Passenger market for suborbital flights.

Just saw this article on Rocketplane XP, which plans to offer suborbital, tourism rocket flights, while using jet engines for take- offs and landings:

Rocketplane reset by Jeff Foust Monday, November 5, 2007

The revised Rocketplane XP design (above) is intended ultimately to be more competitive in the emerging suborbital space tourism conference.

The Second Space Age. March 6, 2008 Patrick Mahoney "Ready for a space cruise? The technology is taxiing to the runway." Rocketplane XP's current design was modified from the original Lear Jet base airframe but still has the look of a passenger business jet, with a rocket in the tail. It has some titanium and steel portions to withstand the heat of reentry in addition to an aluminum frame. This makes it heavier than a Lear Jet and it has to use a long military base runway for take-offs and landings. However, quite likely if it used all composite materials, as does SpaceShipOne, to replace the heavy steel, titanium, and aluminum it could take off and land from a standard sized airport runway.

Bob Clark

The Europeans have also proposed a business jet model for a suborbital tourism rocket:

DATE:14/06/07 SOURCE:Flightglobal.com PICTURES: Astrium aims for 2012 suborbital tourism flights. By Rob Coppinger "The space jet will take off from a conventional runway, powered by two jet engines, and fly to 39,300ft (12,000m), where it will ignite its liquid oxygen, methane rocket engine providing an ascent acceleration of 3g. After 80s the jet will reach 196,000ft and coast to its apogee."

Interestingly, they consider this as a precursor to a point-to-point transport.

Another article on the proposed Astrium rocketplane:

Space planes 'to meet big demand'. By Jonathan Amos, Science reporter, BBC News Monday, 17 March 2008, 13:38 GMT "Aerospace giant EADS says it will need a production line of rocket planes to satisfy the space tourism market."

There is a link to a nice video of a simulated flight on this page. In the video the passengers are wearing helmets with closed visors. But it doesn't look like they are wearing actual spacesuits with independent air supplies because the helmets are not connected to the rest of the suits. The helmets have more the look of motorcycle helmets. I don't know if this is really supposed

Bob Clark

Another suborbital, tourism rocket plane based on a business jet model:

Bristol Spaceplanes - Ascender.

There have been several studies showing just for tourism there would be a sufficient market for such suborbital flights to be profitable. I have to think there would be a bigger market for cases where the traveler would actually want to go somewhere and this method could get him there in 1/10th the time. As a point of comparison I did a search on the Japan Airlines site for round trip business class tickets from my town of Philadelphia to Tokyo. It ranged from $6,600 to $21,000:

=================================================== Select Your Flights

Philadelphia to Tokyo Thursday, April 9, 2009 Tokyo to Philadelphia Tuesday, April 14, 2009 Travelers: 1 Travel class: Business and First

Select your fare: Price differences within a fare type may be due to flight connections or availability. Prices are per adult passenger and include Taxes and Surcharges.

Fare type Fare description Lowest price Business Saver Special Restricted. Bed-style seating on most long- haul routes - Executive Class. more details $6,672.48 Business Saver Restricted. Bed-style seating on most long-haul routes - Executive Class. more details $7,611.48 Business Normal Flexible. Bed-style seating on most long-haul routes - Executive Class. more details $12,330.48 First Normal Flexible. World-renowned service and comfort - First Class. more details $21,589.48 ===================================================

Note also, that the $200,000 ticket price mentioned for suborbital flights on SpaceShipOne is only for the first few flights. After, a few years the price is expected to come down to $20,000.

Bob Clark

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In their usual good reporting, the BBC discusses directly the safety issues for these suborbital tourism flights:

Space ships: the next generation - Space Tourist- BBC Science & Nature.

Bob Clark

In this animation of the SpaceShipTwo suborbital flight, the passengers do not appear to be wearing actual spacesuits, though they do have helmets:

Virgin Galactic SpaceShipTwo Animation.

Bob Clark

Another suborbital tourism project was posted on the SpaceFellowship.com forum:

Project Enterprise.

