Tricky question.

Sometimes fuel tanks and pieces of thermal blanket have survived reentry from orbital speed, although not in good shape. They tend to be large in size and light in weight, so they generally slow down high enough in the atmosphere to avoid the high temperatures that reentering spacecraft see.

Although I have never done any calculations or research to determine what speed a body would start to need heat shielding, I am willing to use the previously accepted assumption that a first stage could not survive reentry. If we assume that a first stage is travelling around 1/5th of orbital speed at main engine cut off, then that speed would be around 1 mile per second, or about 1,500 km per second, or so. An object falling from space would have to start, with no speed, somewhat above 1,000 km in order to reach this speed, but that may only cause damage, not disintegration and vaporization.

Lynx has no thermal protection system, which is capable for a reentry from orbit. And also life support system for a longer mission is missed. To your question: It is not only velocity but also angle of reentry trajectory which determines the thermal loads. I would assume a nearly vertical return from 1000 km altitude at 3-4 km/s equals loads from a normal orbit at 8 km/s.

Any rocket that can reach leo can instead be shot straight up. It is orbital speed that burns up things on re-entry not just height.
How high would something have to be to gain enough entry speed to burn up using just gravity’s pull?

Spaceplan “Lynx” (which is not completed and dead now) could be used only for suborbital flights, its maximum velocity was around Mach 3. No way to go to orbit, even as another’s launchers payload.

The Lynx fits inside most launch fairings so pretty much anyone could have lifted it.
And maybe Russia or China have small enough liquid fueled rocket engines to fit their needs.

But this is a last ditch idea. They might not even be able to get permission to take everything outside of the USA.

“XCOR should had concentrate alone on its initial business, the design of small liquid rocket engines driven by alternative pump systems and supply what market needs.”

Except that is what they did. Last year, XCOR stopped work on Lynx in order to focus on its initial business. It was this main business that was supplying much of the money for Lynx.

XCOR’s problem seems to be that they were dependent upon a single customer, one that chose to stop buying from them.

You are right. XCOR should had concentrate alone on its initial business, the design of small liquid rocket engines driven by alternative pump systems and supply what market needs. Also in this respect, they tried even to sell a special pump design (piston pump). Even if SpaceX was initially quite conservative in respect to selecting its only proven technologies for its launcher subsystems. Design and construction of a manned space plane was 1-2 order of magnitude too large for XCOR as a project.

Before going after a dream you must first build a business that can support it. That means you start the business in a known market. You don’t need a better mousetrap, just a viable one.

What XCOR tried to do was shoot a hole in one. It can be done, but with a very low probability of success. The moral of the story is build a boring business first, then pursue your dreams.

The sad thing is, they were building technologies that could be the basis of a boring, positive cash flow business that wasn’t dependent on any single contract… but they didn’t focus on those first.

It’s easy to be distracted from making money when following a dream. They were not the first or last.