2. The Receiving System

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.

Your new build: a gravity-powered internal delivery track that takes payloads from the receiving deck (top of your build) to a marked Patient Floor zone (bottom of your build). The track must include at least one curve or loop — real hospital hallways aren't straight.

Potential energy — the higher the marble starts, the more energy it has to use. A 12" drop has twice the energy of a 6" drop.

Kinetic energy — as the marble drops, height converts to speed. The lowest point of the track is the fastest point.

Centripetal force — to follow a curve or complete a loop, the marble needs the track to push it inward. Not enough speed = the marble falls off the track on a curve, or falls out of a loop at the top.

Friction — every inch of track surface steals a little energy. Long tracks lose more energy than short ones. Bumpy tape seams steal more than smooth foam.

• 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 doesn't — 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 don't have enough starting height — raise it.

• Starting height
• Did the marble complete the full run? (Y/N)
• If not, where did it fail?
• Approximate time from release to end zone (count seconds, or use phone stopwatch)

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.

Roller coaster engineers spend years calculating the exact starting height a coaster needs to complete every loop and curve while still slowing safely at the station. The same physics shows up in hospital pneumatic tube systems — engineers at companies like Swisslog and Pevco design the bends, drops, and stops that move millions of medical samples every year. Your foam pipe insulation track is the rough version of a real piece of hospital infrastructure.

As a firm, answer these out loud — 60 seconds each, no overthinking:

• What did our firm do well over the last two days?
• What did we get wrong that we'll never do again?
• If a hospital had a different problem next week, what kind of problem would they hire us for?

Your Data Analyst writes down the three sharpest answers in the 📋 Engineering Firm Logbook. These become your firm's identity.

Real engineering firm names usually do one of three things: they describe what they do (Boston Dynamics), they use the founders' names (Bechtel, Jacobs), or they're short and abstract (IDEO, ARUP).

Pick one approach. Settle on a firm name. Then write a tagline — one sentence, under 10 words, that tells the review board what your firm specializes in.

Pencil sketch in your 📋 Engineering Firm Logbook. Don't worry about clean lines — this is a working draft. Aim for something simple enough to redraw on a slide or whiteboard. One shape, one wordmark, optional color note.

If your Presentation Lead has a phone with a drawing app, they can clean it up tonight. Not required.

Fill in the firm profile page of your 📋 Engineering Firm Logbook:

• Firm name + tagline
• Logo sketch
• Lead Engineer, Build Specialist, Data Analyst, Presentation Lead — final assignments
• Three things your firm does well (from Part I)

This page becomes the opening slide of your Engineering Summit defense. Make it real.

Mission: One catapult launch sends a payload across the gap; the payload lands in the receiving deck (top of your track); the track delivers it to the Patient Floor zone.

Acceptance test: 5 successful end-to-end deliveries in a row.

If anything fails — catapult misses, payload bounces off the deck, track stalls — the run does not count. Reset and try again.

Set up your catapult and your delivery track on opposite sides of the room (or as close to your assigned Engineering Summit footprint as you can manage).

The top of your delivery track is now your receiving deck. This is where the catapult's payload needs to land. Adjust the height of your track's start point so it matches where your catapult's payload arcs to.

So far you've used foam balls for the catapult and marbles for the track. Today you need one payload that works for both. Test options:

• Marble: launches okay, rolls great
• Foam ball: launches great, rolls badly
• Ping pong ball: launches okay, rolls okay
• Weighted item (small zip bag with rice or marbles): customizable, but unpredictable

Pick one. Run a few catapult shots with it to re-tune your tension. Then run a few track tests with it to confirm the descent still works. The payload is now part of your system.

Load the payload. Launch. Watch it land. Does it stay in the receiving catch? Does it feed into the track? Does it complete the descent? Does it arrive at the Patient Floor without bouncing out?

If yes — great. Run 4 more and see if it does it again.

If no — pinpoint where it failed. That's your debug target.

Start the streak. Launch. If the full system works — payload launches, lands, rolls, arrives — that's run #1. If anything fails, the streak resets to zero.

Keep going until you hit 5. Or until you fail enough times that you can identify what's breaking.

• Where in the system did it fail? (Catapult? Catch? Track entry? Curve? End zone?)
• What specifically happened? (Bounced out, stalled, flew off, fell short.)
• Best guess at why?
• What did you change before the next attempt?

Most firms find that one failure mode dominates — maybe 70% of failures happen at one specific spot. Find that spot. Fix it once. Watch your reliability jump.

If you hit 5 in a row before time's up:

• Try 10 in a row
• Increase the payload weight (real medical supplies are heavier than marbles)
• Swap to the Fragile Cargo payload (instructor will provide) — must arrive at the Patient Floor undamaged. Adjust your track's end zone to decelerate gracefully.
• Time the full delivery — fastest reliable system wins extra credibility at the Summit

The Summit review board will respect a firm that hit 5/5 and stopped there. They'll be impressed by a firm that hit 10/10 with a heavier payload.

Reliability engineers test medical devices the same way you're testing this system — running them thousands of times, logging every failure, and finding the single weakest point. The FDA requires this kind of testing before any new device reaches a hospital. A pacemaker that works 99.9% of the time still has a 1-in-1,000 failure rate — which means tens of thousands of failures per year across the population. Reliability engineers' job is to find and eliminate those failure modes before the device ever sees a patient.

Every technical defense has the same backbone. Yours will hit these seven sections, in order:

Aim for ~2 minutes per section. That puts your defense around 15 minutes plus Q&A.

Every firm member presents. Assign sections out loud right now:

• Presentation Lead — Firm Profile + Live Demo (you set the tone at the open and close the energy at the demo)
• Lead Engineer — The Problem + What's Next (you frame the contract and own the future-looking judgment)
• Build Specialist — Process & Iteration (you know what broke and why — own that story)
• Data Analyst — The Physics + The Data Story (your logbook IS the evidence)

Open your 📋 Engineering Firm Logbook. Flag the strongest evidence from each day — not all of it, just the strongest:

• The data point or result that proves you hit spec
• The failure log entry that shows the most engineering judgment
• The before-and-after that shows the biggest performance jump
• The 2-3 photos that best show your system
• The video clip(s) of successful runs

You will not use every piece of data you collected. A weak defense includes everything. A strong defense picks the sharpest evidence and explains it clearly.

On the Defense Outline page of your 📋 Engineering Firm Logbook, sketch out one row per section. Each row gets:

• The section name (Firm Profile, The Problem, etc.)
• Who presents it
• The ONE key point that section makes
• The evidence on the slide (photo, video, data, sketch)

Don't build slides yet — that's Day 5. Today you decide what the slides will say. If you can't write the key point in one sentence, the section isn't ready yet.