I noted in their simulated video of the trip, it has the passengers wearing oxygen masks.

Bob Clark

This site is an informative compendium of articles related to space flight, and particularly space tourism:

SPACE FUTURE.

Here's an article re-printed on the site on commercial orbital and suborbital flights:

New Commercial Opportunities in Space. D M Ashford The Aeronautical Journal, February 2007. "Of aeroplanes that have actually flown, and with the possible exception of SpaceShipOne, the one most suitable for providing the basis of a space tourism industry is perhaps the Saunders Roe SR.53 rocket fighter that first flew in 1957. This is probably the most practical rocket-powered aeroplane yet built. If it had entered service, the RAF would soon have had a mature rocketplane with long life and rapid turnaround. With straight-forward development, the SR.53 could have had sub-orbital performance. Indeed, when it was cancelled as a fighter in 1958, Saunders Roe did propose a space research variant(17)."

Note that that the example of the Saunders Roe SR.53 shows that an aircraft can successfully operate with both rocket and jet engines.

Bob Clark

More on the Saunders-Roe SR.53:

Saunders-Roe SR.53.

Bob Clark

variant(17)."

More on the Saunders-Roe SR.53:

Saunders-Roe SR.53.

Bob Clark ==================================== Note that the example of the 1940s German V1 shows that an aircraft can successfully operate with both rocket and jet engines.

hairy deal.

On the Space Future site, another interesting article:

Flight Mechanics of Manned Sub-Orbital Reusable Launch Vehicles with Recommendations for Launch and Recovery. Marti Sarigul-Klijn Ph.D. and Nesrin Sarigul-Klijn*, Ph.D AIAA 2003-0909 January 2003 (Revised April 2003)

Lockheed NF-104 (USAF image) It discusses four separate combined jet/rocket aircraft.

Bob Clark

The launch of a military satellite at the NASA's Wallops Island facility in Virginia reminded me that commercial launches are also being made from the site:

Mid-Atlantic commercial spaceport makes 1st launch. Posted 12/16/2006 7:20 AM ET

There was a push by some to offer a prize for a suborbital commercial transatlantic transport to launch from the site but I don't know if that is still being considered:

Hypersonic Cruise for the V Prize. Wednesday 2008.01.23 by gravityloss

This article did not optimize the cruise velocity to get the best fuel fraction and gets a too high cruise speed of 6,000 m/s. A later article on this web site discusses how this could be optimized, giving a cruise velocity of only 3,000 m/s if you can get a high lift/drag ratio of 7 at hypersonic speeds:

Optimum Rocket Cruise. Friday 2009.03.20 by gravityloss

Some hypersonic waverider shapes can get a lift drag ratio in the range of 6 to 8 when optimized for a set hypersonic cruise speed:

Waverider Design.

If the delta-v required is only 3,000 m/s this could be obtained with a rather low mass ratio: Mi/Mf=3D exp(delta-V/Ve) =3D exp(3,000/3600) =3D

2.3, assuming an exhaust velocity Ve of 3,600 m/s, which can be reached by kerosene/LOX rockets. This is less than the mass ratio of SpaceShipOne.

Bob Clark

Saw these articles linked on the Wikipedia X-33 page:

Lockheed Test Flies Space Plane Prototype. By Leonard David Special Correspondent, SPACE.com posted: 24 April 2008

