www.lesswrong.com/posts/BZZKFnsefeMh6psRb/spacex-will-have-massive-impact-in-the...
2 corrections found
When Tungsten rods are dropped from space onto earth they manage to store a lot of kinetic energy because they have a very high boiling point.
This gets the physics backward. Kinetic energy depends on an object's mass and velocity, not its boiling point; tungsten's very high melting temperature mainly helps it survive reentry heating.
Full reasoning
Kinetic energy is determined by the standard formula KE = 1/2 mv², so the relevant variables are the rod's mass and velocity, not its boiling point or melting point.
NASA's Orbital Debris Program explains that objects made of high melting-point materials are more likely to survive atmospheric reentry, whereas low-melting-point materials tend to burn up earlier. In other words, tungsten's heat resistance matters because it can better withstand reentry heating — not because it somehow lets the rod "store" more kinetic energy.
So the statement is incorrect in its causal explanation: a tungsten rod's impact energy comes from how massive and fast it is, while tungsten's high temperature tolerance affects survivability during reentry.
2 sources
- Kinetic and Potential Energy
Kinetic energy is directly proportional to the mass of the object and to the square of its velocity: K.E. = 1/2 m v^2.
- ARES | Orbital Debris Program Office | Debris Reentry
Spacecraft components that are made of low melting-point materials ... will generally demise at higher altitudes than objects that are made of materials with higher melting points ... Many objects have a very high melt temperature such that they do not demise.
a Boeing 737-800 NG which can carry 184 m³ with a weight of 24 000 kg with 189 seats
This mixes up passenger and freighter specifications. A 737-800 with passenger seating does not have 184 m³/24,000 kg cargo capacity; those figures are for the converted freighter version, which has no passenger seats.
Full reasoning
The numbers in this sentence come from different aircraft configurations.
Boeing's official 737-800 data show that the passenger 737-800 has all-economy seating capacity of 184 and lower-deck cargo volume of 45.1 m³, with max structural payload of 20,275–21,318 kg depending on the variant. By contrast, Boeing's 737-800BCF converted freighter has about 186.4 m³ cargo volume and about 23.9 tonnes / 24 tonnes payload — but it is a freighter, not a 189-seat passenger aircraft.
So the post incorrectly combines the freighter's cargo volume/payload with the passenger model's seating count, creating a configuration that Boeing's own specifications do not support.
3 sources
- 737NG_REV B
737-800 ... MAX STRUCTURAL - PAYLOAD ... 20,275 | 20,275 | 21,318 kg ... SEATING CAPACITY ... ALL-ECONOMY 184 ... MAX CARGO VOLUME - LOWER DECK ... 45.1 cubic meters.
- Boeing Freighter Family
737-800BCF has excellent cargo capability ... Payload | Structural (Gross): 23.9 tonnes / 52,800 lb.
- 737-800 Boeing Converted Freighter | Boeing Global Services
Carries 24 tonnes of payload with excellent operating economics to maximize profit for your cargo operations.