ISRO’s Gaganyaan crew cabin module needed carbon dioxide removed from a sealed atmosphere, and Suracsh worked with ISRO on the filter media for that duty. That single sentence is the entire technical content of the case study we published on the work. ISRO’s own published mission profile gives the volume the problem sits in: a crew of three, at a 400 km orbit, for a three-day mission, returning to Indian waters.
Suracsh has published a case study on this work. It does not publish the grade, the capacity, or the test conditions, and this article does not invent them. What follows is the technical problem, stated from public sources, and an honest account of where the published record stops.
The short version
- The duty was carbon dioxide removal from the crew cabin module of the Gaganyaan human spaceflight programme. That is what the case study establishes, and it is all it establishes.
- The case study contains no numbers — no capacity, no grade, no partial-pressure target, no bed geometry, no date, no contract status, and no statement that the media flew.
- ISRO’s published mission profile is three crew, 400 km, three days. As of August 2026 no Gaganyaan flight has carried crew.
- Suracsh publishes two CO₂ grades: SURSORB PCO-2 (impregnated pellet, CTC min 55 %, apparent density 520 ± 30 kg/m³) and SURSORB PACO-2 (alkali-impregnated), which has no published specification table.
- Carbon dioxide has a kinetic diameter of about 0.33 nm and adsorbs weakly on unmodified carbon at low partial pressure — which is why the case study’s phrase about altering chemical properties is the substantive part of it.
What the case study actually says
The document is a single marketing page, produced by Suracsh Filters Pvt Ltd in Kochi before Suracsh Adsorbents LLC existed in the United States. It states that Gaganyaan is ISRO’s human spaceflight mission to demonstrate crewed flight to Low Earth Orbit; that Suracsh had the opportunity to work with ISRO on developing filter media for the project; that ISRO “was in search of suitable filter media for the crew cabin module” to remove carbon dioxide; and that the chemical and physical properties of the media had to be altered to the requirement.
That is the whole of it. There is no capacity, no isotherm, no breakthrough figure, no bed dimension and no date. Until now it also existed only as a scanned image PDF with no text layer — unreadable to search engines, to screen readers, and to anyone using an answer engine. Publishing it in HTML is most of the point of this article.
What Gaganyaan is, and where it stands
Gaganyaan is ISRO’s human spaceflight programme. ISRO describes the project’s aim as demonstrating human spaceflight capability by launching a crew of three to a 400 km orbit for a three-day mission, with a landing in Indian waters. The Human Space Flight Centre leads it, and the critical technology set includes life support, crew training and a human-rated launch vehicle.
The schedule has moved repeatedly, so the status matters more than the plan. As of August 2026, no Gaganyaan flight has carried crew. The first uncrewed orbital test flight, G1 — which carries the Vyommitra humanoid robot and is intended to exercise the life-support and safety systems end to end — had not launched, and was reported in July 2026 as expected around late 2026, with two further uncrewed flights, G2 and G3, before any crewed mission. The first crewed flight, H1, remains tentatively scheduled for 2027; a ministerial announcement in May 2025 had put it in the first quarter of that year. By mid-2026 ISRO reported more than 8,000 ground tests completed, including qualification of the crew module uprighting system, the crew module to service module connect and disconnect system, and the apex cover that protects the parachutes.
None of that public record says anything about Suracsh, and we are not going to imply that it does. It is the context the media was developed for, nothing more.
Why cabin CO₂ is a different adsorption problem
An industrial adsorber has advantages a crew cabin does not. It can be oversized. It can be changed out on a schedule. It sits in a building where mass is nearly free. Its contaminant is often present at high concentration, which is the condition under which adsorption works best.
A crew cabin inverts all of that.
The volume is fixed and sealed. Metabolic carbon dioxide accumulates continuously in the atmosphere the crew is breathing, and it must be removed or scrubbed for the duration. There is no dilution from outside, so the adsorber is in a closed loop with its own source.
The mass and power budget is fixed before launch. Every kilogram of media is a kilogram not spent on something else, and the trade is made once, on the ground. There is no oversizing your way out of an uncertain capacity figure.
Media cannot be changed out mid-mission. In an industrial bed, breakthrough is a maintenance event. Here it is a design failure. The whole service life has to sit inside the mission, with margin, at conditions verified in advance.
And the contaminant is a difficult one for physical adsorption. Carbon dioxide’s kinetic diameter is about 0.33 nm — near the bottom of the molecular size range, in the region where only the finest micropores contribute usefully. It is weakly adsorbing, and in a cabin atmosphere it is present at low partial pressure. Physisorption capacity falls with partial pressure; a molecule that binds weakly at 1 bar of pure CO₂ binds far more weakly as a dilute component of breathing air.
Carbon dioxide sits near the bottom of the molecular size range at about 0.33 nm kinetic diameter — small, weakly adsorbing, and in a cabin atmosphere present at low partial pressure. That combination is what makes cabin CO₂ a chemistry problem rather than a surface-area problem.
That is why the case study’s one technical sentence — that the chemical and physical properties had to be altered — is the substantive part of it. Altering chemical properties on a carbon means impregnation, and impregnation for CO₂ means adding a basic phase that captures an acidic gas by reaction rather than by physical adsorption alone.
The open literature quantifies the trade that comes with it. In a study of alkaline-earth-oxide impregnation of a waste-derived carbon, an optimum at 12 wt % MgO gave a CO₂ capacity of 94.02 mg/g with an isosteric heat of 34.7 kJ/mol, behaving as combined physisorption and chemisorption, and losing 9.96 % of capacity over six cycles. The same study reports that the unimpregnated carbon had a higher surface area than every impregnated variant. That is the general rule: impregnation buys capture chemistry and pays for it in surface area — in one open-access comparison of five impregnants on a single carbon, BET area fell by up to 96 %.
