FR-TSTO policy

tahanson43206 · 2024-05-28 20:44:16

FR-TSTO Fully Reusable Two Stage to Orbit

I asked ChatGPT4o to address the dilemma we are facing, in trying to envision and talk about a technology that only exists today in the form of the X-37b space plane, and it's Chinese counterpart. ChatGPT4o thought about the question, consulted it's training data and came up with a new term which you have the opportunity to introduce to the world, through our forum.

Introducing a New Term: Fully Reusable Two Stage to Orbit (FR-TSTO)
Introduction
As advancements in space exploration continue, the need for precise terminology becomes increasingly important. With the advent of fully reusable launch systems, it's time to introduce a term that accurately describes these innovative spacecraft.
Proposed Term: Fully Reusable Two Stage to Orbit (FR-TSTO)
Definition
FR-TSTO stands for Fully Reusable Two Stage to Orbit. This term describes a spacecraft system that:
Uses two stages to reach orbit.
Is fully reusable, with both stages designed to return safely to Earth for subsequent missions.
Examples of F R-T S T O Systems
1. SpaceX Starship and Superheavy

Starship: The upper stage that reaches orbit and returns, landing vertically using retropropulsion.
Superheavy: The first stage booster that returns to Earth and lands using retropropulsion.
2. Dream Chaser (with a reusable first stage)
3. Military Orbital Vehicles

The US and Chinese military are developing spaceplanes that reach orbit and glide back to land.
If launched on reusable boosters, they fit the FR-TSTO model.
Benefits of the Term
Clarity: Clearly distinguishes from Single Stage to Orbit (SSTO) and traditional Two Stage to Orbit (TSTO) systems.
Specificity: Emphasizes full reusability and the operational concept involving two stages.
Innovation Acknowledgment: Recognizes the technological advancements enabling fully reusable systems.
Conclusion
The term Fully Reusable Two Stage to Orbit (FR-TSTO) provides a precise and descriptive label for these advanced spacecraft systems. It reflects the direction of modern space exploration, highlighting the capability to reach orbit without discarding any components. By adopting this term, we can better describe and discuss these groundbreaking developments in space technology.

(th)

SpaceNut · 2024-05-30 17:40:04

currently the starship fits into this type of rocket. Also, a carrier plane and rocket would also fit this as well. Then again, the Space Launch Initiative (SLI) was 2 planes doing a rocket plane design.

Here a list of tsto not reusable rockets
https://en.wikipedia.org/wiki/Two-stage-to-orbit

https://en.wikipedia.org/wiki/Space_Launch_Initiative

tahanson43206 · 2024-05-30 17:49:21

For SpaceNut re new Forum....

Thanks very much for providing this new opportunity for NewMars members to contribute to what I am hoping will be a robust collection of topics about the systems that are in development.

To the best of my knowledge, we do not currently have a system that qualifies for this topic, but the military X-37b could qualify if it flies on a Falcon Heavy and all lift elements are landed safely.

However, the trend lines seem favorable, so this new forum is available for NewMars members to track each vehicle. My concept for this forum is that each design would get it's own topic.

(th)

SpaceNut · 2024-05-30 17:53:41

Should we move the space x BFR/starship to this new forum?

There are also 2 other versions that proceeded this version that is being worked on currently.

edit update

Yes, the Facon 9 and its heavy version are a 2-stage rocket, but the second stage is replaced and not recovered on any launch as its expended.

tahanson43206 · 2024-05-30 18:10:48

For SpaceNut .... let's hold off ... there are NO systems that meet the requirements of this topic.

Let's welcome new systems into the topic when they are working.

Starship is close! If it flies and lands the vehicle next month it would qualify.

If it fails to land the vehicle, then we can just wait a bit longer.

Update .... It seems to me we might want to wait until the system actually flies both components a second time.

The qualification to show in this topic is reusability of each stage. Just landing both stages is not proof the system is fully operational.

(th)

tahanson43206 · 2024-05-30 18:17:18

For SpaceNut ....

