A one-page reference for a chapter about judgment. When you read any claim about the future of spaceflight,
run it through the tiering table below before you believe it.
The chapter's one discipline
Separate the possible from the probable from the speculative — and tier every projected number. The
physics does not get a pass because it is wearing a press release. Proven physics, plausible-but-untried
engineering, and hope-with-a-slide-deck are three different piles; keep them apart.
The seven terms this chapter owns
Term
One-line definition
Artemis
NASA-led international program to return humans to the Moon to stay; SLS + Orion + Gateway + commercial HLS.
Gateway
A small crewed station in a near-rectilinear halo orbit (Earth–Moon L2, Ch. 15); staging post and relay.
Human Landing System (HLS)
The crewed lunar lander, bought as a commercial service (Starship, Blue Moon).
Commercial space station
A privately owned, crewed orbital facility that sells access; NASA becomes one customer of many.
Space tourism
Human spaceflight bought by private individuals; suborbital (a hop) or orbital (going around).
Asteroid mining
Extracting materials (esp. water) from small bodies — valuable in space, not returned to Earth.
Space economy
All value produced in/from space; today mostly satellite services, not launch.
The physics behind each future (why the rocket equation still rules)
Claim
The physics that forces it
Gateway sits in a high, looping lunar orbit
NRHO = halo orbit about Earth–Moon L2 (Ch. 15): ~few m/s/yr to hold, always in view; cost pushed to the lander.
Mars missions must make return propellant (ISRU)
Bringing it compounds the rocket equation across land → cruise → launch — a savage gear chain.
Asteroid water beats asteroid platinum
Value is where delivery is cheap; returning bulk mass down Earth's gravity well is prohibitive (and crashes the price).
Orbital tourism ≫ suborbital tourism
~60× the specific energy; the exponential turns that into ~35% vs ~94% propellant — different species of vehicle.
Falling launch cost is the "master variable"
The rocket equation set the price; reusability (theme 5) finally moves it, turning "possible" into "probable."
Numbers worth remembering (tiered)
Quantity
Value
Tier
Delta-v to orbit / propellant fraction
~$9.4\ \text{km/s}$ / ~94%
2
Delta-v for a suborbital hop
~$1.5\ \text{km/s}$ (~35% propellant)
2/3
Orbital vs suborbital specific energy
$30$ vs $0.5\ \text{MJ/kg}$ ≈ 60×
2/3
Mars ascent delta-v (surface → low Mars orbit)
~$4\ \text{km/s}$
2
Sabatier: H₂ to bring per kg CH₄
$0.5\ \text{kg}$ (bonus $2.25\ \text{kg}$ water)
1 (stoichiometry)
Mars round-trip radiation dose
order of $1\ \text{Sv}$
2
ISS retirement
~2030
2
Space economy today / by 2040
~\$0.4–0.6 T / >\$1 T
2
Launch cost $/kg to LEO | Shuttle ~\$54k · Falcon 9 ~\$2.7k · Starship *goal* ~\$150
Martian $\mathrm{CO_2}$ + imported (or mined) hydrogen → methane + water; electrolyze the water for oxygen. Per
kg of methane: $0.5\ \text{kg H}_2$ in, $2.25\ \text{kg H}_2\text{O}$ out. This one reaction is why the return
trip is affordable at all.
The honest ledger (the whole chapter in one column)
Sustained Moon presence; commercial stations; Mars arrival; orbital tourism (slow).
Speculative (Tier 3)
Asteroid industry; crewed Mars return at scale; space solar power; settlements/O'Neill habitats.
Mostly a myth
Bringing asteroid platinum to Earth to get rich.
Common pitfalls
Pitfall
Reality
"Suborbital flying → orbital tourism is near."
Opposite sides of the exponential; ~60× energy, different vehicle class.
"We haven't gone to Mars because it's too far."
Delta-v to Mars ≈ delta-v to escape Earth; the hard parts are time and the return.
"A trillion-dollar space economy = mining and Mars cities."
The projection is mostly satellite services growing; the exotic sectors are upside, not base case.
"Asteroid platinum is a trillion-dollar business."
Return delta-v is prohibitive and a big delivery collapses the price; the prize is water in space.
Treating a projected number as a measured one.
Tier it. ">$1 T by 2040" is Tier 2 (attributed), not Tier 1.
Threads and project
Themes: 5 (reusability changes everything — the master variable) and 6 (history/why: Apollo vs Artemis).
Anchor: the Voyager Grand Tour returns as the closing inspiration — cooperate with the physics
(Ch. 11 gravity assist, Ch. 15 superhighway), with the audacity to outlast your planners.
MDR increment: a "Where this approach is heading" forward-look for your track; no new astrotools
module (survey chapter). Optional code: a launch-cost sensitivity for your vehicle's wet mass.
Bridge: Chapter 40 — you assemble every checkpoint into a complete Mission Design Review and finish your
mission.