Aerospace balloon system, parachute, and method of operation

1. A method for balloon system operation, comprising, at a balloon system comprising a balloon, a payload, and a parachute module:

at the balloon, maintaining the balloon system in flight, comprising exerting upward force on the payload via a tether that mechanically connects the balloon to the payload, wherein, while the balloon exerts upward force on the payload:

a lighter-than-air fluid is contained within the balloon;

at a first time, the parachute module is in a stowed configuration; and

the tether extends through an aperture defined in a canopy of the parachute module, such that the canopy encircles the tether at a point along the tether arranged between the balloon and the payload;

after the first time, while the balloon system is in flight, deploying the parachute module such that the canopy is substantially open; and

after deploying the parachute module, while the balloon system is in flight and the canopy is substantially open, at the canopy, exerting upward force on the payload via a set of suspension lines of the parachute module, wherein the set of suspension lines mechanically connects the payload to the canopy.

2. The method of claim 1 , wherein, in the stowed configuration, the parachute module extends substantially along the tether.

3. The system of claim 1 , wherein, in the stowed configuration, the suspension lines of the set are substantially slack.

4. The method of claim 1 , wherein, at a second time after the first time, while the canopy exerts upward force on the payload, the balloon is not mechanically connected to the payload.

5. The method of claim 4 , wherein:

while the parachute module is in the stowed configuration, the canopy is substantially contained within a sleeve mechanically connected to the balloon; and

the method further comprises, at a third time between the first and second times, mechanically disconnecting the balloon from the payload, wherein, in response to mechanically disconnecting the balloon from the payload, the balloon exerts a force on the sleeve, thereby releasing the canopy from the sleeve.

6. The method of claim 1 , wherein, at a second time after the first time, while the canopy exerts upward force on the payload, the balloon is mechanically connected to the payload by the tether and the lighter-than-air fluid is contained within the balloon.

7. The method of claim 6 , wherein, while the canopy exerts upward force on the payload, the payload is suspended from the balloon by the tether and not by the parachute module.

8. The method of claim 6 , further comprising, after the second time, while the canopy exerts upward force on the payload, mechanically separating the balloon from the payload such that the balloon does not exert upward force on the payload.

9. The method of claim 1 , wherein the aperture is a parachute vent.

10. The method of claim 9 , wherein the parachute module is a pull-down apex parachute module.

11. The method of claim 9 , wherein the parachute module is a toroidal parachute module.

12. The method of claim 1 , wherein:

while the parachute module is in the stowed configuration, the canopy is substantially contained within a sleeve mechanically connected to the balloon; and

deploying the parachute module comprises releasing the canopy from the sleeve.

13. The method of claim 12 , wherein:

while the parachute module is in the stowed configuration, the sleeve is wrapped around the tether and the parachute module, substantially about a long axis of the tether directed from the balloon to the payload; and

releasing the canopy from the sleeve comprises controlling the sleeve to unwrap.

14. The method of claim 12 , wherein:

the balloon system further comprises a drogue;

while the balloon exerts the first upward force on the payload and the parachute module is in the stowed configuration:

the drogue is mechanically connected to the sleeve; and

the drogue mechanically connects the balloon to the tether such that the drogue is held in tension between the balloon and the tether; and

releasing the canopy from the sleeve comprises mechanically separating the balloon from the tether, thereby releasing tension from the drogue such that the drogue opens.

15. A method for balloon system operation, the method comprising operating a balloon system in descending flight, the balloon system comprising a balloon and a payload, wherein operating the balloon system in descending flight comprises:

at the balloon, while a lighter-than-air fluid is contained within the balloon, exerting a first upward force on the payload via a tether that mechanically connects the balloon to the payload; and

while the balloon exerts the first upward force on the payload, at a parachute canopy encircling the tether between the balloon and the payload, exerting a second upward force on the payload via a set of suspension lines that mechanically connect the payload to the parachute canopy;

wherein the payload is not suspended from the balloon by the set of suspension lines.

16. The method of claim 15 , wherein the tether comprises a ladder configured to resist torsion.

17. The method of claim 15 , wherein operating the balloon system in descending flight further comprises, after the balloon exerts the first upward force on the payload and while the parachute canopy is mechanically connected to the payload via the set of suspension lines: mechanically separating the balloon from the payload.

18. The method of claim 15 , wherein, while the balloon exerts the first upward force on the payload, the tether extends from the payload, through a vent defined in the parachute canopy, to the balloon.

19. The method of claim 18 , wherein the parachute canopy and the set of suspension lines cooperatively define a pull-down apex parachute.

20. The method of claim 15 , wherein, while the balloon is mechanically connected to and exerting upward force on the payload via the tether, before the parachute canopy exerts the second upward force on the payload:

at a first time, the parachute canopy is maintained in a stowed configuration by a sleeve; and

operating the balloon system in descending flight further comprises, after the first time, deploying the parachute canopy by controlling the sleeve to release the parachute canopy.

21. The method of claim 20 , wherein:

at the first time, the sleeve is wrapped around the tether and the parachute canopy; and

controlling the sleeve to release the parachute canopy comprises controlling the sleeve to unwrap.