11:41 am ET "Lockheed Martin has tested a prototype reusable launch system by flying a sub-scale flight demonstrator from the site of New Mexico's proposed Spaceport America. "The successful test flight of the proprietary vehicle took place in December and was only recently disclosed. A company official said Lockheed Martin is planning more tests using ever-larger vehicles. "Lockheed Martin Space Systems teamed with launch provider UP Aerospace of Highlands Ranch, Colo., Dec. 19 to conduct a small demonstration launch at Spaceport America in southern New Mexico to evaluate proprietary technology the company currently has under development." Lockheed loses prototype of Space reusable launch vehicle. 18 August 2008 "Golden, Colorado: Lockheed Martin's second test flight of a prototype reusable launch system failed with the craft going out of control and becoming seriously damaged, rendering it unusable. The test, conducted 12 August, saw the winged craft take off from a launch rail under its own power and fly for some 12.5 seconds of a planned flight of less than a minute before it crashed." ... "The 200-pound (91 kg) vehicle reached its planned altitude of roughly 1,500 feet (457 meters). It is 8 feet (2.4 meters) long with a wingspan of about 6 feet (1.8 meters) and is roughly one-fifth in scale. It is being flown to develop techniques and procedures for quick launch, ease of operations and low cost access to space." Anyone know what the scoop on this is? Since the Lockheed X-33 was canceled because of the relatively trivial problem (compared to the complexity of the rest of the system) of the composite hydrogen tank debonding, I'm inclined to think Lockheed solved that problem and it's a version of the X-33. The dimensions given though are small for it actually being a one-fifth scale of the X-33:

X-33 Advanced Technology Demonstrator. X-33 Specifications. Length: 69 ft Width: 77 ft Takeoff weight: 285,000 lbs Fuel: LH2/LO2 Fuel weight: 210,000 lbs Main Propulsion: 2 J-2S Linear Aerospikes Take-off thrust: 410,000 lbs Maximum speed: Mach 13+ Payload to Low Earth Orbit: N/A

If it is a version of the X-33, I wonder why it would now be classified. Perhaps Lockheed found it would be able to provide the suborbital troop delivery system wanted by the defense department. If so, it could also work as a suborbital commercial transport.

This article suggests the composite hydrogen tank debonding has been solved:

New Composite Hydrogen Fuel Tank For RLVs Successfully Tested. Huntsville - Dec 22, 2003 "A team of engineers from Northrop Grumman and NASA's Marshall Space Flight Center, Huntsville, Ala. Have demonstrated that a new, specially designed fuel tank made from composite materials can safely hold and contain liquid hydrogen under simulated launch conditions." ... "Fuel tank problems on the X-33 Venture Star project were critical to ending what was the last major new space transportation R&D program at NASA."

This article says XCOR, the suborbital tourism company, is developing a composite cryogenic tank:

An update on composite tanks for cryogens. More automation, improved materials bring composite fuel tanks for space applications closer to reality. Contributed by: Sara Black, Technical Editor Article Date: 11/1/2005

Bob Clark

On May 27, 9:23=A0am, Robert Clark wrote:

I was looking up other references on the X-33/VentureStar composite tanks when I found this:

Space Access Update #91 2/7/00. The Last Five Years: NASA Gets Handed The Ball, And Drops It. "The advantage of a lifting-body is that it doesn't (shouldn't) need wings to maneuver during orbital reentry then land on a runway; it thus saves the weight of wings - minimum vehicle weight of course being critical to a successful Single Stage To Orbit vehicle. The disadvantage is that the vehicle shape is such that propellant tanks can't be the optimum circular cross-section shape that minimizes tank weight for a given mass of propellant - any tank shape that doesn't have a round cross-section will tend to try to balloon out to being round anyway as soon as it's pressurized; preventing non- round tanks from doing this requires heavy reinforcement. What lifting bodies gain from omitting wings they more than lose again on heavier tanks, at least with traditional tank construction methods. "Lockheed claimed to have solved the tank-weight problem, via "multi- lobed" tanks that combined partial circular sections with clever internal bracing. Further, these tanks were to be made out of graphite-epoxy composite rather than aluminum. The result was supposed to be complex-shaped tanks that would conform to the lifting-body shape while being just as light as conventional circular-section tanks. We'll come back to this." ... "And of course, part of L-M X-33's weight growth was the "multi- lobed" propellant tanks growing considerably heavier than promised. Neither Rockwell nor McDonnell-Douglas bid these; both used proven circular-section tanks. X-33's graphite-epoxy "multi-lobed" liquid hydrogen tanks have ended up over twice as heavy relative to the weight of propellant carried as the Shuttle's 70's vintage aluminum circular-section tanks - yet an X-33 tank still split open in test last fall. Going over to aluminum will make the problem worse; X-

