. With these premises in mind, we need to find an answer that speaks to the conclusion from earlier.

Raxit85 wrote:
A. Tungsten Carbide can also be used to add ballistic protection to astronaut space suits.

Analysis: Great. Tungsten Carbide has yet another use, and the keyword protection is on display, but then we get the bit about space suits. As awful as it may sound, we are not concerned with protecting astronauts, but with protecting vital engine components. This answer falls outside the scope of the conclusion. Red light.

Raxit85 wrote:
B. The increased weight associated with the shift to Tungsten Carbide encasing would create stability and maneuverability problems for most rockets.

Analysis: We do not want problems associated with Tungsten Carbide. In fact, we are looking for quite the opposite, to support a conclusion that calls for a switch from Titanium to Tungsten Carbide. Get rid of this reversal. Red light.

Raxit85 wrote:
C. Tungsten Carbide is a material commonly used for robots involved in commercial manufacturing.

Analysis: Again, this is of marginal interest, but whether Tungsten Carbide is or is not currently being used in any sort of capacity is irrelevant to the conclusion. The conclusion is concerned with protecting engine components, not with how practical a switch to Tungsten Carbide may be. Red light.

Raxit85 wrote:
D. Most scientists believe that Tungsten Carbide is just as scratch-resistant as Titanium.

Analysis: This answer falls into the same camp as (A). You almost feel as if a Tungsten Carbide salesman is giving you his pitch: "But wait, there's more!" Notice that scratch-resistance is not mentioned in the conclusion, nor is it mentioned anywhere else in the passage. This distraction is for the test-taker who picks up on the word resistant and runs amok with it. Red light.

Raxit85 wrote:
E. Tungsten Carbide offers better protection from turbulence and high velocity impacts and has a tensile strength well over 100,000 psi.

Analysis: Sometimes I get a little nervous upon eliminating the first four choices, hoping that that last answer just leaps off the screen at me. (The red-yellow-green-light method I use helps me avoid running back through all the answers if such a last choice fails to get the green light.) In this case, my concerns were allayed the moment I laid eyes on this option. The keyword protection is back, only this time it correctly ties into turbulence from line 1 of the passage and tensile strength from the second line of the passage. If Tungsten Carbide offers better protection for whatever it is encasing from both turbulence and impacts, then it is easy enough to see how this new information would support the conclusion drawn. Green light.

I hope that helps the community.

- Andrew
GMAT Club Bot
Re: Space rockets that are used to launch satellites into orbit protect [#permalink]
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