So far this year there have been 106 orbital launches around the world, the most in a calendar year since 1990. That works out to roughly one launch every three days. Now, as we approach the end of this year, the launch industry has a treat for us—potentially three launches in a single day on Tuesday.

For rocket fanatics, this should make for a fun day, especially with some bigger rockets on the launch pad. Here's a rundown on what to expect and the significance of each launch.

Falcon 9: Cape Canaveral, Florida

SpaceX's final launch of the year, its 21st overall, will be an important one for the company. It is scheduled for 9:11am ET (14:11 UTC) from Cape Canaveral Air Force Station in Florida.

The launch of the Air Force's first GPS 3 satellite is important to the military, because this new generation of satellites will broadcast more secure and more accurate signals than existing GPS spacecraft. The military, in turn, is an important customer for SpaceX (it won this contract in 2016 for $82.7 million). Another indicator of the significance of this launch is that Vice President Mike Pence, who chairs the National Space Council, is expected to attend.

The Air Force has ordered a new Falcon 9 for the first GPS 3 mission, and due to mission requirements there will be no landing attempt. However, the military says it is studying the potential for reusable boosters for future missions to save money.

“We are continuing to look at this as we try to drive down uncertainty,” Walter Lauderdale, mission director of the Air Force Space and Missile Systems Center’s Launch Enterprise Systems Directorate, said, according to Space News. “As we work through this first flight together, we will look at the performance, do all the calculations and analysis so we can continue to look for opportunities in the future.”

Forecast conditions are 80-percent favorable for a Tuesday launch. The launch will be webcast on SpaceX's YouTube channel.

Soyuz: Kourou, French Guiana

The European rocket company Arianespace closes out its 2018 launch campaign on Tuesday as well, with the launch of a Russian-made Soyuz launch vehicle from the Guiana Space Center in South America. Launch time is 11:37am ET (16:37 UTC).

So far, Arianespace has launched 10 rockets this year: six Ariane 5 boosters, two Vega rockets, and two Soyuz medium-lift rockets. Tuesday's planned launch will send the CSO-1 Earth observation satellite, which is intended for defense and security applications, into Sun-synchronous orbit for the French government.

Arianespace has had an agreement in place with the Russian government since 2011 to fly the Soyuz booster as a medium-class rocket that supports payloads sized between the larger (and more expensive) Ariane 5 rocket and the smaller Vega. Tuesday's launch will be the 20th Soyuz flight from the European spaceport in South America since then. An English-version webcast will be available on Arianespace's YouTube page.

Delta IV Heavy: Vandenberg Air Force Base

Provided that weather and technical issues comply, Tuesday's launch activity will cap off with a liftoff of the powerful Delta IV Heavy rocket from Vandenberg Air Force Base in California. Launch time is 8:57pm ET (01:57 UTC Wednesday).

For this mission, which was scrubbed more than a week ago in the last seconds of the countdown when a problem was detected by computers orchestrating the terminal countdown, United Launch Alliance will launch a classified spy satellite for the US National Reconnaissance Office. The mission's name is NROL-71.

The NRO has created an excellent mission patch for the flight, which depicts an eagle wearing a dog tag with the initials "JLC." This is in remembrance of Col. Joshua L. Chamberlain, a Union commander who was awarded the Medal of Honor for heroism at the battle of Gettysburg, July 2, 1863. Chamberlain and his men held the Union Army's southern flank at Little Round Top.

The launch of the Delta IV Heavy rocket will be broadcast here. Unfortunately, weather conditions do not appear overly favorable at this time.