Space shuttle for space tourism and first stage TSTO.

[exoscientist]

Robert Zubrin in his book "Entering Space: Creating a Spacefaring Civilization" makes some interesting observations about the space shuttle:

"The shuttle is a fiscal disaster not because it is reusable, but because both its technical and programmatic bases are incorrect. The shuttle is a partially reusable launch vehicle: Its lower stages are expendable or semi-salvageable while the upper stage (the orbiter ) is reusable. As aesthetically pleasing as this configuration may appear to some, from an engineering point of view this is precisely the opposite of the correct way to design a partially reusable launch system. Instead, the lower stages should be reusable and the upper stage expendable. Why? Becasue the lower stages of a multi-staged booster are far more massive than the upper stage: so if only one or the other is to be reusable, you save much more money by reusing the lowere stage. Furthermore, it is much easier to make the lower stage reusable, since it does not fly as high or as fast, and thus takes much less of a beating during reentry. Finally the negative payload impact of adding those systems required for reusability is much less if they are put on the lower stage than the upper. In a typical two-stage to orbit system for example every kilogram of extra dry mass added to the lower stage reduces the payload delivered to orbit by about 0.1 kilograms, whereas a kilogram of extra dry mass on the upper stage causes a full kilogram of payload loss. The Shuttle is actually a 100-tonne to orbit booster, but because the upper stage is reusable orbiter vehicle with a dry mass of 80 tonnes, only 20 tonnes of payload is actually delivered to orbit. From the amount of smoke, fire, and thrust the Shuttle produces on the launch pad, it should deliver five times the payload to orbit of a Titan IV, but because it must launch the orbiter to space as well as the payload, its net delivery capability only equals that of the Titan. There is no need for 60-odd tonnes of wings, landing gear and thermal protection systems in Earth orbit, but the shuttle drags them up there (at a cost of $10 million per tonne) anyway each time it flies. In short the Space Shuttle is so inefficient because it is built upside down. {emphasis in the original}
"Entering Space", p. 29.

This provides support for the view of the Air Force that reusable first stage boosters can cut the costs to space by 50%:

Spacelift Development Plan.
http://www.acq.osd.mil/nsso/conference/briefs/HampstenSDP Public Release.ppt

The shuttle is quite large for an upper stage. But it is the right size for a first stage. It's my intention to turn the Space Shuttle System right-side up by making the orbiter into a reusable first stage.


Bob Clark

 

[EarthlingX]

So what exactly would you use from the Shuttle ? SSME ? RS-68b would be cheaper and easier for maintenance. Heat protection ? No need for such a heavy TPS with the low speeds of first stage. Wings ? What wings ? It needs cca 20% glide slope to fly, which is a lot, not much room for maneuvers. Avionics, computers ? Ancient (90ish). Logo maybe ?

I heard of this Airforce plan before, and i think, they do the right thing, again.

 

[frodo1008]

Exo, you really must be a riot at geek level parties! When you stated:

"Just a mix up with the units. Not a problem."

I almost fell off of my computer stool with laughter! Just for your information that is a HUGE problem!!!

Just for your information there are just about 2.2 lbs in a single kilogram!!

With all kindness, in the spirit of truth I must state that your ideas are not only non feasible, they are TOTALLY AND PHYSICALLY IMPOSSIBLE!!

Has it not occurred to you yet that the people that originally designed and built the entire Space Transportation System (STS) possibly even knew what they were doing?

You can NOT get the orbiter into LEO without both two of the most powerful solid motors ever built, and the vast amount of fuel and oxidizer that those three very efficient SSME's use. And that IS why (as you even stated with your own statement) the External Tank is so very much larger than even the orbiter itself!

Besides that, if you then even could use the internal bay of the orbiter for the propellants for engines even close to powerful enough to get just the orbiter into sub orbital space, let alone LEO, then where are you going ot put the 100 passengers that you talk about?

