It is a really interesting question because you can answer it from different points of view according to traditional or non-traditional grammar, but first let me start by saying that the structure of the sentence may not be correct because the word substantial could be in a different place.
Now let's remember the definition of an adjectival phrase: An adjective phrase is a phrase which contains an adjective that acts as a modifier and it may also contain words before or after it which could be complements and help in the sense or structure.
Now, based on this, the correct answer would be savings because it is modifying and giving sense to NASA, even though it is not right next to the word, it is the main piece in the sentence.
