# How high can a sounding rocket launch and for how long time can it put a payload in freefall microgravity?

Sounding rockets or suborbital launches basically go straight up and then fall down without entering orbit. That requires much less fuel mass than to achieve 8,000 m/s or so orbital velocity.

• For how long could such a launch put a payload in freefall microgravity (which could be of interest to science, manufacturing, tourism)? I suppose that there won't be much microgravity once atmospheric braking sets in below 100 km altitude or so.
• How would today's most powerful launcher, Delta IV Heavy, perform as a sounding rocket in terms of altitude and payload time in freefall? Or a Saturn V? The EFT-1 with Orion on a DIVH lasted for over 4 hours, but was actually designed to accelerate the payload down through Earth's atmosphere.

If I launch a rocket straight upwards with the same $\Delta v$ as required for a circular orbit, my free-fall time is $\frac{\pi +2}{2\pi}$ times the orbital period of the circular orbit.
Does the atmosphere actually matter? At $8 km/s$ the last 100 km is only a loss of thirteen seconds, negligible compared to the total flight time. Of course the $\Delta v$ lost at ascent is significant, but a rocket launched to orbit also experiences that drag. Thus, the longest meaningful free-fall time a suborbital launch can give you is a little more than an hour.
As for what payloads modern rockets can set into this trajectory, the $\Delta v$ required for the longest meaningful free-fall time is the same as for a launch into orbit. Simply use their payload capacity into LEO. As for a minimal sub-orbital launch, about $1.4 km/s$ of $\Delta v$ is required. For such low requirements, the launcher's thrust to weight ratio is the limit.