Skyhiker-Skyhitch towed SSTO

[IsaacKuo]

The Skyhiker-Skyhitch SSTO system uses a small spaceplane that is towed/pushed most of the way up. The components are:

A) Two small Skyhiker SSTO spaceplanes. The L-SSTO launches from Earth to orbit. The R-SSTO returns from orbit to Earth. Skyhiker is similar to X-37B upscaled by 2X.

B) Two jet tow planes. One tows L-SSTO to altitude. The other tows R-SSTO back to home base. To minimize development costs, these are existing jets with a tow cable added.

C) One large Skyhitch tow rocket. This brakes from orbit and returns to orbit with L-SSTO. To minimize development costs, this is shaped like the Space Shuttle Orbiter. Internally it's a flying fuel tank that uses internal pressure for structural strength and open cycle cooling of the TPS to minimize the mass that must be reboosted back to orbit.

This system assumes CO/LOX resupply in space. See my Deimos dust potato gun rocket for LMO atmospheric scooping.

Skyhiker's launch procedure is:

1) L-SSTO is hitched to tow jet on runway.

2) Jet launches and tows L-SSTO to high altitude. The rocket is optimized for high altitude/vacuum.

3) L-SSTO boosts to 2km/s as R-SSTO brakes to meet it. Mass ratio about 2:1.

10T Payload
10T L-SSTO dry mass
20T Fuel

4) R-SSTO pushes L-SSTO from 2km/s up to 4km/s as Skyhitch brakes to meet it. Mass ratio about 2:1. Note that R-SSTO's cargo tank is filled with fuel.

10T Payload
10T L-SSTO dry mass
10T R-SSTO dry mass
30T Fuel

5) Skyhitch pushes L-SSTO from 4km/s up to 7.8km/s. Mass ratio about 4:1.

10T Payload
10T L-SSTO dry mass
20T Skyhitch dry mass
120T Fuel

6) R-SSTO glides to second jet for towing back toward home base. It lands horizontally.

In a sense, Skyhitch replaces a giant first stage. But since Skyhitch never returns to the ground, it doesn't need landing gear and it doesn't need to be integrated with an upper stage on the ground. This avoids costs associated with a reusable TSTO. Instead, ground operations are airplane-like (very cheap!).

Note that the pushing operations take place in vacuum after L-SSTO has emptied its fuel tanks. This eliminates aerodynamic forces and mitigates pushing ring force. It's quite a contrast with a traditional multi-stage rocket, where the lower stages must accelerate the fully fueled upper stages through the lower atmosphere.

Because Skyhitch externally looks like the STS Orbiter, it might be initially launched by SLS, bolted onto the side. That would look...amusing.

[wuzetian]

The Skyhiker-Skyhitch SSTO system uses a small spaceplane that is towed/pushed most of the way up. The components are:

A) Two small Skyhiker SSTO spaceplanes. The L-SSTO launches from Earth to orbit. The R-SSTO returns from orbit to Earth. Skyhiker is similar to X-37B upscaled by 2X.

B) Two jet tow planes. One tows L-SSTO to altitude. The other tows R-SSTO back to home base. To minimize development costs, these are existing jets with a tow cable added.

C) One large Skyhitch tow rocket. This brakes from orbit and returns to orbit with L-SSTO. To minimize development costs, this is shaped like the Space Shuttle Orbiter. Internally it's a flying fuel tank that uses internal pressure for structural strength and open cycle cooling of the TPS to minimize the mass that must be reboosted back to orbit.

This system assumes CO/LOX resupply in space. See my Deimos dust potato gun rocket for LMO atmospheric scooping.

Skyhiker's launch procedure is:

1) L-SSTO is hitched to tow jet on runway.

2) Jet launches and tows L-SSTO to high altitude. The rocket is optimized for high altitude/vacuum.

3) L-SSTO boosts to 2km/s as R-SSTO brakes to meet it. Mass ratio about 2:1.

10T Payload
10T L-SSTO dry mass
20T Fuel

4) R-SSTO pushes L-SSTO from 2km/s up to 4km/s as Skyhitch brakes to meet it. Mass ratio about 2:1. Note that R-SSTO's cargo tank is filled with fuel.

10T Payload
10T L-SSTO dry mass
10T R-SSTO dry mass
30T Fuel

5) Skyhitch pushes L-SSTO from 4km/s up to 7.8km/s. Mass ratio about 4:1.

10T Payload
10T L-SSTO dry mass
20T Skyhitch dry mass
120T Fuel

6) R-SSTO glides to second jet for towing back toward home base. It lands horizontally.

In a sense, Skyhitch replaces a giant first stage. But since Skyhitch never returns to the ground, it doesn't need landing gear and it doesn't need to be integrated with an upper stage on the ground. This avoids costs associated with a reusable TSTO. Instead, ground operations are airplane-like (very cheap!).

