Roy_H: tethered BA330s around a non-rotating hub (2014)

The thread's opening proposal (16 Feb 2014).

Design summary

• Layout. Two pairs of Bigelow BA330 modules hang on cables around a non-rotating hub. The hub holds power and docking. Roy_H, 2014-02-16
• One pair is a farm and the other is living quarters. The farm supplies food and O₂ and takes back CO₂ Roy_H, 2014-02-16.
• Spin. 2 rpm on 223 m cables, or 1 rpm on 890 m cables, for 1 g Roy_H, 2014-02-16.
• Hub coupling. A magnetic-levitation ring with no physical contact, and inductive power transfer Roy_H, 2014-02-16.
• Elevators. Two Sundancer-based elevators run together for balance. Robotic arms pluck them off the cables, and there is a spare. Transit takes 1–3 min Roy_H, 2014-02-20.
• Balance. Counterweights on the cables for fine balance, plus liquid pumped between tanks Roy_H, 2014-02-19. Oil ballast tanks in each module, with ~1 m off-centre tolerance Roy_H, 2014-03-16.
• Floors. Floor sag in a BA330 is 5.6 cm at 223 m radius and 1.4 cm at 890 m Roy_H, 2014-02-19.
• Orientation. Spin axis perpendicular to orbital velocity Roy_H, 2014-02-20. Altitude ~600 km Roy_H, 2014-03-17.
• Propulsion. VASIMR for reboost. A variant uses LFTR nuclear power + VASIMR as a LEO–LMO cycler Roy_H, 2014-02-16.
• Evolution.
• 2014: a BA990-module full circle of 56 modules + 4 elevators. Full decoupling was abandoned, and microgravity work moved to free-flyers Roy_H, 2015-05-13.
• 2018: the bicycle wheel.

Critiques raised

• No rigidity, so it is a "flexible gyroscope" DMeader, 2014-02-20. Three-axis wobble from mass shifts IRobot, 2014-02-16.
• "No physical connection" is pointless; magnetic bearings and slip rings are old tech RanulfC, 2014-03-19.
• Elevators must be treated as crewed spacecraft, and each move is a docking Jim, 2014-02-20.
• Elevators change the moment of inertia (ballerina effect) and curve the tethers dror, 2014-03-17.
• Many disturbance torques besides precession (crew, docking, drag, gravity gradient) Roy_H, 2014-02-20.
• The rotating hub alternative: rotate everything, and ships match blasphemer, 2014-02-16.

Open questions

• Can cable-hung modules survive loss of spin or an elevator failure?

Related pages

• Tethered bolas · Non-rotating hub · Elevators

Sources

Forum posts

• Roy_H, 2014-02-16 (reply #0, 7 likes): Opening proposal. Post. Attachments: Bigelow.png.
• Roy_H, 2014-02-16 (reply #1): Cycler variant. Post. Attachments: MCT.png.
• Roy_H, 2014-02-16 (reply #2): Farm modules; SpaceStation.pdf. Post. Attachments: SpaceStationDark_small.jpg, CafiteriaModuleCutaway_small.jpg, CafeteriaInterior_small.jpg, SpaceStation.pdf.
• IRobot, 2014-02-16 (reply #6): Wobble. Post.
• blasphemer, 2014-02-16 (reply #7, 2 likes): Rotate hub. Post.
• Roy_H, 2014-02-19 (reply #77): Floor sag. Post. Attachments: Bigelow.png.
• Roy_H, 2014-02-19 (reply #79): Liquid balance. Post.
• DMeader, 2014-02-20 (reply #81): No rigidity. Post.
• Roy_H, 2014-02-20 (reply #82): Transit 1–3 min. Post.
• Jim, 2014-02-20 (reply #86): Elevators = spacecraft. Post.
• Roy_H, 2014-02-20 (reply #92): Axis orientation. Post.
• Roy_H, 2014-03-16 (reply #173): Oil ballast. Post.
• Roy_H, 2014-03-17 (reply #192): ~600 km. Post.
• dror, 2014-03-17 (reply #196): Ballerina effect. Post.
• RanulfC, 2014-03-19 (reply #208): RanulfC critique. Post.
• Roy_H, 2015-05-13 (reply #564, 1 like): BA990 ring. Post.