Whatif - USAF completed the X-33 (after 2001) ?

Archibald

Banned
WARNING: I say the X-33 mach 15 demonstrator, NOT the orbital VentureStar !

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

http://www.hobbyspace.com/AAdmin/archive/RLV/2001/RLVNews2001-06-12.html (browse X-33)

http://www.spacetoday.net/Summary/380

Whatif they did ? To me it is one of the great whatif of the space shuttle era (1971 - 2011)

Even suborbital, the X-33 could be used for all kind of military missions. Also, with an expendable uppper stage it could perhaps launch small payloads to Earth orbit. Sounds familiar ? DARPA XS-1 maybe ?
https://en.wikipedia.org/wiki/XS-1_(spacecraft)
The X-33 would be notably bigger and faster, than the reusable XS-1 stage 1.

An alternative to the Air Force might be DARPA and their RASCAL project
http://www.globalsecurity.org/space/systems/rascal.htm
http://spacenews.com/rascal-contractor-pushes-scaled-back-launcher/
 
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The cost-effectiveness would depend a lot on the upper stage stack and their payload target. With upper stages in the 20-50 metric ton gross mass category, you'd push the burnout velocity of the X-33 from 5.2 km/s down to about 3.6 km/s--roughly the same as SpaceX's first stage. That'd mean you'd knock out the entire TPS problem--you could just go with an aluminum or titanium skin. The cost of the upper stage would be a concern. The larger the upper stages, the better it gets for payload, but the more costly the price per launch is. It'd be capable of 4 metric tons to LEO with a Centaur-class hydrolox stage on its back, but that'd bring in the RL-10 cost problems. A kerolox stage, even one about 40 metric tons, would bit limited to about 1.5 metric tons. That'd take it from competing with Delta II to living more in the Minotaur class which is less popular with payloads--only about 60 launches in that segment between 1990 and 2010 that I can quickly total up--though that could change with a cost per flight of perhaps only $20 million or so. That'd give it a shot at the entire Pegasus and Minotaur line for about half the cost.
 
Weight gain had already pushed the empty X-33's target velocity down to Mach 10 by May of 1999. To make it a useful first stage, you'd need to restrain the empty weight starting in 1997--it was already 33% overweight then. Composite technology, it seems, just wasn't yet up to the challenge of dealing with complex LH2 tanks.

The most likely upper stage would be a solid one--that avoids the handling costs of hypergollics, and the expense of RL-10. They were fairly cheap, too--Castor 120 in volume production would only cost some $3.5 million.

Furthermore, X-33 was in many ways a pet project of Al Gore--he was the one who announced its contract, and so was wedded to it in the 2000 election. Which made it that much easier for Bush to can it. This might be impossible without a Gore victory.
 

Archibald

Banned
Good !
Surely enough, the small satellite market took a long time to soar, but cubesats changed a lot of things.
Quick check of Wikipedia show that the concept of Cubesat was floated circa 1999 or so.
https://en.wikipedia.org/wiki/CubeSat

The most likely upper stage would be a solid one--that avoids the handling costs of hypergollics, and the expense of RL-10. They were fairly cheap, too--Castor 120 in volume production would only cost some $3.5 million.

Ninja'd by Polish Eagle :p

A kerolox stage, even one about 40 metric tons, would bit limited to about 1.5 metric tons.

Does a storable or kerosene or solid-fuel stage has to mass 40 tons + ? I wonder if an IUS could do the job "off the shelf" with its multiple solid-fuel stages ? Would that deliver any payload into orbit ? It would be a sweet irony if the IUS found a new job riding on the Space Shuttle successor...

Furthermore, X-33 was in many ways a pet project of Al Gore--he was the one who announced its contract, and so was wedded to it in the 2000 election. Which made it that much easier for Bush to can it. This might be impossible without a Gore victory.

The butterfly effect - a decision on the X-33 in the middle of the year 2000 could impact NASA > KSC > Florida one way or another - and the recount was so close, it might get Al Gore in the White House... it would be fun if NASA KSC employees voting differently changed the election result.
 
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The stage need not be all that big--the 'Black Colt' design proposed by Zubrin at Martin Marietta and then at Pioneer Rocketplane suggested a Star 48V with a 1000-lb payload staging at Mach 12. If we can get X-33's target speed back up past that, then the 2.6 tonnes of upper stage plus payload isn't all that bad an increase.

Of course, the problem remains 'not letting this thing get so fat.'

As to economics, it would get you Pegasus-sized payloads at the cost of an X-33 flight and a Star 48. How much would each cost?
 
The most likely upper stage would be a solid one--that avoids the handling costs of hypergollics, and the expense of RL-10. They were fairly cheap, too--Castor 120 in volume production would only cost some $3.5 million.
The problem is their performance. Castor 120 on top of the X-33 could push about 900 kg. Adding a Star-48A could dramatically increase that, bringing it to about 2500 kg. The smaller IUS two-stage stack would enable 1500 kg. Not sure what the heck a Star costs, though.
 
When discussing Black Colt, Zubrin quotes a $1.4 million estimate for Star 48V. So how much would an X-33 flight cost?

