# What is the terminal velocity on Mars?

How would I calculate the terminal velocity of Mars?

What is the terminal velocity of a balloon entering Mars' atmosphere?

Would a balloon pop if dropped from space?

• The atmospheric pressure of Mars is about 0.636 kPa, that is 0.63 % of atmospheric pressure on Earth. At a height of about 35 km, the pressure is the same at Mars ground. We should be able to build a glider for 35 km height first. – Uwe Sep 23 '18 at 15:17
• Felix Baumgartner exceeded sound speed in his jump from 39 km height. So the terminal velocity at Mars surface should be supersonic too. – Heopps Sep 23 '18 at 16:26
• Terminal velocity applies to falling objects. Is this balloon falling? – Organic Marble Sep 23 '18 at 17:26
• @OrganicMarble If just "dropped" it would have this nasa.gov/larc/expert-panel-assesses-inflatable-spacecraft-tech on the bottom of the bottom possibly a streamer to keep it down right once terminal velocity has be reached and cooled to temp expand the balloon to a buoyant size. The balloon would fit inside this vacuum. ichef.bbci.co.uk/wwfeatures/wm/live/1280_640/images/live/p0/1t/… – Muze Sep 23 '18 at 18:00
• @uhoh updated question – Muze Sep 25 '18 at 19:32

$$V_t = \sqrt\frac{2W}{\rho C_d A}$$

where

$$V_t$$ = terminal velocity
$$W$$ = weight (mass times local gravity)
$$C_d$$ = the coefficient of drag of the object
$$\rho$$ = atmospheric density
$$A$$ = frontal area of the object

Comparing Mars to Earth, weight is $$\approx 0.38$$ and atmospheric density is $$\approx 0.0167$$ that of Earth, so terminal velocity is $$\sqrt{23} = 4.8$$ times faster on Mars. (Assuming $$C_d$$ doesn't change, which it would, but this is close.)

• A reasonable choice for Cd assuming a spherical blimpish structure would be 0.5, otherwise there are various tables a search engine will find. Strange things happen to Cd above mach 1 but this will at least get an approximation. – GremlinWranger Sep 23 '18 at 23:12