90s SSTO: DC-X and VentureStar

[Redclaws]

So I wasn’t around in the space flight fan community in the mid to late 90s (was just a kid for most of it), but since I’ve been following things for the last few years, something has been bugging me.

How were the 90s SSTO proposals *ever* supposed to close on realistic systems?  I believe DC-X (which was itself a laudable effort) was the prototype for an SSTO, not a landable booster, and then there’s VentureStar.

The people doing these SSTO proposals weren’t insane, even if unrealistic - so how was the payload and cost equation supposed to close on something manageable?  It’s hard to see how hydrolox SSTO could ever have a payload fraction of ... much at all.

So, was it based on fantastical assumptions about a bunch of low TRL tech working out really well?  Or was it more moderate in technical assumptions, but still unrealistic in engineering reality?  Like, were the basic assumptions implausible - was it a tech research program that could never have closed in reality, or was it something that maybe could have but probably wasn’t going to in the real world?  (A more realistic but still doomed effort)

Thanks for your wisdom and information.

[freddo411]

Search the archives of NSF.    There is a thread on this exact topic.

Short answer:   Optimism + add a stage zero, probably solid boosters

[libra]

DC-X, X-33 and VentureStar were loosely related.

DC-X was funded from 1989 on the cheap via the last gasp of Reagan SDI: the SDIO, rebranded BMDO in the Clinton era.

In June 1990 Motorola rolled out Globalstar: a megaconstellation of thousands of satellites in low Earth orbit as early mobile-phone relays. At the time GSM and ground networks were bogged down in infancy and thus to get over frontiers, your mobile phone would need a satellite relay - just like broadband Internet today: mega-constellations. All of sudden the very sleepy launch market / launch vehicles industry - in limbo because Shuttle and because Challenger - went crazy again.

The DC-X was a Douglas product, strictly subsonic and low altitude, and it did a fantastic job: think StarHopper and water towers, in the 90's (I was 11 in 1993 and can remember a non-Internet world)

DC-X was to evolve into the suborbital DC-Y (note the Y as in YF-16, and the X as in X-15: prototype versus pre-serie) and finally, an orbital machine (I can't remember the name, must have been DC-1)

It would take a propellant mass fraction of 0.88 to reach orbit with RL-10s at 460 seconds specific impulse - and in the 80's HAVE REGION and SCIENCE DAWN DARPA programs had Boeing and others build metallic frames with such propellant mass fraction even if they never flew; only ground test articles.

So on paper at least, a hypothetical post DC-Y orbital vehicle was barely feasible.

That was the Douglas / SDIO plan circa 1992-1993 when DC-X flew.  August 18, 1993 at White Sands, with Alan Bean as remote-control pilot (or was he Pete Conrad ?)

Then with Cold War over and SDIO / SDI downrated to BMDO, DC-X and followers went to NASA. Which flew the DC-X until 1996 when it crashed and burn.

And there... come Lockheed. And Rockwell.

NASA couldn't left Douglas alone even with the successfull DC-X so there was a brand new overambitious Goldin-era NASA program; followed by a brief bidding war; and Douglas lost, unfortunately.
Rockwell proposed a Shuttle-shaped SSTO, and Lockheed: a lifting body with composite tanks and aerospike engine.

X-33 was to fly suborbital at Mach 15... then Mach 12... then it fell to Mach 6... it was to fly in 1999 (from a start in July 1996 !) but nothing happened.
It was betrayed by its composite tank, which couldn't stand Lifting body tortured shape on one side and liquid hydrogen on the other.

In November 1999 a prototype composite tank failed, Lockheed went for aluminium and from there, X-33 went downhill until March 2001 when it was canned for SLI, itself canned for "Orbital Space Plane (and capsule !)"Orion (and Constellation) after the STS-107 disaster two years later.

Venturestar was to reach orbital speed (mach 25 +) in the early 2000 but was a deeply flawed concept from day one.

