Receiving System Challenge

Your launch system is working. Payloads now consistently reach the North Tower rooftop receiving deck. The receiving deck is not the final destination.

Patients are on Level 14, inside the building. The hospital needs payloads to travel from the rooftop deck down through an internal delivery chute to the patient floor, without electricity, without crashing, and without damaging fragile contents like IV bags and vials.

• Payload (marble or weighted proxy) travels the full length without falling off or stalling
• At least one curve, turn, or loop. Straight ramps do not count.
• Payload arrives at the Patient Floor zone slowed. Fragile contents must not crash.
• Gravity-powered only. No pushing, no fans, no electricity.

Too slow: payload stalls partway down, cannot complete loops, does not reach the patient floor.

Too fast: payload flies off curves, smashes into the wall at the end, damages contents.

Your job is to find the height that gives just enough energy to complete the run and slow gracefully at the end.

Before you build, sketch your track on scratch paper. Mark:

• The starting height (your "rooftop receiving deck")
• The end zone (your "patient floor")
• At least one curve, turn, or loop
• Where the track will lose the most speed (curves, loops, long flat stretches)

Sketching first will save you 20 minutes of rebuilds. Trust this step.

1. Set the start point. Tape the top of your first foam segment to a stack of books, a chair back, or a tall box. Higher = more energy. Start with about 24 inches.
2. Join segments. Tape segment ends together so the channels line up. Any gap between sections will stop a marble cold. Overlap the foam slightly at the seam to keep the surface smooth.
3. Build supports. Use cardboard braces or stacked books at key bends to hold the track at the right angle. A track that flexes when the marble passes is a track that loses energy.
4. Test the straight descent first. Before you add curves or loops, drop a marble down a straight, banked version of your track. Confirm it reaches the bottom with speed to spare. If it does not, raise your start height.

Foam pipe insulation bends. Use that. To make a curve, tape one segment so it sweeps left or right. To make a loop, bend a segment into a vertical circle and tape it to itself and to the supporting structure.

Test after every change. Drop a marble. Watch what happens. If it flies off a curve, the curve is too tight or the marble is too fast. Lower the start height or widen the curve. If it stalls on a loop, you do not have enough starting height. Raise it.

For each test, notice:

• Starting height
• Did the marble complete the full run?
• If not, where did it fail?
• Approximate time from release to end zone

Stretch goal: A second loop or curve. Or design a "soft landing" at the end. A foam pad, a cardboard catch, anything that decelerates the payload before it hits the wall.

Set up your catapult and your delivery track on opposite sides of your team's space. The top of your delivery track is now your receiving deck. Adjust the height of your track's start point so it matches where your catapult's payload arcs to.

Most firms hit this problem first: the catapult lands payloads in a small target zone, but the top of the track is just an open foam channel. Payloads bounce out and roll off. You need a catch. A shoebox lid, a small bin, a cardboard funnel, something that catches the payload and feeds it into the track.

Once your payload leaves the cup, three things are happening to it at once. Watch this before your next launch.

• Launch angle matters. Too low, it slams short. Too high, it lobs. There is a sweet spot.
• Launch speed comes from tension. More rubber band = more speed = farther range.
• Payload mass matters. Heavier payloads travel less at the same tension.
• Release consistency is huge. Pulling the arm down to a different spot every time is why "the same launcher" fires differently every time.

Real engineers do not guess. They identify one variable, change only that variable, measure what happens, then move on. If you change three things at once and the launch goes farther, you have no idea which change did it.

Some variables you could test:

• Add 2 more rubber band wraps on the tension band
• Change the angle of the front bar
• Pull the arm down to a marked, repeatable position every time
• Raise or widen your catch to make it easier to hit
• Change the height of your track's start point

Engineers do not ship a system because it worked once. They ship it because it worked every time.

Start the streak. Launch. If the full system works, that is run #1. If anything fails (catapult misses, payload bounces off the deck, track stalls), the streak resets to zero. Reset and try again.

Keep going until you hit 3 in a row.

• Marble falls short. Add tension, or lower the catch.
• Marble overshoots the catch. Loosen tension, or pull the arm down less.
• Marble drifts left or right. Recenter the arm on the pivot. Re-lash if the frame has shifted.
• Marble stalls in the loop. Raise the start of the track, or move the loop further down the run.
• Marble falls out at a joint. Overlap and tape that joint again. Loose joints are where deliveries fail.

1. What was the biggest engineering problem you had to solve?
2. What one design choice worked best on your build?
3. Fire a live delivery for the room.