This is an entire forum dedicated to a very important new technology.

While I have recommended holding off on creating topic for systems that are in development, I also recognize our members will be interested in ideas that are floated for systems that might qualify.

Let's think about how we might like to set things up, before we make a lot of topics.

Anyone can create a topic already, so one option is to just let our members create topics as they are inspired.

(th)

RobertDyck · 2024-05-30 19:55:49

Should I post old proposals? In 1968 NASA published requirements for Shuttle. At that time it was required to be fully reusable TSTO, carry 7 astronauts and 11 metric tonnes of supplies for a space station. No cargo bay door because it would be used for supplies and internal equipment only. Construction would be done with a big dumb rocket, Saturn 1B or its replacement. It was expected to be a piloted fly-back booster and lifting body orbiter. In 1969 two contractors submitted bids.

Lockheed: Shuttle LS A - based on X-24A

McDonnell Douglas Corporation: Shuttle MDC A - based on HL-10

Last edited by RobertDyck (2024-05-30 20:49:02)

tahanson43206 · 2024-05-30 20:26:16

For RobertDyck re #7

Thanks for contributing these interesting historical proposals....

And thanks for asking ... This is a brand new forum, with a lot of upside potential.

Providing future readers with a wealth of historical examples would be part of the mix...

I vaguely recall those proposals ... they must have reached the public somehow.

The key is that the original design was for the fully reusable capability.

Since we do not yet have ** any ** systems that qualify, I think a historical topic about this design would be valuable for study.

Thanks again for asking!

Please feel free to create a topic for this proposal.

Posts can link to any historical resources that our members can find.

(th)

GW Johnson · 2025-05-18 07:31:25

Looking at this from a viewpoint of flight mechanics and aeroheating:

With TSTO you have a booster stage that supplies a smaller fraction of the total dV, usually at a lower Isp due to the limitations of nozzle design and of propellant selection (primarily density and volume).

You have an upper stage that supplies a significant majority of the total dV, and usually at the higher Isp associated with vacuum nozzle design and higher-Isp propellant selection, with the density-volume problem far less demanding in a smaller upper stage.

If flown to a landing somewhere, because of the low staging velocity that is typical, the booster hits atmosphere at a speed nearer 1 km/s than 2, which would be supersonic near Mach 3 instead of hypersonic near Mach 6. The aeroheating is far lower the slower you are moving when you hit atmosphere. Depending upon what the stage is constructed of, you may or may not need an "entry burn" to slow down to a survivable entry speed, as a bare metal item with no added heat protection generally. There are some heating issues locally around the engine bay, due to hot engine plume gases plus the hot air, there. And it usually needs some sort of landing legs, which add at least a bit to its loaded-stage inert weight fraction.

The upper stage, if it is to be recovered, will hit atmosphere at speeds that are full orbital class. It takes very little dV to deorbit (on the order of 100 m/s from circular LEO). It would take nearly the same 6 km/s dV as the second stage supplied to ascend, to hit atmosphere at the same slow speed as the booster. No one could ever afford that much propellant! So the second stage MUST BE a fully qualified reentry vehicle, if it is to be recovered.

There are essentially 2 ways to design the upper stage of a TSTO. It can be just a standard rocket stage, with the payload housed in a separate payload fairing that gets jettisoned as you go exo-atmospheric, at or just after staging. Or it can be a vehicle that actually contains the payload inside, so that there is no payload shroud to jettison.

If you design it as a stage with a payload shroud, you are going to have to add a fully-qualified heat shield to its forward end, and enter like a blunt object, nose forward. That can be done, but it is heavy, and there is no way to do that and still achieve a 5% loaded stage inert fraction! It'll be nearer 10, maybe 15%. The heavy heat shield complicates the final landing of the stage, unless you jettison it after entry, which creates a serious falling debris hazard. And because the sides have no tumble-home angle, and attitude control is not perfect, those sides will also likely need at least some heat protection. That also adds to loaded stage inert weight fraction.

