“Anyone who sits on top of the largest hydrogen-oxygen fueled system in the world, knowing they’re going to light the bottom, and doesn’t get a little worried, does not fully understand the situation.”
– John Young
TABLE OF CONTENTS
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VENTURESTAR ARCHITECTURE
We will dust off a decades–old Vertical Takeoff Horizontal Landing (VTHL) Single–Stage–To–Orbit (SSTO) reusable Reentry Vehicle (RV) design called the VentureStar.
Image 1: The X-33 was the proof-of-concept vehicle for the VentureStar
The VentureStar was supposed to start out as the X–33 proof–of–concept vehicle. The X–33 was a smaller–scale version of the VentureStar (Image 1) and would have flown suborbital flight tests, where it would have launched vertically from one location and landed horizontally in another.
All aspects of flight test operations would have been evaluated, from un–crewed drone operations to the Thermal Protection System (TPS) to turnaround times between flights. Once all the bugs had been worked out on the X–33, the VentureStar itself would have then been constructed and flown.
The X–33 was a lifting body–design, but later studies showed that it would not have provided sufficient lift capabilities. The wings were enlarged later in the design process which included a lower dihedral angle.
There was also a problem with the propellant tanks, which were supposed to use composite material instead of aluminum. Since the technology for Composite Propellant Tanks (CPT) was in its infancy in the late 1990s, it was inevitable that the tanks failed. CPTs are, of course, routinely manufactured nowadays, so our spacecraft propellant tanks will be made from the same material.
Work actually began on the X–33 and was almost completed when the funding ax fell. The launch and landing facilities were mostly complete, and the mission control center was essentially operational. They even had a plan to ferry the X–33 on the back of a modified Boeing 747, just like the US Space Shuttle did.
The VentureStar RV would have replaced the US Space Shuttle at the dawn of the 21st Century. Alas, the Funding Equation was inadequate and led to its demise.
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We will incorporate modern technology, techniques, and materials to create an updated version of the VentureStar. The original VentureStar was designed to insert 25,400 kg mass to a 200 km altitude with a gross mass of 1,180,000 kg. Our new and improved VentureStar will deposit just under 32,360 kg to the same orbital altitude even though our design will be slightly heavier than the original design at 1,244,577 kg.
Equations
- PROPELLANT MASS = LH2 MASS + LO2 MASS
- EMPTY MASS = STRUCTURAL MASS + ROCKET ENGINE MASS + SUBSYSTEMS MASS
- PAYLOAD MASS = 32,359 kg to 200 km
- GROSS MASS = PROPELLANT MASS + EMPTY MASS + PAYLOAD MASS
- GROSS LIFTOFF WEIGHT = g0(GROSS MASS)
- g0 = Standard Earth Gravity
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Propellant
PROPELLANT MASS = LH2 Mass + LO2 Mass
= 169262 + 930944
= 1,100,206 kg
Empty Mass
EMPTY MASS = STRUCTURAL MASS + ROCKET ENGINE MASS + SUBSYSTEMS MASS
= 75919 + 28625 + 7467
= 112,012 kg
Gross Mass
GROSS MASS = PROPELLANT MASS + EMPTY MASS + PAYLOAD MASS
= 1100206 + 112012 + 32359
= 1,244,577 kg
Gross Liftoff Weight
GLOW = g0(GROSS MASS)
= 9.80665(1244557)
= 12,205,130 N
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VENTURESTAR AIRFRAME
The VentureStar has a typical launch vehicle internal structure using CPTs. Similar to the Space Shuttle design, the LO2 Tank is placed atop the LH2 Tank. In this case, the LO2 Tank is lobed and two (not one) LH2 Tanks are placed underneath and on either side forming the isosceles triangular shape (Image 2).
Image 2: VentureStar Interior View
The rocket engines are placed underneath the two LH2 Tanks, forming the base of the triangle.
The Cargo Hold is situated between the two LH2 Tanks.
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The VentureStar looks very similar to the US Space Shuttle, with a white surface on the top and a dark metallic Thermal Protection System (TPS) heat shield on the bottom..
On the ground, the VentureStar would look like any other ordinary spaceliner.
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VENTURESTAR POWERPLANT
The VentureStar utilizes a unique type of rocket engine called the RS–2200.
Image 3: The Aerospike nozzle
Instead of the using a normal rocket engine design, we will use a linear aerospike engine (Image 3).
The rocket uses a clever principle of aerodynamics by using the atmosphere to shape part of the rocket exhaust as it pierces through the atmosphere. The ISP of any rocket is always lower at sea level than in the vacuum of space; the aerospike concept helps to mitigate the loss.
The rocket engine specifications are summarized in the Table below.
Name |
RS–200 |
|
Type |
Aerospike |
|
Cycle |
Gas Generator |
|
Oxidizer / Fuel Ratio |
5.5 |
:1 |
Nozzle Area Ratio |
58 |
:1 |
Isp (Sea Level) |
339 |
s |
Isp (Vacuum) |
439 |
s |
Vexh (Sea Level) |
3.324 |
kps |
Vexh (Vacuum) |
4.305 |
kps |
Thrust (Sea Level) |
1,917,000 |
N |
The VentureStar will use a total of seven RS–2200 rocket engines.
