80's Novel that has long-lived people and gyroscopes

Question

Back in the early 80's I read a novel and remember two scenes. The scenes were related, as I recall.

• The first scene had the protagonist looking at his friend, who proved to be an antagonist, standing in the doorway of his rocket (which had fins, landing fins). One fin had been shot off and the rocket continued to stand due to the gyroscope, which whined as it spun up, trying to keep the rocket upright. Eventually the gyroscope blew apart, killing the antagonist.

• The second scene had the protagonist speaking with a woman, who proved to be the now-dead antagonist's mother. She dropped her pretense, allowing the protagonist to see her for who she really was. Being wealthy, she had paid for whatever Clarkean magic allowed for incredibly long life-spans. Though looking like she aged no more than 35-45, she had a look on her face due to all the accumulated knowledge and experience that gave away her condition. The protagonist's response to this moment was, "you're old." Said in surprise or awe.

Answer 1

This is not a novel, but the Larry Niven short story "Grendel".

The Drunkard's Walk stood on two legs, wildly unbalanced, like a ballet dancer halfway through a leap. Only her spinning gyros held her monstrous mass against gravity.

....

Right then, the rest of it fell into place. "You're old."

Answer 2

This sounds like the story Grendel from Larry Niven's Neutron star collection where Beowulf Shaeffer is investigating an abduction of an alien sculptor. Shaeffer gets into a conflict with the kidnapper and the fight results in the following:

The impact has damaged the yacht's landing gear and it is being held upright only by its gyroscopes. Bellamy rushes back aboard to try to deal with this, but the gyros overload and seize up while he is still on the boarding ladder, causing the yacht to spin end-for-end and bounce off into the distance. Bellamy is thrown high into the air and to his death.

There is a character in the story, Margo, who admits to being the kidnappers mother.

Worth a read, as is all Niven's work.