X-33 SSTO: Could It be Feasible With Modern Technology?

[andrew123]

If it is feasible, do you think NASA should make it? Or do you think Lockheed Martin, a member of ULA (Not pals with SpaceX), Would be willing to license the honeycomb and composite fuel tank technology to spaceX?

http://en.wikipedia.org/wiki/Lockheed_Martin_X-33

A lighter fuel tank could increase payload fractions for the new re-usable falcons and enable spaceX to build a ssto. Not to mention the other engine advancements in the x-33 development phase.

Heck, the rs-68 is more efficient than the rd-180 in the atlas v. And only 19% less powerful, albeit much more complex (I think).

http://en.wikipedia.org/wiki/RS-68

Imagine a spaceX ssto with rocket engines derived from the rs-68 and technology from the SABER engine from the REL Skylon. It would be awesome.

Why not even a future ssto with a hybrid fusion engine. The UK already has one of the records for fusion energy.

http://www.extremetech.com/extreme/181298-the-uk-will-be-the-first-to-break-even-with-fusion-power-leading-us-towards-a-future-of-clean-infinite-energy

I can already see either the UNSC in the future...

Or a dystopian PMC run humanity... At least not by the ULA...

http://arstechnica.com/science/2014/05/spacex-says-rocket-purchases-violate-russian-sanctions-gets-injunction/

Edited May 4, 2014 by andrew123

[shynung]

I am not really sure how a spaceplane such as X-33 or VentureStar (the thing whose technology it was supposed to demonstrate) planning on using some RS-68 engines could really be an efficient surface-to-orbit vehicle.

The original design for both planes call for aerospike engines, which supposedly is efficient enough to propel it to orbit without needing external tanks or SRBs (a la Space Shuttle). However, a complete redesign of said spaceplanes, taking into account of currently-available technology and materials, could produce a usable craft.

Unfortunately, I do not see much promise out of this particular design. REL's Skylon SSTO probably can do the same job at less cost per mass.

[Woopert]

There's not much of a use for it. Sierra Nevada Corporation (SNC) is already making the Dream Chaser for orbital flights and it's not too expensive, hopefully. It's not SSTO, but it's cheap and gets into orbit so what's the difference?

DragonRider and CST-100 are capsules, get into orbit, and are still cheap. The Lynx spacecraft is suborbital but takes off like a plane.

For carrying payloads, conventional rockets work just fine.

[R0cketC0der]

What's the advantage of a reusable SSTO against a reusable TSTO? Also I think Elon Musk stated at some point that SpaceX won't try to build an SSTO.

[andrew123]

It would help us gain more technology in the form of r&d programs. Who wants to pass up a chance to fund NASA?

It could even be an excuse to pour military r&d into space travel. Imagine how much money the pentagon would throw at a ssto combat vehicle, but is it moral?

I don't really care. Space travel should be funded more.

Edited May 4, 2014 by andrew123

[SargeRho]

It was feasible back when it was canned, and it's deffinately now.

[Guest]

TBH, Space X could develop a reusable SSTO fairly cheaply. Just take Falcon 9 1st stage, remove some engines, stick a (small) payload to the top, and launch away. The only problem is that the result would be uneconomical, without a 2nd stage, the payload fraction would be really small, and it'd probably won't make it past LEO. We were fairly near SSTOs back in the 60s, with Atlas rockets. They jettisoned engines during flight, but if the design was kept and upgraded with better engines, it'd have no problems making orbit without dropping anything (the downside is, Atlas wasn't reusable).

That is the whole problem with SSTOs: they're uneconomical. For ascent, you mainly need TWR. For orbital insertion, you need high Isp, though, and TWR just puts stress on the rocket. An SSTO would require a throttleable engine, and won't use it's full potential for the vast majority of the flight.

Edited May 4, 2014 by Guest

[Srilania]

Considering part of the cancellation of the X-33 was the failure of the honeycomb composite? I don't know if you really want to borrow that technology when it's proven to fail.

