Which reusable or SSTO concept from the 1980's-90's would be most promising, if revisited today?

[Bill Phil]

There's one problem. It's a big one, too. It takes a LOT of energy. A LOT! A lot of energy and a lot of DeltaV. But it is possible. Practical? Not necessarily. But cars weren't much practical at first. Albeit they're completely different vehicles. But they'll be developed over time, perhaps a lot. But, even the X-33's problems stemmed from the current materials. A lot, a decent amount, but not all. Other things happened, too.

[wumpus]

Under the "did SpaceX kill ULA" thread I claimed that it certainly killed SSTOs (proposals).  The rocket equation killed SSTOs.  I think fredinno (the poster above me) claimed that I wasn't quite right: a rocket with the first stage of the SLS could presumably deliver a falcon-9 sized payload into LEO as a SSTO.  Personally, I think that proves my point.  I would happily permanently* send however many falcon second stages into orbit than try to perform the maintenance required to resend all those shuttle engines (a known billion dollar expense) into orbit again.

SSTO involves one of two things:

magic ISP

a poor understanding of the rocket equation (or perhaps confusion with "magic ISPs cause SSTOs" with "SSTOs cause magic").

To understand why SSTOs are such a failure, just install the realism overhaul mods.

* permanently means with deorbit and total loss.  No Kessler syndrome for me, please.

[cantab]

Maybe I'm biased, but I'm saying HOTOL: https://en.wikipedia.org/wiki/HOTOL

And it's one that is being revisited today - the Skylon proposal, including the very SABRE engine that KSP's RAPIER is based on, owes a lot to HOTOL including being lead by the same person.

[fredinno]

1 hour ago, wumpus said:

Under the "did SpaceX kill ULA" thread I claimed that it certainly killed SSTOs (proposals).  The rocket equation killed SSTOs.  I think fredinno (the poster above me) claimed that I wasn't quite right: a rocket with the first stage of the SLS could presumably deliver a falcon-9 sized payload into LEO as a SSTO.  Personally, I think that proves my point.  I would happily permanently* send however many falcon second stages into orbit than try to perform the maintenance required to resend all those shuttle engines (a known billion dollar expense) into orbit again.

SSTO involves one of two things:

magic ISP

a poor understanding of the rocket equation (or perhaps confusion with "magic ISPs cause SSTOs" with "SSTOs cause magic").

To understand why SSTOs are such a failure, just install the realism overhaul mods.

* permanently means with deorbit and total loss.  No Kessler syndrome for me, please.

The rationale of SSTOs is that being simpler (no staging), maintenance should be easier (along with the fact that without stages, Assembly buildings aren't a requirement)- of course, if you can't reuse in the first place economically, it makes no sense to invest in a SSTO.

[Exoscientist]

On May 30, 2015 at 2:52 PM, cryogen said:

NERVA launch is very unlikely to work. Here's Kirk Sorensen's analysis:

http://selenianboondocks.com/2010/06/ssto-ntr-bad/

Simplified: if you have a nuclear thermal SSTO, with an excellent (optimistic) I_sp of 900 s, it needs a mass ratio of at least

e^{ (9,200 m/s) / (g * 900 s) } = 2.83

...according to the rocket equation, with 9.2 km/s delta-v to LEO.

 

 Chemical propulsion SSTO is not that hard if you only want expendable. Use the highest ISP kerolox engines available now (Russian). Use the highest propellant fraction first stage available now (SpaceX). 

Now note the rocket equation now gives a delta-v higher than 9.2 km/s.

 

   Bob Clark

[Nibb31]

Then add a heat shield, avionics, landing gear, power, RCS, and you'll have pretty much zero payload fraction, if any.

Something like DC-X makes sense as a first stage. Its profile would be similar to the F9 first stage, but it would be optimised for the reentry and landing instead of bolting stuff onto a conventional stage like SpaceX does. 

Edited January 8, 2016 by Nibb31

[RainDreamer]

This is rather an old thread. Can't even see what the original post is supposed to be like since it is all broken up after forum change.

[Elukka]

On 5/30/2015 at 9:52 PM, cryogen said:

NERVA launch is very unlikely to work. Here's Kirk Sorensen's analysis:

http://selenianboondocks.com/2010/06/ssto-ntr-bad/

This makes the mistaken assumption that nuclear thermal rockets haven't evolved since NERVA. Timberwind/SNTP in the 1990s was specced at a thrust-to-weight ratio of 30 (he assumes a tw/r of 3) and an isp of 1000 seconds. A pebble bed reactor design like Timberwind is much more compact too. The only reason it wasn't built was money.

It's also possible to increase an NTR's thrust by injecting LOX into the propellant stream. It inevitably results in a drop in isp, but can potentially increase thrust by 50-100%.

[Silver_Swift]

15 hours ago, Wesley01 said:

SSTO seem to me as possible if you use S/SM/E (s) and this stage principle which means you can still use three stages like stages in today's rockets but keep them inside

I'm hardly an expert on this, but I don't see how you get an advantage from staging if you don't drop the stage after it is spent. Isn't the main advantage of multiple stages that you don't have to carry the weight of the spent stage after it is used?