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.