Kerbal Space Shuttle and rocket Economics

[marach]

This I think I disagree with. It may be true, but we cannot know as the rest of the other systems never flew as many missions as the STS did (Soyuz maybe?). Apollo had one fatal accident and one near miss, out of what, 11 manned missions (plus SkyLabs)? Mercury had 6 manned, Gemini 10 (correct me if those are wrong). Most of the programs never flew enough missions to get a good enough sample size of reliability. I'm not saying your wrong, just that we can never know just how reliable those other programs really were. The STS didn't have it's first fatal incident until STS-51, it's 25th manned flight, and then STS-107 (113th manned).

Soyuz has according to wikipedia 127 official manned flights (over 4 generations) 2 of which ended fatally and another that was almost fatal (landed on an ice lake) the shuttle had I think 135ish NASA acknowledged flights and their problems are pretty widely known. If shuttle crew sizes were as small as soyuz crew it would be ahead on safety...

[nothingSpecial]

Soyuz has according to wikipedia 127 official manned flights (over 4 generations) 2 of which ended fatally and another that was almost fatal (landed on an ice lake) the shuttle had I think 135ish NASA acknowledged flights and their problems are pretty widely known. If shuttle crew sizes were as small as soyuz crew it would be ahead on safety...

It is also really fortunate surprise that neither Vostok nor Voskhod (they used the same blocks A (core) and B, V, G and D (boosters) as Soyuz rocket) had any fatal flights. There were a handful of disasters (unmanned) and crew escape was very limited (or nonexistent in the case of Voskhod). The safety of Soviet aerospace is slightly overestimated. Edited September 15, 2015 by nothingSpecial

[marach]

It is also really fortunate surprise that neither Vostok nor Voskhod (they used the same blocks A (core) and B, V, G and D (boosters) as Soyuz rocket) had any fatal flights. There were a handful of disasters and crew escape was very limited (or nonexistent in the case of Voskhod). The safety of Soviet aerospace is slightly overestimated.

There are at least a few cases where Soyuz terminal landing rockets apparently failed so there's likely many cases of broken bones in there. Also the US has the most "official" deaths but we have no clue about the number of USSR deaths in truth as in at least one case the guy was removed from all records ( Valentin Bondarenko for example)

Edited September 15, 2015 by marach

[GoSlash27]

KerikBalm,

Had I sacrificed the engine, it would have just dropped back down after the SRBs burned out.

Or, perhaps you mean I don't recover the engine... now I need to add that KR-2L's cost to the cost of the launch:

25+27k = 52k for the launch now.

I would also need to add the cost of the internal LFO tank on the orbiter that is used to orbit.

'Zackly. And since your hypothetical payload is now 49.3t instead of 19t, that would put your launch cost at a hair over $1000/tonne. That's the problem; so much of what is put into orbit isn't payload, but rather the delivery truck itself.

Best,

-Slashy

[KerikBalm]

KerikBalm,

'Zackly. And since your hypothetical payload is now 49.3t instead of 19t, that would put your launch cost at a hair over $1000/tonne. That's the problem; so much of what is put into orbit isn't payload, but rather the delivery truck itself.

Best,

-Slashy

Yea, that is one of the problems with the real space shuttle too...

I was hoping it could at least be made to work in KSP where maintenence and refurbishment costs are lacking... but it seems its not possible.

Sure, I could put some air breathers on it, and then it should be able to outperform a disposable air breather.... but a disposable air breather seems a little ridiculous

[nothingSpecial]

Okay.

I tried to make career-useful shuttle. Well, I mostly cheated my way through anything that stood between me and design and test process, yet the results.

First of all, I still fail at shuttles, at Mk3 shuttles at least, I mean.

Second, it is possible to bring Mk3 shuttle stack up to 6 000 m/s of delta-vee for less than ~110 000 funds with solid boosters and for ~140 000 funds with liquid ones with ~40 000 funds recovered - I just need to tweak engine placement (I tried to design stack without RCS building aid mod, because I am too often rely on it).

I used MPL as payload and benchmarked my shuttle against space station contracts. Payment for successful science-lab-including five-kerballed space station is 132 250 funds. Double this figure for the Mun station contract.

That means that the shuttle stack will pay itself in stock career, in three-four runs for Kerbin or if you lucky in one Munshot.

Are there more economically efficient designs? Sure.

Still the STS-alike can be profitable in KSP. Maybe I will refine the design so it will be easy in use even for me in couple days.

[Red Iron Crown]

Something has occurred to me while thinking about this problem:

If an STS-style staged rocket can't be competitive with a disposable launcher economically, how can a rocket SSTO do better than disposables?

[nothingSpecial]

Something has occurred to me while thinking about this problem:

If an STS-style staged rocket can't be competitive with a disposable launcher economically, how can a rocket SSTO do better than disposables?

If it's 100% recoverable and reusable SSTO rocket...

[Red Iron Crown]

That's sort of the point behind my question. It's been purported that an STS-style launcher can't beat a disposable because the additional propellant and recovery equipment mass offsets the added recovery value; why isn't that true for an SSTO rocket?

