Self-Assessment Quiz: Mission Design

Twenty questions on the mission-design process, requirements and trade studies, the delta-v budget, margins, systems engineering, and the review lifecycle. Answer each before opening the key. Aim for 16 or more. Use $g_0 = 9.81\ \text{m/s}^2$.

Question 1

Mission design converts a mission objective into:

A) a single launch vehicle B) a self-consistent architecture that closes C) a delta-v budget only D) a list of requirements only

Question 2

The mission-design "funnel" (objective → requirements → orbit → … → cost) is best described as:

A) a strict one-way waterfall B) an iterative spiral, traversed repeatedly C) a random search D) a single calculation

Question 3

Which is a good (testable, verifiable) requirement?

A) "The spacecraft shall be reliable." B) "The spacecraft shall have enough power." C) "The power subsystem shall deliver ≥ 8 kW to the payload at end of life." D) "The spacecraft shall be as light as possible."

Question 4

Requirements flow down in the order:

A) subsystem → system → mission B) mission → system → subsystem C) cost → mass → power D) they do not have an order

Question 5

The purpose of a trade study is primarily to:

A) prove one option is objectively best regardless of weighting B) make and document a design decision against weighted criteria C) compute a delta-v budget D) pass a design review

Question 6

The delta-v budget is called the master constraint because it:

A) is the largest number in the design B) converts, through the rocket equation, into propellant mass and sizes the whole vehicle C) is set by the customer D) never changes

Question 7

A spacecraft's own delta-v budget is 2,561 m/s ideal. With per-leg margins it becomes 2,726 m/s. The 2,726 is what you use to:

A) choose the launch site B) size the propulsion (propellant and wet mass) C) set the data rate D) pick the orbit

Question 8

Margin is best described as:

A) padding added to make numbers look safe B) deliberate reserve against uncertainty and growth, bought down as the design matures C) the difference between two launch vehicles D) contingency for identified risks only

Question 9

As a program matures from concept to launch, the mass margin typically:

A) increases B) stays constant C) decreases (is bought down as estimates become measurements) D) becomes negative

Question 10

In the mass–power–cost coupling, the arrow that makes it an amplifier rather than a simple sum is:

A) power → array mass B) dry mass → propellant (through the rocket equation) C) payload → power D) wet mass → launch vehicle

Question 11

A comsat has mass ratio 2.38. Adding 100 kg of dry mass adds roughly how much wet mass?

A) 100 kg B) 238 kg C) 42 kg D) 0 kg

Question 12

Systems engineering is chiefly concerned with:

A) designing the best possible single subsystem B) the interfaces and shared budgets that make subsystems work together as a whole C) writing software D) choosing the launch vehicle

Question 13

The driving requirement is:

A) the first requirement written B) the requirement the coupled design is most sensitive to C) the most expensive requirement D) always the mass limit

Question 14

Put the review gates in order:

A) CDR → PDR → MDR B) MDR → PDR → CDR C) PDR → MDR → CDR D) MDR → CDR → PDR

Question 15 (True/False, justify)

"Cutting the delta-v margin to exactly the computed budget is good engineering, because the computed number is our best estimate." True or false? Justify in one sentence.

Question 16 (True/False, justify)

"Because the same delta-v budget applies, a chemical and an electric comsat have the same wet mass." True or false? Explain briefly.

Question 17 (True/False, justify)

"On a higher-delta-v mission, mass growth is more punishing." True or false? Say why.

Question 18 (Short answer)

Give the one-line question each of MDR, PDR, and CDR answers.

Question 19 (Short answer)

A spacecraft must provide 2,726 m/s with $I_{sp} = 320\ \text{s}$ to a 1,500 kg dry mass. Compute its exhaust velocity, mass ratio, and wet mass (show the steps).

Question 20 (Short answer)

In your own words, why is the delta-v budget the master constraint, and how does a mission's route across the delta-v map become the single number that sizes the vehicle?

Answer Key

Q Ans Note
1 B A design that closes within its mass/power/delta-v/cost/schedule limits.
2 B Each trip down the funnel sends you back up to revise; it spirals.
3 C Has a quantity, a condition, and a way to verify it.
4 B A few mission requirements flow down into many subsystem requirements.
5 B Its value is making the weighted reasoning explicit and documented.
6 B Through $m_0/m_f=e^{\Delta v/v_e}$ it sets propellant, hence wet mass, hence cost.
7 B The margined budget is what the propulsion is actually designed to deliver.
8 B Reserve against the unknown; contingency covers identified risks.
9 C You buy down margin by replacing estimates with measurements.
10 B Propellant grows as $e^{\Delta v/v_e}$ times dry mass — multiplication, not addition.
11 B $\Delta m_\text{wet} = (m_0/m_f)\,\Delta m_\text{dry} = 2.38\times100 \approx 238$ kg.
12 B Interfaces + shared budgets + emergent behavior of the whole.
13 B The input the whole coupled system is most sensitive to.
14 B MDR (mission closes) → PDR (design works) → CDR (ready to build).
15 False The estimate is uncertain and masses grow; designing to it guarantees falling short on any adverse deviation.
16 False Same delta-v, but the engine's $I_{sp}$ sets the mass ratio (2.38 vs 1.17), so wet masses differ ~2×.
17 True The mass ratio is exponential in delta-v, so the amplifier is larger and each dry kilogram drags more wet mass.
18 — MDR: does the mission close? PDR: will the design work, with margin? CDR: is it ready to build?
19 — $v_e=320\times9.81\approx3{,}140$ m/s; ratio $=e^{2726/3138}=e^{0.869}\approx2.38$; wet $=2.38\times1{,}500\approx3{,}576$ kg.
20 — It is the one budget that converts (through the exponential rocket equation) into propellant/wet mass; summing the map's legs into a total delta-v and inverting the rocket equation yields the sizing mass.

Topics to review by question

Questions Topic Section
1, 2 The mission-design process / funnel §29.1
3, 4, 5 Requirements & trade studies §29.2
6, 7, 20 Delta-v budget as master constraint §29.3
8, 9, 15 Margins and contingency §29.4
10, 11, 12, 13, 16, 17, 19 Systems engineering & the amplifier §29.5
14, 18 Design lifecycle & review gates §29.6