An Plaorm vs A Tethered Plaorm for Science Applicaons

Robert Fesen Dartmouth Advantages of a Plaorm

A high altude balloon plaorm that is tethered to the ground doesn’t have some of the mass associated with an airship’s power and recovery systems.

‐ no propulsion motors ‐ no propellers ‐ no large solar panels to power the motors ‐ no baeries needed to power propulsion at nighme

‐ maybe no parachute (?) ‐ maybe no balonet and associated mechanisms (?) A Comparison of High Altude Plaorms for Science Applicaons

Item Airship Tethered Balloon Altude Range < 75 k 65 k +

Payload mass ~ 40 kg > 100 kg ? (Hale‐D, HiSennel80)

StaonKeeping only if winds < 10 m/s its tethered

Cost $35M for HALE‐D unknown, probably less

Duraon days to weeks? days to weeks ? A hybrid tether idea is the “StarLight” high altude plaorm under development by Global Near Space Systems Inc (GNSS). It consists of a slightly aerodynamic balloon which is aached to a solar powered propulsion unit hung below. Starlight with narrow‐wing, and with wide‐chord, light‐ high‐speed configuraon… gathering configuraon This arrangement solves several problems associated with the mul‐ balloon tethered to the ground approach.

• No winch needed • No aviaon hazard issues associated with a grounded tether line • Avoids most issues regarding stormy weather • Tether wind loading is modest since tether altudes > 65 k • Simpler deployment process with fewer elements

Separang the propulsion unit & PV panels from the balloon: ‐ propulsion propellers located in denser air and in lower winds ‐ propulsion unit could act like an “anchor” to the balloon ‐ PV panels competely unblocked by the balloon

I’ve run some calculaons and in the next slides I show the results.

65,000 : Spherical Balloon Drag Force @ C = 0.50 5 km/s 10 km/s 20 m/s 54 millibars D 66 k D = 20 m 3 170 N 680N 2700 N 0.086 kg/m Disp:115 kg

C = 0.5 Mission D 65 k 56 millibars D = 1.0 m 0.091kg/m3 payload 1 N 3.6 N 14 N L = 1.0 m

3 k (1 km) 3 mm tether CD = 0.5 2 N 6 N 26 N 6.8 kg wt L = 1 km MBS = 1500 kg

CD = 0.10 0.1 N 0.4 N 1.5 N 64 k 59 millibars D = 0.5 m Propulsion 0.095 kg/m3 L = 2.5 m 65,000 : Aerodynamic Balloon Drag Force @ C = 0.10 5 km/s 10 km/s 20 m/s 54 millibars D 66 k D = 7 m 3 4 N 17 N 66 N 0.086 kg/m L = 30 m Disp: 100 kg

C = 0.5 Mission D 65 k 56 millibars D = 1.0 m 0.091kg/m3 payload 1 N 3.6 N 14 N L = 1.0 m

3 k (1 km) 1.4 mm tether CD = 0.5 1 N 3 N 13 N 1.1 kg wt L = 1 km MBS = 200 kg

CD = 0.10 0.1 N 0.4 N 1.5 N 64 k 59 millibars D = 0.5 m Propulsion 0.095 kg/m3 L = 2.5 m vehicle 65,000 : Best Aerodynamic Shapes Drag Force @ C = 0.05 5 km/s 10 km/s 20 m/s 66 k 54 millibars D D = 7 m 0.086 kg/m3 2 N 9 N 33 N L = 30 m Disp: 100 kg

C = 0.35 56 millibars Mission D 65 k D = 1.0 m 0.091kg/m3 payload 0.8 N 3 N 9N L = 1.0 m

3 k (1 km) 1.4 mm tether CD = 0.5 1 N 3 N 13 N 1.1 kg wt L = 1 km MBS = 200 kg

C = 0.05 64 k D 0.05 N 0.2 N 0.8 N 59 millibars D = 0.5 m Propulsion 0.095 kg/m3 L = 2.5 m vehicle 90,000 : Spherical Balloon Drag Force @ C = 0.50 5 km/s 10 km/s 20 m/s 17 millibars D 91 k D = 40 m 0.027 kg/m3 210 N 850 N 3400 N Disp:285 kg

C = 0.5 Mission D 90 k 18 millibars D = 2 m 0.028 kg/m3 payload 0.5 N 2.0 N 8 N L = 5 m

25 k (7.5 km) 1.7 mm tether CD = 0.5 4 N 16 N 64N 13 kg wt L = 10 km @ 0.05 kg/m3 MBS = 300 kg

65 k 56 millibars C = 0.10 Propulsion D 0.091 kg/m3 D = 0.5 m vehicle 0.1 N 0.4 N 1.5 N L = 2.5 m 90,000 : Aerodynamic Balloon Drag Force @ C = 0.10 5 km/s 10 km/s 20 m/s 17 millibars D 91 k D = 15 m 3 6 N 24 N 95 N 0.027 kg/m L = 60 m Disp:285 kg

18 millibars C = 0.5 Mission D 90 k 0.028 kg/m3 D = 2 m payload 0.5 N 2 N 8 N L = 5 m

25 k (7.5 km) 1.7 mm tether CD = 0.5 4 N 16 N 64 N 13 kg wt L = 7.5 km @ 0.05 kg/m3 MBS = 300 kg

65 k 56 millibars C = 0.10 Propulsion D 0.091 kg/m3 D = 0.5 m vehicle 0.1 N 0.4 N 1.5 N L = 2.5 m 90,000 : Best Aerodynamic Shapes Drag Force @ C = 0.05 5 km/s 10 km/s 20 m/s 17 millibars D 91 k D = 15 m 3 3 N 12 N 50 N 0.027 kg/m L = 60 m Disp:285 kg

18 millibars C = 0.35 Mission D 90 k 0.028 kg/m3 D = 2 m payload 0.2 N 0.8 N 1.6 N L = 5 m

25 k (7.5 km) 1.7 mm tether CD = 0.5 4 N 16 N 64 N 13 kg wt L = 7.5 km @ 0.05 kg/m3 MBS = 300 kg

65 k 56 millibars C = 0.05 Propulsion D 0.091 kg/m3 D = 0.5 m vehicle 005 N 0.2 N 0.8 N L = 2.5 m Airship

The top balloon might have a size like HiSennel80 but without the propulsion motor, parachute, and heavy baery packs.

HISennel80: 60 m long, 15 m wide Payload mass 40 kg Solid mass = 500 kg mass = 100 kg Drop Ballast ~ 20 kg