[nothingSpecial]

Oh, wait, it really depends. Did they said "STS-style launcher" or exactly STS? Because if we somehow manage to recieve boosters at booster refilling center, and external tanks were landing Elon-Musk style into external tanks refilling center, and if shuttle orbiter cut cost of it's protection by using more uniform ones (I'm not an engineer and don't know if it's possible, I am an economist), then cost of launch is cost of transportation and assembly + cost of refilling + cost of fuel + (possibly some orders of magnitude lower then STS) costs of maintenance. I can't see any theoretical reason that vertically launched spaceplane with 100% recoverability can not be better than expendables. In fact, it is nonsense from the industrial point of view - you need to rebuild things vs. you don't need to rebuild things.

Well. Do we have an aerospace engineer on forum?

Edited September 16, 2015 by nothingSpecial

[KerikBalm]

As I figure it, the first stage is still disposable.

The first stage is bigger than the 2nd stage.

As your final stage is heavier, the lower stages must be bigger.

You've now doubled the size of the lower stages, which are often over half the cost of the launcher

So you dispose of a similar amount of stuff, and burn more fuel?

In my case, I dispose of 4x kickbacks and 2x orange tanks (plus decouplers, struts, nosecones, seratrons)...

If that equipment on its own could lift 18 tons to orbit... what the heck am I doing lofting a shuttle?

[The_Rocketeer]

That's sort of the point behind my question. It's been purported that an STS-style launcher can't beat a disposable because the additional propellant and recovery equipment mass offsets the added recovery value; why isn't that true for an SSTO rocket?

Who said SSTO rockets are more economical than staged rockets?

It comes down to whether it costs less to replace everything each time and use less fuel on the way up, or to use more fuel and keep everything for next time. Therefore rockets with low price tags might as well be disposable, and rockets with low dry mass might as well be SSTO.

SSTOs have other advantages, like having fewer things that can go wrong and uncomplicated maths for ascent calculations.

Payload tons for payload tons, though, I doubt a SSTO is more affordable. Your payload fraction gets eaten up by the empty tanks that you don't need to be bringing with you anymore.

[More Boosters]

Who said SSTO rockets are more economical than staged rockets?

It comes down to whether it costs less to replace everything each time and use less fuel on the way up, or to use more fuel and keep everything for next time. Therefore rockets with low price tags might as well be disposable, and rockets with low dry mass might as well be SSTO.

SSTOs have other advantages, like having fewer things that can go wrong and uncomplicated maths for ascent calculations.

Payload tons for payload tons, though, I doubt a SSTO is more affordable. Your payload fraction gets eaten up by the empty tanks that you don't need to be bringing with you anymore.

With perfect recovery you only have an entry cost for the SSTO, so cost per ton is hardly a concern as you only pay once.

[Vegetal]

What I found to be a good use for shuttle style craft in ksp, is going beyond kerbin SOI. Space planes are unbeatable cost-wise for lifting cargo to LKO, but are very inefficient for going beyond that, for obvious reasons.

What I use shuttles mostly for, is for interplanetary missions. I have some that launch shuttle style and have over 7k dV in orbit, then come back and land on the runway for full recovery of the most expensive parts. I think they excel in this role because the atmospheric parts are minimal, but already allow you to land precisely.

I also managed to find an easy way of building piggyback shuttles (mk2 size) which have the same difficulty level during launch than a conventional rocket.

[KerikBalm]

What I found to be a good use for shuttle style craft in ksp, is going beyond kerbin SOI.

I'm sorry, but this sounds ridiculous, now you aren't just carrying a much bigger engine than you need to orbit + wings + a cargo bay... you are carrying it beyond escape velocity.

Even my heavy cargo SSTOs don't go beyond LKO.

I have some lighter SSTOs that will launch small payloads on highly eliptical orbits, so that the payload is already close to escape velocity...

But we're not talking about those. We are talking about non-airbreathing staged designs.

Space planes are unbeatable cost-wise for lifting cargo to LKO, but are very inefficient for going beyond that, for obvious reasons.

We aren't talking about spaceplanes per say. We are talking about vertically launched non-airbreathing spaceplanes with solid rocket boosters and a LFO drop tank.

I have some that launch shuttle style and have over 7k dV in orbit, then come back and land on the runway for full recovery of the most expensive parts. I think they excel in this role because the atmospheric parts are minimal, but already allow you to land precisely.

I highly doubt that recovery of the most expensive parts off-sets the increase in total mass and cost. Recovering 90% of something that is 10x as expensive as a craft in which nothing is recovered does not result in you coming out ahead (you risk losing a lot more in launch and landing, but your marginal cost is the same)

If recovery fraction * increased cost multiplier is greater than 1, it is not viable.

I think that is what is going on here in KSP.

So to make it economically viable, we'd either strip down the orbiter to make it cheaper (and lighter, so the boosters+ external tank are smaller and cheaper), making it more like a disposable rocket... or we'd reduce what gets discarded....

