Martian Ballistic Entry


  1. Anti-satellite space weaponry
  2. Martian ballistic entry
  3. Russian meteor explosion

Current events

The US Defense Intelligence Agency (the Pentagon’s top intelligence arm) issued an extensive report about Chinese and Russian “weaponization of space” and the effort to counter US military superiority. As idealists, we hope that space can be a realm of peaceful scientific expansion, but the hard truth is that space assets are crucial to US defense operations, with classified spy satellites responsible for missile warning, GPS, and target ID. China currently has an operational anti-satellite missile system and is working to field an anti-satellite laser weapon by 2020. And in September, US intelligence captured images of a Russian anti-satellite missile attached to a Russian MiG-31, a supersonic near-space interceptor fighter jet. The 1967 Outer Space Treaty prohibits placing weapons of mass destruction in orbit and in general prohibits the weaponization of space, but questions remain over how enforceable the treaty would be if breached.

Today I learned

On the topic of the amazing Opportunity rover that just died after 15 years on Mars, what makes landing on Mars particularly difficult? All 3 landers the Soviet Union sent in the 1970s failed upon descent, as did the British Beagle 2 lander in 2003, NASA’s Mars Polar Lander in 1999, and the joint European/Russian Schiaparelli lander in 2016. 

Apart from the usual dangers of rocket launch and precise calculations needed for interplanetary travel, Mars’s atmosphere makes ballistic entry challenging because it’s only 1% the density of Earth’s; this is thick enough to require a heat shield on the incoming capsule, but too thin for parachutes alone to be capable of slowing the probe down for landing. As a result, Mars landers must undergo a precisely choreographed sequence of heat shield -> parachute -> retro thrusters -> air bag cushioned impact. See this video for an awesome HD animation of Spirit landing on Mars (landing sequence starts at 2:15)

This day in space history

On February 15, 2013, the Chelyabinsk meteor entered Earth’s atmosphere over Russia and exploded, generating a flash brighter than the Sun and producing a shock wave felt by many residents and injuring around 1,500 people. The meteor measured 66ft in diameter and is the only meteor confirmed to have caused significant injuries (for reference, the one that killed the dinosaurs was about 10-50 miles wide). 

What’s disturbing is the object was completely undetected before atmospheric entry; NASA has a Planetary Defense Office responsible for tracking dangerous near Earth objects, but given the sheer magnitude of their task, many dangerous objects go undetected. And even if a meteor were on a collision course with Earth, it’s uncertain what we could do about it anyway.