Yes, the Venturestar was the offshoot/knockoff attempt to scalesomething like the DC-X to an SSTO craft.
IIRC, the reason they did this was because the DC-X as built was a demonstrator of the VTOL concept- computer-control could turn off-the-shelf parts into a vertical-landing rocket. Scaled up it would not have been able to reach orbit with a viable payload the way it was built (although Pournelle suggested it just might).
Note how all the proposals really need to add one more uproven technology - superlight tanks, aerospike engine, etc. These all suggest that SSTO is just around the corner. They may even be right.
Even if you match the planets rotation at a given altitude, you’d need to constantly lose velocity as you descend (orbit = circle with circumference of pi2altitude).
iirc stable geostationary orbits tend to be rather far out and thus rather fast.
No. Please go back and read the links provided. Other than both being demonstration platforms for proposed SSTO platforms, they have absolutely nothing in common. The DC-X and Delta Clipper were vertical takeoff/vertical landing (VTVL) concepts using a nose-forward reentry mode with passive thermal protection, a cluster of conventional converging/diverging “bell” nozzle engines, and a vertical powered terminal descent mode. The X-33 and VenturStar were vertical takeoff/horizontal landing (VTHL) craft that used a nose-up/belly-forward reentry mode with linear aerospike astent engines and unpowered glide landing terminal mode. They were two completely different concepts from entirely separate companies (McDonnell Douglas, now Boeing) and Lockheed Martin. The only commonality is that they were both at one point NASA programs, although the Delta Clipper started under the Strategic Defense Initiative Office and was passed to NASA (which accepted it relucntantly and with minimal funding) after STIO morphed into Ballistic Missile Defense Organization after the end of the Cold War and no longer had a mandate for deploying space-based weapons or defenses.
The aerospike engine is not an unproved technology. A number of efforts have demonstrated or even qualified annular and linear aerospike engines for flight; in fact, Rocketdyne developed and fully qualified an aerospike engine for the STS system, only to have NASA change requirements to favor what became the RS-25 Space Shuttle Main Engine, a conventional staged combustion engine that ran at pressures and turbine speeds exceeding historical capability with all the problems that followed. Lockheed developed and demonstrated a linear aerospike engine for the X-33.
But neither altitude compensation nor exotic superlight materials is required for an SSTO; single stage capability is technically possible with modest improvements with existing launch vehicle technology. However, reusuable SSTO (which requires more robustness than an expendable vehicle) is not cost effective per unit payload mass, and a single use SSTO will not have comparable performance to a multi-stage vehicle. This leaves little impetus to develop an SSTO for conventional applications such as launching telecommunications satellites or unmanned probes. The applications for an SSTO are a reusable vehicle for either recovering and returning relatively small payloads from space, or regular manned transport to orbit. There is currently little demand for the former, and in the latter area NASA and other space agencies are very conservative in investing in such efforts as opposed to “proven” technologies, especially with the cost overruns on the X-33. (I will point out, however, that those overruns did not prevent NASA from selecting the exact same contractor to develop their Constellation system, only to see the same overruns and busted schedules despite using very conventional technology, suggesting that it may not just be exotic materials and advanced propulsion which are the root problems.)
Again, to clarify: The speed that the Earth rotates at, @ 1000 mph at the equator, is not merely a function of it’s mass. It has to do with the energies involved when it was formed and, in Earth’s case, the effect the Moon had on it. Venus, which is the same size as the Earth, takes longer to rotate on it’s axis than it does to revolve once around the Sun (its ‘day’ is longer than its ‘year’!) A planet the same mass as the Earth doesn’t necessarily have to rotate at the same speed. But as long as it’s the same mass its orbital dynamics *would *be essentially the same even if its rotational speed isn’t. There could be weird tidal forces involved if for some reason the planet had an extremely irregular density, but that’s unlikely.
For spacecraft orbiting the Earth, the biggest thing the rotational speed determines is how much it can be used to boost the way to orbit. This is why almost all spacecraft are launched as close to the equator as possible, and from West to East, to take advantage of that extra, free ~1000 mph delta-v.
To use Felix Baumgartner’s recent parachute jump as an example, you have to remember one important thing: He was NOT in orbit! He was floating on the top of the atmosphere. Orbital dynamics didn’t apply to him or his craft.
It’s actually “rather far out and thus rather slow” - although the circumference is bigger, the orbit is slower. 17,000 mph or about 5 miles per second is the figure for low Earth orbit, but the Moon orbits at a much lower speed, taking one month for a complete circuit instead of the ~90 minutes of the low earth orbit or the (by definition) 24 hours of the geostationary orbit. That gives you an orbital velocity of about 2 miles per second for geostationary (about 25,000 miles above the planet’s surface). Admittedly you would still need to lose that as you are hovering down to a touchdown but it’s not scaled up from low orbit velocity - quite the reverse.