Lockheed wasn't really honest on the entire story. Not sure an orbital DC-Y would have been better althougth its shape was much simpler, a dumb cone rather than a lifting body.

Phew !!!

[libra]

Rocketry and the laws of physics haven't changed by an inch since 1993 or 1999. With a specific impulse of 380 Starship would need at least 0.94 PMF to make it to orbit with little payload. With its superior specific impulse LH2 lowers the PMF to 0.88 at the expense of LH2 difficulties with tankage.

Musk is pushing propellant mass fraction of Starship as far as possible but stops mostly at 0.86 since he has BFR below it to send it to orbit.

Had musk tried a Starship SSTO, DC-1 style he would have faced the same hardships: daunting mass fraction and pitiful payload.

DC-1 and Venture star tried head-on to achieve this, and failed. NASA of the 90's was a mixed bag, Administrator Dan Goldin (1992-2001, still a record)  achieved great things but went too far on "faster better cheaper": this led to disasters with Mars probes (1999 annus horribilis) and later on, to STS-107 tragedy. Also CONTOUR, the last ever JPL probe that failed:  in 2002, nearly twenty years ago !

There were also
- X-prize started in 1996
- NASA X-34
- Motorola Globalstar and Bill Gates (yes, freakkin' Bill Gates very own space venture, Bezos style) Teledesic megaconstellations (not for broadband Internet: for mobile phones that weren't smartphones yet; in place of land networks ruled by GSM)
- To launch the megaconstellation of satellite phones, no SpaceX - Kistler was already there, and a bazillions of others mostly failed and forgotten today. In fact it looked a lot like today with a crapload of newspace companies blooming all over the place. They all died in 2000 when the Dot-Com boom bubble bursted and GSM ground networks  slained satellite phones except in Antarctica.

[mkent]

...insane...unrealistic...fantastical...unrealistic...implausible...never have closed in reality...doomed effort

Wow!  Such arrogance.  Maybe if you'd start from the premise that the people attempting this were not morons but instead some of the best aerospace engineers of their day you'd have a better chance of understanding.

Some other corrections that need to be made:

1) Globalstar was not a Motorola product and was not a megaconstellation.  Globalstar was a 48-satellite telecom constellation built by Loral and Qualcomm to service satellite telephones.

2) Irridium was the satphone constellation financed by Motorola.  It wasn't a megaconstellation either.  It was originally designed to have 77 satellites (hence the name), but that was later reduced to 66 satellites in the active constellation.

3) Teledesic was a proposed 840-satellite constellation of broadband internet satellites financed by Bill Gates and Craig McCaw.

4) Delta Clipper was a product of McDonnell Douglas Astronautics Company (MacDAC), not Douglas, though its acronym intentionally gave homage to the Douglas Commercial (DC) series of commercial airplanes, specifically the DC-1 and DC-3.  The "Delta" part of the name honors the MacDAC Delta family of launch vehicles -- called "the workhorse of space" -- and the "Clipper" part of the name honors the Yankee Clippers of early American nautical tradition.

5) It was Pete Conrad, not Alan Bean, that led the DC-X launch team.

DC-X's sponsor was the Strategic Defense Initiative Organization (SDIO), the DoD agency tasked with developing, deploying, and operating the Strategic Defense Initiative, a space-based constellation of satellites that could shoot down incoming ballistic missiles before those missiles could detonate their payloads.

The SDI design under development at the time was called Brilliant Pebbles, a constellation of up to 100,000 satellites.  Delta Clipper was to launch this constellation.

To be able to cost-effectively deploy such a large system, Delta Clipper would have to be fully and rapidly re-usable.  SSTO was how they would be able to achieve that.  With a single stage, the risk of staging failures was eliminated, as was the cost of stacking the vehicles on the ground.  Delta Clipper was being designed so that each vehicle could land, re-fuel, and fly again several times a day.

