The Balloon Launch The Balloon Launch “Spacecraft” and Environment“Spacecraft” and Environment
ACES Presentation
T. Gregory Guzik
February 20, 2003
Conditions During FlightConditions During Flight
Flight lasts 2 to 3 hours Max altitude 80 kft to 110 kft Max range (20 miles to infinity)
– Try to keep within ~40 miles range Gets cold at the tropopause (~ -60o C) Any water vapor will condense out and cause frost Good vacuum ( < 0.02 atmosphere) Landing can be rough (shock, trees, rocks, dragging) High velocity during initial descent (~500 mph)
Cartoon of BalloonSat TrainCartoon of BalloonSat Train
Typical Flight ProfileTypical Flight Profile
Views of Balloon LaunchViews of Balloon Launch
Ground Perspective Balloon Perspective
Balloon Burst at ~100,000 ftBalloon Burst at ~100,000 ft
Payload is Returned Safely to Payload is Returned Safely to the Ground by Parachutethe Ground by Parachute
Temperatures During FlightTemperatures During Flight
External temperature
Minimum of –60o C
Internal temperature
Minimum of –25o C
PreliminaryPreliminaryBalloon LayoutBalloon Layout
FAA rules – Low density– Single box < 2.7 kg– Total payload < 5.4 kg
Weight estimate– Parachute 300 g– Primary beacon 734 g– Backup beacon 515 g– Cabling 122 g– Contingency 250 g– Payloads 3520 g
Weight Trade OffsWeight Trade Offs
Note that 3520 g / 5 = 704 g Could support up to three payloads of 1 kg each
per flight Last two payloads require second flight
– Require recovery of first flight– Require two consecutive launch days
Trade “weight coupons” between payloads– i.e. Limit all 5 payloads to 3500 g
Limit each payload to 700 g
Option A: Central TelemetryOption A: Central Telemetry Spacecraft controls telemetry by signaling each
payload in turn when it is time to transmit Payload would return a predefined format packet
to the primary beacon over RS232 bus– T#ddd,ddd,ddd,ddd,ddd,ddd,bbbbbbbb,string
Option A: Trade OffsOption A: Trade Offs
Extra weight in spacecraft systems– Reduced weight limit on all payloads
Extra cost to develop this spacecraft service– Allocate $75 of payload budget to pay for this service
Slightly increased software complexity Significantly increased interface complexity No need to store everything on-board or do own
telemetry system
Option B: Store OnboardOption B: Store Onboard No cost hit, minimize weight constraint, no interface
issues Store in EERAM
– No addition components needed– Lifetime of EERAM limited– Major problems if the code is wrong
Store in auxiliary memory chip– Avoid EERAM problems– Significantly increased storage– Increased software complexity
Payload recovery required
Option C: Payload TelemetryOption C: Payload Telemetry
Would need to use 5 W HAM radio– 0.5 W FRS radio insufficient for balloons– Would need two radios at $300 each
Increased payload weight– ~170 g for radio, 150 – 200 g for extra battery
Would need ground station– Spacecraft ground station channels are used by
beacons
Charge to IWGCharge to IWG
Meet now in room 331 for 30 to 45 minutes and bring back decisions on the following issues.
How to handle the payload weight issue.How to handle to data storage / telemetry
issue.