Note that the pushing operations take place in vacuum after L-SSTO has emptied its fuel tanks. This eliminates aerodynamic forces and mitigates pushing ring force. It's quite a contrast with a traditional multi-stage rocket, where the lower stages must accelerate the fully fueled upper stages through the lower atmosphere.

Because Skyhitch externally looks like the STS Orbiter, it might be initially launched by SLS, bolted onto the side. That would look...amusing.

So many throws and catches in supersonic speeds ... Ha ha

[IsaacKuo]

Eh, there are only two encounters at supersonic speeds, and they can both use near vacuum aerodynamic control at the start of the pushing maneuver. We regularly perform aerial refueling which uses the same basic technique. In both cases, the incoming pusher vehicle has an extreme reserve of speed to perform turning and braking maneuvers to meet the client vehicle. In the first case, the client vehicle is also under active rocket power up until right before they meet.

There is no case where anything is "thrown" toward some target position. It's all controlled flight.

The third encounter is between the gliding return SSTO and the second tow jet. There is no reason this needs to take place at supersonic speeds. The returning SSTO can be gliding at, say, 200mph, by the time it meets the tow jet. There's no hurry on this one because it starts off at a high altitude and it just doesn't matter if they lose a lot of altitude while hooking up the tow line.

[Jim]

Skyhitch tow rocket is a non starter.  Braking all the mass of propellant and then reboosting is not viable.  It would take a large surface area to brake the mass.

Also, it is not feasible to brake to a specific velocity and altitude.  They are interrelated.  There still will be heating at 2 km/s.  Propulsion will be require.

The whole concept is unworkable.

[Almurray1958]

Not quite sure that something with 2 tow planes and a tow rocket can be called a SINGLE stage to orbit. The  mission profile is complex

[Jim]

Because Skyhitch externally looks like the STS Orbiter, it might be initially launched by SLS, bolted onto the side. That would look...amusing.

Not doable.  Would require redesign of SLS core and VAB

[Jim]

The other tows R-SSTO back to home base.

Why?  Just let it land itself.

[IsaacKuo]

Well, we typically don't call strap on boosters another stage, nor do we call the payload spacecraft another stage even if it generally has its own thrusters to reach the desired orbit. It's kind of fuzzy.

I call it an SSTO to emphasize that the lack of stage integration on the ground. In a sense, hitching the tow cable is "integrating" the tow jet and the SSTO, but this is practically nothing in time and effort compared to the strap on boosters we ignore.

The Space Shuttle Orbiter has demonstrated that it is indeed possible to brake from orbit, while performing S-turns that provide a large amount of cross-range capability and which reaches a specific narrow target slot and altitude (otherwise, it would crash somewhere other than the landing runway). There is some development required to replace the heavy STS's TPS tiles with an open cycle cooled system, but I think that may be the best option since it reduces the amount of dry mass that must be accelerated back from 4km/s to orbit.

[Jim]

The Space Shuttle Orbiter has demonstrated that it is indeed possible to brake from orbit, while performing S-turns that provide a large amount of cross-range capability and which reaches a specific narrow target slot and altitude (otherwise, it would crash somewhere other than the landing runway). There is some development required to replace the heavy STS's TPS tiles with an open cycle cooled system, but I think that may be the best option since it reduces the amount of dry mass that must be accelerated back from 4km/s to orbit.

Not filled with the amount of propellant (4km/s) that you propose.
The shuttle TPS is not "heavy".  It would be lighter than open cooled system

Landing is not the same as targeting a specific altitude and velocity

[hkultala]

Well, we typically don't call strap on boosters another stage

Who is "we"?

On the world most used launcher family, the "boosters" are called stage 1, the "core" is called stage 2.

And, boosters are universally considered to be a a stage, even when they are not called "stage 1". Booster separation is considered as a staging event.


You call your system "SSTO" because you just think than "SSTO is cool", and you want pto propose something cool, even though on the way you lose then SSTO part.

[IsaacKuo]

The other tows R-SSTO back to home base.

Why?  Just let it land itself.

Depending on the specifics, such as launching to the ISS orbit from KSC, it would be over the Atlantic Ocean heading east. While it might use parachutes and floats to land on the ocean, you've got to deal with ocean water damage (especially to the engines) and a time consuming recovery process.

[Jim]

The other tows R-SSTO back to home base.

Why?  Just let it land itself.

Depending on the specifics, such as launching to the ISS orbit from KSC, it would be over the Atlantic Ocean heading east. While it might use parachutes and floats to land on the ocean, you've got to deal with ocean water damage (especially to the engines) and a time consuming recovery process.

depending on tow is not viable.  Even current mid air refueling have failed hookups.