TOTAL THRUST = 7(RS–2200 THRUST)
= 7(1917000)
= 13,419,000 N
Therefore, the VentureStar Thrust–to–Weight Ratio is:
THRUST–TO–WEIGHT RATIO = (TOTAL THRUST / GLOW) : 1
= (13419000 / 1244577) : 1
= 1.09946 : 1
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ORBITAL PARAMETERS
The minimum altitude needed to orbit the Earth is 200 km. This altitude is temporary since there is a high degree of atmospheric drag causing orbital decay. Orbital altitude is not dependent on the location of the launch site.
An orbital altitude of 282 km happens to work out to exactly 16 revolutions around the planet in one 24–hour period of time. A spacecraft would pass over the same geographic location at the same time of day every day ad nauseum. This situation would allow for regularly scheduled spaceflight launches and recovery since the ground tracks repeat. This altitude, however, is not suitable for a large and heavy space station that would constantly need to be re–boosted due to orbital decay.
A better altitude is 901 km, which orbits the Earth exactly 14 times per day. This altitude provides for an extremely stable orbit essentially free of decay and will be perfect for a large and heavy space station without the inconvenience of repetitive re–boost. More importantly, this situation would allow for regularly scheduled spaceflight launches and recovery since the ground tracks repeat. Launches would occur at the same time of day every day.
The Table below summarizes the required orbital parameters of the VentureStar RRV launching from Spaceport America and flying into Standard Orbit.
Orbital Altitude |
600.96 |
km |
Orbits |
14 |
/day |
Orbital Period |
6,171 |
s |
|
102.9 |
min |
|
1.714 |
hrs |
Inclination |
60o |
|
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PAYLOAD LAUNCH EQUATIONS
We will be operating from Spaceport America in southern New Mexico, USA.
LAUNCH SITE LATITUDE: 33.0o
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ORBITAL INCLINATION = 33.0o
Equation
PAYLOAD = –6.044 x ORBITAL ALTITUDE + 33568
Example
LOW ORBIT = 200 km
PAYLOAD = –6.044 x ORBITAL ALTITUDE + 33568
= –6.044 x 200 + 33568
= 32,359 kg
Example
HIGH ORBIT = 1,000 km
PAYLOAD = –6.044 x ORBITAL ALTITUDE + 33568
= –6.044 x 1000 + 33568
= 27,524 kg
Example
STANDARD ORBIT = 901 km
PAYLOAD = –6.044 x ORBITAL ALTITUDE + 33568
= –6.044 x 901 + 33568
= 28,122 kg
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The blueprint calls for a 60o orbital inclination, requiring the VentureStar RV to make a 27o turn to the south. This turn results in less payload reaching orbit. Therefore, the calculations change as well.
ORBITAL INCLINATION = 60.0o
Equation
PAYLOAD = –5.864 x ORBITAL ALTITUDE + 26286
Example
LOW ORBIT = 200 km
PAYLOAD = –5.864 x ORBITAL ALTITUDE + 26286
= –5.864 x 200 + 28286
= 25,113 kg
Example
HIGH ORBIT = 1,000 km
PAYLOAD = –5.864 x ORBITAL ALTITUDE + 26286
= –5.864 x 1000 + 26286
= 20,422 kg
Example
STANDARD ORBIT = 901 km
PAYLOAD = –5.864 x ORBITAL ALTITUDE + 26286
= –5.864 x 901 + 26286
= 21,003 kg
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Graph 1: 33o Latitude Launch Site payload capability
Graph 1 represents the payload capability of the VentureStar operating from Spaceport America. The endpoints range from 200 km to 1,000 km orbital altitude. Standard Orbit from a 33-degree launch site to a 60o orbital inclination at an altitude of 901 km yields a payload capability of 21,003 kg.
Since we are lifting a lighter load into space, our GLOW has correspondingly changed:
Gross Mass
GROSS MASS = PROPELLANT MASS + EMPTY MASS + STANDARD PAYLOAD MASS
= 1100206 + 112012 + 21003
= 1,233,221 kg
Gross Liftoff Weight
GLOW = g0(GROSS MASS)
= 9.880665(133221)
= 12,093,766 N
Therefore, the new VentureStar Thrust–to–Weight Ratio is:
NEW THRUST–TO–WEIGHT RATIO = (TOTAL THRUST / GLOW) : 1
= (13419000 / 12093766) : 1
= 1.10958 : 1
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BINGO SITES
Each of the 14 orbits will provide the launch vehicle with an opportunity to Bingo in case anything happens.
Each of the Bingo sites will be major airports that can usually handle international flights. Since the launch vehicle will have a limited cross–range capability, the Bingo sites will have to be very close to the ground track of each orbit.
A partial list of possible Bingo Sites include:
- Addis Abbaba
- Antananarivo
- Belem
- Bloemfontein
- Cairo
- Cape Town
- Dar es Salaam
- Hanoi
- Havana
- Huambo
- Islamabad
- Jakarta
- Lima
- Lusaka
- Manila
- Maputo
- Nairobi
- N'Djamena
- Perth
- Phnom Penh
- Quinto
- Riyadh
- San Paulo
- Santiago
- Shanghai
- Shiraz
- Sucre
- Tripoli
- Windhoek