Of course, nothing in life ever comes for free! In order to obtain the required lift, we have to pay a price in drag. In this lecture, Prof. Hoekstra will explain how much drag an aircraft experiences, and how we can counteract it with our propulsion system.

That’s it! You’ve just covered all the essentials of flying! Already, we’ve found some possibilities for improving the sustainability:

• We can use longer, more slender wings decrease the drag.
• We can use thicker wings with more optimized profiles to decrease the drag
• Larger engines are more efficient, producing more thrust for the same amount of fuel.

However, note of course that longer wings, thicker wings, or larger engines, might be significantly heavier. As we’ve seen in the first lecture of this week, this higher weight means we require more lift, and, as you’ve just seen, this also results in more drag, thus potentially cancelling out the gains! One of the major challenges of aerospace engineering in this regard is balancing and optimizing these effects. In the next lecture, we will start exploring how this optimization can be done.