DC-X successfully tested the landing flip maneuver, the low-cost operations, and the rapid re-usability aspects of the system.  DC-X2 was the proposed Mach 13.5 follow-on for the X-33 program that would test the re-entry and hypersonic flight aspects of the system.  DC-Y would then be an operational prototype to test the orbital aspects of the system.

Alas, the lack of support for Brilliant Pebbles in the Bush administration and its transition to the much smaller GPALS system removed the need for Delta Clipper.  The program was moved to NASA who, quite frankly, didn't want it.  They plodded along with a few tests until a maintenance error led to the destruction of the test vehicle, allowing NASA to happily kill the program.

The end of NASA's involvement didn't end the effort, however.  Boeing continued on with it with their own money, planning a Delta-II-sized vehicle to debut around 2010 to service Teledesic and other commercial megaconstellations.  That's why there was never a Delta IV small to go with the Delta IV medium and Delta IV heavy.

The NASDAQ crash of 2000 killed Teledesic and the other megaconstellations, and without adequate customers, Boeing quietly shut the effort down.

But nowhere along the way did anyone in the know dismiss the effort as "insane", "fantastical", or "doomed."

[Redclaws]

...insane...unrealistic...fantastical...unrealistic...implausible...never have closed in reality...doomed effort

Wow!  Such arrogance.  Maybe if you'd start from the premise that the people attempting this were not morons but instead some of the best aerospace engineers of their day you'd have a better chance of understanding.

Thanks for your polite words.  I notice you’re the only person so far to suggest these efforts *weren’t* doomed or disagree with the language.  Have you considered that with the benefit of hindsight, yours might not be the majority view?

I did specifically start with the premise they were excellent engineers, but their projects failed and sank with basically no trace whatsoever in modern practice.  Seriously - what from these programs is ... anywhere in current practice?  So, I asked *why*.  Because presumably people today - hell, it hasn’t been that long, some of them are the same people - aren’t fools either.

[Redclaws]

...insane...unrealistic...fantastical...unrealistic...implausible...never have closed in reality...doomed effort

Wow!  Such arrogance.  Maybe if you'd start from the premise that the people attempting this were not morons but instead some of the best aerospace engineers of their day you'd have a better chance of understanding.

Thanks for your polite words.  I notice you’re the only person so far to suggest these efforts *weren’t* doomed or disagree with the language.  Have you considered that with the benefit of hindsight, yours might not be the majority view?

I did specifically start with the premise they were excellent engineers, but their projects failed and sank with basically no trace whatsoever in modern practice.  Seriously - what from these programs is ... anywhere in current practice?  So, I asked *why*.  Because presumably people today - hell, it hasn’t been that long, some of them are the same people - aren’t fools either.

I also notice you describe various program accomplishments (which I agree with), but nowhere do you engage with questions like “how would they achieve a viable payload fraction with SSTO?”.  I’m specifically asking about the challenges they didn’t solve, and what happened.  It was judged - even in their own time - that these projects weren’t going to work out.  That’s ... you know, why they were cancelled.

I’m trying to understand what the hopes were and where they were wrong.  I come to the conclusion they were wrong because A) the projects failed in their own time (none of them got even close to trying for orbit), and B) broadly speaking,  the approach has since been abandoned, and I don’t think really any of it survived.

[libra]

It would have been pretty hard to build the VentureStar from a strictly engineering point of view.

Goldin's NASA (overambitious on a shrinking budget, basically) and Lockheed shenigans made it a complete failure.

I remember when the program was started early July 1996 (25 years ago next month and counting !) - the timeline was already insane: X-33 by 1999 and VentureStar around 2002.

It was hoped that composite LH2 tank and aerospike technologies could help the design achieving orbit. While aerospike worked correctly,  the composite tank was trickier, broke during ground testing. The program then went downhill and died by March 2001.