[SargeRho]

That 'problem' got solved well before the project was axed. It's thus not proven to fail at all, quite the contrary.

[Nibb31]

X-33 was not an SSTO because it was never intended to reach orbit. It was a subscale suborbital demonstrator for the VentureStar concept.

Whether VentureStar was viable or not depended on results from the X-33, so I guess we'll never know. I suspect that the main reason for the X-33 to be cancelled was the realization that VentureStar would have such a small payload fraction that it wouldn't be viable.

[Streetwind]

Imagine a spaceX ssto with rocket engines derived from the rs-68 and technology from the SABER engine from the REL Skylon.

Why not even a future ssto with a hybrid fusion engine. The UK already has one of the records for fusion energy.

SpaceX isn't going for LH2/LOX engines like the RS-68. Cryogenic hydrogen is expensive and cumbersome, especially on flights beyond Earth orbit, such as those planned by SpaceX - and besides, the RS-68 is one of the least efficient LH2/LOX engines around, owing to the fact that it's focused on high thrust and that it's built on an open gas generator cycle. The most efficient engine the world has seen (measured in absolute Isp) is the space shuttle's RS-25, a closed cycle staged combustion engine with an insane chamber pressure and an Isp of 453 (compared to the RS-68's 410).

SpaceX's current secret sauce receptable is called "Raptor" and will be a liquid methane/LOX engine scheduled to hit the test stand sometime this or next year, with an Isp somewhere in the middle between kerosene and LH2. But likely closer to the former. The number 360 gets thrown around. The most interesting part about it is that it will use the so-called "full flow" staged combustion cycle, which is even more advanced that what the RS-25 offers. While the Russians produced a working test stand prototype in the 1960's (RD-270), no such engine has ever been flown. And it looks like the Raptor might well be the first, with the only other project currently considering it (ESA SpaceLiner) being targeted for 2030-2040.

As for the SABRE engine, it doesn't exist. The precooler does. REL will have to prove they can build the engine over the course of the next couple years... and then they have to prove it actually delivers the specs they're advertising. Patience, young grasshopper

And fusion... yeah. The UK got nothing. Even if the JET somehow achieves a net positive energy balance before 2020, which may not be possible considering the age of the reactor, that still doesn't make it a useful power provider. Just because the reactor is energy positive doesn't mean the entire facility is (there are more things drawing power than just the reactor containment field). And even if that is positive as well, it still isn't enough, because it has to start paying for itself. And for that you need to have a net positive of a dozen or more times the input, not just a few percent. And as for using it in a rocket engine... I hope you are aware that the JET facility is larger than entire rocket launchpads, heavier than the Saturn V, and of a reactor type that's completely unsuited for spacecraft propulsion in general?

So yeah... your "future SSTO" takes the "future" part literally. I doubt we'll even see any sort of fusion reactor small enough before 2050, much less a working engine design that flies. Icarus Interstellar, a scientific organization dedicated to interstellar travel, is pegging fusion powered spaceships capable of leaving the solar system for around 2100.

What's the advantage of a reusable SSTO against a reusable TSTO? Also I think Elon Musk stated at some point that SpaceX won't try to build an SSTO.

That's because SpaceX knows all too well the downsides of SSTO rockets: extremely expensive and awful payload fraction (combining into an abysmal kg-to-orbit price). Full reusability can bring the price of a SSTO down a lot, but it can do the same for individual rocket stages that pull higher payload fractions. Since the company's stated goal is making space access affordable, that's the route they will be going with.

Given equal reusability, literally the only advantage a SSTO has over a multi-staged vehicle is the reduced complexity by eliminating the staging process. You lose too much in return to make it worthwhile.

Now, a spaceplane concept can potentially overcome these difficulties, but only if it doesn't rely on classic chemical rocket engines. That technology peaked in the late 1970's; there's been no advances in Isp since then, not by a single second. Any prospective SSTO must exploit the higher Isp potential of air-breathing engines in order to push its payload fraction into regions that are economical to fly. That's what Skylon is aiming to be, fingers crossed.

