Why does a missile box cavity carry two figures?

A: One is the smallest inscribed rectangle, used to check fit; the other is the clear space after lining, used to check closing clearance.

Is thicker foam always safer?

A: No. Foam has to match the remaining gap. Too stiff and it transmits the shock; too thin and it bottoms out. Neither failure shows outside.

Can the handle take repeated carrying?

A: It depends on root transition and lid stiffness. A short root and thin rim show white marks at the opening ends first.

Is phase-change material always needed?

A: No. Air and closed-cell foam flatten short excursions; phase-change material earns its place only when heat holds longer than the box time constant.

Can stack strength be checked at room temperature?

A: No. Modulus falls with temperature, so a box on the top rack in summer carries a different load. State the temperature and duration. ---

Missile Box: Dimensions, Cushioning and Thermal Control

Quick answer: A missile box starts from three numbers: outside size, cavity size, lid depth. Their difference sets how much cushioning fits, and cushioning sets how flat the shock curve becomes. Thermal control comes from the air layer, phase-change placement and the pressure valve, not from thicker walls.

Where the missile box dimension chain starts
Cavity, lid depth and usable space
Cushioning: foam thickness and remaining gap
Wall, ribs and sealing
Thermal control and stacking
FAQ

1. Where the missile box dimension chain starts

Outside size decides which vehicle and hatch the box fits; cavity size decides what goes in; lid depth decides what is left after closing. The outside is bounded by transport limits, the cavity by the load.

Three-quarter view of the black slim case, latches spanning the lid edge, handle folded at the front, large corner radii

The usual error is confusing nominal with usable. A cavity marked 308mm loses corner radii, ribs and foam, so the real length may be 290mm. Drawings should carry both bare cavity and clear space.

2. Cavity, lid depth and usable space

A rotomolded cavity is not a box. Walls carry draft, corners are radiused, the base often has a grid of pads. State whether a figure is the largest inscribed rectangle or an average section; the two can differ by ten millimetres.

Outline and open interior of the same black case, marked 315mm long, 290mm high, 110mm deep outside, cavity 308mm by 250mm, 54mm deep, lid 42mm

Lid depth also discounts. A marked 42mm runs from the parting line to the lid face, and gasket compression takes one or two millimetres back. Count that margin when foam is stacked.

Clearance for handling is part of usable space. A liner cut to zero clearance means the load has to be tipped out, so two or three millimetres a side is normal.

3. Cushioning: foam thickness and remaining gap

Cushioning lowers the peak acceleration and stretches its duration. For the same change in momentum, a lower peak means less force into the load. Thickness and density shape that curve: too thin and the foam bottoms out; too stiff and it bottoms early.

Compute the remaining gap first, then choose foam. Outside minus cavity minus wall gives a total gap, split across six faces, more on the loaded ones. If the foam compresses less than half, it is too stiff; if it bottoms, it is too thin.

Liners usually run a carrier against the wall and a locating layer against the load. With the same foam in both, the curves add, so stiffness is higher than a single-layer estimate.

4. Wall, ribs and sealing

Thicker is not stronger. Added wall raises mass and stiffness at once, and the transmitted peak rises with them; thin walls absorb energy by bending but puncture easily. Put thickness on the load path: handle root, latch bosses, base corners.

Close view of the moulded handle opening through the lid edge, radiused lower lip, both latch bosses in frame

The handle is the only load point in manual carry. A moulded handle feeds load into the lid and saves a fastener, but needs a long root transition. Judge root thickness and the chamfer at the lower lip, not the opening size.

Sealing and wall thickness are a pair. A thin wall lets a latch pull distort the rim, and the gasket then compresses unevenly. Seal clauses set rim stiffness and latch count together.

5. Thermal control and stacking

The first thermal layer is air. Still air between cavity and load insulates, and thicker air raises resistance while cutting usable space. The second is the liner: closed cells insulate, open cells cushion. The third is phase-change material, where position matters more than mass.

The black case closed face-on, handle centred, three horizontal ribs below the recess, feet visible at the base

Stacking is the underestimated case. Storage applies a long load, and plastic modulus falls as temperature rises, so the same stack deforms more in summer. Check stack strength at the highest storage temperature.

The stacking face also has to be flat. Lid ribs, label recesses and handle bosses become high points, and load concentrates there. Sinking the ribs works better than thickening the lid.

Conclusion

The dimension chain gives space, cushioning flattens the shock, and thermal control with stacking decides how much margin is left after six months in store. When specifying a missile box, ask for a drawing that marks both bare cavity and clear space.

This article discusses the case body only: interior, load points, handling features, marking and fixing. It does not cover any operation or filling of the contents.