The program was moved to NASA who, quite frankly, didn't want it.  They plodded along with a few tests until a maintenance error led to the destruction of the test vehicle, allowing NASA to happily kill the program.

This is not correct. It smells as if NASA sabotaged the program. DC-X actually fit well with Goldin agenda "faster better cheaper" just like clementine, another SDIO space project NASA was happy to collaborate : it provided their first lunar missions since the Apollo days.

I think I got my satphones constellation wrong. There were these three and some others that remained paper bound.
Note that Iridium survived and still exist: they have bridged the gap between the two generation of satellite constellations.

It was pretty amazing circa 2013 to see satellite constellations return from the purgatory they had been stuck since 2001.
Except this time it wasn't a matter of mobile phone, but of broadband internet. The basic issue - GEO not possible because latency - led to similar solution: tons and tons of satellites in LEO.

[libra]

How were the 90s SSTO proposals *ever* supposed to close on realistic systems?

There was a Falcon 9 look alike, the Kistler K-1. It was smaller, with russian engines and no overslam: the stages would have landed downrange using parachutes and airbags. At least both stages would have been reusable; but payload was barely 10 000 pounds to LEO and no higher.

By the way, Kistler survived the 2001 crash and was one of the COTS competitors in 2006, winning along SpaceX.
Except Kistler was a deeply flawed company and even with a juicy  NASA contract they could not close their business case and fly something.
 End result: NASA threw them away the year after, in summer 2007; to the delight of Orbital Sciences and the Cygnus spacecraft. 

The Beal BA-2 was quite a decent concept of a 2-stage big dumb vehicle, except it wasn't reusable and did not survived the 2000 dot-com crash. Shame, they had fired powerful RP-1 / H2O2 rocket engines at the time of cancellation. But Andrew Beal blew a fuse about subsidized EELVs and (unlike Elon Musk a decade later with Falcon 9) threw the towel bitterly.

[Robotbeat]

Just want to point out that DC-Y was to be orbital, not just suborbital. Design design could’ve closed.

X-33 was a suborbital demonstrator for venturestar as you said, but the aero spike didn’t help performance but made it worse due to high weight.

Are you doing, these single stage to orbit concepts where hampered by using hydrogen which was just not dense enough. Some sort of hydrocarbon fuel or maybe a tripropellant would have allowed the designs to close.

Beal bought up the land and built the tripod stand that SpaceX ended up getting for a song, so it wasn’t all wasted effort.

[Robotbeat]

You can also ask HMXHMX who actually helped lead DC-X and is an active forum member.

[Redclaws]

Thanks all, this is exactly the kind of interesting reflection I was hoping for.

And to be clear, I think there were some impressive accomplishments - DC-X was definitely not a failure in any sense.  It’s just the programs as a whole mostly sank without a trace, and I think the whys of all that are fascinating.

[TrevorMonty]

Thanks all, this is exactly the kind of interesting reflection I was hoping for.

And to be clear, I think there were some impressive accomplishments - DC-X was definitely not a failure in any sense.  It’s just the programs as a whole mostly sank without a trace, and I think the whys of all that are fascinating.

The programs weren't waste of time and money. Some of DC-X engineers ended up at Blue and help perfect NS.

[Nomadd]

 The best rundown on VentureStar/X-33 I know was by some guy trying to start a space based forum 15 years ago.
 Not sure what ever happened to him.

https://www.nasaspaceflight.com/2006/01/x-33venturestar-what-really-happened/

[su27k]

Also the idea of SSTO started long before the 90s, Chrysler SERV was proposed in the 60s as a candidate for the Space Shuttle, and after Shuttle decision was made, NASA and Boeing studied RASV as possible successor to Shuttle. There're also a bunch of SSTOs proposed during the NASA late 70s space solar power study.

90s is when SSTO stopped being paper rocket and started to take physical form.

[RoadWithoutEnd]

Others have given the technical answer to this question, but I can offer the (much more depressing) human angle on the '90s SSTO thing.