If you were to consider even just the weight of 100 totally naked passengers at only about 150 lbs each, you are looking at 15,000 lbs of net cargo weight to LEO, and that is to say nothing of the weight of the materials that it would take to keep those passengers alive for the many orbits that it would then take. I would have to say the total weight for those passengers would have to be at the very least 30,000 lbs.

Such levels of weight have indeed been carried into LEO to even the ISS's orbit, but it takes the ENTIRE shuttle system to do it!

You know this sort of rocket science is not just coming up with ideas, and then placing them on a PowerPoint presentation. It is such science as physics and engineering!

If you were even to use the orbiter as just a first stage fly-back booster, and orbiter that you could then launch into LEO would be far too small to carry even the number of passengers as the Spaceshiptwo that Burt Rutan is building just to get into sub orbital space with some 6 passengers!

Both the Dragon capsule of spacex, and the Orion capsule of NASA are going to require Heavy Lift Vehicles just to get to the ISS. The equipment bay of the orbiter is far too small to provide enough propellants for powerful enough engines to get any reasonable amount of human beings into LEO. Let alone do that with all of the extra weight of the current orbiters!

One of the main reasons that the space shuttle is such a kluge (a magnificent kluge, mind you, but still a kluge) was that it would have been far to expensive (Congress inadequate reasoning) to initially develop a true TSTO system. This is because the first stage of a fly back type booster would have been almost as large as the original Saturn V just to get the current orbiter into orbit. It indeed would have been a winged vehicle itself similar to the orbiter, (but not as complicated as it would not have required a full TPS system) but at least twice as large.

I would have to say that it is one of the unfortunate results of the nickle and dime type of thinking of Congress that we did not do this correctly in the first place. Had we done so there would have been far higher upfront costs for the system, but the savings in the long run would have brought the eventual launch of the space shuttle down by at least 50%, and made the shuttle inexpensive enough that it would still be in use many years from now, but that IS hindsight, and if you have as little foresight as Congress does, then that hindsight is all you are going to be able to use. Sad, but true!!

You have however done something very useful here, at least to me anyway. What you have done is to "Stimulate the Little Grey Cells" as the great fictional detective Hercule Peirot would say. What this will hopefully do is to give me the incentive to put forth a thread with a poll of the various methodologies for getting at least some ten none astronaut (wealthy and healthy, but otherwise relatively ordinary) people into LEO. Maybe, that way we can find out just what the people here really think!

But, please forget about using anything but perhaps some of the various propulsion units of the current shuttle system, and certainly NOT the orbiter! NASA IS going to only sell them to museums, where they will rightfully get the attention of future space travelers, and even perhaps the respect that they deserve! While they will never be used again, it should be remembered by us all that they DID "Keep The Dream Alive!" during such a time as it could have died! And gave us such fantastic scientific wonders as the Hubble while doing it. They and the people associated with them certainly deserve that much honor anyway!!

By the way, most of my 37.5 years of working career in aerospace was spent in helping to make one of the greatest single pieces of machinery in the history of mankind, in the truly incredible SSME's!!!!

Have a most excellent day!!

 

[exoscientist]

...
The Air Force is looking for designs for reusable first stage boosters for two-stage-to-orbit (TSTO) systems. Then it might be able to be used for this purpose. Most likely you would use kerosene fuel for this since dense fuels are more suitable for first stages.
The payload bay would be converted to a fuel tank, and the second stage of the TSTO would be carried on top or below the orbiter. High performance kerosene engines such as the Russian NK-33, with a near legendary thrust/weight ratio of 136.66 to 1 at a weight of 1,222 kg, could be used for propulsion:
NK-33.
http://www.astronautix.com/engines/nk33.htm
The orbiter without the SSME engines masses around 68,600 kg:
Atlantis.
http://www.astronautix.com/craft/atlantis.htm
Its payload bay is around 300 cubic meters that could be used for propellant. Using the densities of kerosene and lox given here:
Lox/Kerosene.
http://www.astronautix.com/props/loxosene.htm
and the oxidizer to fuel ratio of the NK-33 of 2.8 to 1 we can calculate the propellant load that can be carried as about 300,000 kg. You would need at least 3 of the NK-33's to lift this fuel load, orbiter and second stage.
The tank weight of kerosene/lox is typically around 1/100th of the propellant weight so around, 3,000 kg. Then the empty weight of the reconfigured orbiter would be 68,600kg + 3*1,222kg + 3,000kg = 75,266kg. And the fully fueled weight of this stage would be 375,266kg.
...