It could even be an excuse to pour military r&d into space travel. Imagine how much money the pentagon would throw at a ssto combat vehicle, but is it moral?

1. NASA is a civilian agency, not a military one.

2. The USA signed and ratified a UN treaty that explicitly forbids putting weapons of any kind into orbit. Which is a great thing to have, especially since a lot of other countries also signed and ratified it. Including, and I kid you not, North Korea.

So in summary, the world's current focus at large is not anywhere near SSTOs. There have been enough canceled projects to outline the difficulties involved, both on the technical side (maximum dV for a single stage is hard limited by engine Isp, which in turn kills the payload fraction dead because chemical rockets are just not efficient enough) and the economic side (a two-stage rocket lifts more for less money). Skylon is the first vessel I've seen that has a chance to succeed on paper, but they're not even anywhere near the project stages in which unpredicted technical difficulties get discovered.

Instead, we're seeing a focus on improving sea level Isp over kerosene through development of methane engines - NASA, ESA and possibly others are testing their own designs. This will improve the payload fraction while simultaneously reducing fuel costs (although fuel is already an extremely minor component unless we're talking LH2/LOX). NASA is also pushing to build the SLS completely out of existing hardware, resulting in something that's hopefully a lot cheaper to fly than the shuttle could ever hope to be. And then there's SpaceX aggressively pursuing reusability of individual rocket stages, trying to combine the advantages postulated for reusable spaceplanes with the much higher performance of staged booster rockets. Having to reserve fuel for the booster return means the Falcon 9's payload fraction isn't very good, but it's still higher than what SSTOs would post, and ultimately the kg-to-orbit price will still improve by significant margins if they can pull it off.

Edited May 5, 2014 by Streetwind

[How2FoldSoup]

*snip*

2. The USA signed and ratified a UN treaty that explicitly forbids putting weapons of any kind into orbit. Which is a great thing to have, especially since a lot of other countries also signed and ratified it. Including, and I kid you not, North Korea.

*snip*

I really hate to nitpick because I really love the topic at hand but I feel it's necessary to point out that NK also signed the non-proliferation treaty and has subsequently backed out. I wouldn't count their word for much..

As for as my opinion for the OP goes we can dream of sci-fi SSTO shuttlecraft from bsg or star trek or what have you, but anywhere within the near future we will unfortunately be relying on reusable rockets more so than SSTOs. That being said if Skylon can make it work then more power to them. I'm certainly hoping they do but I'm holding that thought with a grain of salt.

I'd respond with more detail but I'm procrastinating so I'll stop while I'm ahead(behind).

[Streetwind]

Yeah, but backing out of a widely ratified military treaty usually comes with heavy penalties from the community of ratifying nations, while not signing it in the first place earns you a couple grumbles at best. While North Korea cares little about the UN, they stands to lose something when they back out of this, which is better than them standing to lose nothing. At minimum they'll be straining relations with China, who is their only remaining friend, is definitely interested in all things involving space, and has also signed and ratified the Outer Space Treaty.

The main point I was trying to make, though, is that the USA are diplomatically incapable of backing out of this treaty. If the world's biggest military spender suddenly decides they want weapons hanging over every other nation's heads, that will have a much better chance of starting WW3 than the current Ukraine crisis.

Edited May 5, 2014 by Streetwind

[magnemoe]

TBH, Space X could develop a reusable SSTO fairly cheaply. Just take Falcon 9 1st stage, remove some engines, stick a (small) payload to the top, and launch away. The only problem is that the result would be uneconomical, without a 2nd stage, the payload fraction would be really small, and it'd probably won't make it past LEO. We were fairly near SSTOs back in the 60s, with Atlas rockets. They jettisoned engines during flight, but if the design was kept and upgraded with better engines, it'd have no problems making orbit without dropping anything (the downside is, Atlas wasn't reusable).

