Yes, there are tent heaters! While some might think that taking a heater on a camping trip defeats the purpose of enjoying nature, others find that having a little bit of warmth makes camping much more enjoyable - especially if you're camping in cooler weather or at higher altitudes.
There are two main types of tent heaters: portable propane-powered heaters and battery-operated heated blankets or pads. Propane-powered heaters usually have one or two burners and can put out anywhere from 3,000 to 9,000 BTUs (British Thermal Units) per hour. They typically require ventilation, so make sure to read the instructions carefully before using one inside your tent. Battery-operated heated blankets and pads use either lithium ion batteries or disposable chemical packets to generate heat. They're great for providing targeted warmth to specific body parts or sleeping areas, but they don't put out as much heat as propane-powered models.
If you're interested in purchasing a tent heater, be sure to do your research and choose a model that's right for you and your group. And always use caution when operating any type of heater - never leave it unattended and make sure everyone in your group knows how to safely operate it.