I mentioned before converting the space shuttle orbiter into a first stage use would actually be quite important. I discuss this below.

I.)Weight savings by removing unneeded components.
II.)Replacement of the Ares I first stage by the reconfigured shuttle.
III.)Costs saving by private commercial financing rather than "cost-plus" contracts.

I.) I wanted to get some shuttle component weights to estimate the weight savings we could make by removing systems that would not be needed for a suborbital or first stage use. The Astronautix page on the Shuttle Atlantis gives its "Heat Shield Mass" as 12,100 kg (26,600 lb).
However, Astronautix is sometimes inaccurate. So I found this report after a web search:

Thermal Protection System Sizing and Selection for RLVs Using the Sentry Code.
http://www.sei.aero/eng/papers/uploads/ ... 6-4605.pdf

It gives on page p. 11 a weight of 17,910 lbs for the thermal protection tiles and panels but notes other hardware for the TPS amounts to 4,600 lbs. for a total of 22,510 lbs., 10,232 kg. I'll use this value for the shuttle TPS.
I've been informed by someone who did a study for the Air Force's "Reusable Booster System" program that for first stage use at low hypersonic speeds an aluminum frame would require minimal thermal protection. See the slides from pages 5 and 7 in this report on the Air Force's RBS program:

Spacelift Development Plan.
http://www.acq.osd.mil/nsso/conference/ ... elease.ppt

So I'll subtract off the 10,232 kg TPS weight from the 75,266 kg dry weight I got for a reconfigured orbiter, to get a 65,034 kg dry weight.
This NASA page says a saved weight of 450 lbs off the OMS system amounted to 10% of its weight:

OMS/RCS PODS.
http://science.ksc.nasa.gov/shuttle/tec ... s_oms_pods

So I'll remove the OMS system to save 4500 lbs, 2,000 kg, bringing the dry weight now to 63,035 kg.
This page gives the left payload bay door weight as 2,375 lbs. and the right as 2,535 lbs., and both doors containing radiator systems at an additional weight of 833 lbs each:

PAYLOAD BAY DOORS.
http://science.ksc.nasa.gov/shuttle/tec ... _bay_doors

These won't be needed so removing these would save 6,576 lbs, 2,990 kg, bringing the dry weight to 60,000 kg.
The Buran showed it's possible for the shuttle to have a completely automated ascent and descent, so I'll remove the life support components from the mass to use the orbiter as an unmanned first stage. For lack of any other reference on the mass of these components I'll subtract off the numbers given on the Astronautix Atlantis page of "Crew Seats and Provisions" as 750 kg and "Environmental Control System" as 2,500 kg, for a total saving of 3,250 kg, bringing the dry weight to 56,750 kg.
Probably the fuel cells and the tanks to hold the on board LOX and LH2 for the fuel cells could be removed, since as a first stage its flight would only last minutes rather than the days of a manned orbiter flight. For such short flights, lightweight batteries or electrical generators powered by the engines would suffice. This page gives the fuel cell's oxygen tank weight as 201 lbs. and the hydrogen tank weight as 216, and says there are a maximum of 5 pairs of tanks:

POWER REACTANT STORAGE AND DISTRIBUTION.
http://science.ksc.nasa.gov/shuttle/tec ... s-eps-prsd

I'll take the total fuel cell's tank weight as 2,085 lbs, 948 kg. There are three fuel cells each weighing about 120 kg, for a total of 360 kg. So I'll subtract off 1,308 kg from the dry weight to bring it to 55,442 kg.

