SSTO Sub Forum Policy

kbd512 · 2024-05-19 18:42:19

All contributory ideas related to Single Stage To Orbit / SSTO are welcome here. I only ask that contributed ideas are related to SSTO concepts or technology development. We will have one debate topic where we debate the merits and demerits of Single Stage To Orbit / SSTO vs Two Stage To Orbit / TSTO.

tahanson43206 · 2024-05-19 18:52:12

This post is reserved for an index to posts that will surely be contributed by NewMars members over time.

(th)

RGClark · 2024-05-20 12:23:08

You may also want to move the Radian spaceplane discussion to this subforum:

Radian Aerospace spaceplane.
http://newmars.com/forums/viewtopic.php?id=10781

Bob Clark

Last edited by RGClark (2024-05-20 12:23:49)

SpaceNut · 2024-05-20 12:33:26

done as it does apply

tahanson43206 · 2024-05-29 07:12:28

It appears that the definition of SSTO is fairly restrictive. In order to qualify as a true SSTO, a vehicle must achieve orbit without discarding anything along the way. Here is the Wikipedia definition of SSTO:

A single-stage-to-orbit (SSTO) vehicle reaches orbit from the surface of a body using only propellants and fluids and without expending tanks, engines, or other major hardware. The term usually, but not exclusively, refers to reusable vehicles.
Single-stage-to-orbit - Wikipedia
Wikipedia
https://en.wikipedia.org › wiki › Single-stage-to-orbit

However, there may be a bit of wiggle room at the moment of launch. If the vehicle is given a boost by the launch tower, then the stringent requirements of the definition might be preserved.

However, as of May 2024, no such launch tower assist technologies actually exist.

An example of what such an assist system might look like would be a pneumatic tube that is compressed prior to launch, and which gives the vehicle a surge of upward momentum after the engines light.

(th)

Last edited by tahanson43206 (2024-05-29 07:15:53)

tahanson43206 · 2024-05-29 07:19:15

As of May 2024, there do not appear to be any examples of true SSTO vehicles.

The closest that Google was able to find is the X-37b military research plane.... that vehicle came close.

In December of 2023, the Space Force hired SpaceX to launch the vehicle from Kennedy Space Center, using a Falcon Heavy. The two side boosters returned to launch site, but the center booster was expended.

(th)

RobertDyck · 2024-05-29 11:58:00

Mercury Atlas was SSTO. SM-65A Atlas was designed as a ballistic missile. Later versions were stage and a half: they jettisoed the side booster engines, retaining the central sustainer engine. However the first version, Atlas A, retained the booster engines, so was single stage. That launched Mercury spacecraft into orbit.

Venture Star was supposed to be SSTO, but was cancelled before built. X-33 was a 1/4 scale demonstrator intended to fly suborbital to prove technology. X-33 was cancelled before first launch.

DC-X was the first land-on-tail rocket. It was a technology demonstrator, not even suborbital, just a hopper. It was intended to be scaled up to DC-Y, which would be an unmanned reusable SSTO launch vehicle for small satellites. However, DC-Y was never built.

Last edited by RobertDyck (2024-05-29 12:06:06)

tahanson43206 · 2024-05-29 12:37:21

For RobertDyck re #7

Thanks for the inspiration to read up a little bit on Mercury Atlas...

Quora.com had a discussion on that question, and the opening post was receptive to your idea, but in the end decided that since the Atlas was discarded, the vehicle could not be considered a true SSTO. To qualify as a true SSTO, your design can discard NOTHING.

Here is a follow up post:

Assistant
Bot
May 1
The Mercury-Atlas launch vehicle was not considered a Single Stage To Orbit (SSTO) platform. The term "Single Stage To Orbit" typically refers to a launch vehicle that can reach orbit using only a single stage, without discarding any components during the ascent to orbit.
In the case of the Mercury-Atlas program, the Atlas LV-3B launch vehicle was a two-stage rocket. The Mercury spacecraft was launched atop the Atlas rocket, and the Atlas provided the necessary thrust to propel the Mercury spacecraft into orbit. The Mercury spacecraft itself did not have the capability to reach orbit on its own; it relied on the Atlas rocket for the initial launch and ascent.
Additionally, as you mentioned, the retrorockets on the Mercury spacecraft were used for de-orbiting and re-entry, not for orbit insertion. The Mercury spacecraft would separate from the Atlas rocket once it reached orbit, and then the retrorockets would be used to slow the spacecraft down and initiate re-entry into the Earth's atmosphere.
Therefore, the Mercury-Atlas combination would not be classified as an SSTO platform, as it involved a two-stage launch vehicle (Atlas) to reach orbit, with the Mercury spacecraft serving as the manned capsule that separated from the launch vehicle once in orbit.
Ask follow-up questions on Poe, a free app from Quora
By continuing you agree to create a Poe account, and to its Terms of Service & Privacy Policy

While Mercury Atlas sure comes close, I get the impression it is a bit shy of fully qualifying as SSTO.

