Long mission tethered aerostat and method of accomplishing

• US 20080265086A1
• Filed: 04/27/2007
• Published: 10/30/2008
• Est. Priority Date: 04/27/2007
• Status: Active Grant

• Current Assignee: Stratocomm Corporation
• Original Assignee: Stratocomm Corporation
• Inventors: Lee, Yee-Chun
• Granted Patent: US 7,708,222 B2
• Time in Patent Office: Days
• US Class Current: 244/30
• CPC Class Codes: B64B 1/50 Captive balloons
• CPC Class Codes: B64B 1/56 stabilised by rotary motion
• CPC Class Codes: B64B 1/62 Controlling gas pressure, heating, cooling, or discharging gas
• CPC Class Codes: D07B 1/12 Ropes or cables with a hollow core

Abstract

Apparatus and method for a continuous replenishing of the lift gas and maintaining the proper pressure and lift of a tethered medium altitude aerostat utilizing a novel feed tube running the entire length of the tether. A first end of the feed tube is connected to the aerostat while a second end is connected through a novel slip ring means to a pressure controlled helium ballast chamber and scrubber on the ground to maintain pressure and lift by a reversible compressing pump. A plurality of pressure and temperature sensors and tension gauges strategically placed inside and around the airship continuously monitor the temperature and pressure changes in the aerostat. A data retrieval and communication unit mounted on the aerostat collects measurement data from the pressure, temperature and tension sensors which is relayed to the ground station and the data is used to regulate lifting gas pressure inside the aerostat.

Claims

1. A lift gas ballast system for a tethered aerostat, comprising;

(a) a tethered aerostat;

(b) a hollow flexible feed-tube embedded inside a tether having a first end connected to said tethered aerostat said hollow flexible feed-tube having a second end;

(c) a double slip ring device secured to said second end of said hollow flexible feed-tube; and

(d) a lift gas ballast tank disposed on the ground and connected to said tethered aerostat through said double slip ring and said hollow feed-tube.

2. The lift gas ballast system of claim 1 wherein the lift gas ballast tank has two or more separate pressurized chambers interconnected by a helium pump or compressor.

3. The lift gas ballast system of claim 2 wherein said pump is computer controlled.

4. The system of claim 2 wherein said pump is bi-directional.

5. The system of claim 1 wherein said aerostat has an array of temperature or pressure sensors.

6. The system of claim 1 wherein said tether has a plurality of embedded optical fibers.

7. The system of claim 6 further comprising a ground control station and wherein a proximal end of said embedded optical fibers is connected to said ground control station.

8. The system of claim 7 wherein said embedded optical fibers have a distal end connected to a temperature or pressure sensor in said aerostat and send data to the ground control station.

9. The system of claim 8 further comprises a ballast tank in said aerostat having a temperature of pressure sensor.

10. The system of claim 9 wherein the ground control station includes one or more ground based computers adapted to processing data received from said temperature or pressure sensor.

11. The system of claim 10 wherein the ground control station includes one or more digital controllers adapted to convert a binary input instruction sent by said one or more ground based computers to control voltages or currents to drive a pump or compressor.

12. The system of claim 1 further comprising a plurality of valve-controlled helium storage bottles and wherein said ballast tank disposed on the ground is connected to said plurality of valve-controlled helium storage bottles.

13. The system of claim 1 further comprising a helium scrubber wherein said lift gas ballast tank disposed on the ground is connected to said helium scrubber to separate air from helium and return purified helium gas back to said lift gas ballast tank.

14. The system of claim 13 wherein said helium scrubber also dehumidifies said lift gas.

15. The system of claim 1 wherein said lift gas ballast tank and said hollow feed tube provide a bidirectional flow of lift gas responsive to diurnal pressure and temperature variation.

16. The system of claim 1 wherein said lift gas ballast tank and said aerostat are filled with helium.

17. The system in claim 1 further comprising a second slip ring device disposed between said first end of said hollow flexible feed tube and said tethered aerostat.

18. A slip ring for accommodating a weathervaning aerostat comprising:

(a) a housing having a first end and a second end;

(b) a first rotatable element disposed in said first end of said housing;

(c) a second rotatable element disposed in said second end of said housing;

(d) a flexible coiled tubing connecting said first rotatable element to said second rotatable element;

(e) an electromagnetic coil to maintain said second rotatable element stationary with respect to said first rotatable element until a predetermined number of revolutions of said first rotatable element is exceeded.

