Pegasus II – Balloon Parameters

A few calculations made on the flight of Pegasus II.  We target an ascent rate of 5 m/s, then work out the remaining calculations.  It is always a trade off between max altitude, mass of payload, ascent rate, and balloon size.  We must be careful to avoid a floater (neutral buoyancy) and ensuring the tethering is has enough tension, i.e., > 500 grams of residual lift.  We don’t measure the volume of Helium, rather the Neck Lift as the balloon fills.

Balloon Size 2000 grams
Mass of Payload 3950 grams (8 lbf, 11 oz)
Target Altitude 30480 meters
Launch Altitude 192 meters
Burst Diameter 10.67 meters (35 ft)
Target Ascent Rate 5 meters/sec
Helium Volume 7.4 cubic meters, 260 cubic feet
Launch Diameter 2.4178 meters (7.93 ft)
Free Lift 7745 grams
Neck Lift 5745 grams
Residual Lift 1795 grams
Burst Altitude 32233 meters

How far can Pegasus II see?

How far an Pegasus II see from the apex of the flight?

That question is complicated by the atmospheric conditions at the time.  Light refraction comes into play because the denser layers of the atmosphere, closer to the surface, bend light and extend the visible distance.  There are a host of factors that come into play at the point in time the observation is made, either extending or reducing the theoretical limit due to refraction.  Most of the time it will reduce it.  A calculation without using refraction produces a smaller visible range, a range likely to be exceeded by an unknown amount.

The apex of Pegasus II’s flight ~111K feet, should have enabled us to view some or part of 40% of the number of states in the United States and some of Canada.  Not a bad stat.


Pegasus II – Stats and Pictures

Thank you all for participating in the flight of Pegasus II, you have been the most gracious and patient audience and it is has been our greatest pleasure to present this historic trip to near space to you.  The mission team made a little history by broadcasting to you real-time telemetry from a UAV over 110,000 feet above the surface in the earth to users around the world.  Additionally, we received user messages for the craft from around the world using the mobile apps.  Messages from India, Norway, France, USA, Martinique, New Zealand, Argentina, Belgium, Germany, and Australia were greatly welcome to make the event truly global in nature.

Below are some stats from the flight and a few pictures.  More pictures and video to follow this and week.

With a tear in my eye, we thank you again for giving true meaning to this now not-so-impossible adventure in experiential STEM research.

 Flight Time  2 hours, 8 min, 53 secs
Ascent Time 1 hours, 41 min, 50 secs
Ascent Rate 18 ft/sec, 5.49 m/s
Descent Time 27 min, 3 secs
Descent Rate 67.8 ft/sec, 20.7 m/s
Max Altitude  110,703 feet or 33,750 meters
Min Air Pressure  6.7 mB or 0.65% atm
Max Radiation  23 #/sec
Max UV Rays 3.6 at 98,807 feet
# Users during Flight Time  1,863
% Mobile Users  42%
Total Field Gateway Messages Sent 16,576
# Ground Telemetry Messages 9,706
Total App Messages Received ~ 31,000,000

Recovery Map – Purple indicates point of touchdown.  Other 2 points indicate last GPS location by launch and mobile stations, respectively.


Deformed Balloon due to high wind prior to launch


1 min after launch from the down camera


The Edge of Space near the apex of flight


Balloon Burst in 1/100 second increments from 110,703 feet altitude



Pegasus II – Complete

Brief 43 sec video clip of the flight.

More details for follow:

Launch Time   12:24:58 CDT
Apex Time   14:05:44 CDT
Ascent Time   6,046 secs or 100.76667 min
Launch Altitude   731 ft
Launch Pressure   1000.1 mB
Apex Altitude   110,703 ft
Apex Pressure   6.7 mB
Ascent Rate   18.19 fps or 5.45 m/s
# RT-messages sent   16,576
# Discrete Data Points   301,608
# Users watching   1,863
% Users with Mobile App   42%

Final Checks Complete – GO FOR LAUNCH

The final checks are completed and Pegasus II is GO FOR LAUNCH tomorrow Apr 13, 2016 at 12pm.  Join us for a trip to near space.

Share the event on Facebook and help us promote the flight.


  • Receive text messages it Pegasus II reaches flight milestones.
  • View telemetry in real-time.
  • View live video from Pegasus II’s eye-in-the-sky.
  • Send messages to the craft via our mobile apps and be recorded in the flight record.



Text Message Flight Notifications:
Twitter: @PegasusMission
Web site:
Blog: Facebook:
Mobile Apps: Search for “Pegasus Mission” in your app store

A Users Guide to Pegasus II

Pegasus II is an experiment in real-time “Internet of Things” technologies from the edge of space.   The experiment uses a High Altitude Balloon (HAB) as a delivery system to carry a payload crammed with sensors, video, and radios into the remote and hostile region of the upper atmosphere known as near space.  The ascent of the flight will terminate at 100,000 feet above the surface of the earth. The experiment allows users to participate in the flight in several ways.

We are scheduled for launch on Wednesday April 13th at 12pm CDT.

(1) View telemetry from the craft in only milliseconds from when the measurement is taken from anywhere in the world.

(2) Watch a live video broadcast of the flight and launch. Note: Flight video is highly experimental.  We will learn much from this flight in terms of live video performance from remote UAVs.

(3) Communicate with the craft during flight by sending messages to the craft. These messages get recorded into the video record of the flight.

(4) Receive SMS text messages on your phone as Pegasus II makes flight milestones.

(5) View a live map that updates the positions of the chase vehicle and Pegasus II as it flies.

There are 2 ways to include yourself in the experiment, Web and phone.

Best Experience

  • Go to the Web site and sign up for flight notifications.  These will allow Pegasus II to text your phone when it launches and you will no miss the flight regardless of whether you are using the Web site or mobile apps.
  • Follow us on Twitter @PegasusMission.  This will keep you informed on any flight delays and alert you of time-to-launch.

Web Site

  • Watch the live launch and flight video.
  • Watch live telemetry and mapping during the flight.

Mobile Apps

  • Download and install the mobile app by searching your app store for “Pegasus Mission”.  If you have already installed the app, we suggest that you uninstall and reinstall the app to help us ensure consistency.
  •  Connect to WiFi if possible.  This will help keep the connections “hot” and reduce dropped connections.  Reconnections can be slow if the signal is not strong.
  • Watch live telemetry and mapping
  • Send us a user message.  We love getting “Hello from <location>” from the users around the world.
















Pegasus II – Flight Forecast

Current forecast for Pegasus II.  72.8K (52.3 miles) range.  Sunny and 56 F, should be good for video.  Launch time 12pm (noon) CDT.  We really like those user messages from the mobile apps where you give us location, e.g., “Hello from Norway” or “Hello from North Carolina” as they get recorded into the flight record.

You can download mobile apps from your app stores by searching for Pegasus Mission.

Sign up for SMS text flight notifications at and we will text your phone  when we launch and make flight milestones.

Web site for live telemetry and video