These programs never had real support in Congress, so nobody with power actually cared whether or not it would work.   They would fund it a certain distance, and when it hit any snags, they would cancel it and move on to something else.  The contractors got paid whether it worked or not.

DC-X didn't have support because the Pentagon didn't care about reusable launch vehicles.  They preferred to develop SRBs due to their utility for weapons propulsion, and EELV heavy-lifters for spysats.  Cost was a very low priority, or even seen as a good thing due to the career benefits of working with cost-plus (as in, high profit-margin) contractors.  Also, DC-X got too much attention for a project with so little higher-up support, which tends to bring down the hammer. 

Later in the decade, problems with Shuttle started gnawing on NASA, and it seemed as good a time as any for the White House to make a cheap press release about doing something new.  But they signaled how seriously they took the whole thing by announcing it in some barely-covered, off-cycle press event with Al Gore rather than Bill Clinton, unveiling a little toy model of Lockheed's concept.

Again, no one in the industrial ecosystem was that interested.  Shuttle had persisted due to the sheer size of its workforce, which the SSTO concept was openly trying to cut, so X-33 had no native constituency.  It was treated as little more than a side project for Lockheed to dip its toes in, and given strong hints not to take it too seriously.  When Lockheed figured out the carbon composite tank tech would need significant new funding to develop, the government shrugged and canceled the program as an afterthought.

The horrific thing to realize is that the exact same thing would have happened even if it had been the right idea.  Quite probably it would have been canceled even if it never ran into problems.

[Malcolm Jarmyn]

The Hawk Junior is an Australian SSTO methalox launch rocket, being built in South Australia by Jarmyn Enterprise Space.

[Reynold]

My recollection of the X-33/Venturestar program is that there were three finalist proposals from different companies, and NASA deliberately chose the "most technically challenging" one of the three.  I was a bit dubious about that at the time, after seeing other "technically challenging" Shuttle replacement programs get canceled.  When the composite tank failed and a LOT more money was going to be needed to figure out a solution that was the end of the program. 

I also got the impression that NASA was not very interested in the DC-X after they inherited it from DARPA, but it was a lot harder than it is now to get the inside story of that kind of thing.  The fact that they didn't even bother to rebuild the cheap prototype after a maintenance issue crashed it didn't exactly speak to support at upper levels in NASA or Congress though. 

At the time I was a lot more excited about the DC-X than Venturestar, as I'd also seen the first article that made a mathematical argument for using fuel for a tail landing over the weight, drag and horizontal/vertical landing structure penalty of wings.  That kind of tradeoff was a lot less well understood at the time, I think.  Frankly I think you could have won pretty good money from most rocket scientists as late as 2014 that tail landing recoveries would never work in a REAL rocket. 

[libra]

in the DC-X after they inherited it from DARPA

They inherited it from SDIO 

[WIgorN]

People, why did everyone stick to that HydroLox?
For HTP + RP1, the British in the 70s of last century achieved a MR ~ 0.076. Since then, material science has advanced greatly.

98% Peroxide gives a ISP(vac) of ~ 330s / At a saturated vapor pressure much lower than AT+hydrazine derivatives. Make storage possible of fuel and oxidant in an elastomeric bellows with resistance to peroxide and RP-1. Density is better than semicryogen KeroLox.

There is an idea to catch the spent stage in the landing final (landing supports are not required) - control of landing on a trampoline. Guidance system already allow this, weigh an order of magnitude less

To start constructive "Fitness" with a parallel layout - integrated "carrots" layout, all the "carrot" of the R-7 of the first stage merged into one "carrot". Each stage - sector part cone has its own part of the outer wall of the cone. The outer wall can perform functionality TPS.

What will be your thoughts? Didn't anyone do such or similar?
Thank you, please, in essence. Sorry for google translate. I will be glad to clarify what is not clear.