II.) The manned space program is in a quandary now because of the ballooning costs overruns on the Ares I system that was supposed to act as the next manned transportation system. The primary difficulty was the Ares I first stage boosters. Originally the development cost was set at $1.8 billion dollars, though fixes to for example the excessive vibration generated undoubtedly has increased that cost:

Aug. 10, 2007
NASA Awards First Stage Contract for Ares Rockets.
"WASHINGTON - NASA has signed a $1.8 billion contract with Alliant
Techsystems, known as ATK, located near Brigham City, Utah, for the
design, development, testing, and evaluation of the first stage of the
Ares I and Ares V launch vehicles."
http://www.nasa.gov/home/hqnews/2007/au ... stage.html

Moreover, weight growth and a short fall in the delta-V delivered by this first stage drove costly adjustments of the upper stage as well.
My point is adapting the shuttle or the Buran for first stage use would vastly reduce the cost for a first stage. You would have then several options for manned flight all of which would be cheaper than using the Ares I first stage solid motors and all of which would allow a return to space at a faster time scale than the original Ares I plan.
I'll give a calculation that you could still carry the planned upper stage and payload of the Ares I with the reconfigured shuttle as first stage. This page gives the specifications of the Ares I:

Space Launch Report - Ares I.
http://www.spacelaunchreport.com/ares1.html

The gross weight including payload is given as 912,660 kg and the gross weight of the first stage as 732,550 kg. So the gross weight of the Ares I second stage plus payload is 180,110 kg.
Then the gross weight for the 55,442 kg dry weight of the reconfigured shuttle, plus 300,000 kg propellant load, plus 180,110 kg second stage and payload is 535,552 kg, 1,178,214 lbs. But the 3 NK-33 engines I was suggesting to use only put out a total of 1,018,518 lbs. of thrust at sea level. For this purpose you would need a fourth NK-33. The dry weight is now 56,664, the gross weight is 536,774 kg, 1,180,903 lbs., and the sea level thrust of the 4 engines is 1,358,024 lbs.
Using the average Isp of the NK-33 as the midpoint of the sea level and vacuum Isp's at 315 s, the achieved delta-V would be 315*9.8*ln(536,774/(56,664+180,110)) = 2,527 m/s, comparable to the equivalent delta-V, speed + altitude, provided by the Ares I first stage. The achieved delta-V is actually higher than this since the rocket spends most of the time at high altitude, where the Isp is closer to the vacuum value.
Note that if you want to increase the delta-V, the space occupied by the crew compartment is now empty. This gives an additional 74 cubic meters that could be used for propellant, which amounts to 74,000 kg additional lox/kerosene propellant that could be carried.
Then we could still use the planned upper stage of the Ares I while having a significantly lower development cost and per launch cost of the now reusable first stage. Still the time when we could reach flight status would be dependent on the development of the upper stage. However, we don't need to use the large Ares I upper stage and Orion capsule if we just want manned flight. I'll show in a following post we could get a smaller and reusable manned upper stage at a much lower cost also than the Ares I upper stage and Orion capsule, that will also allow a much quicker return to manned flight.

III.) I wish also to argue however that for these methods, for the reconfigured shuttle/Buran first stage and smaller reusable manned upper stage, we don't want to use the standard procurement methods with the "Old Space" aerospace companies. Robert Zubrin has some insightful observations about the "cost-plus" government contracts that the large aerospace companies get in his book, Entering Space: Creating a Spacefaring Civilization.
In the chapter, "The Age of the Dinosaurs" referring to the "Old Space" companies, he first comments that high launch costs drive the tendency to make satellites be highly reliable which drives the cost for the satellite higher. And conversely if your satellite is already very expensive, say a $1 billion Air Force satellite, then there is little incentive to reduce launch costs since at that satellite price a launch cost of $100 million or zero makes little difference.
Then Zubrin says:

"Beyond these considerations stands the government contracting system known as "cost plus," which has been in place for some time now in the United States. According to the people who invented this system, it is essential that corporations be prevented from earning excessive profits on government contracts. Therefore, rather than negotiate a fixed price for a piece of hardware and allow the company to make a large profit or loss on the job depending on what its internal costs might be, regulators have demanded that the company document its internal costs in detail and then be allowed to charge a small fixed percentage fee (generally in the 10 percent range) above those costs as profit. This system has served to multiply the costs of government contracting tremendously, so much so that it has produced public scandals when news leaks out about the military paying $700 for a hammer or a toilet seat cover."
Entering Space, by Robert Zubrin, p. 24.

Then I'm suggesting that the "New Space" companies rather than going through the usual "cost-plus" financing from the government could purchase a shuttle/Buran on their own and develop the manned reusable upper stage on their own with the idea of making a profit. I'm arguing the development cost of this reconfigured first stage and the small upper stage would be so low that this can be profitable both for satellite launch and for now fully orbital space tourism.


Bob Clark

 

[frodo1008]

Perhaps you did not know this, but the entire EELV contract to both Boeing and Lock Mart was NOT a cost plus contract, and resulted in the development of both the Delta IV and the Atlas V. Which have proven in both their regular versions and the heavy versions to reduce the launch costs of a pound to LEO from $10,000+ to about $5,000, and could go even lower IF there was more demand for such launches! That IS what is driving launch costs, not some kind of a conspiracy of the government! This even applies to the relatively frugal Russians!

As for the costs of satellites, they are made super reliable as they are going to have to operate from the most part from GEO, and there are absolutely no repair facilities at that orbit. So it is better that they be made super reliable at an increased cost and work properly the first time, than to stint on the cost and perhaps have them fail! However, the Air Force did find it to their advantage to put out the money for the EELV contracts so that they could reduce their own launch costs by more than 50% anyway!

I also have both of Dr Zubrin's books. and while he is a brilliant engineer, and has at least one excellent idea of using the materials actually found on Mars as part of the propellant to get back from a Mars mission, therefore saving a great part of the cost of such a mission. His estimates of just what it would cost for a Mars mission, which would be far tougher than anything we have done so far in space are pure hogwash!

With Apollo having cost some $100 billion in terms of today's dollars, and the shuttle program having cost some $100 billion dollars over its 30+ years history, and the ISS having cost some $100 billion dollars over its 25+ years of history, Zubrin states that it will only cost some $20 billion to go on to Mars! I would not even have this guy do my relatively simple tax return, let alone be responsible for $billion dollar governmental contracts!

If either you or Dr Zubrin can somehow convince all of these so very efficient pure private interests to do the things you want them to do (without the guarantee of reasonable profits) then please do so, but please keep your hands off of the governmental space programs!

Do you even have any idea yourself (and I do, as manufacturing was my main area of endeavor for the 37.5 years of my own aerospace career, where I actually cut and inspected metal machining, not just Power Point presentations) just what the manufacturing costs to build the truly vast machines it takes to get us into space are? Somehow, I do not think that you do. And unfortunately, neither does Dr. Zubrin, if he thinks that the actual profit making established aerospace companies of this great country are some kind of dinosaurs!!

Elon Musk also started out with at least some of the same kind of thinking, but much to his credit (and the possible profit margins of his company), he at least now realizes the difficulty of doing what he wants to do in this business!!