33's aluminum multi-lobed liquid oxygen tank is nearly four times as heavy relative to the weight of propellant carried as Shuttle's aluminum circular-section equivalent." This states that the X-33 tank mass to propellant mass carried is actually worse than for usual rockets, such as the space shuttle. This is surprising since I thought the composite tanks were to reduce the weight. However, as described here, the higher mass is because of the unusual shape of the tanks. The author of that article does not like the VentureStar or the decision to fund it. But it is important to keep in mind that the primary subsystems for the X-33 were shown to be viable including the aerospike engines and the metallic thermal protection system, and it was only the comparatively trivial problem of getting the lightweight tanks to work that caused the program cancellation:

X-33/VentureStar - What really happened. January 4th, 2006 by Chris Bergin

The greater tank mass to propellant mass ratio for the X-33 tanks can be confirmed by using the data for the X-33 tank sizes here:

X-33 Program in the Midst of Final Testing and Validation of Key Components. Marshall Space Flight Center Lockheed Martin Skunk Works Sept. 28, 1999

compared to the space shuttle external tank data given here:

EXTERNAL TANK.

I had earlier proposed solving the problem of getting lightweight tanks by using high strength materials that, at their highest strengths, are only available in microscale fibers or particles, by using them in hollowed out form:

From: Robert Clark Newsgroups: sci.astro, sci.space.policy, sci.physics, sci.energy Date: Tue, 29 Jul 2008 09:59:14 -0700 (PDT) Local: Tues, Jul 29 2008 12:59 pm Subject: High strength fibers for hydrogen storage on the VentureStar.

A problem though is that these fibers or particles might be only 10 microns wide. The wall thickness of the aluminum alloy space shuttle external tank is in the range of 5 to 10 millimeters with the tank diameter on the order of 10 meters. This is a diameter to wall thickness ratio of around a 1000 to 1. If the microscale hollow fibers were to match or exceed this they would have a wall thickness of only

10 nanometers or less. This would cause extreme problems in manufacturing them and handling them so as not to damage them. However, this was based on the idea that you had to get a material that was stronger for weight than aluminum alloy. But the real problem is that the X-33 tanks are not of the usual cylindrical or spherical shape. Then we can get the minimal weight by using numerous small diameter cylindrical tubes to make up the shape of the conformal tanks without requiring the ultrahigh strength of the microscale fibers. Because of the large size of X-33 tanks we might even be able to have these cylindrical tubes be as large as say 10 centimeters across, and have them be of varying lengths so when bundled together they make up the conformal shape of the X-33 tanks. If they are 10 cm across and using the aluminum alloy, to be of the 1000 to 1 diameter to thickness ratio of the shuttle ET, they would have to have a 100 micron wall thickness. This is easy to achieve since for example common household aluminum foil may be only 16 microns thick:

Reynolds Wrap* Aluminum Foil.

Smaller diameter tubes if necessary would have a smaller wall thickness. Even tubes 1 cm wide requiring wall thickness of 10 microns is well within the range of commonly used aluminum sheeting. The effect of bundling the many tubes together would also give the complete tank strength as it would be be in the form of a honeycomb, a structure of inherently high strength to weight ratio. The viability of this idea would be easy test by using tubes made from common aluminum foil and testing how well they hold up to the pressures and temperatures seen in the cryogenic tanks. The tubes could be formed by epoxying the edges together and then epoxying the tubes together to form the shape of the conformal tanks. To form stronger tubes and bonds between the tubes we could also use a light brazing technique. The aluminum foil doesn't have the same strength to weight ratio of the aluminum alloys but it would serve to give a first level indication of how well the idea would work. At this first level you would probably also want to use liquid nitrogen rather than liquid hydrogen as well. Assuming the multitube method works to provide similar tank mass to propellant mass ratio as the shuttle ET, the bare mass of the X-33 liquid hydrogen tanks could be reduced from 12,000 lbs. to 6,000 lbs, and the liquid oxygen tank from 6,000 lbs. to 1,500 lbs, quite a large mass saving for a vehicle of bare mass of 65,000 lbs. For so many small cylindrical tanks, probably you would not want to have separate valves for each cylinder that all had to operate in unison. A couple of ways to release the fuel in a throttleable fashion might be to have each small cylinder be completely used up once it is opened, with a group of cylinders being opened sequentially, or to have one end of the cylinders be closed off and a single cap cover the other open end of all the cylinders which would be used to connect to a single valve for the tank. NASA does not seem to have much interest in funding further X-33 development. However, the U.S. Air Force is interested in developing a suborbital troop transport (which of course could also work as a commercial suborbital passenger transport):

