Enlarge / Artist concept of the Demonstration for Rocket to Agile Cislunar Operations (DRACO) spacecraft. (credit: DARPA)

Phoebus 2A, the most powerful space nuclear reactor ever made, was fired up at Nevada Test Site on June 26, 1968. The test lasted 750 seconds and confirmed it could carry first humans to Mars. But Phoebus 2A did not take anyone to Mars. It was too large, it cost too much, and it didn’t mesh with Nixon’s idea that we had no business going anywhere further than low-Earth orbit.

But it wasn’t NASA that first called for rockets with nuclear engines. It was the military that wanted to use them for intercontinental ballistic missiles. And now, the military wants them again.

Nuclear-powered ICBMs

The work on nuclear thermal rockets (NTRs) started with the Rover program initiated by the US Air Force in the mid-1950s. The concept was simple on paper. Take tanks of liquid hydrogen and use turbopumps to feed this hydrogen through a nuclear reactor core to heat it up to very high temperatures and expel it through the nozzle to generate thrust. Instead of causing the gas to heat and expand by burning it in a combustion chamber, the gas was heated by coming into contact with a nuclear reactor.

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Reissued with updates to the country summary.

Reconsider travel due to crime and terrorism. Exercise increased caution due to civil unrest and kidnapping. Some areas have increased risk. Read the entire Travel Advisory.

Do Not Travel to:

• Arauca, Cauca (excluding Popayán), and Norte de Santander departments due to crime and terrorism.
• The Colombia-Venezuela border region due to crime, kidnapping, and risk of detention when crossing into Venezuela from Colombia.  

Country Summary: Violent crime, such as homicide, assault, and armed robbery, is widespread. Organized criminal activities, such as extortion, robbery, and kidnapping, are common in some areas.

Terrorist groups and criminal organizations continue operating and carrying out attacks in Colombia. They may attack with little or no warning, targeting transportation hubs, markets/shopping malls, local government facilities, police stations, military facilities, hotels, clubs, restaurants, airports, other public areas, and U.S. government facilities.

Demonstrations occur regularly throughout the country and can be about a variety of political or economic issues. They can shutdown roads and highways, often without prior notice or estimated reopening timelines. Demonstrations and road closures may significantly reduce access to public transportation and may disrupt travel within and between cities. Protests can become violent and can result in fatalities and injuries.

U.S. direct-hire government employees must adhere to the noted restrictions:

• They are not permitted to travel by road between most cities.
• Colombia’s land border areas are off-limits to U.S. government personnel unless specifically authorized.
• They may not use motorcycles.
• They may not hail street taxis or use public buses.

Read the country information page for additional information on travel to Colombia.

If you decide to travel to Colombia:

• Avoid protest areas and crowds.
• Monitor local media for breaking events and adjust your plans based on new information.
• Keep a low profile.
• Be aware of your surroundings.
• Enroll in the Smart Traveler Enrollment Program (STEP) to receive Alerts and make it easier to locate you in an emergency.
• Follow the Department of State on Facebook and Twitter
• Review the Country Security Report for Colombia.
• Prepare a contingency plan for emergency situations. Review the Traveler’s Checklist.

Arauca, Cauca, and Norte de Santander Departments – Level 4: Do Not Travel

Violent crime, including armed robbery and homicide, is widespread.
Terrorist groups are active in some parts.

The U.S. government has limited ability to provide emergency services to U.S. citizens as U.S. government-personnel travel to these areas is severely restricted due to security concerns.

Colombia - Venezuela Border – Level 4: Do Not Travel

U.S. citizens are advised not to travel to the border of Colombia and Venezuela. U.S. citizens are at risk of detention when crossing into Venezuela.

The Colombia-Venezuela border is not clearly marked, and U.S. citizens should not go near the border due to the risk of crossing into Venezuela accidentally.

U.S. citizens attempting to enter Venezuela without a visa have been charged with terrorism and other serious crimes and detained for long periods. For more information, see the Venezuela Travel Advisory.

Visit our website for Travel to High-Risk Areas.