Besides which, this is just a silly exercise, as NASA is not going to sell the orbiters to any pure private outfit(s) anyway! They are going to honorably be retired to museums, where ordinary citizens will be able to give them the attention and honor that they deserve. And that is that!!!!!!! :x :x

 

[exoscientist]

...
Has it not occurred to you yet that the people that originally designed and built the entire Space Transportation System (STS) possibly even knew what they were doing?
You can NOT get the orbiter into LEO without both two of the most powerful solid motors ever built, and the vast amount of fuel and oxidizer that those three very efficient SSME's use. And that IS why (as you even stated with your own statement) the External Tank is so very much larger than even the orbiter itself!
Besides that, if you then even could use the internal bay of the orbiter for the propellants for engines even close to powerful enough to get just the orbiter into sub orbital space, let alone LEO, then where are you going ot put the 100 passengers that you talk about?
If you were to consider even just the weight of 100 totally naked passengers at only about 150 lbs each, you are looking at 15,000 lbs of net cargo weight to LEO, and that is to say nothing of the weight of the materials that it would take to keep those passengers alive for the many orbits that it would then take. I would have to say the total weight for those passengers would have to be at the very least 30,000 lbs.
Such levels of weight have indeed been carried into LEO to even the ISS's orbit, but it takes the ENTIRE shuttle system to do it!
You know this sort of rocket science is not just coming up with ideas, and then placing them on a PowerPoint presentation. It is such science as physics and engineering!
If you were even to use the orbiter as just a first stage fly-back booster, and orbiter that you could then launch into LEO would be far too small to carry even the number of passengers as the Spaceshiptwo that Burt Rutan is building just to get into sub orbital space with some 6 passengers!
...

We are agreed that the amount of fuel that could be carried in the payload bay would not suffice to take the orbiter itself to LEO. That is why I was arguing for suborbital flights, at significantly less speed than orbital, and first stage booster use only, also at significantly less speed that orbital velocity.
However, in regards to what size vehicles it could boost to orbit. Note that the calculation I made showed it could supply sufficient speed to the Orion capsule, quite a large spacecraft, with an attached second stage booster, so that the second stage could transport the capsule to orbit.


Bob Clark

 

[exoscientist]

In regards to its feasibility, a key fact that needs to be kept in mind is how low is the amount of structural strengthening mass required compared to the mass of propellant when the fuel tank is in the usual position inside the rocket along the center line of the vehicle. Look at the specifications page on Falcon 9:

SpaceX Falcon 9
Updated 4/16/2009
Vehicle Components
http://spacelaunchreport.com/falcon9.html#components

The propellant mass for the first stage is 279,900 kg, while its dry mass is 14,730 kg. But remember a lot of this dry mass is in the 9 engines of the first stage. This page gives its engine a sea level thrust of 95,000 lbs. at a thrust to weight ratio of 92:

SPACEX COMPLETES DEVELOPMENT OF MERLIN REGENERATIVELY COOLED ROCKET ENGINE.
https://www.spacex.com/press.php?page=33

So its weight is 1032 lbs, 470 kg. Then 9 weigh 4230 kg. Lox/kerosene propellant tanks also weigh typically 1/100th the propellant weight, so about 2,800 kg. Then less than 7,700 kg is left over that might be devoted to strengthening mass to support this mass of propellant, and additionally to transmit the nearly 1,000,000 lbs of thrust to the rest of the rocket.
That is why I'm arguing comparatively little additional strengthening mass is required to begin with according to what has always been the case with inline propellant tanks. And considering that already such strengthening mass has to be present to handle the higher thrust and propellant loads in the orbiter in its present configuration little additional mass to this amount would have to be added, though the placement would likely be different.
And in regards to the cost of the addition of our 300,000 kg propellant tank in the orbiter payload bay, the launch cost for Falcon 9 is expected to be ca. $27 to $35 million. This is for the entire two stage rocket with a total of 10 engines. Notice that the development costs are also included in these launch costs. The engines are the hardest part of a rocket development and undoubtedly the cost of these 10 engines represents the lion share of the launch cost. Notice also there must be structural strengthening to connect the nearly 1,000,000 thrust to the rest of the rocket. So this must be part of costs.
The conclusion I draw is that it would cost significantly less than $35 million to build and attach the required propellant tank to the shuttle payload bay.