Yes, sorry, DC-X and Venturestar were the same thing only very different - the point being, to relate to the OP - both were attempts to develop SSTO craft, and in both cases the attempt demonstrated that the technology was scraping the limits of current engineering.
So for the purposes of the OP, both designs relied on aerobraking because it was beyond impractical to carry enough fuel for a powered descent too. Plus, even if we could do it, aerobraking is a heckuva lot cheaper.
Despite the aerospike being well-researched and well-tested, has it actually been used in a serious production craft - i.e. second stage of an existing launch system, or similar application? Or is it, like SSTO, great in theory but outperformed in the niches where the real world uses rockets (i.e. simpler to have a lower atmosphere bell rocket engine first stage, an upper-atmosphere tuned second stage engine, etc. )?
For the OP’s design, in fiction, note the “atomic rocket” in Herge’s Adventures of Tintin - Explorers on the Moon did what the OP suggests - launched vertically direct to the moon, landed, took off, and returned to earth landing using rocket power exactly as it took off. Ah, fiction…
The DC-X demonstrated no such thing. It was not intended to be an SSTO; it was primarily a testbed to demonstrate the technologies for vertical landing under power and control in various flight orientations, which it did with aplumb. Failures due to overtesting, lack of maintenance, and poor manufacturing quality are not failures of the concept. Again, Blue Origin has continued this concept with a significant measure of success, albeit eliminating the nose-forward reentry mode for a base entry mode as they don’t have the requirement for one orbit and return.
The X-33 demonstrated that one contractor’s particular approach was “scraping the limits” of their capability. Again, the very same contractor also failed to implement an entirely conventional two stage launch vehicle and blunt-arsed capsule within budget and schedule, so I think it says more about that contractor than the state of the art.
I don’t believe that there has been a true attempt to demonstrate the capability of a practical SSTO using conventional materials and fabrication technology, but multiple studies on various concepts seem to indicate that it is technically practicable; just not cost competitive to expendable vehicles at this point.
No. This is partially conservatism (see NASA’s tacit rejection of the aerospike engine that Rocketdyne designed and demonstrated for a more conventional but edge of capability staged combustion engine) and partially because the maximal benefit from an aerospike engine requires designing the spacecraft around it (e.g. the SERV) rather than just swapping it out. Most current launch vehicles are built around decades-old heritage (Titan family around the LGM-25C Titan II, Delta II around the PGM-17 Thor) and even “new” designs such as the Atlas V and Delta IV continue to reflect heritage designs and methods (staged combustion, shower-head injection, et cetera) rather than adopting “different” technology.
It isn’t even a matter of the technology being newer or more cutting edge; concepts like OTRAG (modular parallel stages) or Sea Dragon (massive sea-launched rocket that trades lower specific performance for large payload and simplicity of fabrication and operation, achieving capability by scaling) have been rejected despite being evaluated by technical authorities as being entirely practicable and capable of reducing launch costs by an order of magnitude or more. Meanwhile, NASA (under Congressional mandate) developed and sustained the STS system for 35 years despite not meeting original design operation goals, increasing maintenance costs, and fragilities that were apparent during the initial test flights but would have required complete redesign.
The few unique problems with aerospikes–such as the construction of annular chamber or radial distribution of propulsion modules, heating of the inverted nozzle spike, et cetera–have been extensively explored and mitigated. There is really no reason a contractor, starting from a clean sheet, could not design and develop a vehicle built around an aerospike engine. There has just been little impetus by the typically conservative government agencies which fund launch vehicle development to press forward, and the private developers don’t have the funding or experience to design an aerospike engine, which does have more inherent complexity than a conventional de Laval nozzle. The one engine manufacturer which has extensive experience with annular aerospike engines, Rocketdyne, has been merged with competitor Pratt & Whitney and most of their design team gutted.
If your goal is to remain above a certain point on the planets surface your speed would need to scale proportionally with the distance.
I’m guessing you’re thinking in terms of stable or commonly-used orbit speeds, in which case you’re probably right (I don’t know orbital mechanics at all, but I do remember basic geometry pretty well).
No, dstarfire is correct; remaining in a geostationary position requires moving at a speed proportional to the distance from Earth (specifically the centroid). This speed will only be the same speed as orbital speed at one particular distance, called geostationary orbit (GEO), about 35.8 km above Earth’s surface.
I think what the op is looking for is skip reentry. It could theoretically have been used if we knew a shuttle was damaged beyond repair ahead of time.