[Archibald]

You'd better have to mixed propulsion (jet-rocket) suborbital space planes refueling in suborbital flight at the top of a parabola. Only a single rendezvous and propellant transfer.

[IsaacKuo]

You'd better have to mixed propulsion (jet-rocket) suborbital space planes refueling in suborbital flight at the top of a parabola. Only a single rendezvous and propellant transfer.

The dry mass of a jet engine would eat away at the payload, and would add greatly to development costs (in contrast to being towed by an already existing jet). Fuel transfer could, in principle, make things more efficient. Originally, I conceived of the SSTO as refueling in mid-boost.

The launch SSTO could take off much lighter, and it would top off at altitude from a tanker. The returning SSTO could refuel the launch SSTO at 2km/s and the R-SSTO's dry mass wouldn't need to be re-accelerated up to 4km/s.

But carbon monoxide/lox are cryogenic fuels. You'd have to develop a dual feed cryogenic aerial refueling system rather than using an off-the-shelf tanker jet. And such an aerial refueling system would be heavier than a simple tow hook and a pushing ring.

(I'm not sure whether a pushing ring would be better or a tow cable. Here, I illustrate a pushing ring at the rear of the SSTO. But I do like the idea of using a tow cable for all steps.)

[ppb]

You'd better have to mixed propulsion (jet-rocket) suborbital space planes refueling in suborbital flight at the top of a parabola. Only a single rendezvous and propellant transfer.

The dry mass of a jet engine would eat away at the payload, and would add greatly to development costs (in contrast to being towed by an already existing jet). Fuel transfer could, in principle, make things more efficient. Originally, I conceived of the SSTO as refueling in mid-boost.

The launch SSTO could take off much lighter, and it would top off at altitude from a tanker. The returning SSTO could refuel the launch SSTO at 2km/s and the R-SSTO's dry mass wouldn't need to be re-accelerated up to 4km/s.

But carbon monoxide/lox are cryogenic fuels. You'd have to develop a dual feed cryogenic aerial refueling system rather than using an off-the-shelf tanker jet. And such an aerial refueling system would be heavier than a simple tow hook and a pushing ring.

(I'm not sure whether a pushing ring would be better or a tow cable. Here, I illustrate a pushing ring at the rear of the SSTO. But I do like the idea of using a tow cable for all steps.)

Hey you got Jim to critique your idea! Lucky you. Listen to what he says.

[Lars-J]

There's at least 4 stages for this ... "SSTO". 

Google "skyhook structure" for a far more practical way to do what you are trying to accomplish. This is what I assumed you were going to describe based on the thread title.

[IsaacKuo]

There's at least 4 stages for this ... "SSTO". 

Google "skyhook structure" for a far more practical way to do what you are trying to accomplish. This is what I assumed you were going to describe based on the thread title.

Besides being a hazard to LEO use, a tether is extremely inflexible in terms of what orbits and launch sites it can service. It practically can only support one inclination and one launch site.

This Skyhitch concept can support multiple launch sites and can service a different orbit each time thanks to the turning capability of the winged space planes while braking. Bleeding speed down to 2km/s or 4km/s allows turning by a large angle and large cross range capability. Practically speaking, any launch site and any orbit may be serviced.

Also, it's harder to latch onto a skyhook because the window is very brief. An 2km/s arc could start with a 600m/s upward velocity, offering two minutes to hook up before starting to renter thicker air. And even then, gliding together offers more time to hook up. Depending on the mass of the payload, there will be a variable extra margin of delta-v to make up for gliding drag.

[Jim]

This Skyhitch concept can support multiple launch sites and can service a different orbit each time thanks to the turning capability of the winged space planes while braking. Bleeding speed down to 2km/s or 4km/s allows turning by a large angle and large cross range capability.

Wrong.  Not feasible in this concept.    And there is no way to sustain level controlled flight to allow the hookup.  The "braking" vehicle is going to be in a descending flight path.  And still in a entry attitude.

[Jim]

Also, it's harder to latch onto a skyhook because the window is very brief. An 2km/s arc could start with a 600m/s upward velocity, offering two minutes to hook up before starting to renter thicker air. And even then, gliding together offers more time to hook up. Depending on the mass of the payload, there will be a variable extra margin of delta-v to make up for gliding drag.

Wrong.  it will be just as hard to latch up.  It is not "gliding".  It is descending at a high rate.

There is no way two vehicle can rendezvous at 2km/sec is too fast to be "flying" and too slow to be orbiting..
At what altitude do you propose this to happen?

[Jim]

This thread has some of the same nonsense.  It was shown that it is not feasible to work for some of the same reasons.

https://forum.nasaspaceflight.com/index.php?topic=41207.0