19. The slip ring of claim 18 further comprising a second electromagnetic coil to reduce the rotatability of said first rotatable element.

20. The slip ring of claim 19 wherein said housing is substantially airtight.

21. The slip ring of claim 20 wherein the housing includes a port for recovering a gas leaked inside said housing.

22. The slip ring of claim 20 wherein said first rotatable plate includes a tapered perimeter.

23. The slip ring of claim 18 wherein said second rotatable element is of a frustro conical configuration.

24. The slip ring of claim 23 wherein said housing includes a mating frustro conical opening for said second rotatable element.

25. The slip ring of claim 24 wherein said electromagnetic coil is disposed around the outside of said mating frustro conical opening.

26. The slip ring of claim 18 further comprising a tether with a hollow feed tube and a tethered aerostat with a ground based lift gas ballast tank wherein said slip ring is disposed intermediate said tethered aerostat and said ground based lift gas ballast tank.

27. An airship tether comprising:

(a) a hollow coaxial lift gas feed tube providing a bidirectional flow of a lift gas and having a wall thickness of about 0.1 to 0.40 centimeters;

(b) a fibrous strengthening member surrounding said hollow coaxial lift gas feed tube;

(c) an electrical cable disposed in said fibrous strengthening member; and

(d) at least some optical fiber disposed in said strengthening member.

28. The airship tether of claim 27 wherein said hollow coaxial feed tube has a diameter of about 1.2 to 4.0 centimeters.

29. The airship tether of claim 27 wherein said hollow coaxial feed tube weight is about 15 to 140 grams per meter.

30. The airship tether of claim 27 wherein said strengthening member is selected from a group of strengthening members consisting of Kevlar, Vectran, glass or carbon fibers.

31. The airship tether of claim 27 wherein said electrical cable is a plurality of electrical cables.

32. The airship tether of claim 27 wherein said optical fiber is a plurality of optical fibers.

33. The airship tether of claim 27 wherein said hollow coaxial feed tube is axially divided into two coaxial feed tubes to provide said bidirectional flow.

34. A method of extending the duration of deployment of a tethered aerostat comprising:

(a) employing a ground based lift gas reservoir;

(b) utilizing a hollow lift gas feed tube in a tether connected to said ground based lift gas reservoir;

(c) deploying a tethered aerostat connected to said hollow lift gas feed tube; and

(d) providing a bidirectional flow of lift gas between said tethered aerostat and said ground based lift gas reservoir.

35. The method of claim 34 further comprising the step of utilizing diurnal pressure and temperature variations to assist said step of having a bidirectional flow of lift gas.

36. The method of claim 34 further comprising the step of purifying a lift gas in said ground based lift gas reservoir.

37. The method of claim 34 further comprising the step of replenishing a lift gas in said ground based lift gas reservoir.

38. The method of claim 34 further comprising the step of employing a slip ring between said hollow lift gas feed tube and said tethered aerostat.

39. The method of claim 38 wherein said slip ring is substantially airtight.

40. The method of claim 39 wherein said slip ring is connected to said ground based lift gas reservoir.

41. The method of claim 34 further comprising the step of collecting environmental data from said tethered aerostat.

42. The method of claim 34 further comprising the step of collecting pressure and temperature data from said tethered aerostat.

43. The method of claim 34 further comprising the step of computing lift gas pressure and lift force.

44. The method of claim 43 further comprising the step of comparing lift gas pressure with computed lift gas pressure and lift force.

45. The method of claim 44 further comprising the step of increasing or decreasing lift gas pressure in said ground based lift gas reservoir to change lift gas efficiency in said tethered aerostat.

46. The method of claim 44 wherein said lift gas is helium.

47. The method of claim 34 further comprising the step of scrubbing said lift gas in said ground based lift gas reservoir.

48. The method of claim 34 further comprising the step of dehumidifying said lift gas in said ground based lift gas reservoir.

49. The method of claim 34 further comprising the step of utilizing a bidirectional pump to assist in said bidirectional flow of lift gas between said tethered aerostat and said ground based lift gas reservoir.

50. The method of claim 34 further comprising the step of utilizing a computer to compare the quality of the lift gas in said ground based lift gas reservoir and the lift gas pressure and force in said tethered aerostat as measured by sensors in said tethered aerostat.

51. The method of claim 34 further comprising the step of having electrical cables and optical communications cables embedded in a tether surrounding said hollow lift gas feed tube.

52. The method of claim 51 wherein said lift gas is helium.