I think my assertion stands: Humans have not yet achieved true SSTO. Every successful item ever placed in orbit discarded items on the way there.

However, the floor is open for other suggestions. There may well be a vehicle launched in another country than the US that was a true SSTO.

(th)

RobertDyck · 2024-05-29 21:19:14

Tom, as GW Johnson would elaborate, Atlas A was SSTO. It was not reusable, but was single stage. Redstone was also single stage, but suborbital only. The Mercury capsule separated from the rocket, but the capsule was not a stage, did not contribute to delta-V (change in velocity). Yes, the retro-rocket pack did slow just barely enough to allow the capsule to fall just barely enough to enter atmosphere so drag could do the rest. But that didn't contribute to entering orbit.

Be careful. Quora is not an expert.

Last edited by RobertDyck (2024-05-30 06:38:21)

tahanson43206 · 2024-05-29 21:33:22

For RobertDyck re Atlas A as a true SSTO....

You might be right. The Atlas would have had to reach orbit to qualify as a true SSTO.

If it reached orbit, then it would have had to brake to descend.

If it reached orbit ** altitude ** but did not reach orbit, then it was not an SSTO.

I'd like to see you come through on this one. kbd512 and RGClark are discussing modern SSTO possibilities. It would be encouraging if a vehicle built and launched so long ago was a true SSTO.

Please confirm that Atlas A was able to stay in orbit.

From recent runs of the Rocket Equation, I get the impression SSTO from the surface of the Earth is possible, if the right combination of propellant and hardware are chosen.

While you're at it, please attempt to locate the facts that kbd512 or RGClark would need to compute the Rocket Equation values to describe the flight.

Lift off mass and on-orbit mass appear to be needed, in addition to the nature of the propellant so ISP can be deduced.

(th)

Last edited by tahanson43206 (2024-05-29 21:34:08)

RobertDyck · 2024-05-30 07:24:08

Looking into old details. Mercury launched 6 missions with human crew. Before Allan Shepard they launched one with a chimpanzee. Two Mercury missions launched suborbital on a Redstone rocket, four were orbital using Atlas D rockets. However, Atlas D jettisoned its booster engines so was stage and a half. Atlas A was single stage. It launched 8 times, 3 were successful, 5 failed. NASA had a lot of failures in early years.
Wikipedia: Atlas A

Last edited by RobertDyck (2024-05-30 10:33:04)

tahanson43206 · 2024-05-30 07:31:16

For RobertDyck .... thank you for adding details about the early years.

I have created a topic about SSTO history, and would greatly appreciate your adding posts that qualify.

Whatever flights you report must have completed one full orbit (of the launch vehicle (NOT the capsule)) and have discarded nothing.

It appears you have found some candidates that might qualify, and it would be helpful have such a list to study, if it actually exists.

Your reports are promising but I have seen nothing yet that confirms your original premise.

It may well turn out that all early flights were suborbital for the launching stage, but we won't know until we scrub the reports.

(th)

Last edited by tahanson43206 (2024-05-30 07:32:10)

GW Johnson · 2024-05-30 09:19:06

Two cents worth: the more "operational" early Atlas configurations were like what Rob says: stage-and-a-half. They all shut down and jettisoned two engines. Needed the thrust of three to lift off, but not long after the trajectory bends over leaving the sensible atmosphere (at only around Mach 3), it only needed the thrust of one engine. The Atlas design drops engines, but not any tankage., for its staging event.

The old Soviet R-7 that everybody today calls a "Soyuz" is also about a "stage-and-three-quarter", instead of a serial-burn two-stage design. The core burns from launch to orbit. The four liquid strap-ons stage off in their entirety (engines plus tankage), not long after leaving the atmosphere where the trajectory bends over, and the vehicle needs much less thrust. The strap-ons and core burned in parallel.

GW

tahanson43206 · 2024-05-30 10:21:51

For RobertDyck re GW's Post #13

Please put a post about this (to me surprising) variation of "dropping objects" into the history topic

A policy of dropping engines clearly worked, and now one was worrying about how many stages were involved or some Wikipedia definition.

If you find any examples of ** real ** SSTO in the historical record, I would ** really ** like to be able to showcase that history in the new history topic.

(th)

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SSTO Sub Forum Policy

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Re: SSTO Sub Forum Policy

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Re: SSTO Sub Forum Policy

#4 2024-05-20 12:33:26

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Re: SSTO Sub Forum Policy

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