Side airbag assembly

1. A restraint system comprising:

a seat defining a lateral axis;

an airbag housing supported by the seat, the airbag housing including a first arm and a second arm;

the first arm being fixed relative to the seat and the second arm being rotatable relative to the seat about a rotational axis generally parallel to the lateral axis; and

an airbag extending from the first arm to the second arm, the airbag being fixed to the first arm and the second arm.

2. The restraint system of claim 1 , further comprising a plurality of external tethers extending from the first arm to the second arm when the airbag is in an inflated position.

3. The restraint system of claim 2 , wherein the airbag is disposed between the seat and at least some of the plurality of external tethers in the inflated position.

4. The restraint system of claim 2 , wherein the plurality of external tethers are attached to the first arm, the second arm, and the airbag, the external tethers are under tension between the first and second arms when the airbag is in the inflated position.

5. The restraint system of claim 2 , wherein the plurality of external tethers are a reaction surface for the airbag in the inflated position.

6. The restraint system of claim 2 , wherein the plurality of external tethers are fabric.

7. The restraint system of claim 2 , wherein the plurality of external tethers are uninflatable.

8. The restraint system of claim 1 , wherein the first arm and the second arm each include an end spaced from the rotational axis, the airbag is fixed to the end of the first arm and the end of the second arm.

9. The restraint system of claim 8 , wherein the airbag is fixed along the first arm from the second arm to the end of the first arm and along the second arm from the first arm to the end of the second arm.

10. The restraint system of claim 1 , wherein the second arm is rotatable from an undeployed position to a deployed position as a result of the airbag inflating.

11. The restraint system of claim 10 , wherein the second arm extends along the first arm in the undeployed position, and the second arm extends transverse to the first arm in the deployed position.

12. The restraint system of claim 11 , wherein the first and second arms each include an end, the end of the second arm being spaced from the end of the first arm in the undeployed position.

13. The restraint system of claim 10 , wherein the second arm and the seat lock with each other in a fixed position when the second arm is in the deployed position.

14. The restraint system of claim 13 , wherein the second arm includes a bar rotatable relative to the second arm when the second arm rotates relative to the seat to the deployed position.

15. The restraint system of claim 14 , wherein the seat includes a bracket, the bar is engaged with the bracket when the second arm and the seat are locked with each other in the fixed position.

16. The restraint system of claim 1 , further comprising an inflator in fluid communication with the airbag, the inflator is fixed to the seat and spaced from the housing.

17. The restraint system of claim 1 , wherein the seat includes a seatback defining an occupant seating area and a seat bottom supporting the seatback, the airbag and the second arm being adjacent to the seat bottom when the airbag is in the inflated position and the airbag extends from the second arm along the occupant seating area in an inflated position.

18. The restraint system of claim 1 , wherein the seat includes a seatback, the first arm is fixed to the seatback.

19. The restraint system of claim 1 , further comprising a hinge between the first arm and the second arm.

20. The restraint system of claim 19 , wherein the hinge is a locking hinge.