Pentagon seeks military role for space tourism technology. By Stephen Trimble DATE:23/02/09 SOURCE:Flight International

Then considering the low cost nature of the idea, the Air Force might fund this since if viable it would lead to a suborbital transport in the X-33, and likely therefore also to a reusable single stage to orbit vehicle in the VentureStar.

Bob Clark

On May 27, 9:27=A0am, Robert Clark wrote:

AFRL Seeks Reusable Booster X-Plane Ideas. Posted by Graham Warwick at 5/12/2009 2:36 PM CDT "Guy Norris alerted us to it a couple of weeks ago in Aviation Week, but the Air Force Research Laboratory has finally released its request for information on concepts for a reusable launch vehicle. They are calling it the Reusable Booster System (RBS), because the focus is on a fly-back first stage carrying an extendable upper stage. "The RFI's stated objective "is to identify potential operational RBS concepts, including a family of expendable stage variants, and feasible system development approaches." And it is a step towards a potential subscale X-plane demonstrator that could fly in 2017-18."

Reusable Booster Integrated Demo =96 Concept Options Maturation Study. (RBID-COMS) Solicitation Number: RFI-PKV-09-01 Agency: Department of the Air Force Office: Air Force Materiel Command Location: AFRL - Wright Research Site This is for proposals for a reusable vertical launch, horizontal landing unmanned booster to serve as the first stage of a two-stage-to- orbit (TSTO) system. The description seems to be tailored made for the X-33 suborbital system. I'm inclined to think intentionally so. Then this might open up funding for alternative methods for obtaining lightweight tanks for the X-33 such as the multiple cylindrical tanks method. It also would make possible a suborbital troop carrier or commercial transport system.

Bob Clark

More on the Air Force's "Reusable Booster System":

USAF Seeks Reusable Booster Ideas. May 14, 2009 By Graham Warwick "The plan is to conduct an integrated demonstration of technologies and processes culminating in a subscale X-plane vehicle that would fly by 2017-18 and take the concept to a technology readiness level of 6, ready to enter full-scale development. "AFRL has several ground-based experiments already under way involving structures, controls and systems for an operationally responsive launch vehicle. The work is focused on a reference concept for an unmanned vertical takeoff and horizontal landing reusable booster capable of turnaround in 24-48 hours and launch within 4-8 hours of a request."

Spacelift Development Plan.

Also from the Aviation Week article:

"AFRL's reference concept includes an integral all-composite airframe and tank structure that carries both internal pressure and external flight loads. The concept vehicle is powered by pump-fed liquid-oxygen/ hydrocarbon rocket engines."

The suggestion to limit the fuel to hydrocarbon rather than the higher energy liquid hydrogen probably stems from the fact that for this purpose the vehicle only needs to have a max speed in the range of Mach 3.5 to 7, as indicated by slide #5 in the "Spacelift Development Plan" powerpoint presentation. However, all three competing proposals for the X-33 liquid-hydrogen fueled vehicles, which needed to get to Mach 13+, probably could be adapted to use hydrocarbon fuel, for this Mach 7 max. proposal. This would be another method to effectively re-open the X-33 competition. The X-33. It's back on, baby!

X-33.

Bob Clark