That is the whole problem with SSTOs: they're uneconomical. For ascent, you mainly need TWR. For orbital insertion, you need high Isp, though, and TWR just puts stress on the rocket. An SSTO would require a throttleable engine, and won't use it's full potential for the vast majority of the flight.

This, it also has the benefit of not having to harden the large first stage for orbital reentry.

I was thinking about this the first time I saw the delta clipper, who not use it as a first stage,

[Nibb31]

This, it also has the benefit of not having to harden the large first stage for orbital reentry.

I was thinking about this the first time I saw the delta clipper, who not use it as a first stage,

And what you'd get would be very similar to the F9-R. SpaceX are practically replicating DC-X with their Grasshopper project. Note that Grasshopper has only reached 1/3 of the altitude reached by DC-X.

I personally beleive that the DC-X/Delta Clipper was more promising than X-33/VentureStar. It was simpler, cheaper, and it could have been converted to a secondary role as a Moon or Mars lander. But it suffered from "Not Invented Here" syndrome and NASA wanted wings, so there you go.

Edited May 5, 2014 by Nibb31

[R0cketC0der]

SpaceX's current secret sauce receptable is called "Raptor" and will be a liquid methane/LOX engine scheduled to hit the test stand sometime this or next year, with an Isp somewhere in the middle between kerosene and LH2. But likely closer to the former. The number 360 gets thrown around.

Actually the paper specific impulse for Raptor has already been released. It's 363 in vacuum and 321 at sea level.

[Streetwind]

Sounds like they're making good progress then. 321/363 is a great turnout for an engine with more thrust than the RD-180 used in the Atlas V, which is rated at 311/338 and has a great reputation.

Come on SpaceX, I wanna see a test firing already!

EDIT: looking into it, it seems they are indeed further than I thought and are planning to begin test firing the Raptor before the end of May. Neat! Although the test stand can apparently only handle sub-parts and not the full engine, as it would put out something like 10 times the thrust the test stand is rated for. SpaceX will have to build a new one for the full engine test.

Edited May 5, 2014 by Streetwind

[How2FoldSoup]

Yeah, but backing out of a widely ratified military treaty usually comes with heavy penalties from the community of ratifying nations, while not signing it in the first place earns you a couple grumbles at best. While North Korea cares little about the UN, they stands to lose something when they back out of this, which is better than them standing to lose nothing. At minimum they'll be straining relations with China, who is their only remaining friend, is definitely interested in all things involving space, and has also signed and ratified the Outer Space Treaty.

The main point I was trying to make, though, is that the USA are diplomatically incapable of backing out of this treaty. If the world's biggest military spender suddenly decides they want weapons hanging over every other nation's heads, that will have a much better chance of starting WW3 than the current Ukraine crisis.

I think I'm misunderstanding you, NK did ratify and sign the NPT but backed out some 10(2003) years ago. If that's not a widely ratified military treaty I don't know what is

But it's all semantics so ignore it I see the point you're trying to make and it's definitely a valid one. The only way to backout would be to amend the treaty it some way but I can't see that realistically happening. Militaries have no place in space as far as I'm concerned...for now.

[jwenting]

X-33 was viable even at the time, its cancellation was for purely political reasons.

The ship was 90% or so complete, the last components under construction.

Whether scaling up the concept to a production VentureStar would have worked is debatable, but by now we probably could do it, and without using Soviet engines.

[Seret]

Conventional weapons in space are allowed btw, it's only nuclear ones that are prohibited. The USAF has expressed considerable interest in a transatmospheric strike capability over the years. They like the idea of being able to hit anywhere in the globe with a vehicle based in the US that doesn't require hefty tanker support en route.