Bob Clark

 

[exoscientist]

In addition to the Air Force wanting to build reusable first stages with expendable upper stages to cut launch costs, the Europeans are also planning such boosters, though sled launched:

Hopper (spacecraft).
http://en.wikipedia.org/wiki/Hopper_%28spacecraft%29

Europe's space shuttle passes early test.
* 16:05 10 May 2004 by Maggie McKee
"Europe took a step towards creating an unmanned space shuttle on Saturday when a prototype landed autonomously after a test flight in Sweden.
"The shuttle prototype, called Phoenix, is one of several proposals for a European reusable launch vehicle (RLV) planned to cheaply ferry satellites into orbit by 2015."
http://www.newscientist.com/article/dn4975

"An unmanned scale model prototype of the planned European shuttle is
pictured during its first free test flight at the North European
Aerospace Test Range in Kiruna, Sweden 1,230 kilometers (770 miles)
north of Stockholm, Saturday, May 8, 2004. (AP Photo/Peter Degerfeldt,
Blue Sky AB, DLR/EADS)."

Reusable space transport systems to reduce cost.
Bremen/Le Bourget, 01 June 2001
"In its HOPPER concept, Astrium has gone for an autonomous transport system that is noted for its high degree of reusability and comparatively low mission costs. Although the unmanned HOPPER is very similar in appearance to the US Space Shuttle there are, however, some substantial differences: The system will be launched horizontally on a skid sled running on a four kilometre long track. The vehicle itself is more compact than the Space Shuttle. The re-entry angle will be optimised so as to keep the frictional heat at the outer skin substantially lower than that of the Space Shuttle. This will allow the sensitive and expensive thermal protection shield to be replaced by an affordable, low-maintenance heat protection system. Due to these features, Hopper is intended to transport payloads to orbit at 75% lower cost than conventional transport systems."
http://www.eads.net/1024/fr/pressdb/arc ... _reus.html

This article said the "Hopper" is more "compact" than the shuttle orbiter, but actually it's about 13 meters longer with a 3 meter wider wing span. This will allow it to have internal propellant tanks and also an internal payload bay:

The Europeans expect to use upgraded versions of Ariane's hydrogen-fueled Vulcain engine. The choice of the hydrogen-fueled Vulcain, rather then a kerosene engine typically used for first stages, perhaps stems from the desire to have it be sled launched, requiring a lower GLOW, and the desire to use the ESA's most advanced engine.
Rather than expending such large amounts of money building their own Hopper vehicle, it might be cheaper as a technology demonstrator for ESA to adapt the shuttle/Buran for the purpose. NASA seems to want to give the SSME engines away for free, so the ESA could even get the needed engines.
The shuttle/Buran is smaller than the proposed Hopper. To get similar payload to orbit on an expendable upper stage, about 7,500 kg, they could have it be vertically instead of sled launched to allow the upper stage to be attached on the vehicle bottom. This would then allow the full fuselage to be used for propellant.
However, as I have argued by using kerosene instead as the propellant for this first stage you could have the expendable upper stage be as heavy as that of the Ares I second stage at 180,000 kg, and with a much larger payload to orbit than 7,500 kg, at about the size of the Orion capsule, 20,000 kg to 25,000 kg:

viewtopic.php?f=15&t=21971&start=40#p419550


Bob Clark

 

[Valcan]

Ok i dont get it it has been said again and again.

The shuttles wont fly after the last date.

1) There technology is from the 70s early 80s.

2) Restarting the production lines would be a monumental undertaking requiring billions of dollars.

3) The current frames can fly maybe 2 to 4 times more then they will become death traps.

4) stupidly expensive requiring far to large of a work force.

Its not gonna happen people. Shuttle has served well. But it was a messed up system in the first place. There is no point to sending people and cargo on the same rocket.

Want a shuttle for TSTO? Design and build a new one far cheaper.