What is the real use of an SSTO?

[hempa2]

Alot of people are building SSTOs but why, a rocket is so much faster and almost everytime carry alot more fuel.

Can someone familiar to SSTOs tell me the use of them!

[timsfitz]

They're fun and efficient. I rarely use them, but flying one to Laythe and back was one of my favorite missions.

[hempa2]

A rocket transfer stage is also efficient

[allmhuran]

When 0.24 comes out with contracts and costs, you will probably find that SSTO craft that can also land in one piece have the advantage of being cheaper, since throwing away spent engines and fuel tanks every launch is expensive.

[TimePeriod]

There is no real advantage, except that the SSTO can be used again with a refuel. Vice Versa

[Killerdude8]

Efficient?

Nah.

SSTO's can lift a Very, Very tiny Payload compared to their Size.

But they can make a small amount of fuel last a long time to get to orbit, So, Fuel Efficient, Not Practical.

[UmbralRaptor]

Like most things in KSP, because it's there.

In principle, an airbreathing design can (in stock) be 70% payload, though very few are anywhere near that. Also, SSTO != airbreathing, though it's the most commonly used.

[Tex_NL]

As usual the terms SSTO and spaceplane are mixed up. SSTO simply means Single Stage To Orbit. Even a conventional rocket can be an SSTO. What you probably mean is an SSTO spaceplane.

Currently there is no real benefit to SSTO planes in KSP. They're fun and it's an accomplishment to build your first but as has been stated before they usually can't lift that much. A simple conventional rocket can lift a lot more. The real benefit is re-usability once economics becomes part of the game. The entire craft can be used again after refueling and perhaps minor repairs.

[hempa2]

But you need to launch a bunch of fuel and with a dockingport/grappling unit so it will be expensive for an SSTO too

[Wooks]

The efficiency of an SSTO plane comes from reusability. Every time you launch a rocket you lose the entire ship to deliver a payload into orbit, meanwhile an SSTO can deliver the payload and get back safely, and after being refueled and refitted it can launch again for a fraction of the time it takes to assemble a new rocket.

Picture this: How much an airplane ticket would cost if you had to throw away the plane after delivering the passangers? That is what happens with our current real life space programs, and that is why the private space programs are aiming for fully reusable ships.

KSP right now (remember we are still in Beta testing) has no "real" use of SSTO ships because contracts and costs are not implemented (as allmhuran pointed out), but when it happens the we´ll see how SSTOs fare against rockets.

Edited June 1, 2014 by Wooks

[hempa2]

As usual the terms SSTO and spaceplane are mixed up. SSTO simply means Single Stage To Orbit. Even a conventional rocket can be an SSTO. What you probably mean is an SSTO spaceplane.

Currently there is no real benefit to SSTO planes in KSP. They're fun and it's an accomplishment to build your first but as has been stated before they usually can't lift that much. A simple conventional rocket can lift a lot more. The real benefit is re-usability once economics becomes part of the game. The entire craft can be used again after refueling and perhaps minor repairs.

When i say rocket i mean a nonSSTOcraft and SSTO includes rocketSSTOs but the most commonly used is the plane

[hempa2]

The efficiency of an SSTO plane comes from reusability. Every time you launch a rocket you lose the entire ship to deliver a payload to orbit, meanwhile an SSTO can deliver the payload and get back safely, and after being refueled and refitted it can launch again for a fraction of the time it takes to assemble a new rocket.

Picture this: How much an airplane ticket would cost if you had to throw away the plane after delivering the passangers? That is what happens with our current real life space programs, and that is why the private space programs are aiming for fully reusable ships.

KSP right now (remember we are still in Beta testing) has no "real" use of SSTO ships because contracts and costs are not implemented (as allmhuran pointed out), but when it happens the we´ll see how SSTOs fare against rockets.

Reuseable stages with chutes to land and using docking ports/klaws. ROCKETS ALWAYS WIN

[Wooks]

Reuseable stages with chutes to land and using docking ports/klaws. ROCKETS ALWAYS WIN

Well, you are fighting the new wave of future spaceships that are currently in development in at least three different private Space Programs, you should check:

- What SpaceX is up to with their rockets and capsules, all able to get back to earth on power assisted landings (no parachutes) and fully reusable. Pay a visit to http://www.spacex.com/ and watch the videos of what they are doing right now, you might get your mind blown.

- Virgin Galactic´s Spaseship Two is a thing of beauty and is ready to open the first passenger suborbital flights - http://www.virgingalactic.com/

- Skylon is designing an unpiloted, reusable spaceplane that could put 15 tonnes of cargo into space - http://www.reactionengines.co.uk/space_skylon.html

Bare in mind these are REAL ships, being used or under development right now.

Edited June 1, 2014 by Wooks

[hempa2]

Virgin Galactic = non SSTO

SpaceX Falcon9 = non SSTO

Skylon = SSTO

2 of 3 reusable crafts isnt SSTOs

Edited June 1, 2014 by hempa2

[Stargate525]

I would hazard to guess that for personnel transfer, it's easier on the body. I don't think any SSTOs experience the 3-4Gs a rocket hits?