[andrew123]

What about the X-37 ominously hanging over our heads in space? The USAF only made minimal course redirects since it was launched over a year ago, and it is hypothesized to be a precursor to a weapons capable platform. http://www.extremetech.com/extreme/181426-us-militarys-mysterious-x-37b-space-plane-passes-500-days-in-orbit-but-we-still-have-no-clue-what-its-actually-doing-up-there

Did you really think the DOD would care about some treaty? Even JSOC?

Since I already have a reliable Atlas V design in KSP... hehe. My space program will embark on a national security mission... yeah.

Here's a quote from a comment.

Hopefully it is not growing biological weapons in zero g. That is always possible though. I read where Salmonella is something like 7 times more lethal when it grows in zero g. They could be testing hundreds of different viruses and bacteria. Just leaving them up there and letting them grow in various different conditions to see what happens over a prolonged period. The whole thing could be a flying death ship. Of course they could be doing something else with it, and hopefully are.

Looks like the science capsules will be useful after all. Those rebels on Duna might want to stack up on body bags.

Edited May 6, 2014 by andrew123

[Nibb31]

What about the X-37 ominously hanging over our heads in space? The USAF only made minimal course redirects since it was launched over a year ago, and it is hypothesized to be a precursor to a weapons capable

We had a thread a while back about what it might be doing. A weapons platform doesn't make sense - why would you want to bring a weapon back?

It's most likely a technology demonstrator to test long-term exposure of materials or microgravity production of materials (growing crystals or semiconductors). Nothing else makes any sense.

[RuBisCO]

My dream is this Howard Hughes verse TWA in space things (Musk verse ULA) will eventually result in SpaceX winning out big, such that ULA is forced to re-start something like the X-33 and Venturestar if they want any chance of having a market post 2020.

[andrew123]

A reusable weapons delivery platform. Just imagine multiple scramjet missile armed x-37 space planes orbiting earth with the excuse of scientific research. No more escaping terrorist, and no more Edward Snowden. I also think ULA should be forced into innovation again. The ULA becoming a niche research group will benefit us all in the long run. http://www.policymic.com/articles/22214/x-37b-and-the-5-scariest-super-weapons-the-military-is-developing-in-2013

[Nibb31]

A reusable weapons delivery platform. Just imagine multiple scramjet missile armed x-37 space planes orbiting earth with the excuse of scientific research. No more escaping terrorist, and no more Edward Snowden. I also think ULA should be forced into innovation again. The ULA becoming a niche research group will benefit us all in the long run. http://www.policymic.com/articles/22214/x-37b-and-the-5-scariest-super-weapons-the-military-is-developing-in-2013

Debunked plenty of times. Launching an Atlas V to kill a single escaping terrorist would be stupid. At $100 million a pop, it would be massively expensive, even for a prime target like Bin Laden. It takes months to prepare an Atlas V and you would have to launch your X-37 into the correct orbit, let it loiter there for weeks, and wait for the proper reentry window to launch the strike. An ICBM with a conventional warhead would be cheaper and faster. Prepositioning an Ohio-class with Tomahawks is cheaper, quicker, and stealthier. Even sending Navy Seals in speedboats is faster.

Satellites can be monitored by amateur astronomers, including the X-37. In fact, it's constantly tracked on Heavens Above:

http://heavens-above.com/PassSummary.aspx?satid=39025&lat=0&lng=0&loc=Unspecified&alt=0&tz=UCT

Deorbiting over hostile territory would be public knowledge and would give the target 30 minutes to pack up and move. The X-37 would come in hot and on a highly predictable course, so it would be easy to intercept and shoot down. But mostly, if you want to recover it, you're going to need a runway at the end of that reentry trajectory, which means that you already control a runway nearby the target. If you have that sort of capability, then you don't need a "global strike" vehicle in the first place.

There is a reason why both the US and the USSR agreed to ban orbital strikes in the 1960's: they had no strategic or tactical value.

PS. ULA is a launch provider whose only purpose is to sell rides on rockets provided by Boeing and Lockheed Martin. It doesn't do R&D or innovation. That's not what it's for.

Edited May 6, 2014 by Nibb31