If you instead design it as a vehicle that contains the payload inside, where the vehicle structure serves as the "payload shroud", that frees up many possible choices for its shape, and for exactly what attitudes you can use during entry, in turn freeing up more choices for what you can use for heat shielding protection, and for how much of the vehicle needs heavy-duty shielding, and how much does not. But, at entry attitudes that are not nose-first, the wind loads on the structure during entry are much higher and more difficult to design for, compared to simple blunt-shape nose-first entry. Such designs will have loaded stage inert weight fractions in the 15-20+% range, or more (it's 40-50% in jet aircraft, and they still break up if they go broadside at full speed).

If the upper stage really is an entry-qualified vehicle design, you still have two classes of options for its landing: wings or vertical. Wings add yet more inert weight, for the strength to survive entry wind loads at entry attitude, and also for the area needing heat shielding. They also have a long runway requirement. But you can delete landing propellant, if you give up on go-around capability at landing. Or you can land vertically, which means you must have some means to go tail first at lower altitude, and you must have significant landing propellant aboard. Generally, you also need landing legs, too.

Reusability is simply going to increase your stage inert weights, especially the upper stage in a TSTO, there is no way around that ugly little fact of life. You get what you pay for.

Last edited by GW Johnson (2025-05-18 07:35:13)

kbd512 · 2025-05-18 17:31:44

GW,

Such designs will have loaded stage inert weight fractions in the 15-20+% range, or more (it's 40-50% in jet aircraft, and they still break up if they go broadside at full speed).

The Falcon booster weighs 25,600kg empty and contains 395,700kg of propellants. The 9 Merlin engines weigh 4,230kg, so 21,370kg is mostly Al-2195 alloy propellant tank structure. It's a fully reusable vehicle, as proven hundreds of times now. It's dry mass fraction is 6.08%. Suppose we make its structure 30% lighter using composites, so 14,959kg (structures) + 4,230kg (engines), 19,189kg in total, for a 4.63% dry mass fraction. If it's engines had a 200:1 TWR like Raptor 3, then it's engines weigh 3,878kg, so 18,837kg total dry mass, and 4.54% of wet mass.

The Falcon 9 is not mass optimized, so much as it's truck transportability optimized.

Falcon 9's total LOX load is 312,200kg (273.62m^3) and total RP1 load is 186,006kg (229.637kg), or 503.257m^3 in total. That 10m diameter composite cryotank holds 634m^3 of propellant and only weighs 3,037kg, and would only be 80% full. A tank structure for this mass optimized Falcon 9 booster would therefore weigh 7,267kg for propellant tanks (3,037kg) and engines (4,230kg). If we have 200:1 staged combustion engines, then we get an Isp bump and mass reduction. That cube-square law is really helping us out here. Aero drag at low altitude will be much higher, obviously, but we don't spend much time in the lower atmosphere. Our dry mass fraction is only 1.8%, though, or 1.7% using improved engines. Landing gear mass will obviously drive the inert mass fraction up, but now we have a much more stable vehicle when it comes time to land. There's almost no chance of tipping over.

All that said, we've cut our dry mass fraction by more than half by making those changes.

New Mars Forums

Announcement

#1 2024-05-28 20:44:16

FR-TSTO policy

Introducing a New Term: Fully Reusable Two Stage to Orbit (FR-TSTO)

#2 2024-05-30 17:40:04

Re: FR-TSTO policy

#3 2024-05-30 17:49:21

Re: FR-TSTO policy

#4 2024-05-30 17:53:41

Re: FR-TSTO policy

#5 2024-05-30 18:10:48

Re: FR-TSTO policy

#6 2024-05-30 18:17:18

Re: FR-TSTO policy

#7 2024-05-30 19:55:49

Re: FR-TSTO policy

#8 2024-05-30 20:26:16

Re: FR-TSTO policy

#9 2025-05-18 07:31:25

Re: FR-TSTO policy

#10 2025-05-18 17:31:44

Re: FR-TSTO policy

Board footer