EDIT: The payload bay on X-33 limits you to a Star upper stage. It was only 5 by 10 feet--a Castor would be way too big. Star 48 takes up 2/3 of it. Unless you can mount it on the nose (and then you need an interstage and payload fairing), this won't fly with Castor. Even the IUS second stage, at 5'3" diameter, is too big.
 
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Archibald

Banned
When discussing Black Colt, Zubrin quotes a $1.4 million estimate for Star 48V. So how much would an X-33 flight cost?

EDIT: The payload bay on X-33 limits you to a Star upper stage. It was only 5 by 10 feet--a Castor would be way too big. Star 48 takes up 2/3 of it. Unless you can mount it on the nose (and then you need an interstage and payload fairing), this won't fly with Castor. Even the IUS second stage, at 5'3" diameter, is too big.

Hard to find a valuable number. I'd say "somewhere between 500 000 $ and 2 million $". The smaller and slower X-34 was to cost 500 000$ per flight.
 
An even million, then, sounds reasonable. So 1 million for X-33, 1.4 million for Star 48 (possibly falling with mass production?), 450 kg or so payload, for a per-kilo cost of some $5,300 in 2000. I think that's still marginally better than its competitors at the time, and certainly beats the pants off OTL Pegasus. But how much demand can there really be?
 
EDIT: The payload bay on X-33 limits you to a Star upper stage. It was only 5 by 10 feet--a Castor would be way too big. Star 48 takes up 2/3 of it. Unless you can mount it on the nose (and then you need an interstage and payload fairing), this won't fly with Castor. Even the IUS second stage, at 5'3" diameter, is too big.
Yeah, but there's always external carry as an option--they were calling for it on the operational Venturestar by the end.

As for sales outlook, there were IOTL about 60-70 flights in the <500 kg range between 1990 and 2010 IOTL that I see, looking at Minotaur, Pegasus, and the like. That might expand a bit with a per-flight cost of $1m instead of Pegasus' $50m, but 500 kg is only so big.

With a two-stage Castor 120/Star 48 stack, call it $4.5m for 2.5 metric tons. That'd get you into the range of Minotaur IV, Dnepr, the small Deltas, and the like. That'd offer about double the number of launches just from the OTL history in that period, and 2.5 metric tons is large enough to actually do reasonable things with.
 
External carry--as in piggy-backing? That could work better than nose-loading.

$4.5 million seems a little low--you're expending two stages and have the turnaround for X-33 to consider. I'd say $5.5M is more likely. Still, that takes the per-kilo cost under $3,000, which brings you to SpaceX territory.
 
External carry--as in piggy-backing? That could work better than nose-loading.
Yeah, like this:
Image-of-venturestar.jpg


$4.5 million seems a little low--you're expending two stages and have the turnaround for X-33 to consider. I'd say $5.5M is more likely. Still, that takes the per-kilo cost under $3,000, which brings you to SpaceX territory.
And 2.5 metric tons is a payload range that has a lot more upside sales potential. 500 kg can't even launch a single 685 kg Iridum satellite, while a 2.5 metric ton LV could stack 3 or 4. That'd give another 20-odd flights just from Iridium if you can pull them away from Proton and Long March--and at $3000/kg you probably could.
 
There's another constraint on the size of the upper stage--X-33's thrust. To have a T:W ratio of 1.1 at the pad, you need a max take-off weight of 168 tonnes--or X-33 plus 40, including upper stage and payload. Castor 120 is too big for it.

A potential way around this problem is to increase the number of X-33s used as boosters--lifting a Castor plus 10 tons would require 2 of them.

And if you can do that, you could conceivably do more. Replacing the Shuttle SRMs is probably out of the question (you'd need 14 to do it) but I could imagine Lockheed-Martin proposing it as a booster for Atlas V.

Somewhat more 'out there' is a fully-reusable 'pentamese' variant--if you can do cross-feed, you could lash five of them together and drop off two at a time until the top stage gets to orbit.
 

Archibald

Banned
I think an IUS and 1500 kg of payload is a nice compromise. Both vehicles are off-the-shelf. The IUS would ride piggyback on the X-33.
More importantly, the Air Force was one of the major player in IUS development, and flew its last in 2004 atop a Titan IV. So the timing is fine (2001 to 2004).

IUS characteristics

Height 5.2 m (17 ft)
Diameter 2.8 m (9 ft 2 in)
Gross mass 14,700 kg (32,400 lb)
 
I did the math and an Atlas V core with X-33s as boosters would actually be a very capable LV. A single X-33 booster should enable the rocket to put 6 tonnes through GTO, while two of them boosts that to 7.5. The X-33, if used as an Atlas V booster, would enable LockMart to drop the costs of SRBs on that rocket--which Wikipedia says cost $10 million each (unsourced, but that's about the higher-end of a Castor 120 given by Astronautix, and they're similar in size). The issue is a landing site--you'd want to under-load the X-33s, or restart the aerospike at apogee for boost-back, so they don't reach the full 4+ km/s they would stage at if fully loaded. If you don't, they'll fly down-range into the open Atlantic. That would hurt your payload, but not necessarily enough to invalidate the concept.
 
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