There is a second cost, and it is the one that matters most in a closed vehicle. Work funded by NASA on cabin trace-contaminant control notes, of a phosphoric-acid-impregnated commercial carbon used for ammonia, that the impregnation enhances sorption but “also makes regeneration difficult, if not impossible”. Chemisorption is what gives you capacity at low partial pressure, and it is also what takes regenerability away. Where that trade should land is a mission-architecture decision, not a media decision — and it is exactly the kind of decision the published record here does not disclose.
The CO₂ grades Suracsh does publish
Two grades in our range are offered for carbon dioxide duty.
SURSORB PCO-2 — cylindrical pellet, coconut-shell, impregnated, chemistry not disclosed:
| Parameter | Value |
|---|---|
| CTC adsorption | min 55 % |
| Apparent density | 520 ± 30 kg/m³ |
| Moisture | max 5 % |
| Ball pan hardness | min 95 |
| Crushing strength | min 4 kg |
| Ash | max 5 % |
| Sizes | 4 mm; 3 mm; 2 mm |
SURSORB PACO-2 — pellet, alkali impregnant, for CO₂ capture, categorised for industrial-gas and personal-protection duty. It has no published specification table. The sheet states specifications are available on request and that sizes are to customer specification.
That asymmetry is worth naming rather than glossing. Suracsh publishes specifications in HTML for the great majority of its 46 grades, and every published datasheet downloads without a form — the exceptions, SURSORB PACO-2 and SURSORB ZEO, are supplied to specification and say so. The grade whose chemistry is closest to the application described in this case study — alkali impregnation for CO₂ capture — is the one grade in that pair with no published sheet. On a site whose entire posture is publishing specifications, that is a gap, and pointing at it is more useful than writing around it.
Neither grade is identified in the case study as the media supplied to ISRO. We are not going to claim either one was.
What a company can honestly claim from a programme like this
The defensible claim is narrow: Suracsh worked with ISRO on filter media for a stated carbon dioxide removal requirement in the Gaganyaan crew cabin module, and the case study states — as the company’s own account, not as anything a customer has confirmed — that its R&D developed the product to the required parameters. That is the whole of what the case study supports, and it supports it as a claim rather than as a verified outcome. ISRO has published no statement of acceptance, and neither have we.
Everything a reader would reasonably want next — which grade, what capacity, at what partial pressure, in what bed, verified by whom, and whether the media flew — would need ISRO’s confirmation, not ours. A supplier cannot certify its own place in someone else’s programme, and we are not going to write sentences that quietly imply otherwise. If you are evaluating us for a similar duty, the honest basis for that evaluation is the published specification of the grades above and whatever test work we agree to run against your conditions, not a heritage claim.
The other two case studies
Two companion case studies are being republished in the same readable form, for the same reason: both currently exist only as scanned images that no search engine or screen reader can read.
- NBC filter fabric in activated carbon sphere form — the development of a commercial adsorbent for air-permeable chemical protective clothing.
- CO filter regeneration for Indian Navy submarines — recovery and reactivation of palladium-impregnated carbon filters used for carbon monoxide removal in confined spaces.
Both are defence-adjacent, and both will be written to the same rule as this one: educational and technical, no capability claim beyond what is published. Enquiries concerning export-controlled grades require an identified end user and end use before a quotation can be issued.
Suracsh publishes specifications in HTML for the great majority of its 46 grades, and every published datasheet downloads without a form or an NDA. Two grades are the exception — SURSORB PACO-2 and SURSORB ZEO — and both are supplied to specification and say so on the sheet. Where a case study has no number in it, we would rather say so than fill the space.
Sources
- ISRO — Gaganyaan programme
- The Week, 14 July 2026 — ISRO completes three crew module qualification tests
- Space.com — India delays first Gaganyaan astronaut launch to 2027
- Gaganyaan programme overview and flight manifest
- Metal oxides (CaO, SrO, MgO) impregnated waste-derived activated carbon for CO₂ adsorption, Scientific Reports (2023)
- Zulkefli et al., PLOS ONE 14(2):e0211713 (2019) — impregnation and surface-area loss
- Wójtowicz et al., ICES-2015-179 — sorbents for cabin trace contaminant control, NASA NTRS
Questions
What did Suracsh do for ISRO's Gaganyaan programme?
Suracsh worked with ISRO on filter media for the Gaganyaan crew cabin module, where the duty was carbon dioxide removal. The company's published case study states that the chemical and physical properties of the media were altered to the requirement. It does not publish the grade, the capacity or the test conditions.
Which Suracsh grade was used in the Gaganyaan crew module?
Suracsh has not published it, and this article does not guess. The company publishes two carbon dioxide grades — SURSORB PCO-2, an impregnated pellet, and SURSORB PACO-2, an alkali-impregnated grade with no published specification table — but the case study does not say either one was the media supplied.
Why is cabin CO2 removal harder than an industrial adsorption duty?
The volume is small and sealed, the mass and power budget is fixed, media cannot be changed out mid-mission, and carbon dioxide is a small, weakly adsorbing molecule of about 0.33 nm kinetic diameter present at low partial pressure. Physisorption on unmodified carbon is weak under those conditions.
What is the status of the Gaganyaan mission in 2026?
As of August 2026 no Gaganyaan flight has carried crew. The first uncrewed orbital test flight, G1, carrying the Vyommitra humanoid robot, had not launched and was reported in July 2026 as expected around late 2026, with the first crewed flight tentatively in 2027. ISRO's stated profile is three crew at 400 km for three days.