A little off topic but worth posting about, Vector Space, a small satellite launch vehicle provider has recently posted a blog about Aerospike rocket engines.
As stated in the blog post, California State University, Long Beach and Garvey Space Corporation partnered to develop a 1000lbf aerospike and a 1300lbf 10 chamber plug aerospike. I was in Mojave in 2009 and was lucky enough to witness the launch of the P10 vehicle with the multi-chamber aerospike, unfortunately as stated one chamber did not ignite taking out two adjacent chambers, causing the rocket to cartwheel off the launch rail and impact a short distance away. This was the first time I ever saw a liquid fuelled rocket fly, even though it never achieved its purpose on this day, it did not put me off!
Below are a couple of videos about Aerospikes that I found interesting.
Or if you are wanting a greater in depth of the challenges and manufacturing process, the video below is very good.