A Review of Aerospike Nozzles: Current Trends in Aerospace Applications

The abstract brings up SSTOs, but has there been anything in recent invention that will make them anything other than the white whale people have been chasing since forever?

Why make an SSTO when you can make a TSTO? First stage recovery is a solved problem and will always greatly relax the engineering problems over making a SSTO.

Because of course SSTO has benefits over TSTO, simplicity of operation being one example.

The argument for SSTOs was that staging was too scary. But experience since then shows this argument was bogus. Staging can be made highly reliable.

Even a small amount of delta V provided by a first stage makes the job of the "almost SSTO" second stage much easier. And a low delta V first stage can be rugged, with high high safety factors, and is easy to recover at the launch site.

Put another way: if you have an SSTO, its payload increases dramatically if you stack it on a very low performance recoverable first stage.

I don't see any way SSTOs are going to be preferable to TSTOs, especially if the SSTO has to use hydrogen to get off the ground.

Everybody may have their own criteria of preferences, so the same solution with fail for one and succeed for another.

Sure, you can cook up whatever BS criteria you want, but when it hits the market SSTO doesn't make sense.