I know, I'll make a STS style shuttle: Take a winged SSTO rocket... strap a FL-t800 tank on its belly... put the cheapest decouplers on it, attach a pair of sepratrons to the decoupler... now the cost of the discarded parts is minimal..... lulz

Or slightly more seriously... use my recoverable SRB booster packs, as in this craft file:

https://www.dropbox.com/s/0zxv4728zhed0ol/SSTNope.craft?dl=0

The SRBs have about a 2 second burn time, but they get the craft going ~150 m/s, and get fully recovered.

Use a bunch of those, and get rid of the external tank (make the orbiter carry fuel internally)

- But now the asymetry is gone, and its very dissimilar to the shuttle

FYI: The most economical way to go interplanetary is to use a tug that boosts your payload to escape velocity, then aerobrakes down to low orbit, ready to be refueled again and have a new payload attached.

[The_Rocketeer]

With perfect recovery you only have an entry cost for the SSTO, so cost per ton is hardly a concern as you only pay once.

You pay per flight for the fuel. If you can save enough fuel to offset the cost of disposable parts, you're better off with disposable stages even if you fly 100 times.

[GoSlash27]

All,

There's no reason why a lifter would necessarily have to be 100% disposable or 100% recoverable.

If I have staging, I assume that anything chucked overboard is gone; nonrecoverable.

Whatever I put into orbit, OTOH, is recoverable at at least 90% value.

For disposable launch stages, nothing beats SRBs for $/tonne.

For the rest, 90% of the empty value can be recovered simply by slapping some 'chutes on it.

Best,

-Slashy

[nothingSpecial]

All,

There's no reason why a lifter would necessarily have to be 100% disposable or 100% recoverable.

If I have staging, I assume that anything chucked overboard is gone; nonrecoverable.

Whatever I put into orbit, OTOH, is recoverable at at least 90% value.

For disposable launch stages, nothing beats SRBs for $/tonne.

For the rest, 90% of the empty value can be recovered simply by slapping some 'chutes on it.

Best,

-Slashy

What about recoverable SRB-powered SAS and winglets-controled rockets?

[Norcalplanner]

After reading all this, I can't help thinking that this is a topic which is ripe for a challenge. Let's see some actual designs with relevant numbers attached and see who can do what.

[KerikBalm]

You pay per flight for the fuel. If you can save enough fuel to offset the cost of disposable parts, you're better off with disposable stages even if you fly 100 times.

Except that the cost of the fuel for a SSTO isn't so high.

Especially if you have an airbreathing SSTO, and those OP 3,200 - 4,000 Isp rapiers and turbojets.

My airbreathing SSTOs will put up 100 tons into orbit for about 15k. That is 150 per ton.

So far for a disposable rocket, I haven't seen under 1k per ton.

I think the non airbreathing SSTOs cost about 300-400 per ton, but I'm not so experienced with those.

[GoSlash27]

What about recoverable SRB-powered SAS and winglets-controled rockets?

Sorry, I'm not following...

If it is jettisoned from the stack during launch, then it's toast AFAIC. I know there are mods to help with that, but I'm assuming a stock career game.

All,

Rocket SSTOs can be very economical compared to their disposable and semi- disposable counterparts. No reason they can't outperform them so long as they can be recovered at 90% value or so.

A 25t semi- disposable staged rocket with SRB first stage would cost about $850/tonne. A 25t SSTO rocket based on a Rhino could do it for about $550.

Best,

-Slashy

[The_Rocketeer]

Sorry, I'm not following...

If it is jettisoned from the stack during launch, then it's toast AFAIC. I know there are mods to help with that, but I'm assuming a stock career game.

All,

Rocket SSTOs can be very economical compared to their disposable and semi- disposable counterparts. No reason they can't outperform them so long as they can be recovered at 90% value or so.

A 25t semi- disposable staged rocket with SRB first stage would cost about $850/tonne. A 25t SSTO rocket based on a Rhino could do it for about $550.

Best,

-Slashy

I find it hard to see how a rocket SSTO can compete economically with a staged rocket for massive payloads. I'm prepared to be proven wrong, but it seems obvious to me that a SSTO is sacrificing lifting power (edit: and needs much more wet mass) to bring useless recoverables to orbit.

Anybody?

[KerikBalm]

size of the payload doesn't matter....

Why would it be economical for a 25 ton payload but not a 50 ton payload?

you bring up more non payload mass, but its proportional to the amount of payload mass you bring up

[GoSlash27]

I find it hard to see how a rocket SSTO can compete economically with a staged rocket for massive payloads. I'm prepared to be proven wrong, but it seems obvious to me that a SSTO is sacrificing lifting power (edit: and needs much more wet mass) to bring useless recoverables to orbit.

Anybody?

Well basically... the cost of additional fuel to heft the more massive SSTO is less than the cost of the discarded stage(s) and fuel for the upper stage. It's less efficient, but still works out cheaper.

Best,

-Slashy

[marach]

Sorry, I'm not following...

If it is jettisoned from the stack during launch, then it's toast AFAIC. I know there are mods to help with that, but I'm assuming a stock career game.

-Slashy

Not quite true if it leaves the atmosphere, climb fairly steeply so that you have time to circularise before it re-enters switch to it and ride it down to a landing. SRB's can't really be done this way in stock but liquid boosters are fine with it just add a probe core for safety.