# NASA's Mars helicopter blade & weight

I've been really interested in NASA's Mars helicopter and have been reading bits of articles on that recently. But I have a few questions I hope people can help me understand — in this article, it says that the helicopter blades had to be more rigid than those on Earth, but it doesn't really provide an explanation why.

Also, I remember reading here that the weight of the helicopter has to be really light on Mars...

The reduced gravity on Mars (about 38 percent of Earth's gravity) will help JPL pack a few more components onto the Mars Helicopter. But even so, the entire vehicle must weigh less than 1.8 kilograms (4 lbs).

Why is this so? How does the reduced gravity allow them to pack more weight but why does it still need to weigh so little?

• The extremely low air density makes it hard to generate much lift. – Organic Marble Oct 16 '18 at 3:32
• Here is a search on this site for things with the mars tag and contain the word "helicopter", you may find some of these interesting and/or helpful: space.stackexchange.com/search?q=%5Bmars%5D+helicopter – uhoh Oct 16 '18 at 12:56
• The explanation is there within that article, just read carefully 1. and 2. – Uwe Oct 16 '18 at 17:57

What is different for a helicopter on Mars compared to Earth?

There is less gravity, but there is also much less atmosphere.

The reduced gravity is good for a helicopter, but the thin atmosphere is very bad.

To produce enough lift force, the rotor of the helicopter has to move much more volume with more speed. A very large and fast rotating rotor is needed. But thee centrifugal forces to the blades increase with diameter as well as speed.

The blades should be very strong but lightweight.

The record for the highest takeoff for a helicopter from Earth is 8,848 m (Everest), but the pressure there is still much higher than that of Mars.

• Got a link for that record take-off? I find this link: en.wikipedia.org/wiki/Flight_altitude_record#Rotorcraft (which isn't the record take-off, but the record height before a flame-out 12,440 m). – Magic Octopus Urn Oct 17 '18 at 21:11
• @MagicOctopusUrn helicopter takeoff record info here en.wikipedia.org/wiki/Didier_Delsalle – Organic Marble Oct 25 '18 at 0:27
• @Uwe I’m just a little confused though bc my physics teacher always says centrifugal force is not a force...? – jjhh Oct 26 '18 at 9:52
• @jjhh: Your physics teacher should do a ride at the 20 G centrifuge. After experiencing about 10 G for some minutes he should explain why he could not lift an arm or leg. – Uwe Oct 26 '18 at 10:05
• @Uwe — so is he wrong...? – jjhh Oct 26 '18 at 15:40