[jwenting]

SSTOs are only more cost efficient than rockets if fuel for them is extremely cheap relative to the cost of the rocket stages you'd throw away.

A far better solution is to have a way to recover and recondition spent stages, kinda like what NASA tried with the SRBs for the Shuttle and what SpaceX is working on with the Falcon series.

That way you have most of the benefit of lower weight on the upper stages of a throwaway launcher, combined with part of the cost benefit of reusing the vehicle that an SSTO would bring.

Of course every design is going to be a tradeoff between cost of vehicle, cost of fuel, and cost of reconditioning.

In KSP, where fuel is effectively free and parts are effectively free (though that might of course change as career mode gets more involved/complete/complex) there's no cost penalty to any design...

[R0cketC0der]

In KSP, where fuel is effectively free and parts are effectively free (though that might of course change as career mode gets more involved/complete/complex) there's no cost penalty to any design...

In real life, fuel is also effectively free. Less than 0.3% of the launch cost of a falcon 9 are fuel costs.

[Monger]

Virgin Galactic = non SSTO

SpaceX Falcon9 = non SSTO

Skylon = SSTO

2 of 3 reusable crafts isnt SSTOs

SpaceX is working on SSTOs as well. In the meantime they try to build vessels that are at least fully reusable. As mentioned a few times in this forum: reusability is kind of the holy grail in space travel. The first one who achieves to build a true SSTO will cut transport costs by 99%, making space truly available for everyone (well, almost).

The way KSP is currently built, it doesn't matter. But still: it is one of the most challenging and interesting tasks one can currently imagine in KSP.

[kahlzun]

The main benefit is getting a K-Prize! Go backstage with the Kerbettes!

Seriously though, it is hard and challenging. When you start to get really good at the game, SSTOs and Eve returners are pretty much the only challenges left..

[Jouni]

Seriously though, it is hard and challenging. When you start to get really good at the game, SSTOs and Eve returners are pretty much the only challenges left..

They're similar challenges as reaching orbit or landing on the Mun. Do it a couple of times, and you'll estabilish best practices that allow you to do it again without too much trouble.

Edited June 1, 2014 by Jouni

[Monger]

Reuseable stages with chutes to land and using docking ports/klaws. ROCKETS ALWAYS WIN

Only in KSP.

In real life, air breathers are far more efficient, because they get most of their lift and their fuel from outside, so their loading capacity is far better. Also: reusable parts that land with chutes still need to be carried back to their launch site and put together for the next launch. Imagine a plane that would need to be towed back to the terminal every time it landed.

SSTO naturally have much smaller downtime, and less maintenance costs. When the time is due, SSTO will probably replace most of the "usual" space traffic which is currently based on non-SSTOs.

[jfull]

Yes, in KSP rockets are almost always an easier option than an SSTO plane.

However, KSP is almost entirely based around the goals that players set for themselves, so they don't always use the easiest option.

personally, I don't use SSTOs for payloads, but I do like to use them to bring large crews to and from Kerbin orbit.

[Jouni]

Only in KSP.

In real life, air breathers are far more efficient, because they get most of their lift and their fuel from outside, so their loading capacity is far better. Also: reusable parts that land with chutes still need to be carried back to their launch site and put together for the next launch. Imagine a plane that would need to be towed back to the terminal every time it landed.

KSP jet engines are lighter, more powerful, and much more efficient than real jet engines, and they can also operate in much thinner air. Combine this with the fact that Kerbin is so small that jet engines can get the SSTO almost all the way to orbit, and it becomes obvious that airbreathing engines are much more useful in KSP than for real SSTOs.

Concerning the efficiency: Basic jet engines have 150 kN of thrust and a specific impulse of 2000 seconds at sea level. This means that 150/9.81 tonnes or about 3060 units of liquid fuel would last for 2000 seconds under full thrust. Yet in practice, that amount of fuel lasts for almost 9 hours, meaning that the actual Isp of the basic jet is over 30000. There's apparently a bug in the way KSP calculates fuel usage for airbreathing engines: it counts the mass of both the fuel and the air, when it only should count the mass of the fuel. In the future, we'll hopefully get a bug fix that increases the fuel usage of the jet engines 16-fold.

[Epthelyn]

Virgin Galactic = non SSTO

SpaceX Falcon9 = non SSTO

Skylon = SSTO

2 of 3 reusable crafts isnt SSTOs

Even if parts are reused after being sent back to Earth as spent stages, they still have to be reattached. That costs money, although nowhere near as much as building new parts each time.

An SSTO only needs to be refueled between each flight (plus additional maintenance, because rockets aren't friendly) and nothing necessarily needs to bolted back on for the next launch.

It's probably better to say SSTO + landing in this case. A rocket capable of reaching orbit in a single stage might not necessarily return with that stage.

[Tank Buddy]

In real life SSTOs are a cheap way to get humans and cargo to orbit because they do not throw away spent stages and burn less fuel. The re-usability is key. Unfortunately, KSP has no incentive, at least at the moment, to take advantage of these benefits. A lot of things people do in KSP is just for a cool factor, or simply to say they achieved a difficult task.