Self-Assessment Quiz: Life Support and Human Spaceflight

Twenty questions to check your grasp of human requirements, closed-loop life support, radiation, microgravity, artificial gravity, and the human factor. Answer each before opening the key. Aim for 16 or more. Use the chapter's planning figures and $g_0 = 9.81\ \text{m/s}^2$.

Question 1

The integrated spacecraft subsystem that supplies oxygen and water, removes CO$_2$, and maintains pressure and temperature is abbreviated:

A) GN&C B) ECLSS C) TPS D) RTG

Question 2

Roughly how much mass of consumables (oxygen + potable water + food) must be supplied per crew member per day, open-loop?

A) ~0.5 kg B) ~5 kg C) ~25 kg D) ~50 kg

Question 3

For breathing, the human body responds primarily to:

A) the total cabin pressure B) the partial pressure of oxygen C) the partial pressure of nitrogen D) the cabin temperature

Question 4

Apollo used a low-pressure pure-oxygen cabin; the ISS uses a sea-level-pressure oxygen/nitrogen mix. The chief hazard that makes pure oxygen dangerous is:

A) hypoxia B) fire C) the bends D) carbon-dioxide buildup

Question 5

In the regenerative loop, oxygen is regenerated from water by:

A) the Sabatier reaction B) electrolysis C) lithium hydroxide scrubbing D) reverse osmosis

Question 6

A Sabatier-based system recovers only about $50\%$ of the crew's oxygen because:

A) the reactor is too small B) carbon dioxide is toxic C) there is only about half the hydrogen needed, so half the CO$_2$ goes unreduced D) water cannot be electrolyzed in microgravity

Question 7

Which loop has essentially not been closed on any flown spacecraft?

A) water B) oxygen C) food D) carbon-dioxide removal

Question 8

Open-loop life support is preferred over closed-loop when:

A) the mission is long and far from resupply B) the mission is short or resupply is cheap C) the crew is large D) power is abundant

Question 9

Equivalent radiation dose is measured in:

A) grays B) sieverts C) watts D) pascals

Question 10

The acute radiation threat that a storm shelter is designed to protect against is:

A) galactic cosmic rays B) a solar particle event C) the Van Allen belts D) ultraviolet light

Question 11

Per unit mass, the best material for radiation shielding is generally:

A) lead B) aluminum C) a hydrogen-rich material such as water or polyethylene D) titanium

Question 12

Which is not a documented effect of prolonged microgravity?

A) bone demineralization B) headward fluid shift C) muscle atrophy D) permanent increase in bone density

Question 13

On the ISS, the primary countermeasure against bone and muscle loss is:

A) medication alone B) about two hours a day of exercise, especially resistive exercise C) artificial gravity D) a high-calcium diet alone

Question 14

Artificial gravity from rotation is given by:

A) $a = \omega r$ B) $a = \omega^2 r$ C) $a = \omega^2 / r$ D) $a = \tfrac{1}{2}\omega r^2$

Question 15

Shrinking a $1\,g$ rotating habitat's radius (keeping $1\,g$) forces a higher spin rate, which worsens:

A) the fire risk B) the Coriolis effect and the gravity gradient C) the radiation dose D) the CO$_2$ level

Question 16 (True/False, justify)

"A larger spacecraft is easier to shield against galactic cosmic rays to a given areal density." True or false? Justify in one sentence.

Question 17 (True/False, justify)

"Because the mass out of a crew member roughly balances the mass in, a perfectly closed life-support system could in principle resupply no water or air at all." True or false? Explain briefly.

Question 18 (True/False, justify)

"Exercise fully prevents the health effects of microgravity, so artificial gravity is unnecessary." True or false? Say why.

Question 19 (Short answer)

The one-way light time between Earth and Mars ranges from about $3$ to about $22$ minutes. State one concrete consequence for how a crewed Mars mission must be operated, and link it to a concept from an earlier chapter.

Question 20 (Short answer)

A crew of $4$ flies for $180$ days open-loop. Compute the total supplied-consumables mass (show the per-crew-day rate and the arithmetic), and name the mission-design reason this number pushes long missions toward recycling.

Answer Key

Q Ans Note
1 B Environmental Control and Life Support System.
2 B $0.84 + 2.5 + 1.8 \approx 5.1\ \text{kg}$ per crew-day.
3 B Hypoxia and fire risk are set by $p_{\text{O}_2}$, not total pressure.
4 B A pure-O$_2$ atmosphere is a severe fire hazard (Apollo 1, 1967).
5 B Electrolysis $2\text{H}_2\text{O}\to 2\text{H}_2+\text{O}_2$.
6 C Electrolysis yields ~2 H$_2$ per CO$_2$; Sabatier needs 4, so only ~half is reduced.
7 C No flown system grows all its food; the food loop is open.
8 B Open-loop mass rises linearly; it wins below the break-even day (short/cheap-resupply missions).
9 B Sieverts (equivalent dose); grays are absorbed dose.
10 B The storm shelter defends against the acute proton flux of an SPE.
11 C Hydrogen-rich materials shield best per kilogram and make fewer secondaries.
12 D Microgravity reduces bone density; it does not increase it.
13 B ~2 h/day, with resistive exercise (ARED) most important for bone.
14 B Centripetal acceleration $a=\omega^2 r$.
15 B Higher $\omega$ raises Coriolis ($2\omega v$) and steepens the head-to-foot gradient.
16 False Shielding scales with surface area; a larger vehicle has more area, so reaching a given areal density costs more mass, not less.
17 True (in principle) Mass is conserved, so a perfect recycler needs no air/water makeup — but food (fixed carbon) still must be supplied, and real systems never close perfectly.
18 False Exercise slows but does not stop bone loss, fluid shift, or SANS; that residual loss is exactly why artificial gravity is still studied.
19 — No real-time help from Earth, so the crew must be autonomous in emergencies — the human parallel to machine autonomy (Ch. 27) and comm latency (Ch. 26).
20 — $4\times180\times5.14 = 3{,}701\ \text{kg}\approx 3.7\ \text{t}$; that mass grows linearly with duration, so beyond the break-even day recycling is lighter (Ch. 3: every kg costs propellant to launch).

Topics to review by question

Questions Topic Section
1, 2, 3, 4, 20 Human requirements & atmosphere §28.1
5, 6, 7, 8, 17 Open- vs closed-loop; loop chemistry §28.2
9, 10, 11, 16 Radiation and shielding §28.3
12, 13, 18 Microgravity physiology & countermeasures §28.4
14, 15 Artificial gravity §28.5
19 The human factor & comm delay §28.6