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The Balloon Launch “Spacecraft” and Environment ACES Presentation T. Gregory Guzik February 20, 2003
Conditions 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)
Views of Balloon Launch Ground Perspective Balloon Perspective
Temperatures During Flight External temperature Minimum of –60o C Internal temperature Minimum of –25o C
PreliminaryBalloon 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 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 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 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 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 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 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.